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xz-archive/src/common/tuklib_integer.h
Lasse Collin 77bc5bc6dd Revise tuklib_integer.h and .m4. 
Add a configure option --enable-unsafe-type-punning to get the
old non-conforming memory access methods. It can be useful with
old compilers or in some other less typical situations but
shouldn't normally be used.

Omit the packed struct trick for unaligned access. While it's
best in some cases, this is simpler. If the memcpy trick doesn't
work, one can request unsafe type punning from configure.

Because CRC32/CRC64 code needs fast aligned reads, if no very
safe way to do it is found, type punning is used as a fallback.
This sucks but since it currently works in practice, it seems to
be the least bad option. It's never needed with GCC >= 4.7 or
Clang >= 3.6 since these support __builtin_assume_aligned and
thus fast aligned access can be done with the memcpy trick.

Other things:
  - Support GCC/Clang __builtin_bswapXX
  - Cleaner bswap fallback macros
  - Minor cleanups
2019-12-31 00:18:24 +02:00

746 lines
17 KiB
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///////////////////////////////////////////////////////////////////////////////
//
/// \file tuklib_integer.h
/// \brief Various integer and bit operations
///
/// This file provides macros or functions to do some basic integer and bit
/// operations.
///
/// Native endian inline functions (XX = 16, 32, or 64):
/// - Unaligned native endian reads: unaligned_readXXne(ptr)
/// - Unaligned native endian writes: unaligned_writeXXne(ptr, num)
/// - Aligned native endian reads: readXXne(ptr)
/// - Aligned native endian writes: writeXXne(ptr, num)
///
/// Endianness-converting integer operations (these can be macros!)
/// (XX = 16, 32, or 64; Y = b or l):
/// - Byte swapping: bswapXX(num)
/// - Byte order conversions to/from native (byteswaps if Y isn't
/// the native endianness): convXXYe(num)
/// - Aligned reads: readXXYe(ptr)
/// - Aligned writes: writeXXYe(ptr, num)
/// - Unaligned reads (16/32-bit only): unaligned_readXXYe(ptr)
/// - Unaligned writes (16/32-bit only): unaligned_writeXXYe(ptr, num)
///
/// Since the above can macros, the arguments should have no side effects
/// because they may be evaluated more than once.
///
/// Bit scan operations for non-zero 32-bit integers (inline functions):
/// - Bit scan reverse (find highest non-zero bit): bsr32(num)
/// - Count leading zeros: clz32(num)
/// - Count trailing zeros: ctz32(num)
/// - Bit scan forward (simply an alias for ctz32()): bsf32(num)
///
/// The above bit scan operations return 0-31. If num is zero,
/// the result is undefined.
//
// Authors: Lasse Collin
// Joachim Henke
//
// This file has been put into the public domain.
// You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef TUKLIB_INTEGER_H
#define TUKLIB_INTEGER_H
#include "tuklib_common.h"
#include <string.h>
// Newer Intel C compilers require immintrin.h for _bit_scan_reverse()
// and such functions.
#if defined(__INTEL_COMPILER) && (__INTEL_COMPILER >= 1500)
# include <immintrin.h>
#endif
///////////////////
// Byte swapping //
///////////////////
#if defined(HAVE___BUILTIN_BSWAPXX)
// GCC >= 4.8 and Clang
# define bswap16(n) __builtin_bswap16(n)
# define bswap32(n) __builtin_bswap32(n)
# define bswap64(n) __builtin_bswap64(n)
#elif defined(HAVE_BYTESWAP_H)
// glibc, uClibc, dietlibc
# include <byteswap.h>
# ifdef HAVE_BSWAP_16
# define bswap16(num) bswap_16(num)
# endif
# ifdef HAVE_BSWAP_32
# define bswap32(num) bswap_32(num)
# endif
# ifdef HAVE_BSWAP_64
# define bswap64(num) bswap_64(num)
# endif
#elif defined(HAVE_SYS_ENDIAN_H)
// *BSDs and Darwin
# include <sys/endian.h>
#elif defined(HAVE_SYS_BYTEORDER_H)
// Solaris
# include <sys/byteorder.h>
# ifdef BSWAP_16
# define bswap16(num) BSWAP_16(num)
# endif
# ifdef BSWAP_32
# define bswap32(num) BSWAP_32(num)
# endif
# ifdef BSWAP_64
# define bswap64(num) BSWAP_64(num)
# endif
# ifdef BE_16
# define conv16be(num) BE_16(num)
# endif
# ifdef BE_32
# define conv32be(num) BE_32(num)
# endif
# ifdef BE_64
# define conv64be(num) BE_64(num)
# endif
# ifdef LE_16
# define conv16le(num) LE_16(num)
# endif
# ifdef LE_32
# define conv32le(num) LE_32(num)
# endif
# ifdef LE_64
# define conv64le(num) LE_64(num)
# endif
#endif
#ifndef bswap16
# define bswap16(n) (uint16_t)( \
(((n) & 0x00FFU) << 8) \
| (((n) & 0xFF00U) >> 8) \
)
#endif
#ifndef bswap32
# define bswap32(n) (uint32_t)( \
(((n) & UINT32_C(0x000000FF)) << 24) \
| (((n) & UINT32_C(0x0000FF00)) << 8) \
| (((n) & UINT32_C(0x00FF0000)) >> 8) \
| (((n) & UINT32_C(0xFF000000)) >> 24) \
)
#endif
#ifndef bswap64
# define bswap64(n) (uint64_t)( \
(((n) & UINT64_C(0x00000000000000FF)) << 56) \
| (((n) & UINT64_C(0x000000000000FF00)) << 40) \
| (((n) & UINT64_C(0x0000000000FF0000)) << 24) \
| (((n) & UINT64_C(0x00000000FF000000)) << 8) \
| (((n) & UINT64_C(0x000000FF00000000)) >> 8) \
| (((n) & UINT64_C(0x0000FF0000000000)) >> 24) \
| (((n) & UINT64_C(0x00FF000000000000)) >> 40) \
| (((n) & UINT64_C(0xFF00000000000000)) >> 56) \
)
#endif
// Define conversion macros using the basic byte swapping macros.
#ifdef WORDS_BIGENDIAN
# ifndef conv16be
# define conv16be(num) ((uint16_t)(num))
# endif
# ifndef conv32be
# define conv32be(num) ((uint32_t)(num))
# endif
# ifndef conv64be
# define conv64be(num) ((uint64_t)(num))
# endif
# ifndef conv16le
# define conv16le(num) bswap16(num)
# endif
# ifndef conv32le
# define conv32le(num) bswap32(num)
# endif
# ifndef conv64le
# define conv64le(num) bswap64(num)
# endif
#else
# ifndef conv16be
# define conv16be(num) bswap16(num)
# endif
# ifndef conv32be
# define conv32be(num) bswap32(num)
# endif
# ifndef conv64be
# define conv64be(num) bswap64(num)
# endif
# ifndef conv16le
# define conv16le(num) ((uint16_t)(num))
# endif
# ifndef conv32le
# define conv32le(num) ((uint32_t)(num))
# endif
# ifndef conv64le
# define conv64le(num) ((uint64_t)(num))
# endif
#endif
////////////////////////////////
// Unaligned reads and writes //
////////////////////////////////
// The traditional way of casting e.g. *(const uint16_t *)uint8_pointer
// is bad even if the uint8_pointer is properly aligned because this kind
// of casts break strict aliasing rules and result in undefined behavior.
// With unaligned pointers it's even worse: compilers may emit vector
// instructions that require aligned pointers even if non-vector
// instructions work with unaligned pointers.
//
// Using memcpy() is the standard compliant way to do unaligned access.
// Many modern compilers inline it so there is no function call overhead.
// For those compilers that don't handle the memcpy() method well, the
// old casting method (that violates strict aliasing) can be requested at
// build time. A third method, casting to a packed struct, would also be
// an option but isn't provided to keep things simpler (it's already a mess).
// Hopefully this is flexible enough in practice.
static inline uint16_t
unaligned_read16ne(const uint8_t *buf)
{
#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
&& defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING)
return *(const uint16_t *)buf;
#else
uint16_t num;
memcpy(&num, buf, sizeof(num));
return num;
#endif
}
static inline uint32_t
unaligned_read32ne(const uint8_t *buf)
{
#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
&& defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING)
return *(const uint32_t *)buf;
#else
uint32_t num;
memcpy(&num, buf, sizeof(num));
return num;
#endif
}
static inline uint64_t
unaligned_read64ne(const uint8_t *buf)
{
#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
&& defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING)
return *(const uint64_t *)buf;
#else
uint64_t num;
memcpy(&num, buf, sizeof(num));
return num;
#endif
}
static inline void
unaligned_write16ne(uint8_t *buf, uint16_t num)
{
#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
&& defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING)
*(uint16_t *)buf = num;
#else
memcpy(buf, &num, sizeof(num));
#endif
return;
}
static inline void
unaligned_write32ne(uint8_t *buf, uint32_t num)
{
#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
&& defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING)
*(uint32_t *)buf = num;
#else
memcpy(buf, &num, sizeof(num));
#endif
return;
}
static inline void
unaligned_write64ne(uint8_t *buf, uint64_t num)
{
#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
&& defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING)
*(uint64_t *)buf = num;
#else
memcpy(buf, &num, sizeof(num));
#endif
return;
}
static inline uint16_t
unaligned_read16be(const uint8_t *buf)
{
#if defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
uint16_t num = unaligned_read16ne(buf);
return conv16be(num);
#else
uint16_t num = ((uint16_t)buf[0] << 8) | (uint16_t)buf[1];
return num;
#endif
}
static inline uint16_t
unaligned_read16le(const uint8_t *buf)
{
#if !defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
uint16_t num = unaligned_read16ne(buf);
return conv16le(num);
#else
uint16_t num = ((uint16_t)buf[0]) | ((uint16_t)buf[1] << 8);
return num;
#endif
}
static inline uint32_t
unaligned_read32be(const uint8_t *buf)
{
#if defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
uint32_t num = unaligned_read32ne(buf);
return conv32be(num);
#else
uint32_t num = (uint32_t)buf[0] << 24;
num |= (uint32_t)buf[1] << 16;
num |= (uint32_t)buf[2] << 8;
num |= (uint32_t)buf[3];
return num;
#endif
}
static inline uint32_t
unaligned_read32le(const uint8_t *buf)
{
#if !defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
uint32_t num = unaligned_read32ne(buf);
return conv32le(num);
#else
uint32_t num = (uint32_t)buf[0];
num |= (uint32_t)buf[1] << 8;
num |= (uint32_t)buf[2] << 16;
num |= (uint32_t)buf[3] << 24;
return num;
#endif
}
// NOTE: Possible byte swapping must be done in a macro to allow the compiler
// to optimize byte swapping of constants when using glibc's or *BSD's
// byte swapping macros. The actual write is done in an inline function
// to make type checking of the buf pointer possible.
#if defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
# define unaligned_write16be(buf, num) \
unaligned_write16ne(buf, conv16be(num))
# define unaligned_write32be(buf, num) \
unaligned_write32ne(buf, conv32be(num))
#endif
#if !defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
# define unaligned_write16le(buf, num) \
unaligned_write16ne(buf, conv16le(num))
# define unaligned_write32le(buf, num) \
unaligned_write32ne(buf, conv32le(num))
#endif
#ifndef unaligned_write16be
static inline void
unaligned_write16be(uint8_t *buf, uint16_t num)
{
buf[0] = (uint8_t)(num >> 8);
buf[1] = (uint8_t)num;
return;
}
#endif
#ifndef unaligned_write16le
static inline void
unaligned_write16le(uint8_t *buf, uint16_t num)
{
buf[0] = (uint8_t)num;
buf[1] = (uint8_t)(num >> 8);
return;
}
#endif
#ifndef unaligned_write32be
static inline void
unaligned_write32be(uint8_t *buf, uint32_t num)
{
buf[0] = (uint8_t)(num >> 24);
buf[1] = (uint8_t)(num >> 16);
buf[2] = (uint8_t)(num >> 8);
buf[3] = (uint8_t)num;
return;
}
#endif
#ifndef unaligned_write32le
static inline void
unaligned_write32le(uint8_t *buf, uint32_t num)
{
buf[0] = (uint8_t)num;
buf[1] = (uint8_t)(num >> 8);
buf[2] = (uint8_t)(num >> 16);
buf[3] = (uint8_t)(num >> 24);
return;
}
#endif
//////////////////////////////
// Aligned reads and writes //
//////////////////////////////
// Separate functions for aligned reads and writes are provided since on
// strict-align archs aligned access is much faster than unaligned access.
//
// Just like in the unaligned case, memcpy() is needed to avoid
// strict aliasing violations. However, on archs that don't support
// unaligned access the compiler cannot know that the pointers given
// to memcpy() are aligned which results in slow code. As of C11 there is
// no standard way to tell the compiler that we know that the address is
// aligned but some compilers have language extensions to do that. With
// such language extensions the memcpy() method gives excellent results.
//
// What to do on a strict-align system when no known language extentensions
// are available? Falling back to byte-by-byte access would be safe but ruin
// optimizations that have been made specifically with aligned access in mind.
// As a compromise, aligned reads will fall back to non-compliant type punning
// but aligned writes will be byte-by-byte, that is, fast reads are preferred
// over fast writes. This obviously isn't great but hopefully it's a working
// compromise for now.
//
// __builtin_assume_aligned is support by GCC >= 4.7 and clang >= 3.6.
#ifdef HAVE___BUILTIN_ASSUME_ALIGNED
# define tuklib_memcpy_aligned(dest, src, size) \
memcpy(dest, __builtin_assume_aligned(src, size), size)
#else
# define tuklib_memcpy_aligned(dest, src, size) \
memcpy(dest, src, size)
# ifndef TUKLIB_FAST_UNALIGNED_ACCESS
# define TUKLIB_USE_UNSAFE_ALIGNED_READS 1
# endif
#endif
static inline uint16_t
read16ne(const uint8_t *buf)
{
#if defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING) \
|| defined(TUKLIB_USE_UNSAFE_ALIGNED_READS)
return *(const uint16_t *)buf;
#else
uint16_t num;
tuklib_memcpy_aligned(&num, buf, sizeof(num));
return num;
#endif
}
static inline uint32_t
read32ne(const uint8_t *buf)
{
#if defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING) \
|| defined(TUKLIB_USE_UNSAFE_ALIGNED_READS)
return *(const uint32_t *)buf;
#else
uint32_t num;
tuklib_memcpy_aligned(&num, buf, sizeof(num));
return num;
#endif
}
static inline uint64_t
read64ne(const uint8_t *buf)
{
#if defined(TUKLIB_USE_UNSAFE_TYPE_PUNNING) \
|| defined(TUKLIB_USE_UNSAFE_ALIGNED_READS)
return *(const uint64_t *)buf;
#else
uint64_t num;
tuklib_memcpy_aligned(&num, buf, sizeof(num));
return num;
#endif
}
static inline void
write16ne(uint8_t *buf, uint16_t num)
{
#ifdef TUKLIB_USE_UNSAFE_TYPE_PUNNING
*(uint16_t *)buf = num;
#else
tuklib_memcpy_aligned(buf, &num, sizeof(num));
#endif
return;
}
static inline void
write32ne(uint8_t *buf, uint32_t num)
{
#ifdef TUKLIB_USE_UNSAFE_TYPE_PUNNING
*(uint32_t *)buf = num;
#else
tuklib_memcpy_aligned(buf, &num, sizeof(num));
#endif
return;
}
static inline void
write64ne(uint8_t *buf, uint64_t num)
{
#ifdef TUKLIB_USE_UNSAFE_TYPE_PUNNING
*(uint64_t *)buf = num;
#else
tuklib_memcpy_aligned(buf, &num, sizeof(num));
#endif
return;
}
static inline uint16_t
read16be(const uint8_t *buf)
{
uint16_t num = read16ne(buf);
return conv16be(num);
}
static inline uint16_t
read16le(const uint8_t *buf)
{
uint16_t num = read16ne(buf);
return conv16le(num);
}
static inline uint32_t
read32be(const uint8_t *buf)
{
uint32_t num = read32ne(buf);
return conv32be(num);
}
static inline uint32_t
read32le(const uint8_t *buf)
{
uint32_t num = read32ne(buf);
return conv32le(num);
}
static inline uint64_t
read64be(const uint8_t *buf)
{
uint64_t num = read64ne(buf);
return conv64be(num);
}
static inline uint64_t
read64le(const uint8_t *buf)
{
uint64_t num = read64ne(buf);
return conv64le(num);
}
// These need to be macros like in the unaligned case.
#define write16be(buf, num) write16ne((buf), conv16be(num))
#define write16le(buf, num) write16ne((buf), conv16le(num))
#define write32be(buf, num) write32ne((buf), conv32be(num))
#define write32le(buf, num) write32ne((buf), conv32le(num))
#define write64be(buf, num) write64ne((buf), conv64be(num))
#define write64le(buf, num) write64ne((buf), conv64le(num))
////////////////////
// Bit operations //
////////////////////
static inline uint32_t
bsr32(uint32_t n)
{
// Check for ICC first, since it tends to define __GNUC__ too.
#if defined(__INTEL_COMPILER)
return _bit_scan_reverse(n);
#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
// GCC >= 3.4 has __builtin_clz(), which gives good results on
// multiple architectures. On x86, __builtin_clz() ^ 31U becomes
// either plain BSR (so the XOR gets optimized away) or LZCNT and
// XOR (if -march indicates that SSE4a instructions are supported).
return (uint32_t)__builtin_clz(n) ^ 31U;
#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
uint32_t i;
__asm__("bsrl %1, %0" : "=r" (i) : "rm" (n));
return i;
#elif defined(_MSC_VER)
unsigned long i;
_BitScanReverse(&i, n);
return i;
#else
uint32_t i = 31;
if ((n & 0xFFFF0000) == 0) {
n <<= 16;
i = 15;
}
if ((n & 0xFF000000) == 0) {
n <<= 8;
i -= 8;
}
if ((n & 0xF0000000) == 0) {
n <<= 4;
i -= 4;
}
if ((n & 0xC0000000) == 0) {
n <<= 2;
i -= 2;
}
if ((n & 0x80000000) == 0)
--i;
return i;
#endif
}
static inline uint32_t
clz32(uint32_t n)
{
#if defined(__INTEL_COMPILER)
return _bit_scan_reverse(n) ^ 31U;
#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
return (uint32_t)__builtin_clz(n);
#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
uint32_t i;
__asm__("bsrl %1, %0\n\t"
"xorl $31, %0"
: "=r" (i) : "rm" (n));
return i;
#elif defined(_MSC_VER)
unsigned long i;
_BitScanReverse(&i, n);
return i ^ 31U;
#else
uint32_t i = 0;
if ((n & 0xFFFF0000) == 0) {
n <<= 16;
i = 16;
}
if ((n & 0xFF000000) == 0) {
n <<= 8;
i += 8;
}
if ((n & 0xF0000000) == 0) {
n <<= 4;
i += 4;
}
if ((n & 0xC0000000) == 0) {
n <<= 2;
i += 2;
}
if ((n & 0x80000000) == 0)
++i;
return i;
#endif
}
static inline uint32_t
ctz32(uint32_t n)
{
#if defined(__INTEL_COMPILER)
return _bit_scan_forward(n);
#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX >= UINT32_MAX
return (uint32_t)__builtin_ctz(n);
#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
uint32_t i;
__asm__("bsfl %1, %0" : "=r" (i) : "rm" (n));
return i;
#elif defined(_MSC_VER)
unsigned long i;
_BitScanForward(&i, n);
return i;
#else
uint32_t i = 0;
if ((n & 0x0000FFFF) == 0) {
n >>= 16;
i = 16;
}
if ((n & 0x000000FF) == 0) {
n >>= 8;
i += 8;
}
if ((n & 0x0000000F) == 0) {
n >>= 4;
i += 4;
}
if ((n & 0x00000003) == 0) {
n >>= 2;
i += 2;
}
if ((n & 0x00000001) == 0)
++i;
return i;
#endif
}
#define bsf32 ctz32
#endif
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