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CRC

This is a Julia module for calculating Cyclic Redundancy Checksums (CRCs).

  • All the algorithms in the RevEng Catalogue are supported.

  • New algorithms can be easily added.

  • Calculation can be direct or via cached tables.

  • Only arrays of bytes are accepted as data (it's certainly possible to handle arbitrary sized sequences; previous versions did this, but it complicated the code for little practical gain so I removed it - please contact me if you want me to add it back).

Although the performance of CRC.jl is good, even faster CRC-32 checksums are possible using the heavily optimized C implementation in zlib via the CRC32.jl package, or using hardware-accelerated CRC-32c checksums in the CRC32c standard library.

Examples

Calculate a CRC-32 Sum

julia> using CRC

julia> crc32 = crc(CRC_32)
(anonymous function)

julia> crc32("123456789")
0xcbf43926

The function crc() constructs a lookup table, which is cached in the returned function (here, crc32()). Re-using crc32() to calculate a series of CRCs is therefore more efficient than starting with crc() each time.

The returned function can also be called with a file handle, so calling open(crc32, file) will return the checksum of file.

Within Your Program

The same example as above, but inside your program, would look like this:

using CRC
...
crc32 = crc(CRC_32)  # create our own crc function, just once
...
function some_func(...)
    ...
    x = crc32(data)  # use the crc function created above, many times
    ...
end
...

Force Direct (Tableless) Calculation

julia> crc(CRC_32, tables=NoTables)("123456789")
0xcbf43926

Define an Algorithm

For example, CRC-7, catalogued as width=7 poly=0x09 init=0x00 refin=false refout=false xorout=0x00 check=0x75 name="CRC-7"

julia> myCRC7 = spec(7, 0x09, 0x00, false, false, 0x00, 0x75)
CRC.Spec{UInt8}(7, 0x09, 0x00, false, false, 0x00, 0x75)

julia> @assert crc(myCRC7)(CHECK) == myCRC7.check

Of course, this is already defined:

julia> CRC_7
CRC.Spec{UInt8}(7, 0x09, 0x00, false, false, 0x00, 0x75)

Installation

Julia can be downloaded here. Once Julia is working you can install this package using:

julia> Pkg.add("CRC")

Versions

  • 4.0.0 - 2020-11-27 Remove command line functionality.

  • 3.1.0 - 2020-11-07 Update ArgParse dependency and add Project.toml.

  • 3.0.0 - 2018-02-28 Update for Julia 1.0

  • 1.2.0 - 2016-09-28 Drop Julia 0.3 support and switch to Libz.

  • 1.1.0 - 2015-06-09 Small fixes for Julia 0.4, Travis + Coverage.

  • 1.0.0 - 2014-06-31 Changed handler method so that a String is converted to bytes (instead of being treated as a file path). This will break existing code that uses the current handler (sorry!), but I hope I don't have many users (particularly users that are calling that method)!

  • 0.2.0 - Initial release(s).