# infectious

[![GoDoc](https://godoc.org/github.com/vivint/infectious?status.png)](https://godoc.org/github.com/vivint/infectious)

Infectious implements
[Reed-Solomon forward error correction](https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction).
It uses the
[Berlekamp-Welch error correction algorithm](https://en.wikipedia.org/wiki/Berlekamp%E2%80%93Welch_algorithm)
to achieve the ability to actually correct errors.

[We wrote a blog post about how this library works!](https://innovation.vivint.com/introduction-to-reed-solomon-bc264d0794f8)

### Example

```golang
const (
	required = 8
	total    = 14
)

// Create a *FEC, which will require required pieces for reconstruction at
// minimum, and generate total total pieces.
f, err := infectious.NewFEC(required, total)
if err != nil {
	panic(err)
}

// Prepare to receive the shares of encoded data.
shares := make([]infectious.Share, total)
output := func(s infectious.Share) {
	// the memory in s gets reused, so we need to make a deep copy
	shares[s.Number] = s.DeepCopy()
}

// the data to encode must be padded to a multiple of required, hence the
// underscores.
err = f.Encode([]byte("hello, world! __"), output)
if err != nil {
	panic(err)
}

// we now have total shares.
for _, share := range shares {
	fmt.Printf("%d: %#v\n", share.Number, string(share.Data))
}

// Let's reconstitute with two pieces missing and one piece corrupted.
shares = shares[2:]     // drop the first two pieces
shares[2].Data[1] = '!' // mutate some data

result, err := f.Decode(nil, shares)
if err != nil {
	panic(err)
}

// we have the original data!
fmt.Printf("got: %#v\n", string(result))
```

**Caution:** this package API leans toward providing the user more power and
performance at the expense of having some really sharp edges! Read the
documentation about memory lifecycles carefully!

Please see the docs at http://godoc.org/github.com/vivint/infectious

### Thanks

We're forever indebted to the giants on whose shoulders we stand. The LICENSE
has our full copyright history, but an extra special thanks to Klaus Post for
much of the initial Go code. See his post for more:
http://blog.klauspost.com/blazingly-fast-reed-solomon-coding/

### LICENSE

 * Copyright (C) 2016-2017 Vivint, Inc.
 * Copyright (c) 2015 Klaus Post
 * Copyright (c) 2015 Backblaze
 * Copyright (C) 2011 Billy Brumley (billy.brumley@aalto.fi)
 * Copyright (C) 2009-2010 Jack Lloyd (lloyd@randombit.net)
 * Copyright (C) 1996-1998 Luigi Rizzo (luigi@iet.unipi.it)

Portions derived from code by Phil Karn (karn@ka9q.ampr.org),
Robert Morelos-Zaragoza (robert@spectra.eng.hawaii.edu) and Hari
Thirumoorthy (harit@spectra.eng.hawaii.edu), Aug 1995

**Portions of this project (labeled in each file) are licensed under this
license:**

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright
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   documentation and/or other materials provided with the
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