xz/src/liblzma/check/crc64_fast.c

///////////////////////////////////////////////////////////////////////////////
//
/// \file       crc64.c
/// \brief      CRC64 calculation
//
//  Authors:    Lasse Collin
//              Ilya Kurdyukov
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "check.h"
#include "crc_common.h"

#ifdef CRC_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 = bswap64(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 = bswap64(crc);
#endif

	return ~crc;
}
#endif

#if defined(CRC_GENERIC) && defined(CRC_CLMUL)
//////////////////////////
// Function dispatching //
//////////////////////////

// If both the generic and CLMUL 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);

#if defined(HAVE_FUNC_ATTRIBUTE_IFUNC) && defined(__clang__)
#	pragma GCC diagnostic push
#	pragma GCC diagnostic ignored "-Wunused-function"
#endif

static crc64_func_type
crc64_resolve(void)
{
	return is_clmul_supported() ? &lzma_crc64_clmul : &crc64_generic;
}

#if defined(HAVE_FUNC_ATTRIBUTE_IFUNC) && defined(__clang__)
#	pragma GCC diagnostic pop
#endif

#ifndef HAVE_FUNC_ATTRIBUTE_IFUNC

#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
#endif


#ifdef CRC_USE_IFUNC
extern LZMA_API(uint64_t)
lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
		__attribute__((__ifunc__("crc64_resolve")));
#else
extern LZMA_API(uint64_t)
lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
{
#if defined(CRC_GENERIC) && defined(CRC_CLMUL)

#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(CRC_CLMUL)
	// If CLMUL 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 lzma_crc64_clmul(buf, size, crc);

#else
	return crc64_generic(buf, size, crc);
#endif
}
#endif