varint

What is varint?

The varint npm package is used for encoding and decoding variable-length integers. It is particularly useful in scenarios where you need to efficiently store or transmit integers that can vary greatly in size, such as in network protocols or file formats.

What are varint's main functionalities?

Encoding Integers

This feature allows you to encode an integer into a variable-length format. The encoded result is an array of bytes.

const varint = require('varint');
const encoded = varint.encode(300); // [172, 2]
console.log(encoded);

Decoding Integers

This feature allows you to decode a variable-length encoded integer back into its original integer form.

const varint = require('varint');
const decoded = varint.decode([172, 2]); // 300
console.log(decoded);

Encoding Integers to Buffer

This feature allows you to encode an integer directly into a Buffer, which can be useful for more advanced use cases involving binary data.

const varint = require('varint');
const buffer = Buffer.alloc(10);
const bytesWritten = varint.encode(300, buffer, 0); // 2
console.log(buffer.slice(0, bytesWritten));

Decoding Integers from Buffer

This feature allows you to decode an integer from a Buffer, which is useful when working with binary data streams.

const varint = require('varint');
const buffer = Buffer.from([172, 2]);
const decoded = varint.decode(buffer); // 300
console.log(decoded);

Other packages similar to varint

protobufjs

protobufjs is a comprehensive library for working with Protocol Buffers, which includes functionality for encoding and decoding variable-length integers. It is more feature-rich compared to varint, offering schema definitions and more complex data structures.

msgpack-lite

msgpack-lite is a library for encoding and decoding data in the MessagePack format, which includes support for variable-length integers. It is similar to varint but also supports a wider range of data types and is optimized for performance.

leb128

leb128 is a library for encoding and decoding LEB128 (Little Endian Base 128) integers, which is another form of variable-length integer encoding. It is similar to varint but uses a different encoding scheme.

README

varint

encode whole numbers to an array of protobuf-style varint bytes and also decode them.

var varint = require('varint')

var bytes = varint.encode(300) // === [0xAC, 0x02]
varint.decode(bytes) // 300
varint.decode.bytesRead // 2 (the last decode() call required 2 bytes)

api

varint = require('varint')

varint.encode(num[, output=[], offset=0]) -> array

encodes num into either the array given by offset or a new array at offset and returns that array filled with integers.

varint.decode(data[, offset=0]) -> number

decodes data, which can be either a buffer or array of integers, from position offset or default 0 and returns the decoded original integer.

varint.decode.bytesRead

if you also require the length (number of bytes) that were required to decode the integer you can access it via varint.decode.bytesRead. this is an integer property that will tell you the number of bytes that the last .decode() call had to use to decode.

usage notes

if you are using this to decode buffers from a streaming source it's up to you to make sure that you send 'complete' buffers into varint.decode. the maximum number of bytes that varint will need to decode is 8, so all you have to do is make sure you are sending buffers that are at least 8 bytes long from the point at which you know a varint range begins.

for example, if you are reading buffers from a fs.createReadStream, imagine the first buffer contains one full varint range and half of a second one, and the second buffer contains the second half of the second varint range. in order to be safe across the buffer boundaries you'd just have to make sure the buffer you give to varint.decode contains the full varint range (8 bytes), otherwise you'll get an error.

License

MIT