cyclic-32


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

[CRC32]: https://en.wikipedia.org/wiki/Cyclic_redundancy_check
[crypto.Hash API]: https://nodejs.org/api/crypto.html#crypto_class_hash

Install via npm

``sh
$ 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

$3

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

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

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

Builtin tables:

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

$3

`js
var crc32 = require( 'cyclic-32' )
`

Calculate the CRC32 checksum of a Buffer:

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

Pass a seed value:

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

Calculate the CRC32 checksum over a Stream:

`js
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:

`js
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:

`js
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:

`sh
$ crc32 filename
0a0ca5aa
`

Pipe stuff into it via stdin:

`sh
$ cat filename | crc32
ffe6bbc0
``