https://github.com/whatyouhide/small_ints

varint and ZigZag encoding/decoding for Erlang
https://github.com/whatyouhide/small_ints

erlang varint zigzag

Last synced: about 2 months ago
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varint and ZigZag encoding/decoding for Erlang

• Host: GitHub
• URL: https://github.com/whatyouhide/small_ints
• Owner: whatyouhide
• License: other
• Created: 2015-06-20T22:00:32.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2016-05-16T13:29:55.000Z (over 8 years ago)
• Last Synced: 2024-05-09T10:49:12.579Z (8 months ago)
• Topics: erlang, varint, zigzag
• Language: Erlang
• Homepage:
• Size: 3.91 KB
• Stars: 11
• Watchers: 4
• Forks: 5
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# small_ints

`small_ints` is an Erlang module that can help you deal with encoding and

decoding of integers using the varint and ZigZag algorithms described in the

["Encoding" section][docs-protobuf] of Google Protocol Buffer's docs.

## Building

    $ rebar3 compile

### Varint

Basically, you use a variable number of bytes to represent a positive

integer. You can encode varints to binaries and decode them from binaries like

this:

```erlang

small_ints:encode_varint(5).    %=> <<5>>

small_ints:encode_varint(1034). %=> <<138,8>>

small_ints:decode_varint(<<5,"foo">>). %=> {5, <<"foo">>}

small_ints:decode_varint(<<138,8>>). %=> {1034, <<>>}

```

### ZigZag

The ZigZag algorithm is used to encode small positive *and negative* numbers

with a small number of bytes.

```erlang

small_ints:encode_zigzag(1).  %=> 2

small_ints:encode_zigzag(-5). %=> 9

small_ints:decode_zigzag(6).  %=> 3

```

### Other stuff

`small_ints` also provides two utility functions which just combine the varint

and ZigZag algorithms:

* `small_ints:decode_zigzag_varint/1`: decodes the next varint from the given

  binary and then decodes it with ZigZag

* `small_ints:encode_zigzag_varint/1`: encodes the given integer with ZigZag,

  then encodes the result with varint

## License

MIT License © 2015, Andrea Leopardi

[docs-protobuf]: https://developers.google.com/protocol-buffers/docs/encoding