tuklib_integer.h

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//
//
//  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
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
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
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
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
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
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
read16be(const uint8_t *buf)
{
#if defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
    uint16_t num = 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
read16le(const uint8_t *buf)
{
#if !defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
    uint16_t num = 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
read32be(const uint8_t *buf)
{
#if defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
    uint32_t num = 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
read32le(const uint8_t *buf)
{
#if !defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
    uint32_t num = 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 write16be(buf, num) write16ne(buf, conv16be(num))
#   define write32be(buf, num) write32ne(buf, conv32be(num))
#endif
 
#if !defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
#   define write16le(buf, num) write16ne(buf, conv16le(num))
#   define write32le(buf, num) write32ne(buf, conv32le(num))
#endif
 
 
#ifndef write16be
static inline void
write16be(uint8_t *buf, uint16_t num)
{
    buf[0] = (uint8_t)(num >> 8);
    buf[1] = (uint8_t)num;
    return;
}
#endif
 
 
#ifndef write16le
static inline void
write16le(uint8_t *buf, uint16_t num)
{
    buf[0] = (uint8_t)num;
    buf[1] = (uint8_t)(num >> 8);
    return;
}
#endif
 
 
#ifndef write32be
static inline void
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 write32le
static inline void
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
aligned_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
aligned_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
aligned_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
aligned_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
aligned_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
aligned_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
aligned_read16be(const uint8_t *buf)
{
    uint16_t num = aligned_read16ne(buf);
    return conv16be(num);
}
 
 
static inline uint16_t
aligned_read16le(const uint8_t *buf)
{
    uint16_t num = aligned_read16ne(buf);
    return conv16le(num);
}
 
 
static inline uint32_t
aligned_read32be(const uint8_t *buf)
{
    uint32_t num = aligned_read32ne(buf);
    return conv32be(num);
}
 
 
static inline uint32_t
aligned_read32le(const uint8_t *buf)
{
    uint32_t num = aligned_read32ne(buf);
    return conv32le(num);
}
 
 
static inline uint64_t
aligned_read64be(const uint8_t *buf)
{
    uint64_t num = aligned_read64ne(buf);
    return conv64be(num);
}
 
 
static inline uint64_t
aligned_read64le(const uint8_t *buf)
{
    uint64_t num = aligned_read64ne(buf);
    return conv64le(num);
}
 
 
// These need to be macros like in the unaligned case.
#define aligned_write16be(buf, num) aligned_write16ne((buf), conv16be(num))
#define aligned_write16le(buf, num) aligned_write16ne((buf), conv16le(num))
#define aligned_write32be(buf, num) aligned_write32ne((buf), conv32be(num))
#define aligned_write32le(buf, num) aligned_write32ne((buf), conv32le(num))
#define aligned_write64be(buf, num) aligned_write64ne((buf), conv64be(num))
#define aligned_write64le(buf, num) aligned_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