Update tuklib_integer.h with bit scan functions.
Thanks to Joachim Henke for the original patch.
This commit is contained in:
Lasse Collin
parent
c74c132f7f
commit
7ac3985d89
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@ -1,10 +1,12 @@
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///////////////////////////////////////////////////////////////////////////////
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//
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/// \file tuklib_integer.h
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/// \brief Byte swapping and endianness related macros and functions
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/// \brief Various integer and bit operations
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///
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/// This file provides macros or functions to do basic endianness related
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/// integer operations (XX = 16, 32, or 64; Y = b or l):
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/// This file provides macros or functions to do some basic integer and bit
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/// operations.
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///
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/// Endianness related integer operations (XX = 16, 32, or 64; Y = b or l):
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/// - Byte swapping: bswapXX(num)
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/// - Byte order conversions to/from native: convXXYe(num)
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/// - Aligned reads: readXXYe(ptr)
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@ -18,8 +20,18 @@
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/// \todo PowerPC and possibly some other architectures support
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/// byte swapping load and store instructions. This file
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/// doesn't take advantage of those instructions.
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///
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/// Bit scan operations for non-zero 32-bit integers:
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/// - Bit scan reverse (find highest non-zero bit): bsr32(num)
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/// - Count leading zeros: clz32(num)
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/// - Count trailing zeros: ctz32(num)
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/// - Bit scan forward (simply an alias for ctz32()): bsf32(num)
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///
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/// The above bit scan operations return 0-31. If num is zero,
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/// the result is undefined.
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//
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// Author: Lasse Collin
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// Authors: Lasse Collin
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// Joachim Henke
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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@ -213,8 +225,7 @@ read64le(const uint8_t *buf)
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// to optimize byte swapping of constants when using glibc's or *BSD's
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// byte swapping macros. The actual write is done in an inline function
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// to make type checking of the buf pointer possible similarly to readXXYe()
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// functions. This also seems to silence a probably bogus GCC warning about
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// strict aliasing when buf points to the beginning of an uint8_t array.
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// functions.
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#define write16be(buf, num) write16ne((buf), conv16be(num))
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#define write16le(buf, num) write16ne((buf), conv16le(num))
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@ -272,7 +283,7 @@ write64ne(uint8_t *buf, uint64_t num)
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static inline uint16_t
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unaligned_read16be(const uint8_t *buf)
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{
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uint16_t num = ((uint16_t)buf[0] << 8) | buf[1];
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uint16_t num = ((uint16_t)buf[0] << 8) | (uint16_t)buf[1];
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return num;
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}
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@ -280,7 +291,7 @@ unaligned_read16be(const uint8_t *buf)
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static inline uint16_t
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unaligned_read16le(const uint8_t *buf)
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{
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uint16_t num = ((uint32_t)buf[0]) | ((uint16_t)buf[1] << 8);
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uint16_t num = ((uint16_t)buf[0]) | ((uint16_t)buf[1] << 8);
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return num;
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}
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@ -347,4 +358,166 @@ unaligned_write32le(uint8_t *buf, uint32_t num)
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}
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#endif
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static inline uint32_t
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bsr32(uint32_t n)
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{
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// Check for ICC first, since it tends to define __GNUC__ too.
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#if defined(__INTEL_COMPILER)
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return _bit_scan_reverse(n);
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#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
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// GCC >= 3.4 has __builtin_clz(), which gives good results on
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// multiple architectures. On x86, __builtin_clz() ^ 31U becomes
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// either plain BSR (so the XOR gets optimized away) or LZCNT and
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// XOR (if -march indicates that SSE4a instructions are supported).
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return __builtin_clz(n) ^ 31U;
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#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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uint32_t i;
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__asm__("bsrl %1, %0" : "=r" (i) : "rm" (n));
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return i;
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#elif defined(_MSC_VER) && _MSC_VER >= 1400
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// MSVC isn't supported by tuklib, but since this code exists,
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// it doesn't hurt to have it here anyway.
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uint32_t i;
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_BitScanReverse((DWORD *)&i, n);
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return i;
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#else
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uint32_t i = 31;
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if ((n & UINT32_C(0xFFFF0000)) == 0) {
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n <<= 16;
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i = 15;
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}
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if ((n & UINT32_C(0xFF000000)) == 0) {
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n <<= 8;
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i -= 8;
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}
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if ((n & UINT32_C(0xF0000000)) == 0) {
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n <<= 4;
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i -= 4;
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}
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if ((n & UINT32_C(0xC0000000)) == 0) {
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n <<= 2;
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i -= 2;
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}
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if ((n & UINT32_C(0x80000000)) == 0)
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--i;
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return i;
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#endif
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}
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static inline uint32_t
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clz32(uint32_t n)
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{
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#if defined(__INTEL_COMPILER)
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return _bit_scan_reverse(n) ^ 31U;
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#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
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return __builtin_clz(n);
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#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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uint32_t i;
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__asm__("bsrl %1, %0\n\t"
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"xorl $31, %0"
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: "=r" (i) : "rm" (n));
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return i;
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#elif defined(_MSC_VER) && _MSC_VER >= 1400
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uint32_t i;
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_BitScanReverse((DWORD *)&i, n);
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return i ^ 31U;
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#else
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uint32_t i = 0;
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if ((n & UINT32_C(0xFFFF0000)) == 0) {
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n <<= 16;
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i = 16;
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}
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if ((n & UINT32_C(0xFF000000)) == 0) {
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n <<= 8;
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i += 8;
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}
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if ((n & UINT32_C(0xF0000000)) == 0) {
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n <<= 4;
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i += 4;
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}
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if ((n & UINT32_C(0xC0000000)) == 0) {
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n <<= 2;
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i += 2;
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}
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if ((n & UINT32_C(0x80000000)) == 0)
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++i;
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return i;
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#endif
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}
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static inline uint32_t
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ctz32(uint32_t n)
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{
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#if defined(__INTEL_COMPILER)
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return _bit_scan_forward(n);
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#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX >= UINT32_MAX
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return __builtin_ctz(n);
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#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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uint32_t i;
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__asm__("bsfl %1, %0" : "=r" (i) : "rm" (n));
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return i;
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#elif defined(_MSC_VER) && _MSC_VER >= 1400
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uint32_t i;
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_BitScanForward((DWORD *)&i, n);
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return i;
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#else
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uint32_t i = 0;
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if ((n & UINT32_C(0x0000FFFF)) == 0) {
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n >>= 16;
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i = 16;
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}
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if ((n & UINT32_C(0x000000FF)) == 0) {
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n >>= 8;
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i += 8;
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}
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if ((n & UINT32_C(0x0000000F)) == 0) {
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n >>= 4;
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i += 4;
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}
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if ((n & UINT32_C(0x00000003)) == 0) {
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n >>= 2;
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i += 2;
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}
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if ((n & UINT32_C(0x00000001)) == 0)
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++i;
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return i;
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#endif
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}
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#define bsf32 ctz32
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#endif
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