Compute CRC-32 checksums for text, hex bytes, or files. Supports IEEE 802.3 (zip, gzip, PNG), Castagnoli (CRC-32C used by iSCSI, ext4, Btrfs), and BZIP2 variants.
IEEE 802.3 (poly 0xEDB88320 reflected): used by zip, gzip, PNG, Ethernet — the most common "CRC32".
CRC-32C (Castagnoli) (poly 0x82F63B78): iSCSI, SCTP, ext4, Btrfs, SSE4.2 — better error detection for small payloads.
CRC-32/BZIP2 (poly 0x04C11DB7, non-reflected): used by bzip2, AAL5, MPEG-2.
All three are computed via a precomputed 256-entry table for speed. Results match python -c "import zlib; hex(zlib.crc32(b'...'))" for IEEE.