In a Nutshell

Small library implememting Unix sum(1) and cksum(1) algorithms. Both, BSD and SysV variants of sum(1) are supported. Also CRC32 and CRC32C algorithms are supported.

Reference

The most powerful way is to use the class interface:

'use strict';

const uc = require('unix-checksum');

(function() {
    var c1 = new uc.BsdSum();
    var c2 = new uc.SysvSum();
    var c3 = new uc.CkSum();
    var c4 = new uc.CRC32();
    var c5 = new uc.CRC32C();
    var len = 0;
    process.stdin.on('data', function(d) {
        c1.update(d);
        c2.update(d);
        c3.update(d);
        c4.update(d);
        c5.update(d);
        len += d.length;
    }).on('end', function() {
        console.log('len:    ' + len);
        console.log('bsd:    ' + c1.final());
        console.log('sysv:   ' + c2.final());
        console.log('cksum:  ' + c3.final());
        console.log('crc32:  ' + c4.final('hex'));
        console.log('crc32c: ' + c5.final('hex'));
        process.exit(0);
    });
})();

There are also one-shot interfaces for all algorithms:

'use strict';

const uc = require('unix-checksum');

console.log(uc.bsdSum('foo'));
console.log(uc.sysvSum(Buffer.from( [ 1,2,3,4,5 ])));
console.log(uc.ckSum('Kekkonen, Kekkonen, Kekkonen'));
console.log(uc.crc32('Paasikivi, Paasikivi, Paasikivi'));
console.log(uc.crc32c('Fagerholm, Fagerholm, Fagerholm', 'hex'));

Encoding can be provided as an optional parameter to final() method of the class interface or optional second parameter to the one shot interface. The default is 'number'. Constant length (per checksum algorithm) Buffer object is returned, if encoding 'buffer' is used. Values 'hex' and 'base64' return the checksum value encoded as hexadecimal or BASE64 encoded string respectively. While also other encodings supported by Buffer.toString() can be passed as encofing, the results are arbitrary and really should not be used.

The current amount of bytes processed by the algorighm can be read from the context property length. After final() method is called, the length property is the total number of bytes processed while calculating the checksum.

For BsdSum and SysvSum, after final() method is called, the block count can be read from the context property block. This is needed to duplicate the full information returned by the historical command line tools.

Calling final() method multiple times triggers an error. An error is also triggered, if update() method is called after final() has already been called.

Command line interface is provided only for demonstration purposes.

$ sum GPL-2.0.TXT
42571    18

$ sum --sysv GPL-2.0.TXT
34111 36 GPL-2.0.TXT

$ cksum GPL-2.0.TXT
2811767965 18092 GPL-2.0.TXT

$ node dumpchecksum.js GPL-2.0.TXT
file:         GPL-2.0.TXT
input length: 18092
bsd:          42571 (blocks: 18)
sysv:         34111 (blocks: 36)
cksum:        2811767965
crc32:        1313272993 (4e46f4a1)
crc32c:       1750386445 (6854c70d)

Disclaimer

As a developer you should be aware of the fact that the algorithms in this package MUST NOT in any circumstances to be considered cryptographically strong. In fact they are extremely weak. The intended use for this library is to help backwards compatible implementations of some outdated standards, such as RFC 3230. Maintaining historical legacy is also among the motivations behind making this library public.

Author

Timo J. Rinne tri@iki.fi

License

GPL-2.0