SimpleChecksums

Checksums you shouldn't use written in a language you should.

Synopsis

Installation

using Pkg
Pkg.add("SimpleChecksums")

Use

using SimpleChecksums

data = UInt8.(0:255);

# super-simple sums:
@assert additive_checksum(UInt16, data) == additive16(data) == 0x7f80
@assert additive_checksum(UInt32, data) == additive32(data) == 0x00007f80
@assert additive_checksum(UInt64, data) == additive64(data) == 0x0000000000007f80

# BSD and SYS-V checksums from GNU sum utility:
@assert bsd_checksum(UInt16, data) == bsd16(data) == 0x0200
@assert sysv_checksum(UInt16, data) == sysv16(data) == 0x7f80

# Fletcher's and Adler's checksums:
@assert fletcher_checksum(UInt16, data) == fletcher16(data) == 0x5500
@assert fletcher_checksum(UInt32, data) == fletcher32(data) == 0xaaaa7f80
@assert fletcher_checksum(UInt64, data) == fletcher64(data) == 0x002aaa8000007f80

@assert fletcher_checksum(UInt16, data, UInt16(0), 0x100) == fletcher16a(data) == 0x8080
@assert fletcher_checksum(UInt32, data, UInt32(0), 0x10000) == fletcher32a(data) == 0xaa807f80
@assert fletcher_checksum(UInt64, data, UInt64(0), 0x100000000) == fletcher64a(data) == 0x002aaa8000007f80

@assert fletcher_checksum(UInt32, data, UInt32(1), UInt32(65521), 5552) == adler32(data) == 0xadf67f81

Why?

Checksums are small summaries of data that can be used to detect errors introduced to the data during transmission or storage. In modern times, checksums have largely been replaced with cryptographic hashes like MD5 and SHA, but these functions and the computational power required to compute them in a reasonable amount of time did not exist when many of the data transmission and storage standards we use today were invented. If we want to use the checksums that appear in these standards in Julia code, it helps to have a standard library to compute them correctly and efficiently.

If you are building a new data transmission or storage standard and need a way to check for errors, consider using a cryptographic hash like SHA, or at least a better error-detecting code like CRC, before choosing any of these functions.