diff options
| -rw-r--r-- | src/common/tuklib_integer.h | 189 |
1 files changed, 181 insertions, 8 deletions
diff --git a/src/common/tuklib_integer.h b/src/common/tuklib_integer.h index f13dd1d8..e6daa772 100644 --- a/src/common/tuklib_integer.h +++ b/src/common/tuklib_integer.h @@ -1,10 +1,12 @@ /////////////////////////////////////////////////////////////////////////////// // /// \file tuklib_integer.h -/// \brief Byte swapping and endianness related macros and functions +/// \brief Various integer and bit operations /// -/// This file provides macros or functions to do basic endianness related -/// integer operations (XX = 16, 32, or 64; Y = b or l): +/// 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) @@ -18,8 +20,18 @@ /// \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. // -// Author: Lasse Collin +// Authors: Lasse Collin +// Joachim Henke // // This file has been put into the public domain. // You can do whatever you want with this file. @@ -213,8 +225,7 @@ read64le(const uint8_t *buf) // 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. This also seems to silence a probably bogus GCC warning about -// strict aliasing when buf points to the beginning of an uint8_t array. +// functions. #define write16be(buf, num) write16ne((buf), conv16be(num)) #define write16le(buf, num) write16ne((buf), conv16le(num)) @@ -272,7 +283,7 @@ write64ne(uint8_t *buf, uint64_t num) static inline uint16_t unaligned_read16be(const uint8_t *buf) { - uint16_t num = ((uint16_t)buf[0] << 8) | buf[1]; + uint16_t num = ((uint16_t)buf[0] << 8) | (uint16_t)buf[1]; return num; } @@ -280,7 +291,7 @@ unaligned_read16be(const uint8_t *buf) static inline uint16_t unaligned_read16le(const uint8_t *buf) { - uint16_t num = ((uint32_t)buf[0]) | ((uint16_t)buf[1] << 8); + uint16_t num = ((uint16_t)buf[0]) | ((uint16_t)buf[1] << 8); return num; } @@ -347,4 +358,166 @@ unaligned_write32le(uint8_t *buf, uint32_t num) } #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 __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) && _MSC_VER >= 1400 + // MSVC isn't supported by tuklib, but since this code exists, + // it doesn't hurt to have it here anyway. + uint32_t i; + _BitScanReverse((DWORD *)&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 __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) && _MSC_VER >= 1400 + uint32_t i; + _BitScanReverse((DWORD *)&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 __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) && _MSC_VER >= 1400 + uint32_t i; + _BitScanForward((DWORD *)&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 |