CRC-32 Checksums
The compiler-checked checksum module contract is the sole authority for public signatures. It provides the reflected ISO-HDLC CRC-32 parameters: polynomial 0x04C11DB7 (0xEDB88320 in reflected form), initial value 0xFFFFFFFF, input and output reflection, and final exclusive-or 0xFFFFFFFF. The check value for 123456789 is 0xCBF43926.
crc32 computes one complete checksum. Crc32 applies the same state transition incrementally; input chunk boundaries do not affect the result. value does not mutate or consume the state, so repeated observation is stable and later update calls continue from the bytes already supplied. All operations are allocation-free.
The implementation owns one reflected four-bit lookup table. Standard-library tests derive all sixteen entries from the reflected polynomial before checking public vectors and arbitrary chunk boundaries. No transport, record framing, storage, or parsing component maintains another CRC-32 transition.
CRC-32 detects common accidental corruption. It is not collision-resistant, does not authenticate data, and must not be used as a security boundary.