README

cyclic-32

A tiny, streaming, seedable CRC32 library, compatible with Node's crypto.Hash API. In less than 100 LOC.

Install via npm

$ npm install --save cyclic-32

Features

Speed: ~300 MB/s on a 2012 Macbook Air
Size: It's 96 lines of code (plus 22 lines of comments, and 17 blank)
Streams: .pipe().pipe().pipe()
Seedable: If you have more complex things in mind
CLI: Possibly useful for npm run scripts

Usage

API

var checksum = crc32( buffer, seed = 0, table = crc32.TABLE.DEFAULT )

// Shorthand for Castagnoli
var castagnoli = crc32.c( buffer, seed = 0, table = crc32.TABLE.DEFAULT )

var checksumStream = crc32.createHash({
  seed: 0,
  table: crc32.TABLE.DEFAULT,
})

Builtin tables:

crc32.TABLE.DEFAULT: Standard CRC32
crc32.TABLE.CASTAGNOLI: Castagnoli

Examples

var crc32 = require( 'cyclic-32' )

Calculate the CRC32 checksum of a Buffer:

var buffer = new Buffer( 'I shall be summed', 'ascii' )
console.log( crc32( buffer ) ) // -476443423

Pass a seed value:

var buffer = new Buffer( 'I shall be summoned', 'ascii' )
console.log( crc32( buffer, 666 ) ) // -823676065

Calculate the CRC32 checksum over a Stream:

fs.createReadStream( filename )
  .pipe( crc32.createHash() )
  .on( 'data', function( buffer ) {
    console.log( 'CRC32:', buffer.toString( 'hex' ) )
  })

If you want to pass an encoding, or seed:

fs.createReadStream( filename )
  .pipe( new crc32.Hash({ encoding: 'hex', seed: -12345678 }) )
  .on( 'data', function( checksum ) {
    console.log( 'CRC32:', checksum )
  })

Or, if you'd rather stick to the crypto.Hash API:

var hash = crc32.createHash()

hash.update( 'I shall' )
  .update( 'be summed' )

console.log( 'CRC32:', hash.digest( 'hex' ) )

CLI Usage

Calculate the checksum of a file:

$ crc32 filename
0a0ca5aa

Pipe stuff into it via stdin:

$ cat filename | crc32
ffe6bbc0

Usage no npm install needed!