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69 lines
2.4 KiB
C++
69 lines
2.4 KiB
C++
// This file is under the public domain.
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#pragma once
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#include <cstdint>
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#include <cstdlib> // for byte swapping
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#include <cstddef>
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#include "CommonTypes.h"
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// Helper functions:
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#ifdef _WIN32
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#include <intrin.h>
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template <typename T>
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inline int CountSetBits(T v) {
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// from https://graphics.stanford.edu/~seander/bithacks.html
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// GCC has this built in, but MSVC's intrinsic will only emit the actual
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// POPCNT instruction, which we're not depending on
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v = v - ((v >> 1) & (T)~(T)0/3);
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v = (v & (T)~(T)0/15*3) + ((v >> 2) & (T)~(T)0/15*3);
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v = (v + (v >> 4)) & (T)~(T)0/255*15;
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return (T)(v * ((T)~(T)0/255)) >> (sizeof(T) - 1) * 8;
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}
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inline int LeastSignificantSetBit(u32 val)
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{
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unsigned long index;
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_BitScanForward(&index, val);
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return (int)index;
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}
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#ifdef _M_X64
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inline int LeastSignificantSetBit(u64 val)
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{
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unsigned long index;
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_BitScanForward64(&index, val);
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return (int)index;
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}
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#endif
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#else
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inline int CountSetBits(u32 val) { return __builtin_popcount(val); }
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inline int CountSetBits(u64 val) { return __builtin_popcountll(val); }
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inline int LeastSignificantSetBit(u32 val) { return __builtin_ctz(val); }
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inline int LeastSignificantSetBit(u64 val) { return __builtin_ctzll(val); }
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#endif
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// Byteswapping
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// Just in case this has been defined by platform
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#undef swap16
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#undef swap32
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#undef swap64
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#ifdef _WIN32
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inline uint16_t swap16(uint16_t _data) { return _byteswap_ushort(_data); }
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inline uint32_t swap32(uint32_t _data) { return _byteswap_ulong(_data); }
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inline uint64_t swap64(uint64_t _data) { return _byteswap_uint64(_data); }
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#elif defined(__GNUC__)
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inline uint16_t swap16(uint16_t _data) { return __builtin_bswap16(_data); }
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inline uint32_t swap32(uint32_t _data) { return __builtin_bswap32(_data); }
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inline uint64_t swap64(uint64_t _data) { return __builtin_bswap64(_data); }
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#else
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// Slow generic implementation. Hopefully this never hits
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inline uint16_t swap16(uint16_t data) { return (data >> 8) | (data << 8); }
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inline uint32_t swap32(uint32_t data) { return (swap16(data) << 16) | swap16(data >> 16); }
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inline uint64_t swap64(uint64_t data) { return ((uint64_t)swap32(data) << 32) | swap32(data >> 32); }
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#endif
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inline uint16_t swap16(const uint8_t* _pData) { return swap16(*(const uint16_t*)_pData); }
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inline uint32_t swap32(const uint8_t* _pData) { return swap32(*(const uint32_t*)_pData); }
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inline uint64_t swap64(const uint8_t* _pData) { return swap64(*(const uint64_t*)_pData); }
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