mirror of
https://github.com/Xevion/easy7zip.git
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125 lines
4.3 KiB
C
125 lines
4.3 KiB
C
/*
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* Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under both the BSD-style license (found in the
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* LICENSE file in the root directory of this source tree) and the GPLv2 (found
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* in the COPYING file in the root directory of this source tree).
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* You may select, at your option, one of the above-listed licenses.
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*/
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#ifndef ZSTD_COUNT_H_
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#define ZSTD_COUNT_H_
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#include "mem.h"
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#if defined (__cplusplus)
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extern "C" {
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#endif
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/*-*************************************
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* Match length counter
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***************************************/
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static unsigned ZSTD_NbCommonBytes(register size_t val)
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{
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if (MEM_isLittleEndian()) {
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if (MEM_64bits()) {
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# if defined(_MSC_VER) && defined(_WIN64)
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unsigned long r = 0;
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_BitScanForward64(&r, (U64)val);
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return (unsigned)(r >> 3);
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# elif defined(__GNUC__) && (__GNUC__ >= 4)
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return (__builtin_ctzll((U64)val) >> 3);
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# else
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static const int DeBruijnBytePos[64] = { 0, 0, 0, 0, 0, 1, 1, 2,
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0, 3, 1, 3, 1, 4, 2, 7,
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0, 2, 3, 6, 1, 5, 3, 5,
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1, 3, 4, 4, 2, 5, 6, 7,
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7, 0, 1, 2, 3, 3, 4, 6,
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2, 6, 5, 5, 3, 4, 5, 6,
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7, 1, 2, 4, 6, 4, 4, 5,
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7, 2, 6, 5, 7, 6, 7, 7 };
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return DeBruijnBytePos[((U64)((val & -(long long)val) * 0x0218A392CDABBD3FULL)) >> 58];
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# endif
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}
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else { /* 32 bits */
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# if defined(_MSC_VER)
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unsigned long r = 0;
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_BitScanForward(&r, (U32)val);
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return (unsigned)(r >> 3);
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# elif defined(__GNUC__) && (__GNUC__ >= 3)
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return (__builtin_ctz((U32)val) >> 3);
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# else
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static const int DeBruijnBytePos[32] = { 0, 0, 3, 0, 3, 1, 3, 0,
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3, 2, 2, 1, 3, 2, 0, 1,
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3, 3, 1, 2, 2, 2, 2, 0,
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3, 1, 2, 0, 1, 0, 1, 1 };
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return DeBruijnBytePos[((U32)((val & -(S32)val) * 0x077CB531U)) >> 27];
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# endif
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}
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}
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else { /* Big Endian CPU */
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if (MEM_64bits()) {
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# if defined(_MSC_VER) && defined(_WIN64)
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unsigned long r = 0;
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_BitScanReverse64(&r, val);
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return (unsigned)(r >> 3);
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# elif defined(__GNUC__) && (__GNUC__ >= 4)
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return (__builtin_clzll(val) >> 3);
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# else
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unsigned r;
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const unsigned n32 = sizeof(size_t) * 4; /* calculate this way due to compiler complaining in 32-bits mode */
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if (!(val >> n32)) { r = 4; }
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else { r = 0; val >>= n32; }
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if (!(val >> 16)) { r += 2; val >>= 8; }
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else { val >>= 24; }
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r += (!val);
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return r;
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# endif
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}
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else { /* 32 bits */
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# if defined(_MSC_VER)
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unsigned long r = 0;
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_BitScanReverse(&r, (unsigned long)val);
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return (unsigned)(r >> 3);
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# elif defined(__GNUC__) && (__GNUC__ >= 3)
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return (__builtin_clz((U32)val) >> 3);
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# else
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unsigned r;
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if (!(val >> 16)) { r = 2; val >>= 8; }
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else { r = 0; val >>= 24; }
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r += (!val);
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return r;
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# endif
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}
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}
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}
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static size_t ZSTD_count(const BYTE* pIn, const BYTE* pMatch, const BYTE* const pInLimit)
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{
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const BYTE* const pStart = pIn;
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const BYTE* const pInLoopLimit = pInLimit - (sizeof(size_t) - 1);
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if (pIn < pInLoopLimit) {
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{ size_t const diff = MEM_readST(pMatch) ^ MEM_readST(pIn);
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if (diff) return ZSTD_NbCommonBytes(diff); }
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pIn += sizeof(size_t); pMatch += sizeof(size_t);
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while (pIn < pInLoopLimit) {
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size_t const diff = MEM_readST(pMatch) ^ MEM_readST(pIn);
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if (!diff) { pIn += sizeof(size_t); pMatch += sizeof(size_t); continue; }
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pIn += ZSTD_NbCommonBytes(diff);
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return (size_t)(pIn - pStart);
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}
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}
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if (MEM_64bits() && (pIn<(pInLimit - 3)) && (MEM_read32(pMatch) == MEM_read32(pIn))) { pIn += 4; pMatch += 4; }
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if ((pIn<(pInLimit - 1)) && (MEM_read16(pMatch) == MEM_read16(pIn))) { pIn += 2; pMatch += 2; }
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if ((pIn<pInLimit) && (*pMatch == *pIn)) pIn++;
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return (size_t)(pIn - pStart);
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}
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#if defined (__cplusplus)
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}
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#endif
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#endif /* ZSTD_COUNT_H_ */ |