///////////////////////////////////////////////////////////////////////////////
//
/// \file tuklib_integer.h
/// \brief Various integer and bit operations
///
/// This file provides macros or functions to do some basic integer and bit
/// operations.
///
/// Endianness related integer operations (XX = 16, 32, or 64; Y = b or l):
/// - Byte swapping: bswapXX(num)
/// - Byte order conversions to/from native: 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 they can macros, the arguments should have no side effects since
/// they may be evaluated more than once.
///
/// \todo PowerPC and possibly some other architectures support
/// byte swapping load and store instructions. This file
/// doesn't take advantage of those instructions.
///
/// Bit scan operations for non-zero 32-bit integers:
/// - 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>
////////////////////////////////////////
// Operating system specific features //
////////////////////////////////////////
#if 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
////////////////////////////////
// Compiler-specific features //
////////////////////////////////
// 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 //
///////////////////
#ifndef bswap16
# define bswap16(num) \
(((uint16_t)(num) << 8) | ((uint16_t)(num) >> 8))
#endif
#ifndef bswap32
# define bswap32(num) \
( (((uint32_t)(num) << 24) ) \
| (((uint32_t)(num) << 8) & UINT32_C(0x00FF0000)) \
| (((uint32_t)(num) >> 8) & UINT32_C(0x0000FF00)) \
| (((uint32_t)(num) >> 24) ) )
#endif
#ifndef bswap64
# define bswap64(num) \
( (((uint64_t)(num) << 56) ) \
| (((uint64_t)(num) << 40) & UINT64_C(0x00FF000000000000)) \
| (((uint64_t)(num) << 24) & UINT64_C(0x0000FF0000000000)) \
| (((uint64_t)(num) << 8) & UINT64_C(0x000000FF00000000)) \
| (((uint64_t)(num) >> 8) & UINT64_C(0x00000000FF000000)) \
| (((uint64_t)(num) >> 24) & UINT64_C(0x0000000000FF0000)) \
| (((uint64_t)(num) >> 40) & UINT64_C(0x000000000000FF00)) \
| (((uint64_t)(num) >> 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
//////////////////////////////
// Aligned reads and writes //
//////////////////////////////
static inline uint16_t
read16be(const uint8_t *buf)
{
uint16_t num = *(const uint16_t *)buf;
return conv16be(num);
}
static inline uint16_t
read16le(const uint8_t *buf)
{
uint16_t num = *(const uint16_t *)buf;
return conv16le(num);
}
static inline uint32_t
read32be(const uint8_t *buf)
{
uint32_t num = *(const uint32_t *)buf;
return conv32be(num);
}
static inline uint32_t
read32le(const uint8_t *buf)
{
uint32_t num = *(const uint32_t *)buf;
return conv32le(num);
}
static inline uint64_t
read64be(const uint8_t *buf)
{
uint64_t num = *(const uint64_t *)buf;
return conv64be(num);
}
static inline uint64_t
read64le(const uint8_t *buf)
{
uint64_t num = *(const uint64_t *)buf;
return conv64le(num);
}
// NOTE: Possible byte swapping must be done in a macro to allow GCC
// 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 similarly to readXXYe()
// functions.
#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))
static inline void
write16ne(uint8_t *buf, uint16_t num)
{
*(uint16_t *)buf = num;
return;
}
static inline void
write32ne(uint8_t *buf, uint32_t num)
{
*(uint32_t *)buf = num;
return;
}
static inline void
write64ne(uint8_t *buf, uint64_t num)
{
*(uint64_t *)buf = num;
return;
}
////////////////////////////////
// Unaligned reads and writes //
////////////////////////////////
// The traditional way of casting e.g. *(const uint16_t *)uint8_pointer
// is bad (at least) because compilers can 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.
//
// However, it seems that some compilers generate better code with a cast
// to a packed struct than with memcpy():
// - Old GCC versions (early 4.x and older) on x86
// - GCC <= 8.2 (and possibly newer) on ARMv5 (but ARMv5 is old and maybe
// doesn't matter so much)
// - GCC <= 5.x on ARMv7 (on 4.x neither is great but packed is less bad)
// - Intel C Compiler <= 19 (and possibly newer)
//
// GCC on ARMv6 is weird:
// - GCC >= 6.x is better with memcpy() than with a packed struct.
// - On GCC < 6 neither method is good, but packed seems less bad.
//
// https://gcc.godbolt.org/ was useful for seeing what kind of code is
// generated by different compilers on different archs. Note that one
// may need to try a little less trivial code than than these functions
// alone to spot differences. For example this is better with packed method
// on Intel C Compiler 19:
//
// int foo(const uint8_t *a, const uint8_t *b)
// {
// return unaligned_read16ne(a) == unaligned_read16ne(b);
// }
//
// Based on the above information, prefer the memcpy() method in
// general (including all Clang versions), but use the packed struct
// with GCC 5.x and older and with the Intel C Compiler. This isn't
// optimal but at least it covers some known special cases.
#if defined(__GNUC__) && !defined(__clang__) \
&& (__GNUC__ < 6 || defined(__INTEL_COMPILER))
# define TUKLIB_UNALIGNED_WITH_PACKED 1
#endif
static inline uint16_t
unaligned_read16ne(const uint8_t *buf)
{
#ifdef TUKLIB_UNALIGNED_WITH_PACKED
struct __attribute__((__packed__)) s { uint16_t v; };
const struct s *p = (const struct s *)buf;
return p->v;
#else
uint16_t num;
memcpy(&num, buf, sizeof(num));
return num;
#endif
}
static inline uint32_t
unaligned_read32ne(const uint8_t *buf)
{
#ifdef TUKLIB_UNALIGNED_WITH_PACKED
struct __attribute__((__packed__)) s { uint32_t v; };
const struct s *p = (const struct s *)buf;
return p->v;
#else
uint32_t num;
memcpy(&num, buf, sizeof(num));
return num;
#endif
}
static inline uint64_t
unaligned_read64ne(const uint8_t *buf)
{
#ifdef TUKLIB_UNALIGNED_WITH_PACKED
struct __attribute__((__packed__)) s { uint64_t v; };
const struct s *p = (const struct s *)buf;
return p->v;
#else
uint64_t num;
memcpy(&num, buf, sizeof(num));
return num;
#endif
}
static inline void
unaligned_write16ne(uint8_t *buf, uint16_t num)
{
#ifdef TUKLIB_UNALIGNED_WITH_PACKED
struct __attribute__((__packed__)) s { uint16_t v; };
struct s *p = (struct s *)buf;
p->v = num;
#else
memcpy(buf, &num, sizeof(num));
#endif
return;
}
static inline void
unaligned_write32ne(uint8_t *buf, uint32_t num)
{
#ifdef TUKLIB_UNALIGNED_WITH_PACKED
struct __attribute__((__packed__)) s { uint32_t v; };
struct s *p = (struct s *)buf;
p->v = num;
#else
memcpy(buf, &num, sizeof(num));
#endif
return;
}
static inline void
unaligned_write64ne(uint8_t *buf, uint64_t num)
{
#ifdef TUKLIB_UNALIGNED_WITH_PACKED
struct __attribute__((__packed__)) s { uint64_t v; };
struct s *p = (struct s *)buf;
p->v = num;
#else
memcpy(buf, &num, sizeof(num));
#endif
return;
}
// NOTE: TUKLIB_FAST_UNALIGNED_ACCESS indicates only support for 16-bit and
// 32-bit unaligned integer loads and stores. It's possible that 64-bit
// unaligned access doesn't work or is slower than byte-by-byte access.
// Since unaligned 64-bit is probably not needed as often as 16-bit or
// 32-bit, we simply don't support 64-bit unaligned access for now.
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
}
#if defined(WORDS_BIGENDIAN) || defined(TUKLIB_FAST_UNALIGNED_ACCESS)
// Like in the aligned case, these need to be macros.
# 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
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 & UINT32_C(0xFFFF0000)) == 0) {
n <<= 16;
i = 15;
}
if ((n & UINT32_C(0xFF000000)) == 0) {
n <<= 8;
i -= 8;
}
if ((n & UINT32_C(0xF0000000)) == 0) {
n <<= 4;
i -= 4;
}
if ((n & UINT32_C(0xC0000000)) == 0) {
n <<= 2;
i -= 2;
}
if ((n & UINT32_C(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 & UINT32_C(0xFFFF0000)) == 0) {
n <<= 16;
i = 16;
}
if ((n & UINT32_C(0xFF000000)) == 0) {
n <<= 8;
i += 8;
}
if ((n & UINT32_C(0xF0000000)) == 0) {
n <<= 4;
i += 4;
}
if ((n & UINT32_C(0xC0000000)) == 0) {
n <<= 2;
i += 2;
}
if ((n & UINT32_C(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 & UINT32_C(0x0000FFFF)) == 0) {
n >>= 16;
i = 16;
}
if ((n & UINT32_C(0x000000FF)) == 0) {
n >>= 8;
i += 8;
}
if ((n & UINT32_C(0x0000000F)) == 0) {
n >>= 4;
i += 4;
}
if ((n & UINT32_C(0x00000003)) == 0) {
n >>= 2;
i += 2;
}
if ((n & UINT32_C(0x00000001)) == 0)
++i;
return i;
#endif
}
#define bsf32 ctz32
#endif
