/******************************************************
Copyright (c) 2017 Percona LLC and/or its affiliates.

Zlib compatible CRC-32 implementation.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

*******************************************************/

#include "crc_glue.h"
#include <stdint.h>
#include <string.h>
#include <zlib.h>
#include "config.h"
#include "crc-intel-pclmul.h"

#if __GNUC__ >= 4 && defined(__x86_64__)
static int pclmul_enabled = 0;
#endif

#if defined(__GNUC__) && defined(__x86_64__)
static uint32_t cpuid(uint32_t *ecx, uint32_t *edx) {
  uint32_t level;

  asm("cpuid" : "=a"(level) : "a"(0) : "ebx", "ecx", "edx");

  if (level < 1) {
    return level;
  }

  asm("cpuid" : "=c"(*ecx), "=d"(*edx) : "a"(1) : "ebx");

  return level;
}
#endif

void crc_init() {
#if defined(__GNUC__) && defined(__x86_64__)
  uint32_t ecx, edx;

  if (cpuid(&ecx, &edx) > 0) {
    pclmul_enabled = ((ecx >> 19) & 1) && ((ecx >> 1) & 1);
  }
#endif
}

ulong crc32_iso3309(ulong crc, const uchar *buf, uint len) {
#if __GNUC__ >= 4 && defined(__x86_64__) && defined(HAVE_CLMUL_INSTRUCTION)
  if (pclmul_enabled) {
    uint32_t crc_accum = crc ^ 0xffffffffL;
    crc32_intel_pclmul(&crc_accum, buf, len);
    return crc_accum ^ 0xffffffffL;
  }
#endif
  return crc32(crc, buf, len);
}
