Quickly calculate CRC checksums in many variants using lookup tables.

ExCRC is implemented entirely in Elixir using recursion. There is a penalty for this: this library is much slower than if written in C or other pure binary NIF implementation. The advantage to using this library is that there are no extra dependencies on any platform and requires no external tools or compilation. If you need speed, use a NIF. If you want flexibility this library is a good choice.

There are variants of CRC so it's important to know which one you want to use. Refer to the CRC catalogue for full details. The key parameter in identifying the variant is the check value, the CRC checksum of the string 123456789.

Ported to Elixir from Lammert Bies' libCRC which seems to be the defacto implementation on StackExchange. Having looked at and tried porting many C libs, I found they didn't adapt well to functional recursion. All credit for the original work goes to Lammert.

It took me 3 days to convert 100 or so lines of C to 7 lines of Elixir :-)

I make no guarantees that this software works. Test it thoroughly before you use it in your heart-lung machine.

The API for this module is simple. Feed these a binary and it will poop out an integer CRC value computed with a variant of the CRC algorithm:

• crc16ccitt/1 - CRC16/CCITT
• crc16xmodem/1 - CRC16/XMODEM
• crc16kermit/1 - CRC16/KERMIT

Available in Hex. Install the package by adding ex_crc to your list of dependencies in your mix.exs:

def deps do
  [
    {:ex_crc, "~> 1.0.0"}
  ]
end

Find the docs at https://hexdocs.pm/ex_crc.

If your desired flavour isn't included, please feel free to add support and shoot me a pull request. Please include the 4 test cases from the libCRC test suite. If it proves conformity I'll merge it.