source: vbox/trunk/src/libs/liblzma-5.6.4/check/crc64_fast.c@ 109020

// 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
}