buzhash

BuzHash for js

Usage:

var BuzHash = require('BuzHash');
var buz = new BuzHash(32);
...
var hash = buz.update(byte)

Useful for generating rolling hashes for variable sized chunk deduplication. Pure js implementation though so it's probably slow as balls.

Run node test.js to see 3 test cases with data that has been slightly modified each time. The first column is the byte index, the second is the first 10 characters of the sha256 for that chunk.

Notice that the sha's match up again after the modified sections. With this you can see what chunk is different.

Example Run

$ node test.js
157     matbC9U/2N
698     1NPo9tEVvV
1597    Zz8MfmjG/c <- this chunk will change
1674    g1cpKHjnvw
1983    PWffkkf9eK
2071    KqRcYjnTvQ
2072    Nqnn8clbgv
2073    jjXCzTv2ZB
2517    oMNCS+EtCu
2919    UVdFmFcO0D
3082    sQWGagpnlk
10 0.32%           
157     matbC9U/2N
698     1NPo9tEVvV
1404    f85sZne8lj <- notice it's different to the first data set
1710    OVnGk3Z/6l
1787    g1cpKHjnvw <- but it syncs back up
2096    PWffkkf9eK
2184    KqRcYjnTvQ
2185    Nqnn8clbgv
2186    jjXCzTv2ZB
2630    oMNCS+EtCu
3032    UVdFmFcO0D
3195    sQWGagpnlk
11 0.34%           
157     matbC9U/2N
698     1NPo9tEVvV
1404    lxN32Ed3sv <- in this set I changed one letter and we can see where
1710    OVnGk3Z/6l
1787    g1cpKHjnvw
2096    PWffkkf9eK
2184    KqRcYjnTvQ
2185    Nqnn8clbgv
2186    jjXCzTv2ZB
2630    oMNCS+EtCu
3032    UVdFmFcO0D
3195    sQWGagpnlk
11 0.34%