CRC32 C or C++ implementation [closed]

Answer 1

The mhash library works pretty good for me. It's fast enough, supports multiple types of hashing (crc32, MD5, SHA-1, HAVAL, RIPEMD128, RIPEMD160, TIGER, GOST, etc.). To get CRC32 of a string you would do something like this:

 MHASH td = mhash_init(MHASH_CRC32);

 if (td == MHASH_FAILED) return -1; // handle failure

 mhash(td, s, strlen(s));

 unsigned int digest = 0; // crc32 will be stored here

 mhash_deinit(td, &digest);

 // do endian swap here if desired

Answer 2

The SNIPPETS C Source Code Archive has a CRC32 implementation that is freely usable:

/* Copyright (C) 1986 Gary S. Brown.  You may use this program, or
   code or tables extracted from it, as desired without restriction.*/

(Unfortunately, c.snippets.org seems to have died. Fortunately, the Wayback Machine has it archived.)

In order to be able to compile the code, you'll need to add typedefs for BYTE as an unsigned 8-bit integer and DWORD as an unsigned 32-bit integer, along with the header files crc.h & sniptype.h.

The only critical item in the header is this macro (which could just as easily go in CRC_32.c itself:

#define UPDC32(octet, crc) (crc_32_tab[((crc) ^ (octet)) & 0xff] ^ ((crc) >> 8))

Answer 3

pycrc is a Python script that generates C CRC code, with options to select the CRC size, algorithm and model.

It's released under the MIT licence. Is that acceptable for your purposes?