# ruby-multihash

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> A simple [Multihash](https://github.com/multiformats/multihash) implementation for ruby.

A multihash is a digest with an embedded hash function code (and length) (['cause you never know](https://twitter.com/matthew_d_green/status/597409850381836288)). It was developed primarily for use with [IPFS](https://github.com/ipfs/ipfs), but is not specific to it.

## Install

Add this line to your application's Gemfile:

```ruby
gem 'multihashes'
```

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install multihashes

## Usage

This is a low-level library. Bring your own digest. A binary digest goes in, a binary digest goes out. To compute a sha256 multihash that would work nicely with [IPFS](https://github.com/ipfs/ipfs):

```ruby
require 'multihashes'
require 'digest'

digest = Digest::SHA256.digest 'Dade Murphy will never figure this one out'
multihash_binary_string = Multihashes.encode digest, 'sha2-256'

multihash_binary_string.unpack('H*').first # hex: "1220142711d38ca7a33c521841..."

out = Multihashes.decode multihash_binary_string
# => {:code=>18, :hash_function=>"sha2-256", :length=>32, :digest=>"\x14'\x11\xD3\x8C\xA7\xA3<R\x18Ao\x8F\xFC\xC6FH\xCAF\x16\xA6%\xB5\xE0\xA0\xAB=\xA1\x91\x1D]z"}

```

Hash function names (latest is [here](https://github.com/multiformats/multihash/blob/master/hashtable.csv))

    code name
    0xd5 md5
    0x11 sha1
    0x12 sha2-256
    0x13 sha2-512
    0x14 sha3
    0x40 blake2b
    0x41 blake2s
    # 0x00-0x0f reserved for application specific functions
    # 0x10-0x3f reserved for SHA standard functions

## Development

After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run `bundle exec rake install`.

## Maintainers

[@kyledrake](https://github.com/kyledrake)

## Contribute

Bug reports and pull requests are welcome on GitHub at https://github.com/multiformats/ruby-multihash.

Check out our [contributing document](https://github.com/multiformats/multiformats/blob/master/contributing.md) for more information on how we work, and about contributing in general. Please be aware that all interactions related to multiformats are subject to the IPFS [Code of Conduct](https://github.com/ipfs/community/blob/master/code-of-conduct.md).

Small note: If editing the README, please conform to the [standard-readme](https://github.com/RichardLitt/standard-readme) specification.

## License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT) © 2015 Kyle Drake.