// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////

//

/// \file       crc64.c

/// \brief      CRC64 calculation

//

//  Authors:    Lasse Collin

//              Ilya Kurdyukov

//

///////////////////////////////////////////////////////////////////////////////

#include "check.h"

#include "crc_common.h"

#if defined(CRC_X86_CLMUL)

# define BUILDING_CRC64_CLMUL

# include "crc_x86_clmul.h"

#endif

#ifdef CRC64_GENERIC

/////////////////////////////////

// Generic slice-by-four CRC64 //

/////////////////////////////////

#ifdef WORDS_BIGENDIAN

# define A1(x) ((x) >> 56)

#else

# define A1 A

#endif

// See the comments in crc32_fast.c. They aren't duplicated here.

static uint64_t

crc64_generic(const uint8_t *buf, size_t size, uint64_t crc)

{

  crc = ~crc;

#ifdef WORDS_BIGENDIAN

  crc = byteswap64(crc);

#endif

  if (size > 4) {

    while ((uintptr_t)(buf) & 3) {

      crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);

      --size;

    }

    const uint8_t *const limit = buf + (size & ~(size_t)(3));

    size &= (size_t)(3);

    while (buf < limit) {

#ifdef WORDS_BIGENDIAN

      const uint32_t tmp = (uint32_t)(crc >> 32)

          ^ aligned_read32ne(buf);

#else

      const uint32_t tmp = (uint32_t)crc

          ^ aligned_read32ne(buf);

#endif

      buf += 4;

      crc = lzma_crc64_table[3][A(tmp)]

          ^ lzma_crc64_table[2][B(tmp)]

          ^ S32(crc)

          ^ lzma_crc64_table[1][C(tmp)]

          ^ lzma_crc64_table[0][D(tmp)];

    }

  }

  while (size-- != 0)

    crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);

#ifdef WORDS_BIGENDIAN

  crc = byteswap64(crc);

#endif

  return ~crc;

}

#endif

#if defined(CRC64_GENERIC) && defined(CRC64_ARCH_OPTIMIZED)

//////////////////////////

// Function dispatching //

//////////////////////////

// If both the generic and arch-optimized implementations are usable, then

// the function that is used is selected at runtime. See crc32_fast.c.

typedef uint64_t (*crc64_func_type)(

    const uint8_t *buf, size_t size, uint64_t crc);

static crc64_func_type

crc64_resolve(void)

{

  return is_arch_extension_supported()

      ? &crc64_arch_optimized : &crc64_generic;

}

#ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR

# define CRC64_SET_FUNC_ATTR __attribute__((__constructor__))

static crc64_func_type crc64_func;

#else

# define CRC64_SET_FUNC_ATTR

static uint64_t crc64_dispatch(const uint8_t *buf, size_t size, uint64_t crc);

static crc64_func_type crc64_func = &crc64_dispatch;

#endif

CRC64_SET_FUNC_ATTR

static void

crc64_set_func(void)

{

  crc64_func = crc64_resolve();

  return;

}

#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR

static uint64_t

crc64_dispatch(const uint8_t *buf, size_t size, uint64_t crc)

{

  crc64_set_func();

  return crc64_func(buf, size, crc);

}

#endif

#endif

extern LZMA_API(uint64_t)

lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)

{

#if defined(CRC64_GENERIC) && defined(CRC64_ARCH_OPTIMIZED)

#ifdef CRC_USE_GENERIC_FOR_SMALL_INPUTS

  if (size <= 16)

    return crc64_generic(buf, size, crc);

#endif

  return crc64_func(buf, size, crc);

#elif defined(CRC64_ARCH_OPTIMIZED)

  // If arch-optimized version is used unconditionally without runtime

  // CPU detection then omitting the generic version and its 8 KiB

  // lookup table makes the library smaller.

  //

  // FIXME: Lookup table isn't currently omitted on 32-bit x86,

  // see crc64_table.c.

  return crc64_arch_optimized(buf, size, crc);

#else

  return crc64_generic(buf, size, crc);

#endif

}