adler-32 - npm Package Compare versions

Comparing version 0.4.0 to 1.0.0

README.md

+# adler32
+
+Signed ADLER-32 algorithm implementation in JS (for the browser and nodejs).
+Emphasis on correctness, performance, and IE6+ support.
+
+## Installation
+
+With [npm](https://www.npmjs.org/package/adler-32):
+
+```bash
+$ npm install adler-32
+```
+
+In the browser:
+
+```html
+<script lang="javascript" src="adler32.js"></script>
+```
+
+The browser exposes a variable `ADLER32`.
+
+When installed globally, npm installs a script `adler32` that computes the
+checksum for a specified file or standard input.
+
+The script will manipulate `module.exports` if available (e.g. in a CommonJS
+`require` context).  This is not always desirable.  To prevent the behavior,
+define `DO_NOT_EXPORT_ADLER`.
+
+## Usage
+
+In all cases, the relevant function takes an argument representing data and an
+optional second argument representing the starting "seed" (for running hash).
+
+The return value is a signed 32-bit integer.
+
+- `ADLER32.buf(byte array or buffer[, seed])` assumes the argument is a sequence
+  of 8-bit unsigned integers (e.g. nodejs `Buffer` or simple array of ints).
+
+- `ADLER32.bstr(binary string[, seed])` assumes the argument as a binary string
+  where byte `i` is the low byte of the UCS-2 char: `str.charCodeAt(i) & 0xFF`
+
+- `ADLER32.str(string)` assumes the argument as a standard JS string and
+  calculates the hash of the UTF-8 encoding.
+
+For example:
+
+```js
+// var ADLER32 = require('adler-32');           // uncomment if in node
+ADLER32.str("SheetJS")                          // 176947863
+ADLER32.bstr("SheetJS")                         // 176947863
+ADLER32.buf([ 83, 104, 101, 101, 116, 74, 83 ]) // 176947863
+
+adler32 = ADLER32.buf([83, 104])                // 17825980  "Sh"
+adler32 = ADLER32.str("eet", adler32)           // 95486458  "Sheet"
+ADLER32.bstr("JS", adler32)                     // 176947863  "SheetJS"
+
+[ADLER32.str("\u2603"),  ADLER32.str("\u0003")]  // [ 73138686, 262148 ]
+[ADLER32.bstr("\u2603"), ADLER32.bstr("\u0003")] // [ 262148,   262148 ]
+[ADLER32.buf([0x2603]),  ADLER32.buf([0x0003])]  // [ 262148,   262148 ]
+```
+
+## Testing
+
+`make test` will run the nodejs-based test.
+
+To run the in-browser tests, run a local server and go to the `ctest` directory.
+`make ctestserv` will start a python `SimpleHTTPServer` server on port 8000.
+
+To update the browser artifacts, run `make ctest`.
+
+To generate the bits file, use the `adler32` function from python zlib:
+
+```python
+>>> from zlib import adler32
+>>> x="foo bar baz٪☃🍣"
+>>> adler32(x)
[phone]
+>>> adler32(x+x)
+-2076896149
+>>> adler32(x+x+x)
[phone]
+```
+
+The included `adler32.njs` script can process files or stdin:
+
+```bash
+$ echo "this is a test" > t.txt
+$ bin/adler32.njs t.txt
[phone]
+```
+
+For comparison, the included `adler32.py` script uses python zlib:
+
+```bash
+$ bin/adler32.py t.txt
[phone]
+```
+
+## Performance
+
+`make perf` will run algorithmic performance tests (which should justify certain
+decisions in the code).
+
+Bit twiddling is much faster than taking the mod on Safari and older Firefoxes.
+Instead of taking the literal mod 65521, it is faster to keep it in the integers
+by bit-shifting: `65536 ~ 15 mod 65521` so for nonnegative integer `a`:
+
+```
+    a = (a >>> 16) * 65536 + (a & 65535)            [equality]
+    a ~ (a >>> 16) * 15    + (a & 65535) mod 65521
+```
+
+The mod is taken at the very end, since the intermediate result may exceed 65521
+
+## Magic Number
+
+The magic numbers were chosen so as to not overflow a 31-bit integer:
+
+```mathematica
+F[n_] := Reduce[x*(x + 1)*n/2 + (x + 1)*(65521) < (2^31 - 1) && x > 0, x, Integers]
+F[255] (* bstr:  x \[Element] Integers && 1 <= x <= 3854 *)
+F[127] (* ascii: x \[Element] Integers && 1 <= x <= 5321 *)
+```
+
+Subtract up to 4 elements for the unicode case.
+
+## License
+
+Please consult the attached LICENSE file for details.  All rights not explicitly
+granted by the Apache 2.0 license are reserved by the Original Author.
+
+## Badges
+
+[![Sauce Test Status](https://saucelabs.com/browser-matrix/adler32.svg)](https://saucelabs.com/u/adler32)
+
+[![Build Status](https://travis-ci.org/SheetJS/js-adler32.svg?branch=master)](https://travis-ci.org/SheetJS/js-adler32)
+
+[![Coverage Status](http://img.shields.io/coveralls/SheetJS/js-adler32/master.svg)](https://coveralls.io/r/SheetJS/js-adler32?branch=master)
+
+[![Analytics](https://ga-beacon.appspot.com/UA-36810333-1/SheetJS/js-adler32?pixel)](https://github.com/SheetJS/js-adler32)

adler32.js

@@ -24,12 +24,10 @@ /* adler32.js (C) 2014-present SheetJS -- http://sheetjs.com */
 }(function(ADLER32) {
-ADLER32.version = '0.4.0';
-/*global Buffer */
-var use_buffer = typeof Buffer !== 'undefined';
-function adler32_bstr(bstr) {
-	if(bstr.length > 32768) if(use_buffer) return adler32_buf(new Buffer(bstr));
+ADLER32.version = '1.0.0';
+function adler32_bstr(bstr, seed) {
 	var a = 1, b = 0, L = bstr.length, M = 0;
+	if(typeof seed === 'number') { a = seed & 0xFFFF; b = seed >>> 16; }
 	for(var i = 0; i < L;) {
 		M = Math.min(L-i, 3850)+i;
 		for(;i<M;i++) {
-			a += bstr.charCodeAt(i);
+			a += bstr.charCodeAt(i)&0xFF;
 			b += a;
@@ -43,8 +41,9 @@ }
 
-function adler32_buf(buf) {
+function adler32_buf(buf, seed) {
 	var a = 1, b = 0, L = buf.length, M = 0;
+	if(typeof seed === 'number') { a = seed & 0xFFFF; b = (seed >>> 16) & 0xFFFF; }
 	for(var i = 0; i < L;) {
 		M = Math.min(L-i, 3850)+i;
 		for(;i<M;i++) {
-			a += buf[i];
+			a += buf[i]&0xFF;
 			b += a;
@@ -58,4 +57,5 @@ }
 
-function adler32_str(str) {
+function adler32_str(str, seed) {
 	var a = 1, b = 0, L = str.length, M = 0, c = 0, d = 0;
+	if(typeof seed === 'number') { a = seed & 0xFFFF; b = seed >>> 16; }
 	for(var i = 0; i < L;) {
@@ -85,3 +85,3 @@ M = Math.min(L-i, 3850);
 	}
-	return (b << 16) | a;
+	return ((b%65521) << 16) | (a%65521);
 }
@@ -88,0 +88,0 @@ ADLER32.bstr = adler32_bstr;

package.json

 {
 	"name": "adler-32",
-	"version": "0.4.0",
+	"version": "1.0.0",
 	"author": "sheetjs",
@@ -13,2 +13,3 @@ "description": "Pure-JS ADLER-32",
 		"concat-stream":"",
+		"printj":"",
 		"exit-on-epipe":""
@@ -18,3 +19,2 @@ },
 		"mocha":"",
-		"xlsjs":"",
 		"codepage":""
@@ -21,0 +21,0 @@ },

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Improved metrics

Total package byte prevSize

10951

141.58%

Dev dependency count

2

-33.33%

Number of package files

5

25%

Number of low quality alerts

1

-50%

Number of lines in readme file

141

Infinity%

Worsened metrics

Dependency count

3

50%

Dependency changes

• + Added

  printj@

• + Added

  printj@1.3.1
  (transitive)