0.1.2 • Published 10 years ago
node-rollsum v0.1.2
node-rollsum: rollsum library for node.js
This library is a node.js wrapper of librsync's rollsum module.
see test/test.js for more info. You can run it with node test/test.js <filename>
.
My email is eldereal@gmail.com
and any suggestions and discussions are welcomed.
Module
var Rollsum = require("node-rollsum")
var s = new Rollsum(ChunkSize, DigestSize);
Rollsum is a writable stream which you can write data into it. The constructor has two arguments:
ChunkSize
: The size of the data that calculate one digest.DigestSize
: When the digest is rolling, it is not efficient to get notified in each byte. So I use a buffer to store calculated digests. The buffer's size is DigestSize. When the buffer is full (or the input stream ends), a "digest" event is fire.
Events
on('digest', function(length){ })
: when digest buffer is full filled or the stream ends, you will get notified by this event. The argumentlength
represents the number of digests in the buffer. In most cases it should be equal toDigestSize
. Only when the stream ends, the event will be fired with the number of remaining digests.on('end', function(){ })
: Called after the stream ends and the lastdigest
event is fired.Rollsum
is a writable stream so other events of stream is also availiable.
Methods
getLength()
: Get length in bytes of the processed data.getDigest(index)
: When the eventdigest
is fired, you can get digests in the event handler. The argumentindex
should be non-negative and less than the callback argumentlength
. This function will return a 32-bit non-negative integer as the digest.getDigestData(index)
: You should call it in the callback of eventdigest
just asgetDigest(index)
. Sometimes you want to know the actual data that calculates the digest. For example, in rsync algorithm, You should calculate a stronger digest of the content when the rolling digest matches the input. This function returns a Buffer which contains the desired data.