js_zfec

This is a port of zfec https://pypi.python.org/pypi/zfec, a fast erasure codec for Python, into JavaScript.

Overview

This package performs two operations, encoding and decoding. Encoding takes some input data and expands its size by producing extra "check blocks", also called "secondary blocks". Decoding takes some data -- any combination of blocks of the original data (called "primary blocks") and "secondary blocks", and produces the original data.

The encoding is parameterized by two integers, K and N. N is the total number of blocks produced, and K is how many of those blocks are necessary to reconstruct the original data. N is required to be at least 1 and at most 256, and k is required to be at least 1 and at most N.

Usage

The fec.js file exports the symbol "fec".

Create an instance, passing in K and N.

    // To encode:

    var array_of_uint8
    var f = fec(3, 10);
    var encoded = f.encode(array_of_uint8);

    // encoded now contains 10 arrays of uint8, each just over 1/3rd the size
    // of the original array_of_uint8 array.


    // To decode

    // three arbitrary parts, from above

    var f = fec(3, 10);
    var parts = [encoded[3], encoded[6], encoded[7]];
    var decoded = f.decode(parts);

    // now, decoded will equal the original array_of_uint8 above.

The data produced is compatible with the Python-based command-line tools zfec and zunfec.