This module is used to calculate CRC (Cyclic Redundancy Check) values for binary data. It uses NIF functions written in C to iterate over the given binary calculating the CRC checksum value. The NIFs are written to report their time slice usage and will not interfere with the schedulers.
Add :crc
to your list of dependencies in mix.exs
:
def deps do
[
{:crc, "~> 0.10"}
]
end
Add crc
to your rebar.config
:
{deps, [
{crc, "0.10.5"}
]}.
Or erlang.mk
:
dep_crc = hex 0.10.5
Run CRC.list/0
to get a full list of all pre-defined models or CRC.list/1
with a filter to search for a pre-defined model.
To calculate a CRC-16 X-Modem checksum for the binary <<1,2,3,4,5,4,3,2,1>>
using the pre-defined model:
iex> CRC.crc(:crc_16_xmodem, <<1,2,3,4,5,4,3,2,1>>)
31763
iex> CRC.calculate(<<1,2,3,4,5,4,3,2,1>>, :crc_16_xmodem)
31763
Or you can create a model at runtime, this can be done with a map:
iex> CRC.crc(
%{
width: 16,
poly: 0x1021,
init: 0x00,
refin: false,
refout: false,
xorout: 0x00
},
<<1,2,3,4,5,4,3,2,1>>
)
31763
iex> CRC.calculate(
<<1,2,3,4,5,4,3,2,1>>,
%{
width: 16,
poly: 0x1021,
init: 0x00,
refin: false,
refout: false,
xorout: 0x00
}
)
31763
Or you can extend one of the pre-defined models:
iex> CRC.crc(
%{
extend: :crc_16_xmodem,
init: 0x00,
},
<<1,2,3,4,5,4,3,2,1>>
)
31763
CRC.crc_init/1
is used to create a resource and be used to do partial updates to a calculation that is then finalized later:
iex> resource = CRC.crc_init(:crc_16_xmodem)
#Reference<x.x.x.x>
iex> resource2 = CRC.crc_update(resource, <<1, 2, 3, 4, 5>>)
#Reference<y.y.y.y>
iex> resource3 = CRC.crc_update(resource2, <<4, 3, 2, 1>>)
#Reference<z.z.z.z>
iex> CRC.crc_final(resource3)
31763
This could be useful to calculate a CRC for a larger binary that you are receiving asynchronously.
CRC implementations have been tested against these online calculators to validate their correctness to the best of our ability.
There are also two property tests that can use PyCRC or CRC RevEng if installed and configured locally.
$ export PYCRC_BIN=~/pycrc-0.9.1/pycrc.py
$ export REVENG_BIN=~/reveng-1.5.2/reveng
$ mix test
PyCRC is used as a part of the TravisCI test suite.
Copyright (c) 2015 Rodney Norris
CRC is released under the MIT License. See the LICENSE.md file for further details.