#CRC32

#define FIO_CRC32
#include "fio-stl.h"

Fast CRC32 using the ITU-T V.42 / ISO 3309 / gzip polynomial (0xEDB88320). Useful for gzip, PNG, and anything else that expects this particular CRC32 flavor.

The implementation picks the best available path at compile time:

• ARM aarch64 with the CRC32 extension uses scalar CRC32 instructions, with a PMULL bulk-fold path when the crypto / PMULL feature is available.
• x86 / x64 with SSE4.2 and PCLMULQDQ uses a PCLMULQDQ bulk path and the software tail path.
• Other builds use the always-present slicing-by-16 software fallback.

Note: this is not CRC32-C (Castagnoli, polynomial 0x82F63B78). The ARM scalar path uses the gzip-polynomial CRC32 instructions (__crc32b, __crc32w, __crc32d), not the Castagnoli variants.

#API Functions

#fio_crc32

SFUNC uint32_t fio_crc32(const void *data, size_t len, uint32_t initial_crc);

Computes the CRC32 of len bytes at data. Pass 0 for initial_crc to start fresh, or pass a previous result to continue an incremental checksum across multiple buffers.

Returns: the CRC32 checksum.

#Example — single buffer

#define FIO_CRC32
#include "fio-stl.h"

int main(void) {
  const char *msg = "Hello, World!";
  uint32_t crc = fio_crc32(msg, strlen(msg), 0);
  printf("CRC32: 0x%08X\n", crc);
  return 0;
}

#Example — incremental

uint32_t crc = 0;
crc = fio_crc32("Hello, ", 7, crc);
crc = fio_crc32("World!", 6, crc);
/* crc matches a single call over "Hello, World!" */