I'm looking for an implementation of CRC32 in C or C++ that is explicitly licensed as being no cost or public domain. The implementation here seems nice, but the only thing it says about the license is "source code", which isn't good enough. I'd prefer non LGPL so I don't have to fool around with a DLL (my app is closed source). I saw the adler32 implementation in zlib, but I'm checking small chunks of data, which adler is not good for.
Answer
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))