Build Tools

Package bindata converts any file into manageable Go source code. Useful for embedding binary data into a go program. The file data is optionally gzip compressed before being converted to a raw byte slice. The following paragraphs cover some of the customization options which can be specified in the Config struct, which must be passed into the Translate() call. When used with the `Debug` option, the generated code does not actually include the asset data. Instead, it generates function stubs which load the data from the original file on disk. The asset API remains identical between debug and release builds, so your code will not have to change. This is useful during development when you expect the assets to change often. The host application using these assets uses the same API in both cases and will not have to care where the actual data comes from. An example is a Go webserver with some embedded, static web content like HTML, JS and CSS files. While developing it, you do not want to rebuild the whole server and restart it every time you make a change to a bit of javascript. You just want to build and launch the server once. Then just press refresh in the browser to see those changes. Embedding the assets with the `debug` flag allows you to do just that. When you are finished developing and ready for deployment, just re-invoke `go-bindata` without the `-debug` flag. It will now embed the latest version of the assets. The `NoMemCopy` option will alter the way the output file is generated. It will employ a hack that allows us to read the file data directly from the compiled program's `.rodata` section. This ensures that when we call call our generated function, we omit unnecessary memcopies. The downside of this, is that it requires dependencies on the `reflect` and `unsafe` packages. These may be restricted on platforms like AppEngine and thus prevent you from using this mode. Another disadvantage is that the byte slice we create, is strictly read-only. For most use-cases this is not a problem, but if you ever try to alter the returned byte slice, a runtime panic is thrown. Use this mode only on target platforms where memory constraints are an issue. The default behaviour is to use the old code generation method. This prevents the two previously mentioned issues, but will employ at least one extra memcopy and thus increase memory requirements. For instance, consider the following two examples: This would be the default mode, using an extra memcopy but gives a safe implementation without dependencies on `reflect` and `unsafe`: Here is the same functionality, but uses the `.rodata` hack. The byte slice returned from this example can not be written to without generating a runtime error. The NoCompress option indicates that the supplied assets are *not* GZIP compressed before being turned into Go code. The data should still be accessed through a function call, so nothing changes in the API. This feature is useful if you do not care for compression, or the supplied resource is already compressed. Doing it again would not add any value and may even increase the size of the data. The default behaviour of the program is to use compression. The keys used in the `_bindata` map are the same as the input file name passed to `go-bindata`. This includes the path. In most cases, this is not desirable, as it puts potentially sensitive information in your code base. For this purpose, the tool supplies another command line flag `-prefix`. This accepts a [regular expression](https://github.com/google/re2/wiki/Syntax) string, which will be used to match a portion of the map keys and function names that should be stripped out. For example, running without the `-prefix` flag, we get: Running with the `-prefix` flag, we get: With the optional Tags field, you can specify any go build tags that must be fulfilled for the output file to be included in a build. This is useful when including binary data in multiple formats, where the desired format is specified at build time with the appropriate tags. The tags are appended to a `// +build` line in the beginning of the output file and must follow the build tags syntax specified by the go tool. When you want to embed big files or plenty of files, then the generated output is really big (maybe over 3Mo). Even if the generated file shouldn't be read, you probably need use analysis tool or an editor which can become slower with a such file. Generating big files can be avoided with `-split` command line option. In that case, the given output is a directory path, the tool will generate one source file per file to embed, and it will generate a common file nammed `common.go` which contains commons parts like API.

Package crypto provides a toolbox of advanced cryptographic primitives, for applications that need more than straightforward signing and encryption. The cornerstone of this toolbox is the 'abstract' sub-package, which defines abstract interfaces to cryptographic primitives designed to be independent of specific cryptographic algorithms, to facilitate upgrading applications to new cryptographic algorithms or switching to alternative algorithms for experimentation purposes. This toolkit's public-key crypto API includes an abstract.Group interface generically supporting a broad class of group-based public-key primitives including DSA-style integer residue groups and elliptic curve groups. Users of this API can thus write higher-level crypto algorithms such as zero-knowledge proofs without knowing or caring exactly what kind of group, let alone which precise security parameters or elliptic curves, are being used. The abstract group interface supports the standard algebraic operations on group elements and scalars that nontrivial public-key algorithms tend to rely on. The interface uses additive group terminology typical for elliptic curves, such that point addition is homomorphically equivalent to adding their (potentially secret) scalar multipliers. But the API and its operations apply equally well to DSA-style integer groups. The abstract.Suite interface builds further on the abstract.Group API to represent an abstraction of entire pluggable ciphersuites, which include a group (e.g., curve) suitable for advanced public-key crypto together with a suitably matched set of symmetric-key crypto algorithms. As a trivial example, generating a public/private keypair is as simple as: The first statement picks a private key (Scalar) from a specified source of cryptographic random or pseudo-random bits, while the second performs elliptic curve scalar multiplication of the curve's standard base point (indicated by the 'nil' argument to Mul) by the scalar private key 'a'. Similarly, computing a Diffie-Hellman shared secret using Alice's private key 'a' and Bob's public key 'B' can be done via: Note that we use 'Mul' rather than 'Exp' here because the library uses the additive-group terminology common for elliptic curve crypto, rather than the multiplicative-group terminology of traditional integer groups - but the two are semantically equivalent and the interface itself works for both elliptic curve and integer groups. See below for more complete examples. Various sub-packages provide several specific implementations of these abstract cryptographic interfaces. In particular, the 'nist' sub-package provides implementations of modular integer groups underlying conventional DSA-style algorithms, and of NIST-standardized elliptic curves built on the Go crypto library. The 'edwards' sub-package provides the abstract group interface using more recent Edwards curves, including the popular Ed25519 curve. The 'openssl' sub-package offers an alternative implementation of NIST-standardized elliptic curves and symmetric-key algorithms, built as wrappers around OpenSSL's crypto library. Other sub-packages build more interesting high-level cryptographic tools atop these abstract primitive interfaces, including: - poly: Polynomial commitment and verifiable Shamir secret splitting for implementing verifiable 't-of-n' threshold cryptographic schemes. This can be used to encrypt a message so that any 2 out of 3 receivers must work together to decrypt it, for example. - proof: An implementation of the general Camenisch/Stadler framework for discrete logarithm knowledge proofs. This system supports both interactive and non-interactive proofs of a wide variety of statements such as, "I know the secret x associated with public key X or I know the secret y associated with public key Y", without revealing anything about either secret or even which branch of the "or" clause is true. - anon: Anonymous and pseudonymous public-key encryption and signing, where the sender of a signed message or the receiver of an encrypted message is defined as an explicit anonymity set containing several public keys rather than just one. For example, a member of an organization's board of trustees might prove to be a member of the board without revealing which member she is. - shuffle: Verifiable cryptographic shuffles of ElGamal ciphertexts, which can be used to implement (for example) voting or auction schemes that keep the sources of individual votes or bids private without anyone having to trust the shuffler(s) to shuffle votes/bids honestly. For now this library should currently be considered experimental: it will definitely be changing in non-backward-compatible ways, and it will need independent security review before it should be considered ready for use in security-critical applications. However, we intend to bring the library closer to stability and real-world usability as quickly as development resources permit, and as interest and application demand dictates. As should be obvious, this library is intended the use of developers who are at least moderately knowledgeable about crypto. If you want a crypto library that makes it easy to implement "basic crypto" functionality correctly - i.e., plain public-key encryption and signing - then the NaCl/Sodium pursues this worthy goal (http://doc.libsodium.org). This toolkit's purpose is to make it possible - and preferably but not necessarily easy - to do slightly more interesting things that most current crypto libraries don't support effectively. The one existing crypto library that this toolkit is probably most comparable to is the Charm rapid prototyping library for Python (http://charm-crypto.com/). This library incorporates and/or builds on existing code from a variety of sources, as documented in the relevant sub-packages. This example illustrates how to use the crypto toolkit's abstract group API to perform basic Diffie-Hellman key exchange calculations, using the NIST-standard P256 elliptic curve in this case. Any other suitable elliptic curve or other cryptographic group may be used simply by changing the first line that picks the suite. This example illustrates how the crypto toolkit may be used to perform "pure" ElGamal encryption, in which the message to be encrypted is small enough to be embedded directly within a group element (e.g., in an elliptic curve point). For basic background on ElGamal encryption see for example http://en.wikipedia.org/wiki/ElGamal_encryption. Most public-key crypto libraries tend not to support embedding data in points, in part because for "vanilla" public-key encryption you don't need it: one would normally just generate an ephemeral Diffie-Hellman secret and use that to seed a symmetric-key crypto algorithm such as AES, which is much more efficient per bit and works for arbitrary-length messages. However, in many advanced public-key crypto algorithms it is often useful to be able to embedded data directly into points and compute with them: as just one of many examples, the proactively verifiable anonymous messaging scheme prototyped in Verdict (see http://dedis.cs.yale.edu/dissent/papers/verdict-abs). For fancier versions of ElGamal encryption implemented in this toolkit see for example anon.Encrypt, which encrypts a message for one of several possible receivers forming an explicit anonymity set.

Package ff provides a flags-first approach to runtime configuration. The central function is Parse, which populates a flag set from commandline arguments, environment variables, and/or config files. Parse takes either an implementation of the Flags interface, or (for compatibility reasons) a concrete flag.FlagSet. Option values can be used to control parsing behavior. FlagSet is provided as a standard implementation of the Flags interface, inspired by getopts(3). It supports single (-f) and long (--foo) flag names. Command is provided as a tool for building CLI applications, like docker or kubectl, in a simple and declarative style. It's intended to be easier to understand and maintain than common alternatives.

Package ql implements a pure Go embedded SQL database engine. Builder results available at QL is a member of the SQL family of languages. It is less complex and less powerful than SQL (whichever specification SQL is considered to be). 2020-12-10: sql/database driver now supports url parameter removeemptywal=N which has the same semantics as passing RemoveEmptyWAL = N != 0 to OpenFile options. 2020-11-09: Add IF NOT EXISTS support for the INSERT INTO statement. Add IsDuplicateUniqueIndexError function. 2018-11-04: Back end file format V2 is now released. To use the new format for newly created databases set the FileFormat field in *Options passed to OpenFile to value 2 or use the driver named "ql2" instead of "ql". - Both the old and new driver will properly open and use, read and write the old (V1) or new file (V2) format of an existing database. - V1 format has a record size limit of ~64 kB. V2 format record size limit is math.MaxInt32. - V1 format uncommitted transaction size is limited by memory resources. V2 format uncommitted transaction is limited by free disk space. - A direct consequence of the previous is that small transactions perform better using V1 format and big transactions perform better using V2 format. - V2 format uses substantially less memory. 2018-08-02: Release v1.2.0 adds initial support for Go modules. 2017-01-10: Release v1.1.0 fixes some bugs and adds a configurable WAL headroom. 2016-07-29: Release v1.0.6 enables alternatively using = instead of == for equality operation. 2016-07-11: Release v1.0.5 undoes vendoring of lldb. QL now uses stable lldb (modernc.org/lldb). 2016-07-06: Release v1.0.4 fixes a panic when closing the WAL file. 2016-04-03: Release v1.0.3 fixes a data race. 2016-03-23: Release v1.0.2 vendors gitlab.com/cznic/exp/lldb and github.com/camlistore/go4/lock. 2016-03-17: Release v1.0.1 adjusts for latest goyacc. Parser error messages are improved and changed, but their exact form is not considered a API change. 2016-03-05: The current version has been tagged v1.0.0. 2015-06-15: To improve compatibility with other SQL implementations, the count built-in aggregate function now accepts * as its argument. 2015-05-29: The execution planner was rewritten from scratch. It should use indices in all places where they were used before plus in some additional situations. It is possible to investigate the plan using the newly added EXPLAIN statement. The QL tool is handy for such analysis. If the planner would have used an index, but no such exists, the plan includes hints in form of copy/paste ready CREATE INDEX statements. The planner is still quite simple and a lot of work on it is yet ahead. You can help this process by filling an issue with a schema and query which fails to use an index or indices when it should, in your opinion. Bonus points for including output of `ql 'explain <query>'`. 2015-05-09: The grammar of the CREATE INDEX statement now accepts an expression list instead of a single expression, which was further limited to just a column name or the built-in id(). As a side effect, composite indices are now functional. However, the values in the expression-list style index are not yet used by other statements or the statement/query planner. The composite index is useful while having UNIQUE clause to check for semantically duplicate rows before they get added to the table or when such a row is mutated using the UPDATE statement and the expression-list style index tuple of the row is thus recomputed. 2015-05-02: The Schema field of table __Table now correctly reflects any column constraints and/or defaults. Also, the (*DB).Info method now has that information provided in new ColumInfo fields NotNull, Constraint and Default. 2015-04-20: Added support for {LEFT,RIGHT,FULL} [OUTER] JOIN. 2015-04-18: Column definitions can now have constraints and defaults. Details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. 2015-03-06: New built-in functions formatFloat and formatInt. Thanks urandom! (https://github.com/urandom) 2015-02-16: IN predicate now accepts a SELECT statement. See the updated "Predicates" section. 2015-01-17: Logical operators || and && have now alternative spellings: OR and AND (case insensitive). AND was a keyword before, but OR is a new one. This can possibly break existing queries. For the record, it's a good idea to not use any name appearing in, for example, [7] in your queries as the list of QL's keywords may expand for gaining better compatibility with existing SQL "standards". 2015-01-12: ACID guarantees were tightened at the cost of performance in some cases. The write collecting window mechanism, a formerly used implementation detail, was removed. Inserting rows one by one in a transaction is now slow. I mean very slow. Try to avoid inserting single rows in a transaction. Instead, whenever possible, perform batch updates of tens to, say thousands of rows in a single transaction. See also: http://www.sqlite.org/faq.html#q19, the discussed synchronization principles involved are the same as for QL, modulo minor details. Note: A side effect is that closing a DB before exiting an application, both for the Go API and through database/sql driver, is no more required, strictly speaking. Beware that exiting an application while there is an open (uncommitted) transaction in progress means losing the transaction data. However, the DB will not become corrupted because of not closing it. Nor that was the case before, but formerly failing to close a DB could have resulted in losing the data of the last transaction. 2014-09-21: id() now optionally accepts a single argument - a table name. 2014-09-01: Added the DB.Flush() method and the LIKE pattern matching predicate. 2014-08-08: The built in functions max and min now accept also time values. Thanks opennota! (https://github.com/opennota) 2014-06-05: RecordSet interface extended by new methods FirstRow and Rows. 2014-06-02: Indices on id() are now used by SELECT statements. 2014-05-07: Introduction of Marshal, Schema, Unmarshal. 2014-04-15: Added optional IF NOT EXISTS clause to CREATE INDEX and optional IF EXISTS clause to DROP INDEX. 2014-04-12: The column Unique in the virtual table __Index was renamed to IsUnique because the old name is a keyword. Unfortunately, this is a breaking change, sorry. 2014-04-11: Introduction of LIMIT, OFFSET. 2014-04-10: Introduction of query rewriting. 2014-04-07: Introduction of indices. QL imports zappy[8], a block-based compressor, which speeds up its performance by using a C version of the compression/decompression algorithms. If a CGO-free (pure Go) version of QL, or an app using QL, is required, please include 'purego' in the -tags option of go {build,get,install}. For example: If zappy was installed before installing QL, it might be necessary to rebuild zappy first (or rebuild QL with all its dependencies using the -a option): The syntax is specified using Extended Backus-Naur Form (EBNF) Lower-case production names are used to identify lexical tokens. Non-terminals are in CamelCase. Lexical tokens are enclosed in double quotes "" or back quotes “. The form a … b represents the set of characters from a through b as alternatives. The horizontal ellipsis … is also used elsewhere in the spec to informally denote various enumerations or code snippets that are not further specified. QL source code is Unicode text encoded in UTF-8. The text is not canonicalized, so a single accented code point is distinct from the same character constructed from combining an accent and a letter; those are treated as two code points. For simplicity, this document will use the unqualified term character to refer to a Unicode code point in the source text. Each code point is distinct; for instance, upper and lower case letters are different characters. Implementation restriction: For compatibility with other tools, the parser may disallow the NUL character (U+0000) in the statement. Implementation restriction: A byte order mark is disallowed anywhere in QL statements. The following terms are used to denote specific character classes The underscore character _ (U+005F) is considered a letter. Lexical elements are comments, tokens, identifiers, keywords, operators and delimiters, integer, floating-point, imaginary, rune and string literals and QL parameters. Line comments start with the character sequence // or -- and stop at the end of the line. A line comment acts like a space. General comments start with the character sequence /* and continue through the character sequence */. A general comment acts like a space. Comments do not nest. Tokens form the vocabulary of QL. There are four classes: identifiers, keywords, operators and delimiters, and literals. White space, formed from spaces (U+0020), horizontal tabs (U+0009), carriage returns (U+000D), and newlines (U+000A), is ignored except as it separates tokens that would otherwise combine into a single token. The formal grammar uses semicolons ";" as separators of QL statements. A single QL statement or the last QL statement in a list of statements can have an optional semicolon terminator. (Actually a separator from the following empty statement.) Identifiers name entities such as tables or record set columns. There are two kinds of identifiers, normal idententifiers and quoted identifiers. An normal identifier is a sequence of one or more letters and digits. The first character in an identifier must be a letter. For example A quoted identifier is a string of any charaters between guillmets «». Quoted identifiers allow QL key words or phrases with spaces to be used as identifiers. The guillemets were chosen because QL already uses double quotes, single quotes, and backticks for other quoting purposes. «TRANSACTION» «duration» «lovely stories» No identifiers are predeclared, however note that no keyword can be used as a normal identifier. Identifiers starting with two underscores are used for meta data virtual tables names. For forward compatibility, users should generally avoid using any identifiers starting with two underscores. For example The following keywords are reserved and may not be used as identifiers. Keywords are not case sensitive. The following character sequences represent operators, delimiters, and other special tokens Operators consisting of more than one character are referred to by names in the rest of the documentation An integer literal is a sequence of digits representing an integer constant. An optional prefix sets a non-decimal base: 0 for octal, 0x or 0X for hexadecimal. In hexadecimal literals, letters a-f and A-F represent values 10 through 15. For example A floating-point literal is a decimal representation of a floating-point constant. It has an integer part, a decimal point, a fractional part, and an exponent part. The integer and fractional part comprise decimal digits; the exponent part is an e or E followed by an optionally signed decimal exponent. One of the integer part or the fractional part may be elided; one of the decimal point or the exponent may be elided. For example An imaginary literal is a decimal representation of the imaginary part of a complex constant. It consists of a floating-point literal or decimal integer followed by the lower-case letter i. For example A rune literal represents a rune constant, an integer value identifying a Unicode code point. A rune literal is expressed as one or more characters enclosed in single quotes. Within the quotes, any character may appear except single quote and newline. A single quoted character represents the Unicode value of the character itself, while multi-character sequences beginning with a backslash encode values in various formats. The simplest form represents the single character within the quotes; since QL statements are Unicode characters encoded in UTF-8, multiple UTF-8-encoded bytes may represent a single integer value. For instance, the literal 'a' holds a single byte representing a literal a, Unicode U+0061, value 0x61, while 'ä' holds two bytes (0xc3 0xa4) representing a literal a-dieresis, U+00E4, value 0xe4. Several backslash escapes allow arbitrary values to be encoded as ASCII text. There are four ways to represent the integer value as a numeric constant: \x followed by exactly two hexadecimal digits; \u followed by exactly four hexadecimal digits; \U followed by exactly eight hexadecimal digits, and a plain backslash \ followed by exactly three octal digits. In each case the value of the literal is the value represented by the digits in the corresponding base. Although these representations all result in an integer, they have different valid ranges. Octal escapes must represent a value between 0 and 255 inclusive. Hexadecimal escapes satisfy this condition by construction. The escapes \u and \U represent Unicode code points so within them some values are illegal, in particular those above 0x10FFFF and surrogate halves. After a backslash, certain single-character escapes represent special values All other sequences starting with a backslash are illegal inside rune literals. For example A string literal represents a string constant obtained from concatenating a sequence of characters. There are two forms: raw string literals and interpreted string literals. Raw string literals are character sequences between back quotes “. Within the quotes, any character is legal except back quote. The value of a raw string literal is the string composed of the uninterpreted (implicitly UTF-8-encoded) characters between the quotes; in particular, backslashes have no special meaning and the string may contain newlines. Carriage returns inside raw string literals are discarded from the raw string value. Interpreted string literals are character sequences between double quotes "". The text between the quotes, which may not contain newlines, forms the value of the literal, with backslash escapes interpreted as they are in rune literals (except that \' is illegal and \" is legal), with the same restrictions. The three-digit octal (\nnn) and two-digit hexadecimal (\xnn) escapes represent individual bytes of the resulting string; all other escapes represent the (possibly multi-byte) UTF-8 encoding of individual characters. Thus inside a string literal \377 and \xFF represent a single byte of value 0xFF=255, while ÿ, \u00FF, \U000000FF and \xc3\xbf represent the two bytes 0xc3 0xbf of the UTF-8 encoding of character U+00FF. For example These examples all represent the same string If the statement source represents a character as two code points, such as a combining form involving an accent and a letter, the result will be an error if placed in a rune literal (it is not a single code point), and will appear as two code points if placed in a string literal. Literals are assigned their values from the respective text representation at "compile" (parse) time. QL parameters provide the same functionality as literals, but their value is assigned at execution time from an expression list passed to DB.Run or DB.Execute. Using '?' or '$' is completely equivalent. For example Keywords 'false' and 'true' (not case sensitive) represent the two possible constant values of type bool (also not case sensitive). Keyword 'NULL' (not case sensitive) represents an untyped constant which is assignable to any type. NULL is distinct from any other value of any type. A type determines the set of values and operations specific to values of that type. A type is specified by a type name. Named instances of the boolean, numeric, and string types are keywords. The names are not case sensitive. Note: The blob type is exchanged between the back end and the API as []byte. On 32 bit platforms this limits the size which the implementation can handle to 2G. A boolean type represents the set of Boolean truth values denoted by the predeclared constants true and false. The predeclared boolean type is bool. A duration type represents the elapsed time between two instants as an int64 nanosecond count. The representation limits the largest representable duration to approximately 290 years. A numeric type represents sets of integer or floating-point values. The predeclared architecture-independent numeric types are The value of an n-bit integer is n bits wide and represented using two's complement arithmetic. Conversions are required when different numeric types are mixed in an expression or assignment. A string type represents the set of string values. A string value is a (possibly empty) sequence of bytes. The case insensitive keyword for the string type is 'string'. The length of a string (its size in bytes) can be discovered using the built-in function len. A time type represents an instant in time with nanosecond precision. Each time has associated with it a location, consulted when computing the presentation form of the time. The following functions are implicitly declared An expression specifies the computation of a value by applying operators and functions to operands. Operands denote the elementary values in an expression. An operand may be a literal, a (possibly qualified) identifier denoting a constant or a function or a table/record set column, or a parenthesized expression. A qualified identifier is an identifier qualified with a table/record set name prefix. For example Primary expression are the operands for unary and binary expressions. For example A primary expression of the form denotes the element of a string indexed by x. Its type is byte. The value x is called the index. The following rules apply - The index x must be of integer type except bigint or duration; it is in range if 0 <= x < len(s), otherwise it is out of range. - A constant index must be non-negative and representable by a value of type int. - A constant index must be in range if the string a is a literal. - If x is out of range at run time, a run-time error occurs. - s[x] is the byte at index x and the type of s[x] is byte. If s is NULL or x is NULL then the result is NULL. Otherwise s[x] is illegal. For a string, the primary expression constructs a substring. The indices low and high select which elements appear in the result. The result has indices starting at 0 and length equal to high - low. For convenience, any of the indices may be omitted. A missing low index defaults to zero; a missing high index defaults to the length of the sliced operand The indices low and high are in range if 0 <= low <= high <= len(a), otherwise they are out of range. A constant index must be non-negative and representable by a value of type int. If both indices are constant, they must satisfy low <= high. If the indices are out of range at run time, a run-time error occurs. Integer values of type bigint or duration cannot be used as indices. If s is NULL the result is NULL. If low or high is not omitted and is NULL then the result is NULL. Given an identifier f denoting a predeclared function, calls f with arguments a1, a2, … an. Arguments are evaluated before the function is called. The type of the expression is the result type of f. In a function call, the function value and arguments are evaluated in the usual order. After they are evaluated, the parameters of the call are passed by value to the function and the called function begins execution. The return value of the function is passed by value when the function returns. Calling an undefined function causes a compile-time error. Operators combine operands into expressions. Comparisons are discussed elsewhere. For other binary operators, the operand types must be identical unless the operation involves shifts or untyped constants. For operations involving constants only, see the section on constant expressions. Except for shift operations, if one operand is an untyped constant and the other operand is not, the constant is converted to the type of the other operand. The right operand in a shift expression must have unsigned integer type or be an untyped constant that can be converted to unsigned integer type. If the left operand of a non-constant shift expression is an untyped constant, the type of the constant is what it would be if the shift expression were replaced by its left operand alone. Expressions of the form yield a boolean value true if expr2, a regular expression, matches expr1 (see also [6]). Both expression must be of type string. If any one of the expressions is NULL the result is NULL. Predicates are special form expressions having a boolean result type. Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be comparable as defined in "Comparison operators". Another form of the IN predicate creates the expression list from a result of a SelectStmt. The SelectStmt must select only one column. The produced expression list is resource limited by the memory available to the process. NULL values produced by the SelectStmt are ignored, but if all records of the SelectStmt are NULL the predicate yields NULL. The select statement is evaluated only once. If the type of expr is not the same as the type of the field returned by the SelectStmt then the set operation yields false. The type of the column returned by the SelectStmt must be one of the simple (non blob-like) types: Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be ordered as defined in "Comparison operators". Expressions of the form yield a boolean value true if expr does not have a specific type (case A) or if expr has a specific type (case B). In other cases the result is a boolean value false. Unary operators have the highest precedence. There are five precedence levels for binary operators. Multiplication operators bind strongest, followed by addition operators, comparison operators, && (logical AND), and finally || (logical OR) Binary operators of the same precedence associate from left to right. For instance, x / y * z is the same as (x / y) * z. Note that the operator precedence is reflected explicitly by the grammar. Arithmetic operators apply to numeric values and yield a result of the same type as the first operand. The four standard arithmetic operators (+, -, *, /) apply to integer, rational, floating-point, and complex types; + also applies to strings; +,- also applies to times. All other arithmetic operators apply to integers only. sum integers, rationals, floats, complex values, strings difference integers, rationals, floats, complex values, times product integers, rationals, floats, complex values / quotient integers, rationals, floats, complex values % remainder integers & bitwise AND integers | bitwise OR integers ^ bitwise XOR integers &^ bit clear (AND NOT) integers << left shift integer << unsigned integer >> right shift integer >> unsigned integer Strings can be concatenated using the + operator String addition creates a new string by concatenating the operands. A value of type duration can be added to or subtracted from a value of type time. Times can subtracted from each other producing a value of type duration. For two integer values x and y, the integer quotient q = x / y and remainder r = x % y satisfy the following relationships with x / y truncated towards zero ("truncated division"). As an exception to this rule, if the dividend x is the most negative value for the int type of x, the quotient q = x / -1 is equal to x (and r = 0). If the divisor is a constant expression, it must not be zero. If the divisor is zero at run time, a run-time error occurs. If the dividend is non-negative and the divisor is a constant power of 2, the division may be replaced by a right shift, and computing the remainder may be replaced by a bitwise AND operation The shift operators shift the left operand by the shift count specified by the right operand. They implement arithmetic shifts if the left operand is a signed integer and logical shifts if it is an unsigned integer. There is no upper limit on the shift count. Shifts behave as if the left operand is shifted n times by 1 for a shift count of n. As a result, x << 1 is the same as x*2 and x >> 1 is the same as x/2 but truncated towards negative infinity. For integer operands, the unary operators +, -, and ^ are defined as follows For floating-point and complex numbers, +x is the same as x, while -x is the negation of x. The result of a floating-point or complex division by zero is not specified beyond the IEEE-754 standard; whether a run-time error occurs is implementation-specific. Whenever any operand of any arithmetic operation, unary or binary, is NULL, as well as in the case of the string concatenating operation, the result is NULL. For unsigned integer values, the operations +, -, *, and << are computed modulo 2n, where n is the bit width of the unsigned integer's type. Loosely speaking, these unsigned integer operations discard high bits upon overflow, and expressions may rely on “wrap around”. For signed integers with a finite bit width, the operations +, -, *, and << may legally overflow and the resulting value exists and is deterministically defined by the signed integer representation, the operation, and its operands. No exception is raised as a result of overflow. An evaluator may not optimize an expression under the assumption that overflow does not occur. For instance, it may not assume that x < x + 1 is always true. Integers of type bigint and rationals do not overflow but their handling is limited by the memory resources available to the program. Comparison operators compare two operands and yield a boolean value. In any comparison, the first operand must be of same type as is the second operand, or vice versa. The equality operators == and != apply to operands that are comparable. The ordering operators <, <=, >, and >= apply to operands that are ordered. These terms and the result of the comparisons are defined as follows - Boolean values are comparable. Two boolean values are equal if they are either both true or both false. - Complex values are comparable. Two complex values u and v are equal if both real(u) == real(v) and imag(u) == imag(v). - Integer values are comparable and ordered, in the usual way. Note that durations are integers. - Floating point values are comparable and ordered, as defined by the IEEE-754 standard. - Rational values are comparable and ordered, in the usual way. - String and Blob values are comparable and ordered, lexically byte-wise. - Time values are comparable and ordered. Whenever any operand of any comparison operation is NULL, the result is NULL. Note that slices are always of type string. Logical operators apply to boolean values and yield a boolean result. The right operand is evaluated conditionally. The truth tables for logical operations with NULL values Conversions are expressions of the form T(x) where T is a type and x is an expression that can be converted to type T. A constant value x can be converted to type T in any of these cases: - x is representable by a value of type T. - x is a floating-point constant, T is a floating-point type, and x is representable by a value of type T after rounding using IEEE 754 round-to-even rules. The constant T(x) is the rounded value. - x is an integer constant and T is a string type. The same rule as for non-constant x applies in this case. Converting a constant yields a typed constant as result. A non-constant value x can be converted to type T in any of these cases: - x has type T. - x's type and T are both integer or floating point types. - x's type and T are both complex types. - x is an integer, except bigint or duration, and T is a string type. Specific rules apply to (non-constant) conversions between numeric types or to and from a string type. These conversions may change the representation of x and incur a run-time cost. All other conversions only change the type but not the representation of x. A conversion of NULL to any type yields NULL. For the conversion of non-constant numeric values, the following rules apply 1. When converting between integer types, if the value is a signed integer, it is sign extended to implicit infinite precision; otherwise it is zero extended. It is then truncated to fit in the result type's size. For example, if v == uint16(0x10F0), then uint32(int8(v)) == 0xFFFFFFF0. The conversion always yields a valid value; there is no indication of overflow. 2. When converting a floating-point number to an integer, the fraction is discarded (truncation towards zero). 3. When converting an integer or floating-point number to a floating-point type, or a complex number to another complex type, the result value is rounded to the precision specified by the destination type. For instance, the value of a variable x of type float32 may be stored using additional precision beyond that of an IEEE-754 32-bit number, but float32(x) represents the result of rounding x's value to 32-bit precision. Similarly, x + 0.1 may use more than 32 bits of precision, but float32(x + 0.1) does not. In all non-constant conversions involving floating-point or complex values, if the result type cannot represent the value the conversion succeeds but the result value is implementation-dependent. 1. Converting a signed or unsigned integer value to a string type yields a string containing the UTF-8 representation of the integer. Values outside the range of valid Unicode code points are converted to "\uFFFD". 2. Converting a blob to a string type yields a string whose successive bytes are the elements of the blob. 3. Converting a value of a string type to a blob yields a blob whose successive elements are the bytes of the string. 4. Converting a value of a bigint type to a string yields a string containing the decimal decimal representation of the integer. 5. Converting a value of a string type to a bigint yields a bigint value containing the integer represented by the string value. A prefix of “0x” or “0X” selects base 16; the “0” prefix selects base 8, and a “0b” or “0B” prefix selects base 2. Otherwise the value is interpreted in base 10. An error occurs if the string value is not in any valid format. 6. Converting a value of a rational type to a string yields a string containing the decimal decimal representation of the rational in the form "a/b" (even if b == 1). 7. Converting a value of a string type to a bigrat yields a bigrat value containing the rational represented by the string value. The string can be given as a fraction "a/b" or as a floating-point number optionally followed by an exponent. An error occurs if the string value is not in any valid format. 8. Converting a value of a duration type to a string returns a string representing the duration in the form "72h3m0.5s". Leading zero units are omitted. As a special case, durations less than one second format using a smaller unit (milli-, micro-, or nanoseconds) to ensure that the leading digit is non-zero. The zero duration formats as 0, with no unit. 9. Converting a string value to a duration yields a duration represented by the string. A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h". 10. Converting a time value to a string returns the time formatted using the format string When evaluating the operands of an expression or of function calls, operations are evaluated in lexical left-to-right order. For example, in the evaluation of the function calls and evaluation of c happen in the order h(), i(), j(), c. Floating-point operations within a single expression are evaluated according to the associativity of the operators. Explicit parentheses affect the evaluation by overriding the default associativity. In the expression x + (y + z) the addition y + z is performed before adding x. Statements control execution. The empty statement does nothing. Alter table statements modify existing tables. With the ADD clause it adds a new column to the table. The column must not exist. With the DROP clause it removes an existing column from a table. The column must exist and it must be not the only (last) column of the table. IOW, there cannot be a table with no columns. For example When adding a column to a table with existing data, the constraint clause of the ColumnDef cannot be used. Adding a constrained column to an empty table is fine. Begin transactions statements introduce a new transaction level. Every transaction level must be eventually balanced by exactly one of COMMIT or ROLLBACK statements. Note that when a transaction is roll-backed because of a statement failure then no explicit balancing of the respective BEGIN TRANSACTION is statement is required nor permitted. Failure to properly balance any opened transaction level may cause dead locks and/or lose of data updated in the uppermost opened but never properly closed transaction level. For example A database cannot be updated (mutated) outside of a transaction. Statements requiring a transaction A database is effectively read only outside of a transaction. Statements not requiring a transaction The commit statement closes the innermost transaction nesting level. If that's the outermost level then the updates to the DB made by the transaction are atomically made persistent. For example Create index statements create new indices. Index is a named projection of ordered values of a table column to the respective records. As a special case the id() of the record can be indexed. Index name must not be the same as any of the existing tables and it also cannot be the same as of any column name of the table the index is on. For example Now certain SELECT statements may use the indices to speed up joins and/or to speed up record set filtering when the WHERE clause is used; or the indices might be used to improve the performance when the ORDER BY clause is present. The UNIQUE modifier requires the indexed values tuple to be index-wise unique or have all values NULL. The optional IF NOT EXISTS clause makes the statement a no operation if the index already exists. A simple index consists of only one expression which must be either a column name or the built-in id(). A more complex and more general index is one that consists of more than one expression or its single expression does not qualify as a simple index. In this case the type of all expressions in the list must be one of the non blob-like types. Note: Blob-like types are blob, bigint, bigrat, time and duration. Create table statements create new tables. A column definition declares the column name and type. Table names and column names are case sensitive. Neither a table or an index of the same name may exist in the DB. For example The optional IF NOT EXISTS clause makes the statement a no operation if the table already exists. The optional constraint clause has two forms. The first one is found in many SQL dialects. This form prevents the data in column DepartmentName to be NULL. The second form allows an arbitrary boolean expression to be used to validate the column. If the value of the expression is true then the validation succeeded. If the value of the expression is false or NULL then the validation fails. If the value of the expression is not of type bool an error occurs. The optional DEFAULT clause is an expression which, if present, is substituted instead of a NULL value when the colum is assigned a value. Note that the constraint and/or default expressions may refer to other columns by name: When a table row is inserted by the INSERT INTO statement or when a table row is updated by the UPDATE statement, the order of operations is as follows: 1. The new values of the affected columns are set and the values of all the row columns become the named values which can be referred to in default expressions evaluated in step 2. 2. If any row column value is NULL and the DEFAULT clause is present in the column's definition, the default expression is evaluated and its value is set as the respective column value. 3. The values, potentially updated, of row columns become the named values which can be referred to in constraint expressions evaluated during step 4. 4. All row columns which definition has the constraint clause present will have that constraint checked. If any constraint violation is detected, the overall operation fails and no changes to the table are made. Delete from statements remove rows from a table, which must exist. For example If the WHERE clause is not present then all rows are removed and the statement is equivalent to the TRUNCATE TABLE statement. Drop index statements remove indices from the DB. The index must exist. For example The optional IF EXISTS clause makes the statement a no operation if the index does not exist. Drop table statements remove tables from the DB. The table must exist. For example The optional IF EXISTS clause makes the statement a no operation if the table does not exist. Insert into statements insert new rows into tables. New rows come from literal data, if using the VALUES clause, or are a result of select statement. In the later case the select statement is fully evaluated before the insertion of any rows is performed, allowing to insert values calculated from the same table rows are to be inserted into. If the ColumnNameList part is omitted then the number of values inserted in the row must be the same as are columns in the table. If the ColumnNameList part is present then the number of values per row must be same as the same number of column names. All other columns of the record are set to NULL. The type of the value assigned to a column must be the same as is the column's type or the value must be NULL. If there exists an unique index that would make the insert statement fail, the optional IF NOT EXISTS turns the insert statement in such case into a no-op. For example If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. Explain statement produces a recordset consisting of lines of text which describe the execution plan of a statement, if any. For example, the QL tool treats the explain statement specially and outputs the joined lines: The explanation may aid in uderstanding how a statement/query would be executed and if indices are used as expected - or which indices may possibly improve the statement performance. The create index statements above were directly copy/pasted in the terminal from the suggestions provided by the filter recordset pipeline part returned by the explain statement. If the statement has nothing special in its plan, the result is the original statement. To get an explanation of the select statement of the IN predicate, use the EXPLAIN statement with that particular select statement. The rollback statement closes the innermost transaction nesting level discarding any updates to the DB made by it. If that's the outermost level then the effects on the DB are as if the transaction never happened. For example The (temporary) record set from the last statement is returned and can be processed by the client. In this case the rollback is the same as 'DROP TABLE tmp;' but it can be a more complex operation. Select from statements produce recordsets. The optional DISTINCT modifier ensures all rows in the result recordset are unique. Either all of the resulting fields are returned ('*') or only those named in FieldList. RecordSetList is a list of table names or parenthesized select statements, optionally (re)named using the AS clause. The result can be filtered using a WhereClause and orderd by the OrderBy clause. For example If Recordset is a nested, parenthesized SelectStmt then it must be given a name using the AS clause if its field are to be accessible in expressions. A field is an named expression. Identifiers, not used as a type in conversion or a function name in the Call clause, denote names of (other) fields, values of which should be used in the expression. The expression can be named using the AS clause. If the AS clause is not present and the expression consists solely of a field name, then that field name is used as the name of the resulting field. Otherwise the field is unnamed. For example The SELECT statement can optionally enumerate the desired/resulting fields in a list. No two identical field names can appear in the list. When more than one record set is used in the FROM clause record set list, the result record set field names are rewritten to be qualified using the record set names. If a particular record set doesn't have a name, its respective fields became unnamed. The optional JOIN clause, for example is mostly equal to except that the rows from a which, when they appear in the cross join, never made expr to evaluate to true, are combined with a virtual row from b, containing all nulls, and added to the result set. For the RIGHT JOIN variant the discussed rules are used for rows from b not satisfying expr == true and the virtual, all-null row "comes" from a. The FULL JOIN adds the respective rows which would be otherwise provided by the separate executions of the LEFT JOIN and RIGHT JOIN variants. For more thorough OUTER JOIN discussion please see the Wikipedia article at [10]. Resultins rows of a SELECT statement can be optionally ordered by the ORDER BY clause. Collating proceeds by considering the expressions in the expression list left to right until a collating order is determined. Any possibly remaining expressions are not evaluated. All of the expression values must yield an ordered type or NULL. Ordered types are defined in "Comparison operators". Collating of elements having a NULL value is different compared to what the comparison operators yield in expression evaluation (NULL result instead of a boolean value). Below, T denotes a non NULL value of any QL type. NULL collates before any non NULL value (is considered smaller than T). Two NULLs have no collating order (are considered equal). The WHERE clause restricts records considered by some statements, like SELECT FROM, DELETE FROM, or UPDATE. It is an error if the expression evaluates to a non null value of non bool type. Another form of the WHERE clause is an existence predicate of a parenthesized select statement. The EXISTS form evaluates to true if the parenthesized SELECT statement produces a non empty record set. The NOT EXISTS form evaluates to true if the parenthesized SELECT statement produces an empty record set. The parenthesized SELECT statement is evaluated only once (TODO issue #159). The GROUP BY clause is used to project rows having common values into a smaller set of rows. For example Using the GROUP BY without any aggregate functions in the selected fields is in certain cases equal to using the DISTINCT modifier. The last two examples above produce the same resultsets. The optional OFFSET clause allows to ignore first N records. For example The above will produce only rows 11, 12, ... of the record set, if they exist. The value of the expression must a non negative integer, but not bigint or duration. The optional LIMIT clause allows to ignore all but first N records. For example The above will return at most the first 10 records of the record set. The value of the expression must a non negative integer, but not bigint or duration. The LIMIT and OFFSET clauses can be combined. For example Considering table t has, say 10 records, the above will produce only records 4 - 8. After returning record #8, no more result rows/records are computed. 1. The FROM clause is evaluated, producing a Cartesian product of its source record sets (tables or nested SELECT statements). 2. If present, the JOIN cluase is evaluated on the result set of the previous evaluation and the recordset specified by the JOIN clause. (... JOIN Recordset ON ...) 3. If present, the WHERE clause is evaluated on the result set of the previous evaluation. 4. If present, the GROUP BY clause is evaluated on the result set of the previous evaluation(s). 5. The SELECT field expressions are evaluated on the result set of the previous evaluation(s). 6. If present, the DISTINCT modifier is evaluated on the result set of the previous evaluation(s). 7. If present, the ORDER BY clause is evaluated on the result set of the previous evaluation(s). 8. If present, the OFFSET clause is evaluated on the result set of the previous evaluation(s). The offset expression is evaluated once for the first record produced by the previous evaluations. 9. If present, the LIMIT clause is evaluated on the result set of the previous evaluation(s). The limit expression is evaluated once for the first record produced by the previous evaluations. Truncate table statements remove all records from a table. The table must exist. For example Update statements change values of fields in rows of a table. For example Note: The SET clause is optional. If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. To allow to query for DB meta data, there exist specially named tables, some of them being virtual. Note: Virtual system tables may have fake table-wise unique but meaningless and unstable record IDs. Do not apply the built-in id() to any system table. The table __Table lists all tables in the DB. The schema is The Schema column returns the statement to (re)create table Name. This table is virtual. The table __Colum lists all columns of all tables in the DB. The schema is The Ordinal column defines the 1-based index of the column in the record. This table is virtual. The table __Colum2 lists all columns of all tables in the DB which have the constraint NOT NULL or which have a constraint expression defined or which have a default expression defined. The schema is It's possible to obtain a consolidated recordset for all properties of all DB columns using The Name column is the column name in TableName. The table __Index lists all indices in the DB. The schema is The IsUnique columns reflects if the index was created using the optional UNIQUE clause. This table is virtual. Built-in functions are predeclared. The built-in aggregate function avg returns the average of values of an expression. Avg ignores NULL values, but returns NULL if all values of a column are NULL or if avg is applied to an empty record set. The column values must be of a numeric type. The built-in function coalesce takes at least one argument and returns the first of its arguments which is not NULL. If all arguments are NULL, this function returns NULL. This is useful for providing defaults for NULL values in a select query. The built-in function contains returns true if substr is within s. If any argument to contains is NULL the result is NULL. The built-in aggregate function count returns how many times an expression has a non NULL values or the number of rows in a record set. Note: count() returns 0 for an empty record set. For example Date returns the time corresponding to in the appropriate zone for that time in the given location. The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1. A daylight savings time transition skips or repeats times. For example, in the United States, March 13, 2011 2:15am never occurred, while November 6, 2011 1:15am occurred twice. In such cases, the choice of time zone, and therefore the time, is not well-defined. Date returns a time that is correct in one of the two zones involved in the transition, but it does not guarantee which. A location maps time instants to the zone in use at that time. Typically, the location represents the collection of time offsets in use in a geographical area, such as "CEST" and "CET" for central Europe. "local" represents the system's local time zone. "UTC" represents Universal Coordinated Time (UTC). The month specifies a month of the year (January = 1, ...). If any argument to date is NULL the result is NULL. The built-in function day returns the day of the month specified by t. If the argument to day is NULL the result is NULL. The built-in function formatTime returns a textual representation of the time value formatted according to layout, which defines the format by showing how the reference time, would be displayed if it were the value; it serves as an example of the desired output. The same display rules will then be applied to the time value. If any argument to formatTime is NULL the result is NULL. NOTE: The string value of the time zone, like "CET" or "ACDT", is dependent on the time zone of the machine the function is run on. For example, if the t value is in "CET", but the machine is in "ACDT", instead of "CET" the result is "+0100". This is the same what Go (time.Time).String() returns and in fact formatTime directly calls t.String(). returns on a machine in the CET time zone, but may return on a machine in the ACDT zone. The time value is in both cases the same so its ordering and comparing is correct. Only the display value can differ. The built-in functions formatFloat and formatInt format numbers to strings using go's number format functions in the `strconv` package. For all three functions, only the first argument is mandatory. The default values of the rest are shown in the examples. If the first argument is NULL, the result is NULL. returns returns returns Unlike the `strconv` equivalent, the formatInt function handles all integer types, both signed and unsigned. The built-in function hasPrefix tests whether the string s begins with prefix. If any argument to hasPrefix is NULL the result is NULL. The built-in function hasSuffix tests whether the string s ends with suffix. If any argument to hasSuffix is NULL the result is NULL. The built-in function hour returns the hour within the day specified by t, in the range [0, 23]. If the argument to hour is NULL the result is NULL. The built-in function hours returns the duration as a floating point number of hours. If the argument to hours is NULL the result is NULL. The built-in function id takes zero or one arguments. If no argument is provided, id() returns a table-unique automatically assigned numeric identifier of type int. Ids of deleted records are not reused unless the DB becomes completely empty (has no tables). For example If id() without arguments is called for a row which is not a table record then the result value is NULL. For example If id() has one argument it must be a table name of a table in a cross join. For example The built-in function len takes a string argument and returns the lentgh of the string in bytes. The expression len(s) is constant if s is a string constant. If the argument to len is NULL the result is NULL. The built-in aggregate function max returns the largest value of an expression in a record set. Max ignores NULL values, but returns NULL if all values of a column are NULL or if max is applied to an empty record set. The expression values must be of an ordered type. For example The built-in aggregate function min returns the smallest value of an expression in a record set. Min ignores NULL values, but returns NULL if all values of a column are NULL or if min is applied to an empty record set. For example The column values must be of an ordered type. The built-in function minute returns the minute offset within the hour specified by t, in the range [0, 59]. If the argument to minute is NULL the result is NULL. The built-in function minutes returns the duration as a floating point number of minutes. If the argument to minutes is NULL the result is NULL. The built-in function month returns the month of the year specified by t (January = 1, ...). If the argument to month is NULL the result is NULL. The built-in function nanosecond returns the nanosecond offset within the second specified by t, in the range [0, 999999999]. If the argument to nanosecond is NULL the result is NULL. The built-in function nanoseconds returns the duration as an integer nanosecond count. If the argument to nanoseconds is NULL the result is NULL. The built-in function now returns the current local time. The built-in function parseTime parses a formatted string and returns the time value it represents. The layout defines the format by showing how the reference time, would be interpreted if it were the value; it serves as an example of the input format. The same interpretation will then be made to the input string. Elements omitted from the value are assumed to be zero or, when zero is impossible, one, so parsing "3:04pm" returns the time corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is 0, this time is before the zero Time). Years must be in the range 0000..9999. The day of the week is checked for syntax but it is otherwise ignored. In the absence of a time zone indicator, parseTime returns a time in UTC. When parsing a time with a zone offset like -0700, if the offset corresponds to a time zone used by the current location, then parseTime uses that location and zone in the returned time. Otherwise it records the time as being in a fabricated location with time fixed at the given zone offset. When parsing a time with a zone abbreviation like MST, if the zone abbreviation has a defined offset in the current location, then that offset is used. The zone abbreviation "UTC" is recognized as UTC regardless of location. If the zone abbreviation is unknown, Parse records the time as being in a fabricated location with the given zone abbreviation and a zero offset. This choice means that such a time can be parses and reformatted with the same layout losslessly, but the exact instant used in the representation will differ by the actual zone offset. To avoid such problems, prefer time layouts that use a numeric zone offset. If any argument to parseTime is NULL the result is NULL. The built-in function second returns the second offset within the minute specified by t, in the range [0, 59]. If the argument to second is NULL the result is NULL. The built-in function seconds returns the duration as a floating point number of seconds. If the argument to seconds is NULL the result is NULL. The built-in function since returns the time elapsed since t. It is shorthand for now()-t. If the argument to since is NULL the result is NULL. The built-in aggregate function sum returns the sum of values of an expression for all rows of a record set. Sum ignores NULL values, but returns NULL if all values of a column are NULL or if sum is applied to an empty record set. The column values must be of a numeric type. The built-in function timeIn returns t with the location information set to loc. For discussion of the loc argument please see date(). If any argument to timeIn is NULL the result is NULL. The built-in function weekday returns the day of the week specified by t. Sunday == 0, Monday == 1, ... If the argument to weekday is NULL the result is NULL. The built-in function year returns the year in which t occurs. If the argument to year is NULL the result is NULL. The built-in function yearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, and [1,366] in leap years. If the argument to yearDay is NULL the result is NULL. Three functions assemble and disassemble complex numbers. The built-in function complex constructs a complex value from a floating-point real and imaginary part, while real and imag extract the real and imaginary parts of a complex value. The type of the arguments and return value correspond. For complex, the two arguments must be of the same floating-point type and the return type is the complex type with the corresponding floating-point constituents: complex64 for float32, complex128 for float64. The real and imag functions together form the inverse, so for a complex value z, z == complex(real(z), imag(z)). If the operands of these functions are all constants, the return value is a constant. If any argument to any of complex, real, imag functions is NULL the result is NULL. For the numeric types, the following sizes are guaranteed Portions of this specification page are modifications based on work[2] created and shared by Google[3] and used according to terms described in the Creative Commons 3.0 Attribution License[4]. This specification is licensed under the Creative Commons Attribution 3.0 License, and code is licensed under a BSD license[5]. Links from the above documentation This section is not part of the specification. WARNING: The implementation of indices is new and it surely needs more time to become mature. Indices are used currently used only by the WHERE clause. The following expression patterns of 'WHERE expression' are recognized and trigger index use. The relOp is one of the relation operators <, <=, ==, >=, >. For the equality operator both operands must be of comparable types. For all other operators both operands must be of ordered types. The constant expression is a compile time constant expression. Some constant folding is still a TODO. Parameter is a QL parameter ($1 etc.). Consider tables t and u, both with an indexed field f. The WHERE expression doesn't comply with the above simple detected cases. However, such query is now automatically rewritten to which will use both of the indices. The impact of using the indices can be substantial (cf. BenchmarkCrossJoin*) if the resulting rows have low "selectivity", ie. only few rows from both tables are selected by the respective WHERE filtering. Note: Existing QL DBs can be used and indices can be added to them. However, once any indices are present in the DB, the old QL versions cannot work with such DB anymore. Running a benchmark with -v (-test.v) outputs information about the scale used to report records/s and a brief description of the benchmark. For example Running the full suite of benchmarks takes a lot of time. Use the -timeout flag to avoid them being killed after the default time limit (10 minutes).

Package kyber provides a toolbox of advanced cryptographic primitives, for applications that need more than straightforward signing and encryption. This top level package defines the interfaces to cryptographic primitives designed to be independent of specific cryptographic algorithms, to facilitate upgrading applications to new cryptographic algorithms or switching to alternative algorithms for experimentation purposes. This toolkits public-key crypto API includes a kyber.Group interface supporting a broad class of group-based public-key primitives including DSA-style integer residue groups and elliptic curve groups. Users of this API can write higher-level crypto algorithms such as zero-knowledge proofs without knowing or caring exactly what kind of group, let alone which precise security parameters or elliptic curves, are being used. The kyber.Group interface supports the standard algebraic operations on group elements and scalars that nontrivial public-key algorithms tend to rely on. The interface uses additive group terminology typical for elliptic curves, such that point addition is homomorphically equivalent to adding their (potentially secret) scalar multipliers. But the API and its operations apply equally well to DSA-style integer groups. As a trivial example, generating a public/private keypair is as simple as: The first statement picks a private key (Scalar) from a the suites's source of cryptographic random or pseudo-random bits, while the second performs elliptic curve scalar multiplication of the curve's standard base point (indicated by the 'nil' argument to Mul) by the scalar private key 'a'. Similarly, computing a Diffie-Hellman shared secret using Alice's private key 'a' and Bob's public key 'B' can be done via: Note that we use 'Mul' rather than 'Exp' here because the library uses the additive-group terminology common for elliptic curve crypto, rather than the multiplicative-group terminology of traditional integer groups - but the two are semantically equivalent and the interface itself works for both elliptic curve and integer groups. Various sub-packages provide several specific implementations of these cryptographic interfaces. In particular, the 'group/mod' sub-package provides implementations of modular integer groups underlying conventional DSA-style algorithms. The `group/nist` package provides NIST-standardized elliptic curves built on the Go crypto library. The 'group/edwards25519' sub-package provides the kyber.Group interface using the popular Ed25519 curve. Other sub-packages build more interesting high-level cryptographic tools atop these primitive interfaces, including: - share: Polynomial commitment and verifiable Shamir secret splitting for implementing verifiable 't-of-n' threshold cryptographic schemes. This can be used to encrypt a message so that any 2 out of 3 receivers must work together to decrypt it, for example. - proof: An implementation of the general Camenisch/Stadler framework for discrete logarithm knowledge proofs. This system supports both interactive and non-interactive proofs of a wide variety of statements such as, "I know the secret x associated with public key X or I know the secret y associated with public key Y", without revealing anything about either secret or even which branch of the "or" clause is true. - sign: The sign directory contains different signature schemes. - sign/anon provides anonymous and pseudonymous public-key encryption and signing, where the sender of a signed message or the receiver of an encrypted message is defined as an explicit anonymity set containing several public keys rather than just one. For example, a member of an organization's board of trustees might prove to be a member of the board without revealing which member she is. - sign/cosi provides collective signature algorithm, where a bunch of signers create a unique, compact and efficiently verifiable signature using the Schnorr signature as a basis. - sign/eddsa provides a kyber-native implementation of the EdDSA signature scheme. - sign/schnorr provides a basic vanilla Schnorr signature scheme implementation. - shuffle: Verifiable cryptographic shuffles of ElGamal ciphertexts, which can be used to implement (for example) voting or auction schemes that keep the sources of individual votes or bids private without anyone having to trust more than one of the shuffler(s) to shuffle votes/bids honestly. As should be obvious, this library is intended to be used by developers who are at least moderately knowledgeable about cryptography. If you want a crypto library that makes it easy to implement "basic crypto" functionality correctly - i.e., plain public-key encryption and signing - then [NaCl secretbox](https://godoc.org/golang.org/x/crypto/nacl/secretbox) may be a better choice. This toolkit's purpose is to make it possible - and preferably easy - to do slightly more interesting things that most current crypto libraries don't support effectively. The one existing crypto library that this toolkit is probably most comparable to is the Charm rapid prototyping library for Python (https://charm-crypto.com/category/charm). This library incorporates and/or builds on existing code from a variety of sources, as documented in the relevant sub-packages. This library is offered as-is, and without a guarantee. It will need an independent security review before it should be considered ready for use in security-critical applications. If you integrate Kyber into your application it is YOUR RESPONSIBILITY to arrange for that audit. If you notice a possible security problem, please report it to dedis-security@epfl.ch.

Package godb is query builder and struct mapper. godb does not manage relationships like Active Record or Entity Framework, it's not a full-featured ORM. Its goal is to be more productive than manually doing mapping between Go structs and databases tables. godb needs adapters to use databases, some are packaged with godb for : Start with an adapter, and the Open method which returns a godb.DB pointer : There are three ways to executes SQL with godb : Using raw queries you can execute any SQL queries and get the results into a slice of structs (or single struct) using the automatic mapping. Structs tools looks more 'orm-ish' as they're take instances of objects or slices to run select, insert, update and delete. Statements tools stand between raw queries and structs tools. It's easier to use than raw queries, but are limited to simpler cases. The statements tools are based on types : Example : The SelectStatement type could also build a query using columns from a structs. It facilitates the build of queries returning values from multiple table (or views). See struct mapping explanations, in particular the `rel` part. Example : The structs tools are based on types : Examples : Raw queries are executed using the RawSQL type. The query could be a simple hand-written string, or something complex builded using SQLBuffer and Conditions. Example : Stucts contents are mapped to databases columns with tags, like in previous example with the Book struct. The tag is 'db' and its content is : For autoincrement identifier simple use both 'key' and 'auto'. Example : More than one field could have the 'key' keyword, but with most databases drivers none of them could have the 'auto' keyword, because executing an insert query only returns one value : the last inserted id : https://golang.org/pkg/database/sql/driver/#RowsAffected.LastInsertId . With PostgreSQL you cas have multiple fields with 'key' and 'auto' options. Structs could be nested. A nested struct is mapped only if has the 'db' tag. The tag value is a columns prefix applied to all fields columns of the struct. The prefix is not mandatory, a blank string is allowed (no prefix). A nested struct could also have an optionnal `rel` attribute of the form `rel=relationname`. It's useful to build a select query using multiples relations (table, view, ...). See the example using the BooksWithInventories type. Example Databases columns are : The mapping is managed by the 'dbreflect' subpackage. Normally its direct use is not necessary, except in one case : some structs are scannable and have to be considered like fields, and mapped to databases columns. Common case are time.Time, or sql.NullString, ... You can register a custom struct with the `RegisterScannableStruct` and a struct instance, for example the time.Time is registered like this : The structs statements use the struct name as table name. But you can override this simply by simplementing a TableName method : Statements and structs tools manage 'where' and 'group by' sql clauses. These conditional clauses are build either with raw sql code, or build with the Condition struct like this : WhereQ methods take a Condition instance build by godb.Q . Where mathods take raw SQL, but is just a syntactic sugar. These calls are equivalents : Multiple calls to Where or WhereQ are allowed, these calls are equivalents : Slices are managed in a particular way : a single placeholder is replaced with multiple ones. This allows code like : The SQLBuffer exists to ease the build of complex raw queries. It's also used internaly by godb. Its use and purpose are simple : concatenate sql parts (accompagned by their arguments) in an efficient way. Example : For all databases, structs updates and deletes manage optimistic locking when a dedicated integer row is present. Simply tags it with `oplock` : When an update or delete operation fails, Do() returns the `ErrOpLock` error. With PostgreSQL and SQL Server, godb manages optimistic locking with automatic fields. Just add a dedicated field in the struct and tag it with `auto,oplock`. With PostgreSQL you can use the `xmin` system column like this : For more informations about `xmin` see https://www.postgresql.org/docs/10/static/ddl-system-columns.html With SQL Server you can use a `rowversion` field with the `mssql.Rowversion` type like this : For more informations about the `rowversion` data type see https://docs.microsoft.com/en-us/sql/t-sql/data-types/rowversion-transact-sql godb keep track of time consumed while executing queries. You can reset it and get the time consumed since Open or the previous reset : You can log all executed queried and details of condumed time. Simply add a logger : godb takes advantage of PostgreSQL RETURNING clause, and SQL Server OUTPUT clause. With statements tools you have to add a RETURNING clause with the Suffix method and call DoWithReturning method instead of Do(). It's optionnal. With StructInsert it's transparent, the RETURNING or OUTPUT clause is added for all 'auto' columns and it's managed for you. One of the big advantage is with BulkInsert : for others databases the rows are inserted but the new keys are unkonwns. With PostgreSQL and SQL Server the slice is updated for all inserted rows. It also enables optimistic locking with *automatic* columns. godb has two prepared statements caches, one to use during transactions, and one to use outside of a transaction. Both use a LRU algorithm. The transaction cache is enabled by default, but not the other. A transaction (sql.Tx) isn't shared between goroutines, using prepared statement with it has a predictable behavious. But without transaction a prepared statement could have to be reprepared on a different connection if needed, leading to unpredictable performances in high concurrency scenario. Enabling the non transaction cache could improve performances with single goroutine batch. With multiple goroutines accessing the same database : it depends ! A benchmark would be wise. Using statements tools and structs tools you can execute select queries and get an iterator instead of filling a slice of struct instances. This could be useful if the request's result is big and you don't want to allocate too much memory. On the other side you will write almost as much code as with the `sql` package, but with an automatic struct mapping, and a request builder. Iterators are also available with raw queries. In this cas you cas executes any kind of sql code, not just select queries. To get an interator simply use the `DoWithIterator` method instead of `Do`. The iterator usage is similar to the standard `sql.Rows` type. Don't forget to check that there are no errors with the `Err` method, and don't forget to call `Close` when the iterator is no longer useful, especially if you don't scan all the resultset. To avoid performance cost godb.DB does not implement synchronization. So a given instance of godb.DB should not be used by multiple goroutines. But a godb.DB instance can be created and used as a blueprint and cloned for each goroutine. See Clone and Clear methods. A typical use case is a web server. When the application starts a godb.DB is created, and cloned in each http handler with Clone, and ressources are to be freed calling Clear (use defer statement).

bindata converts any file into managable Go source code. Useful for embedding binary data into a go program. The file data is optionally gzip compressed before being converted to a raw byte slice. The following paragraphs cover some of the customization options which can be specified in the Config struct, which must be passed into the Translate() call. When used with the `Debug` option, the generated code does not actually include the asset data. Instead, it generates function stubs which load the data from the original file on disk. The asset API remains identical between debug and release builds, so your code will not have to change. This is useful during development when you expect the assets to change often. The host application using these assets uses the same API in both cases and will not have to care where the actual data comes from. An example is a Go webserver with some embedded, static web content like HTML, JS and CSS files. While developing it, you do not want to rebuild the whole server and restart it every time you make a change to a bit of javascript. You just want to build and launch the server once. Then just press refresh in the browser to see those changes. Embedding the assets with the `debug` flag allows you to do just that. When you are finished developing and ready for deployment, just re-invoke `go-bindata` without the `-debug` flag. It will now embed the latest version of the assets. The `NoMemCopy` option will alter the way the output file is generated. It will employ a hack that allows us to read the file data directly from the compiled program's `.rodata` section. This ensures that when we call call our generated function, we omit unnecessary memcopies. The downside of this, is that it requires dependencies on the `reflect` and `unsafe` packages. These may be restricted on platforms like AppEngine and thus prevent you from using this mode. Another disadvantage is that the byte slice we create, is strictly read-only. For most use-cases this is not a problem, but if you ever try to alter the returned byte slice, a runtime panic is thrown. Use this mode only on target platforms where memory constraints are an issue. The default behaviour is to use the old code generation method. This prevents the two previously mentioned issues, but will employ at least one extra memcopy and thus increase memory requirements. For instance, consider the following two examples: This would be the default mode, using an extra memcopy but gives a safe implementation without dependencies on `reflect` and `unsafe`: Here is the same functionality, but uses the `.rodata` hack. The byte slice returned from this example can not be written to without generating a runtime error. The NoCompress option indicates that the supplied assets are *not* GZIP compressed before being turned into Go code. The data should still be accessed through a function call, so nothing changes in the API. This feature is useful if you do not care for compression, or the supplied resource is already compressed. Doing it again would not add any value and may even increase the size of the data. The default behaviour of the program is to use compression. The keys used in the `_bindata` map are the same as the input file name passed to `go-bindata`. This includes the path. In most cases, this is not desireable, as it puts potentially sensitive information in your code base. For this purpose, the tool supplies another command line flag `-prefix`. This accepts a portion of a path name, which should be stripped off from the map keys and function names. For example, running without the `-prefix` flag, we get: Running with the `-prefix` flag, we get: With the optional Tags field, you can specify any go build tags that must be fulfilled for the output file to be included in a build. This is useful when including binary data in multiple formats, where the desired format is specified at build time with the appropriate tags. The tags are appended to a `// +build` line in the beginning of the output file and must follow the build tags syntax specified by the go tool.

Package egoscale is a mapping for the Exoscale API (https://community.exoscale.com/api/compute/). To build a request, construct the adequate struct. This library expects a pointer for efficiency reasons only. The response is a struct corresponding to the data at stake. E.g. DeployVirtualMachine gives a VirtualMachine, as a pointer as well to avoid big copies. Then everything within the struct is not a pointer. Find below some examples of how egoscale may be used. If anything feels odd or unclear, please let us know: https://github.com/exoscale/egoscale/issues This example deploys a virtual machine while controlling the job status as it goes. It enables a finer control over errors, e.g. HTTP timeout, and eventually a way to kill it of (from the client side). As this library is mostly an HTTP client, you can reuse all the existing tools around it. Nota bene: when running the tests or the egoscale library via another tool, e.g. the exo cli, the environment variable EXOSCALE_TRACE=prefix does the above configuration for you. As a developer using egoscale as a library, you'll find it more convenient to plug your favorite io.Writer as it's a Logger. All the available APIs on the server and provided by the API Discovery plugin. Security Groups provide a way to isolate traffic to VMs. Rules are added via the two Authorization commands. Security Group also implement the generic List, Get and Delete interfaces (Listable and Deletable). See: https://community.exoscale.com/documentation/compute/security-groups/ A Zone corresponds to a Data Center. You may list them. Zone implements the Listable interface, which let you perform a list in two different ways. The first exposes the underlying request while the second one hide them and you only manipulate the structs of your interest. An Elastic IP is a way to attach an IP address to many Virtual Machines. The API side of the story configures the external environment, like the routing. Some work is required within the machine to properly configure the interfaces. See: https://community.exoscale.com/documentation/compute/eip/

Package gimlet is a toolkit for building JSON/HTTP interfaces (e.g. REST). Gimlet builds on standard library and common tools for building web applciations (e.g. Negroni and gorilla,) and is only concerned with JSON/HTTP interfaces, and omits support for aspects of HTTP applications outside of the scope of JSON APIs (e.g. templating, sessions.) Gimilet attempts to provide minimal convinences on top of great infrastucture so that your application can omit boilerplate and you don't have to build potentially redundant infrastructure.

Package fees provides decred-specific methods for tracking and estimating fee rates for new transactions to be mined into the network. Fee rate estimation has two main goals: Although it was primarily written for dcrd, this package has intentionally been designed so it can be used as a standalone package for any projects needing the functionality provided. There are two main regimes against which fee estimation needs to be evaluated according to how full blocks being mined are (and consequently how important fee rates are): _low contention_ and _high contention_: In a low contention regime, the mempool sits mostly empty, transactions are usually mined very soon after being published and transaction fees are mostly sent using the minimum relay fee. In a high contention regime, the mempool is usually filled with unmined transactions, there is active dispute for space in a block (by transactions using higher fees) and blocks are usually full. The exact point of where these two regimes intersect is arbitrary, but it should be clear in the examples and simulations which of these is being discussed. Note: a very high contention scenario (> 90% of blocks being full and transactions remaining in the mempool indefinitely) is one in which stakeholders should be discussing alternative solutions (increase block size, provide other second layer alternatives, etc). Also, the current fill rate of blocks in decred is low, so while we try to account for this regime, I personally expect that the implementation will need more tweaks as it approaches this. The current approach to implement this estimation is based on bitcoin core's algorithm. References [1] and [2] provide a high level description of how it works there. Actual code is linked in references [3] and [4]. The algorithm is currently based in fee estimation as used in v0.14 of bitcoin core (which is also the basis for the v0.15+ method). A more comprehensive overview is available in reference [1]. This particular version was chosen because it's simpler to implement and should be sufficient for low contention regimes. It probably overestimates fees in higher contention regimes and longer target confirmation windows, but as pointed out earlier should be sufficient for current fill rate of decred's network. The basic algorithm is as follows (as executed by a single full node): Stats building stage: Estimation stage: Development of the estimator was originally performed and simulated using the code in [5]. Simulation of the current code can be performed by using the dcrfeesim tool available in [6]. Thanks to @davecgh for providing the initial review of the results and the original developers of the bitcoin core code (the brunt of which seems to have been made by @morcos). ## References [1] Introduction to Bitcoin Core Estimation: https://bitcointechtalk.com/an-introduction-to-bitcoin-core-fee-estimation-27920880ad0 [2] Proposed Changes to Fee Estimation in version 0.15: https://gist.github.com/morcos/d3637f015bc4e607e1fd10d8351e9f41 [3] Source for fee estimation in v0.14: https://github.com/bitcoin/bitcoin/blob/v0.14.2/src/policy/fees.cpp [4] Source for fee estimation in version 0.16.2: https://github.com/bitcoin/bitcoin/blob/v0.16.2/src/policy/fees.cpp [5] Source for the original dcrfeesim and estimator work: https://github.com/matheusd/dcrfeesim_dev [6] Source for the current dcrfeesim, using this module: https://github.com/matheusd/dcrfeesim

Package merkletree provides tools for calculating the Merkle root of a dataset, for creating a proof that a piece of data is in a Merkle tree of a given root, and for verifying proofs that a piece of data is in a Merkle tree of a given root. The tree is implemented according to the specification for Merkle trees provided in RFC 6962. Package merkletree also supports building roots and proofs from cached subroots of the Merkle tree. For example, a large file could be cached by building the Merkle root for each 4MB sector and remembering the Merkle roots of each sector. Using a cached tree, the Merkle root of the whole file can be computed by passing the cached tree each of the roots of the 4MB sector. Building proofs using these cached roots is also supported. A proof must be built within the target sector using a normal Tree, requiring the whole sector to be hashed. The results of that proof can then be passed into the Prove() function of a cached tree, which will create the full proof without needing to hash the entire file. Caching also makes it inexpensive to update the Merkle root of the file after changing or deleting segments of the larger file. Examples can be found in the README for the package.

Fresh is a command line tool that builds and (re)starts your web application everytime you save a go or template file. If the web framework you are using supports the Fresh runner, it will show build errors on your browser. It currently works with Traffic (https://github.com/pilu/traffic), Martini (https://github.com/codegangsta/martini) and gocraft/web (https://github.com/gocraft/web). Fresh will watch for file events, and every time you create/modifiy/delete a file it will build and restart the application. If `go build` returns an error, it will logs it in the tmp folder. Traffic (https://github.com/pilu/traffic) already has a middleware that shows the content of that file if it is present. This middleware is automatically added if you run a Traffic web app in dev mode with Fresh.

Package merkletree provides tools for calculating the Merkle root of a dataset, for creating a proof that a piece of data is in a Merkle tree of a given root, and for verifying proofs that a piece of data is in a Merkle tree of a given root. The tree is implemented according to the specification for Merkle trees provided in RFC 6962. Package merkletree also supports building roots and proofs from cached subroots of the Merkle tree. For example, a large file could be cached by building the Merkle root for each 4MB sector and remembering the Merkle roots of each sector. Using a cached tree, the Merkle root of the whole file can be computed by passing the cached tree each of the roots of the 4MB sector. Building proofs using these cached roots is also supported. A proof must be built within the target sector using a normal Tree, requiring the whole sector to be hashed. The results of that proof can then be passed into the Prove() function of a cached tree, which will create the full proof without needing to hash the entire file. Caching also makes it inexpensive to update the Merkle root of the file after changing or deleting segments of the larger file. Examples can be found in the README for the package.

Package configo is designed to handle configuration more easier. Writing and parsing configuration is very easy with configo, there is not any pain to add more keys in conf because configo can generate the configuration file based on your struct definition. Define struct with tags `cfg` Marshal to configuration Unmarshal from file Dump to file The dumpped content is configuration friendly like this Load from file Update an exist file This is really useful when you add new member of struct and want to preserve the content of your configuration file. Configo comes along with a command tool to help to generate and update configuration file for you. Build a generator with configo-build or use relative package path if you are under configo directory Run the built program(name with format "<package>.<struct>.cfg") Update example.toml when you have updated struct conf.Configo

gvt, a simple go vendoring tool based on gb-vendor. Usage: The commands are: Use "gvt help [command]" for more information about a command. Usage: fetch vendors an upstream import path. Recursive dependencies are fetched (at their master/tip/HEAD revision), unless they or their parent package are already present. If a subpackage of a dependency being fetched is already present, it will be deleted. The import path may include a url scheme. This may be useful when fetching dependencies from private repositories that cannot be probed. Flags: Usage: restore fetches the dependencies listed in the manifest. It's meant for workflows that don't include checking in to VCS the vendored source, for example if .gitignore includes lines like Note that such a setup requires "gvt restore" to build the source, relies on the availability of the dependencies repositories and breaks "go get". Flags: Usage: update replaces the source with the latest available from the head of the fetched branch. Updating from one copy of a dependency to another is ONLY possible when the dependency was fetched by branch, without using -tag or -revision. It will be updated to the HEAD of that branch, switching branches is not supported. To update across branches, or from one tag/revision to another, you must first use delete to remove the dependency, then fetch [ -tag | -revision | -branch ] to replace it. Flags: Usage: list formats the contents of the manifest file. Flags: Usage: delete removes a dependency from the vendor directory and the manifest Flags:

Command gcli generates a skeleon (codes and its directory structure) you need to start building CLI tool by Golang. https://github.com/tcnksm/gcli Usage: Available commands: Use "gcli <command> -help" for more information about command. Apply design template file for generating cli project. You can generate design template file via 'gcli design' command. If framework name is not specified gcli use codegangsta/cli. You can set framework name via '-F' option. To check cli framework you can use, run 'gcli list'. Usage: Options: Generate project design template (as toml file). You can pass that file to 'gcli apply' command and generate CLI tool based on template file. You can define what command and what flag you need on that file. Usage: Options: Show all avairable cli frameworks. Usage: Generate new cli skeleton project. At least, you must provide executable name. You can select cli package and set commands via command line option. See more about that on Options section. By default, gcli use codegangsta/cli. To check cli framework you can use, run 'gcli list'. Usage: Options: Examples: To create todo command application skeleton which has 'add' and 'delete' command, Validate design template file which has required filed. If not it returns error and non zero value. Usage:

fperf allows you to build your performace tools easily 1. Create the "NewClient" function 2. Implement the UnaryClient or StreamClient 3. Register to fperf http is a simple builtin testcase to benchmark http servers

Package goaction enables writing Github Actions in Go. The idea is: write a standard Go script, one that works with `go run`, and use it as Github action. The script's inputs - flags and environment variables, are set though the Github action API. This project will generate all the required files for the script (This generation can be done automattically with Github action integration). The library also exposes neat API to get workflow information. - [x] Write a Go script. - [x] Add `goaction` configuration in `.github/workflows/goaction.yml`. - [x] Push the project to Github. See simplest example for a Goaction script: (posener/goaction-example) https://github.com/posener/goaction-example, or an example that demonstrait using Github APIs: (posener/goaction-issues-example) https://github.com/posener/goaction-issues-example. Write Github Action by writing Go code! Just start a Go module with a main package, and execute it as a Github action using Goaction, or from the command line using `go run`. A go executable can get inputs from the command line flag and from environment variables. Github actions should have a `action.yml` file that defines this API. Goaction bridges the gap by parsing the Go code and creating this file automatically for you. The main package inputs should be defined with the standard `flag` package for command line arguments, or by `os.Getenv` for environment variables. These inputs define the API of the program and `goaction` automatically detect them and creates the `action.yml` file from them. Additionally, goaction also provides a library that exposes all Github action environment in an easy-to-use API. See the documentation for more information. Code segments which should run only in Github action (called "CI mode"), and not when the main package runs as a command line tool, should be protected by a `if goaction.CI { ... }` block. In order to convert the repository to a Github action, goaction command line should run on the **"main file"** (described above). This command can run manually (by ./cmd/goaction) but luckily `goaction` also comes as a Github action :-) Goaction Github action keeps the Github action file updated according to the main Go file automatically. When a PR is made, goaction will post a review explaining what changes to expect. When a new commit is pushed, Goaction makes sure that the Github action files are updated if needed. Add the following content to `.github/workflows/goaction.yml` ./action.yml: A "metadata" file for Github actions. If this file exists, the repository is considered as Github action, and the file contains information that instructs how to invoke this action. See (metadata syntax) https://help.github.com/en/actions/building-actions/metadata-syntax-for-github-actions. for more info. ./Dockerfile: A file that contains instructions how to build a container, that is used for Github actions. Github action uses this file in order to create a container image to the action. The container can also be built and tested manually: Goaction parses Go script file and looks for annotations that extends the information that exists in the function calls. Goaction annotations are a comments that start with `//goaction:` (no space after slashes). They can only be set on a `var` definition. The following annotations are available: * `//goaction:required` - sets an input definition to be "required". * `//goaction:skip` - skips an input out output definition. * `//goaction:description <description>` - add description for `os.Getenv`. * `//goaction:default <value>` - add default value for `os.Getenv`. A list of projects which are using Goaction (please send a PR if your project uses goaction and does not appear her). * (posener/goreadme) http://github.com/posener/goreadme

Package kyber provides a toolbox of advanced cryptographic primitives, for applications that need more than straightforward signing and encryption. This top level package defines the interfaces to cryptographic primitives designed to be independent of specific cryptographic algorithms, to facilitate upgrading applications to new cryptographic algorithms or switching to alternative algorithms for experimentation purposes. This toolkits public-key crypto API includes a kyber.Group interface supporting a broad class of group-based public-key primitives including DSA-style integer residue groups and elliptic curve groups. Users of this API can write higher-level crypto algorithms such as zero-knowledge proofs without knowing or caring exactly what kind of group, let alone which precise security parameters or elliptic curves, are being used. The kyber.Group interface supports the standard algebraic operations on group elements and scalars that nontrivial public-key algorithms tend to rely on. The interface uses additive group terminology typical for elliptic curves, such that point addition is homomorphically equivalent to adding their (potentially secret) scalar multipliers. But the API and its operations apply equally well to DSA-style integer groups. As a trivial example, generating a public/private keypair is as simple as: The first statement picks a private key (Scalar) from a the suites's source of cryptographic random or pseudo-random bits, while the second performs elliptic curve scalar multiplication of the curve's standard base point (indicated by the 'nil' argument to Mul) by the scalar private key 'a'. Similarly, computing a Diffie-Hellman shared secret using Alice's private key 'a' and Bob's public key 'B' can be done via: Note that we use 'Mul' rather than 'Exp' here because the library uses the additive-group terminology common for elliptic curve crypto, rather than the multiplicative-group terminology of traditional integer groups - but the two are semantically equivalent and the interface itself works for both elliptic curve and integer groups. Various sub-packages provide several specific implementations of these cryptographic interfaces. In particular, the 'group/mod' sub-package provides implementations of modular integer groups underlying conventional DSA-style algorithms. The `group/nist` package provides NIST-standardized elliptic curves built on the Go crypto library. The 'group/edwards25519' sub-package provides the kyber.Group interface using the popular Ed25519 curve. Other sub-packages build more interesting high-level cryptographic tools atop these primitive interfaces, including: - share: Polynomial commitment and verifiable Shamir secret splitting for implementing verifiable 't-of-n' threshold cryptographic schemes. This can be used to encrypt a message so that any 2 out of 3 receivers must work together to decrypt it, for example. - proof: An implementation of the general Camenisch/Stadler framework for discrete logarithm knowledge proofs. This system supports both interactive and non-interactive proofs of a wide variety of statements such as, "I know the secret x associated with public key X or I know the secret y associated with public key Y", without revealing anything about either secret or even which branch of the "or" clause is true. - sign: The sign directory contains different signature schemes. - sign/anon provides anonymous and pseudonymous public-key encryption and signing, where the sender of a signed message or the receiver of an encrypted message is defined as an explicit anonymity set containing several public keys rather than just one. For example, a member of an organization's board of trustees might prove to be a member of the board without revealing which member she is. - sign/cosi provides collective signature algorithm, where a bunch of signers create a unique, compact and efficiently verifiable signature using the Schnorr signature as a basis. - sign/eddsa provides a kyber-native implementation of the EdDSA signature scheme. - sign/schnorr provides a basic vanilla Schnorr signature scheme implementation. - shuffle: Verifiable cryptographic shuffles of ElGamal ciphertexts, which can be used to implement (for example) voting or auction schemes that keep the sources of individual votes or bids private without anyone having to trust more than one of the shuffler(s) to shuffle votes/bids honestly. For now this library should currently be considered experimental: it will definitely be changing in non-backward-compatible ways, and it will need independent security review before it should be considered ready for use in security-critical applications. However, we intend to bring the library closer to stability and real-world usability as quickly as development resources permit, and as interest and application demand dictates. As should be obvious, this library is intended to be used by developers who are at least moderately knowledgeable about cryptography. If you want a crypto library that makes it easy to implement "basic crypto" functionality correctly - i.e., plain public-key encryption and signing - then [NaCl secretbox](https://godoc.org/golang.org/x/crypto/nacl/secretbox) may be a better choice. This toolkit's purpose is to make it possible - and preferably easy - to do slightly more interesting things that most current crypto libraries don't support effectively. The one existing crypto library that this toolkit is probably most comparable to is the Charm rapid prototyping library for Python (https://charm-crypto.com/category/charm). This library incorporates and/or builds on existing code from a variety of sources, as documented in the relevant sub-packages.

bindata converts any file into managable Go source code. Useful for embedding binary data into a go program. The file data is optionally gzip compressed before being converted to a raw byte slice. The following paragraphs cover some of the customization options which can be specified in the Config struct, which must be passed into the Translate() call. When used with the `Debug` option, the generated code does not actually include the asset data. Instead, it generates function stubs which load the data from the original file on disk. The asset API remains identical between debug and release builds, so your code will not have to change. This is useful during development when you expect the assets to change often. The host application using these assets uses the same API in both cases and will not have to care where the actual data comes from. An example is a Go webserver with some embedded, static web content like HTML, JS and CSS files. While developing it, you do not want to rebuild the whole server and restart it every time you make a change to a bit of javascript. You just want to build and launch the server once. Then just press refresh in the browser to see those changes. Embedding the assets with the `debug` flag allows you to do just that. When you are finished developing and ready for deployment, just re-invoke `go-bindata` without the `-debug` flag. It will now embed the latest version of the assets. The `NoMemCopy` option will alter the way the output file is generated. It will employ a hack that allows us to read the file data directly from the compiled program's `.rodata` section. This ensures that when we call call our generated function, we omit unnecessary memcopies. The downside of this, is that it requires dependencies on the `reflect` and `unsafe` packages. These may be restricted on platforms like AppEngine and thus prevent you from using this mode. Another disadvantage is that the byte slice we create, is strictly read-only. For most use-cases this is not a problem, but if you ever try to alter the returned byte slice, a runtime panic is thrown. Use this mode only on target platforms where memory constraints are an issue. The default behavior is to use the old code generation method. This prevents the two previously mentioned issues, but will employ at least one extra memcopy and thus increase memory requirements. For instance, consider the following two examples: This would be the default mode, using an extra memcopy but gives a safe implementation without dependencies on `reflect` and `unsafe`: Here is the same functionality, but uses the `.rodata` hack. The byte slice returned from this example can not be written to without generating a runtime error. The NoCompress option indicates that the supplied assets are *not* GZIP compressed before being turned into Go code. The data should still be accessed through a function call, so nothing changes in the API. This feature is useful if you do not care for compression, or the supplied resource is already compressed. Doing it again would not add any value and may even increase the size of the data. The default behavior of the program is to use compression. The keys used in the `_bindata` map are the same as the input file name passed to `go-bindata`. This includes the path. In most cases, this is not desireable, as it puts potentially sensitive information in your code base. For this purpose, the tool supplies another command line flag `-prefix`. This accepts a portion of a path name, which should be stripped off from the map keys and function names. For example, running without the `-prefix` flag, we get: Running with the `-prefix` flag, we get: With the optional Tags field, you can specify any go build tags that must be fulfilled for the output file to be included in a build. This is useful when including binary data in multiple formats, where the desired format is specified at build time with the appropriate tags. The tags are appended to a `// +build` line in the beginning of the output file and must follow the build tags syntax specified by the go tool.

Package frauddetector provides the API client, operations, and parameter types for Amazon Fraud Detector. This is the Amazon Fraud Detector API Reference. This guide is for developers who need detailed information about Amazon Fraud Detector API actions, data types, and errors. For more information about Amazon Fraud Detector features, see the Amazon Fraud Detector User Guide. We provide the Query API as well as AWS software development kits (SDK) for Amazon Fraud Detector in Java and Python programming languages. The Amazon Fraud Detector Query API provides HTTPS requests that use the HTTP verb GET or POST and a Query parameter Action . AWS SDK provides libraries, sample code, tutorials, and other resources for software developers who prefer to build applications using language-specific APIs instead of submitting a request over HTTP or HTTPS. These libraries provide basic functions that automatically take care of tasks such as cryptographically signing your requests, retrying requests, and handling error responses, so that it is easier for you to get started. For more information about the AWS SDKs, go to Tools to build on AWSpage, scroll down to the SDK section, and choose plus (+) sign to expand the section.

Package pkcs11key implements crypto.Signer for PKCS #11 private keys. See ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-11/v2-30/pkcs-11v2-30b-d6.pdf for details of the Cryptoki PKCS#11 API. Package pkcs11key exists to satisfy Go build tools. Some Go tools will complain "no buildable Go source files in ..." because pkcs11key.go only builds when the pkcs11 tag is supplied. This empty file exists only to suppress that error, which blocks completion in some tools (specifically godep).

Package kyber provides a toolbox of advanced cryptographic primitives, for applications that need more than straightforward signing and encryption. This top level package defines the interfaces to cryptographic primitives designed to be independent of specific cryptographic algorithms, to facilitate upgrading applications to new cryptographic algorithms or switching to alternative algorithms for experimentation purposes. This toolkits public-key crypto API includes a kyber.Group interface supporting a broad class of group-based public-key primitives including DSA-style integer residue groups and elliptic curve groups. Users of this API can write higher-level crypto algorithms such as zero-knowledge proofs without knowing or caring exactly what kind of group, let alone which precise security parameters or elliptic curves, are being used. The kyber.Group interface supports the standard algebraic operations on group elements and scalars that nontrivial public-key algorithms tend to rely on. The interface uses additive group terminology typical for elliptic curves, such that point addition is homomorphically equivalent to adding their (potentially secret) scalar multipliers. But the API and its operations apply equally well to DSA-style integer groups. As a trivial example, generating a public/private keypair is as simple as: The first statement picks a private key (Scalar) from a the suites's source of cryptographic random or pseudo-random bits, while the second performs elliptic curve scalar multiplication of the curve's standard base point (indicated by the 'nil' argument to Mul) by the scalar private key 'a'. Similarly, computing a Diffie-Hellman shared secret using Alice's private key 'a' and Bob's public key 'B' can be done via: Note that we use 'Mul' rather than 'Exp' here because the library uses the additive-group terminology common for elliptic curve crypto, rather than the multiplicative-group terminology of traditional integer groups - but the two are semantically equivalent and the interface itself works for both elliptic curve and integer groups. Various sub-packages provide several specific implementations of these cryptographic interfaces. In particular, the 'group/mod' sub-package provides implementations of modular integer groups underlying conventional DSA-style algorithms. The `group/nist` package provides NIST-standardized elliptic curves built on the Go crypto library. The 'group/edwards25519' sub-package provides the kyber.Group interface using the popular Ed25519 curve. Other sub-packages build more interesting high-level cryptographic tools atop these primitive interfaces, including: - share: Polynomial commitment and verifiable Shamir secret splitting for implementing verifiable 't-of-n' threshold cryptographic schemes. This can be used to encrypt a message so that any 2 out of 3 receivers must work together to decrypt it, for example. - proof: An implementation of the general Camenisch/Stadler framework for discrete logarithm knowledge proofs. This system supports both interactive and non-interactive proofs of a wide variety of statements such as, "I know the secret x associated with public key X or I know the secret y associated with public key Y", without revealing anything about either secret or even which branch of the "or" clause is true. - sign: The sign directory contains different signature schemes. - sign/anon provides anonymous and pseudonymous public-key encryption and signing, where the sender of a signed message or the receiver of an encrypted message is defined as an explicit anonymity set containing several public keys rather than just one. For example, a member of an organization's board of trustees might prove to be a member of the board without revealing which member she is. - sign/cosi provides collective signature algorithm, where a bunch of signers create a unique, compact and efficiently verifiable signature using the Schnorr signature as a basis. - sign/eddsa provides a kyber-native implementation of the EdDSA signature scheme. - sign/schnorr provides a basic vanilla Schnorr signature scheme implementation. - shuffle: Verifiable cryptographic shuffles of ElGamal ciphertexts, which can be used to implement (for example) voting or auction schemes that keep the sources of individual votes or bids private without anyone having to trust more than one of the shuffler(s) to shuffle votes/bids honestly. For now this library should currently be considered experimental: it will definitely be changing in non-backward-compatible ways, and it will need independent security review before it should be considered ready for use in security-critical applications. However, we intend to bring the library closer to stability and real-world usability as quickly as development resources permit, and as interest and application demand dictates. As should be obvious, this library is intended to be used by developers who are at least moderately knowledgeable about cryptography. If you want a crypto library that makes it easy to implement "basic crypto" functionality correctly - i.e., plain public-key encryption and signing - then [NaCl secretbox](https://godoc.org/golang.org/x/crypto/nacl/secretbox) may be a better choice. This toolkit's purpose is to make it possible - and preferably easy - to do slightly more interesting things that most current crypto libraries don't support effectively. The one existing crypto library that this toolkit is probably most comparable to is the Charm rapid prototyping library for Python (https://charm-crypto.com/category/charm). This library incorporates and/or builds on existing code from a variety of sources, as documented in the relevant sub-packages.

Package graphql-go-tools is library to create GraphQL services using the go programming language. GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools. Source: https://graphql.org This library is intended to be a set of low level building blocks to write high performance and secure GraphQL applications. Use cases could range from writing layer seven GraphQL proxies, firewalls, caches etc.. You would usually not use this library to write a GraphQL server yourself but to build tools for the GraphQL ecosystem. To achieve this goal the library has zero dependencies at its core functionality. It has a full implementation of the GraphQL AST and supports lexing, parsing, validation, normalization, introspection, query planning as well as query execution etc. With the execution package it's possible to write a fully functional GraphQL server that is capable to mediate between various protocols and formats. In it's current state you can use the following DataSources to resolve fields: - Static data (embed static data into a schema to extend a field in a simple way) - HTTP JSON APIs (combine multiple Restful APIs into one single GraphQL Endpoint, nesting is possible) - GraphQL APIs (you can combine multiple GraphQL APIs into one single GraphQL Endpoint, nesting is possible) - Webassembly/WASM Lambdas (e.g. resolve a field using a Rust lambda) If you're looking for a ready to use solution that has all this functionality packaged as a Gateway have a look at: https://wundergraph.com Created by Jens Neuse

modgv converts “go mod graph” output into Graphviz's DOT language, for use with Graphviz visualization and analysis tools like dot, dotty, and sccmap. Usage: modgv takes no options or arguments; it reads a graph in the format generated by “go mod graph” on standard input and writes DOT language on standard output. For each module, the node representing the greatest version (i.e., the version chosen by Go's minimal version selection algorithm) is colored green. Other nodes, which aren't in the final build list, are colored grey. See http://www.graphviz.org/doc/info/lang.html for details of the DOT language and http://www.graphviz.org/about/ for Graphviz itself.

Package fees provides decred-specific methods for tracking and estimating fee rates for new transactions to be mined into the network. Fee rate estimation has two main goals: Although it was primarily written for dcrd, this package has intentionally been designed so it can be used as a standalone package for any projects needing the functionality provided. There are two main regimes against which fee estimation needs to be evaluated according to how full blocks being mined are (and consequently how important fee rates are): _low contention_ and _high contention_: In a low contention regime, the mempool sits mostly empty, transactions are usually mined very soon after being published and transaction fees are mostly sent using the minimum relay fee. In a high contention regime, the mempool is usually filled with unmined transactions, there is active dispute for space in a block (by transactions using higher fees) and blocks are usually full. The exact point of where these two regimes intersect is arbitrary, but it should be clear in the examples and simulations which of these is being discussed. Note: a very high contention scenario (> 90% of blocks being full and transactions remaining in the mempool indefinitely) is one in which stakeholders should be discussing alternative solutions (increase block size, provide other second layer alternatives, etc). Also, the current fill rate of blocks in decred is low, so while we try to account for this regime, I personally expect that the implementation will need more tweaks as it approaches this. The current approach to implement this estimation is based on bitcoin core's algorithm. References [1] and [2] provide a high level description of how it works there. Actual code is linked in references [3] and [4]. The algorithm is currently based in fee estimation as used in v0.14 of bitcoin core (which is also the basis for the v0.15+ method). A more comprehensive overview is available in reference [1]. This particular version was chosen because it's simpler to implement and should be sufficient for low contention regimes. It probably overestimates fees in higher contention regimes and longer target confirmation windows, but as pointed out earlier should be sufficient for current fill rate of decred's network. The basic algorithm is as follows (as executed by a single full node): Stats building stage: Estimation stage: Development of the estimator was originally performed and simulated using the code in [5]. Simulation of the current code can be performed by using the dcrfeesim tool available in [6]. Thanks to @davecgh for providing the initial review of the results and the original developers of the bitcoin core code (the brunt of which seems to have been made by @morcos). ## References [1] Introduction to Bitcoin Core Estimation: https://bitcointechtalk.com/an-introduction-to-bitcoin-core-fee-estimation-27920880ad0 [2] Proposed Changes to Fee Estimation in version 0.15: https://gist.github.com/morcos/d3637f015bc4e607e1fd10d8351e9f41 [3] Source for fee estimation in v0.14: https://github.com/bitcoin/bitcoin/blob/v0.14.2/src/policy/fees.cpp [4] Source for fee estimation in version 0.16.2: https://github.com/bitcoin/bitcoin/blob/v0.16.2/src/policy/fees.cpp [5] Source for the original dcrfeesim and estimator work: https://github.com/matheusd/dcrfeesim_dev [6] Source for the current dcrfeesim, using this module: https://github.com/matheusd/dcrfeesim

Package reform is a better ORM for Go, based on non-empty interfaces and code generation. See README (https://github.com/go-reform/reform/blob/v1-stable/README.md) for quickstart information. reform allows one to add tags (comments) to generated queries with WithTag Querier method. They can be used to track queries from RDBMS logs and tools back to application code. For example, this code: will generate the following query: Please keep in mind that dynamic tags can affect RDBMS query cache. Consult your RDBMS documentation for details. Some known links: This example shows some reform features. It uses https://github.com/AlekSi/pointer to get pointers to values of build-in types.

Copyright The OpenTelemetry Authors Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. Deprecated: Please use checkfile with argument --file-name README.md instead.

Package antlr implements the Go version of the ANTLR 4 runtime. ANTLR (ANother Tool for Language Recognition) is a powerful parser generator for reading, processing, executing, or translating structured text or binary files. It's widely used to build languages, tools, and frameworks. From a grammar, ANTLR generates a parser that can build parse trees and also generates a listener interface (or visitor) that makes it easy to respond to the recognition of phrases of interest. ANTLR supports the generation of code in a number of target languages, and the generated code is supported by a runtime library, written specifically to support the generated code in the target language. This library is the runtime for the Go target. To generate code for the go target, it is generally recommended to place the source grammar files in a package of their own, and use the `.sh` script method of generating code, using the go generate directive. In that same directory it is usual, though not required, to place the antlr tool that should be used to generate the code. That does mean that the antlr tool JAR file will be checked in to your source code control though, so you are free to use any other way of specifying the version of the ANTLR tool to use, such as aliasing in `.zshrc` or equivalent, or a profile in your IDE, or configuration in your CI system. Here is a general template for an ANTLR based recognizer in Go: Make sure that the package statement in your grammar file(s) reflects the go package they exist in. The generate.go file then looks like this: And the generate.sh file will look similar to this: depending on whether you want visitors or listeners or any other ANTLR options. From the command line at the root of your package “myproject” you can then simply issue the command: Copyright (c) 2012-2022 The ANTLR Project. All rights reserved. Use of this file is governed by the BSD 3-clause license, which can be found in the LICENSE.txt file in the project root.

Package merkletree provides tools for calculating the Merkle root of a dataset, for creating a proof that a piece of data is in a Merkle tree of a given root, and for verifying proofs that a piece of data is in a Merkle tree of a given root. The tree is implemented according to the specification for Merkle trees provided in RFC 6962. Package merkletree also supports building roots and proofs from cached subroots of the Merkle tree. For example, a large file could be cached by building the Merkle root for each 4MB sector and remembering the Merkle roots of each sector. Using a cached tree, the Merkle root of the whole file can be computed by passing the cached tree each of the roots of the 4MB sector. Building proofs using these cached roots is also supported. A proof must be built within the target sector using a normal Tree, requiring the whole sector to be hashed. The results of that proof can then be passed into the Prove() function of a cached tree, which will create the full proof without needing to hash the entire file. Caching also makes it inexpensive to update the Merkle root of the file after changing or deleting segments of the larger file. Examples can be found in the README for the package.

Package anser provides a document transformation and processing tool to support data migrations. The anser.Application is the primary interface in which migrations are defined and executed. Applications are constructed with a list of MigrationGenerators, and relevant operations. Then the Setup method configures the application, with an anser.Environment, which sets up and collects dependency information. Finally, the Run method executes the migrations in two phases: first by generating migration jobs, and finally by running all migration jobs. The ordering of migrations is derived from the dependency information between generators and the jobs that they generate. When possible jobs are executed in parallel, but the execution of migration operations is a property of the queue object configured in the anser.Environment. The anser package provides a custom amboy/dependency.Manager object, which allows migrations to express dependencies to other migrations. The State() method ensures that all migration IDs specified as edges are satisfied before reporting as "ready" for work. Anser provides the Environment interface, with a global instance accessible via the exported GetEnvironment() function to provide access to runtime configuration state: database connections; amboy.Queue objects, and registries for task implementations. The Environment is an interface: you can build a mock, or use one provided for testing purposes by anser (coming soon). Generators create migration operations and are the first step in an anser Migration. They are supersets of amboy.Job interfaces. The current limitation is that the generated jobs must be stored within the implementation of the generator job, which means they must either all fit in memory *or* be serializable independently (e.g. fit in the 16mb document limit if using a MongoDB backed queue.)