// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause/* ****************************************************************** * Common functions of New Generation Entropy library * Copyright (c) Meta Platforms, Inc. and affiliates. * *  You can contact the author at : *  - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy *  - Public forum : https://groups.google.com/forum/#!forum/lz4c * * This source code is licensed under both the BSD-style license (found in the * LICENSE file in the root directory of this source tree) and the GPLv2 (found * in the COPYING file in the root directory of this source tree). * You may select, at your option, one of the above-listed licenses.****************************************************************** */ /* **************************************  Dependencies***************************************/#include "mem.h"#include "error_private.h"       /* ERR_*, ERROR */#define FSE_STATIC_LINKING_ONLY  /* FSE_MIN_TABLELOG */#include "fse.h"#include "huf.h"#include "bits.h"                /* ZSDT_highbit32, ZSTD_countTrailingZeros32 */  /*===   Version   ===*/unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }  /*===   Error Management   ===*/unsigned FSE_isError(size_t code) { return ERR_isError(code); }const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); } unsigned HUF_isError(size_t code) { return ERR_isError(code); }const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); }  /*-***************************************************************  FSE NCount encoding-decoding****************************************************************/FORCE_INLINE_TEMPLATEsize_t FSE_readNCount_body(short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,                           const void* headerBuffer, size_t hbSize){    const BYTE* const istart = (const BYTE*) headerBuffer;    const BYTE* const iend = istart + hbSize;    const BYTE* ip = istart;    int nbBits;    int remaining;    int threshold;    U32 bitStream;    int bitCount;    unsigned charnum = 0;    unsigned const maxSV1 = *maxSVPtr + 1;    int previous0 = 0;     if (hbSize < 8) {        /* This function only works when hbSize >= 8 */        char buffer[8] = {0};        ZSTD_memcpy(buffer, headerBuffer, hbSize);        {   size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr,                                                    buffer, sizeof(buffer));            if (FSE_isError(countSize)) return countSize;            if (countSize > hbSize) return ERROR(corruption_detected);            return countSize;    }   }    assert(hbSize >= 8);     /* init */    ZSTD_memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0]));   /* all symbols not present in NCount have a frequency of 0 */    bitStream = MEM_readLE32(ip);    nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG;   /* extract tableLog */    if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);    bitStream >>= 4;    bitCount = 4;    *tableLogPtr = nbBits;    remaining = (1<<nbBits)+1;    threshold = 1<<nbBits;    nbBits++;     for (;;) {        if (previous0) {            /* Count the number of repeats. Each time the             * 2-bit repeat code is 0b11 there is another             * repeat.             * Avoid UB by setting the high bit to 1.             */            int repeats = ZSTD_countTrailingZeros32(~bitStream | 0x80000000) >> 1;            while (repeats >= 12) {                charnum += 3 * 12;                if (LIKELY(ip <= iend-7)) {                    ip += 3;                } else {                    bitCount -= (int)(8 * (iend - 7 - ip));                    bitCount &= 31;                    ip = iend - 4;                }                bitStream = MEM_readLE32(ip) >> bitCount;                repeats = ZSTD_countTrailingZeros32(~bitStream | 0x80000000) >> 1;            }            charnum += 3 * repeats;            bitStream >>= 2 * repeats;            bitCount += 2 * repeats;             /* Add the final repeat which isn't 0b11. */            assert((bitStream & 3) < 3);            charnum += bitStream & 3;            bitCount += 2;             /* This is an error, but break and return an error             * at the end, because returning out of a loop makes             * it harder for the compiler to optimize.             */            if (charnum >= maxSV1) break;             /* We don't need to set the normalized count to 0             * because we already memset the whole buffer to 0.             */             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {                assert((bitCount >> 3) <= 3); /* For first condition to work */                ip += bitCount>>3;                bitCount &= 7;            } else {                bitCount -= (int)(8 * (iend - 4 - ip));                bitCount &= 31;                ip = iend - 4;            }            bitStream = MEM_readLE32(ip) >> bitCount;        }        {            int const max = (2*threshold-1) - remaining;            int count;             if ((bitStream & (threshold-1)) < (U32)max) {                count = bitStream & (threshold-1);                bitCount += nbBits-1;            } else {                count = bitStream & (2*threshold-1);                if (count >= threshold) count -= max;                bitCount += nbBits;            }             count--;   /* extra accuracy */            /* When it matters (small blocks), this is a             * predictable branch, because we don't use -1.             */            if (count >= 0) {                remaining -= count;            } else {                assert(count == -1);                remaining += count;            }            normalizedCounter[charnum++] = (short)count;            previous0 = !count;             assert(threshold > 1);            if (remaining < threshold) {                /* This branch can be folded into the                 * threshold update condition because we                 * know that threshold > 1.                 */                if (remaining <= 1) break;                nbBits = ZSTD_highbit32(remaining) + 1;                threshold = 1 << (nbBits - 1);            }            if (charnum >= maxSV1) break;             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {                ip += bitCount>>3;                bitCount &= 7;            } else {                bitCount -= (int)(8 * (iend - 4 - ip));                bitCount &= 31;                ip = iend - 4;            }            bitStream = MEM_readLE32(ip) >> bitCount;    }   }    if (remaining != 1) return ERROR(corruption_detected);    /* Only possible when there are too many zeros. */    if (charnum > maxSV1) return ERROR(maxSymbolValue_tooSmall);    if (bitCount > 32) return ERROR(corruption_detected);    *maxSVPtr = charnum-1;     ip += (bitCount+7)>>3;    return ip-istart;} /* Avoids the FORCE_INLINE of the _body() function. */static size_t FSE_readNCount_body_default(        short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,        const void* headerBuffer, size_t hbSize){    return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);} #if DYNAMIC_BMI2BMI2_TARGET_ATTRIBUTE static size_t FSE_readNCount_body_bmi2(        short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,        const void* headerBuffer, size_t hbSize){    return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);}#endif size_t FSE_readNCount_bmi2(        short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,        const void* headerBuffer, size_t hbSize, int bmi2){#if DYNAMIC_BMI2    if (bmi2) {        return FSE_readNCount_body_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);    }#endif    (void)bmi2;    return FSE_readNCount_body_default(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);} size_t FSE_readNCount(        short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,        const void* headerBuffer, size_t hbSize){    return FSE_readNCount_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize, /* bmi2 */ 0);}  /*! HUF_readStats() :    Read compact Huffman tree, saved by HUF_writeCTable().    `huffWeight` is destination buffer.    `rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.    @return : size read from `src` , or an error Code .    Note : Needed by HUF_readCTable() and HUF_readDTableX?() .*/size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,                     U32* nbSymbolsPtr, U32* tableLogPtr,                     const void* src, size_t srcSize){    U32 wksp[HUF_READ_STATS_WORKSPACE_SIZE_U32];    return HUF_readStats_wksp(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, wksp, sizeof(wksp), /* flags */ 0);} FORCE_INLINE_TEMPLATE size_tHUF_readStats_body(BYTE* huffWeight, size_t hwSize, U32* rankStats,                   U32* nbSymbolsPtr, U32* tableLogPtr,                   const void* src, size_t srcSize,                   void* workSpace, size_t wkspSize,                   int bmi2){    U32 weightTotal;    const BYTE* ip = (const BYTE*) src;    size_t iSize;    size_t oSize;     if (!srcSize) return ERROR(srcSize_wrong);    iSize = ip[0];    /* ZSTD_memset(huffWeight, 0, hwSize);   *//* is not necessary, even though some analyzer complain ... */     if (iSize >= 128) {  /* special header */        oSize = iSize - 127;        iSize = ((oSize+1)/2);        if (iSize+1 > srcSize) return ERROR(srcSize_wrong);        if (oSize >= hwSize) return ERROR(corruption_detected);        ip += 1;        {   U32 n;            for (n=0; n<oSize; n+=2) {                huffWeight[n]   = ip[n/2] >> 4;                huffWeight[n+1] = ip[n/2] & 15;    }   }   }    else  {   /* header compressed with FSE (normal case) */        if (iSize+1 > srcSize) return ERROR(srcSize_wrong);        /* max (hwSize-1) values decoded, as last one is implied */        oSize = FSE_decompress_wksp_bmi2(huffWeight, hwSize-1, ip+1, iSize, 6, workSpace, wkspSize, bmi2);        if (FSE_isError(oSize)) return oSize;    }     /* collect weight stats */    ZSTD_memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));    weightTotal = 0;    {   U32 n; for (n=0; n<oSize; n++) {            if (huffWeight[n] > HUF_TABLELOG_MAX) return ERROR(corruption_detected);            rankStats[huffWeight[n]]++;            weightTotal += (1 << huffWeight[n]) >> 1;    }   }    if (weightTotal == 0) return ERROR(corruption_detected);     /* get last non-null symbol weight (implied, total must be 2^n) */    {   U32 const tableLog = ZSTD_highbit32(weightTotal) + 1;        if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected);        *tableLogPtr = tableLog;        /* determine last weight */        {   U32 const total = 1 << tableLog;            U32 const rest = total - weightTotal;            U32 const verif = 1 << ZSTD_highbit32(rest);            U32 const lastWeight = ZSTD_highbit32(rest) + 1;            if (verif != rest) return ERROR(corruption_detected);    /* last value must be a clean power of 2 */            huffWeight[oSize] = (BYTE)lastWeight;            rankStats[lastWeight]++;    }   }     /* check tree construction validity */    if ((rankStats[1] < 2) || (rankStats[1] & 1)) return ERROR(corruption_detected);   /* by construction : at least 2 elts of rank 1, must be even */     /* results */    *nbSymbolsPtr = (U32)(oSize+1);    return iSize+1;} /* Avoids the FORCE_INLINE of the _body() function. */static size_t HUF_readStats_body_default(BYTE* huffWeight, size_t hwSize, U32* rankStats,                     U32* nbSymbolsPtr, U32* tableLogPtr,                     const void* src, size_t srcSize,                     void* workSpace, size_t wkspSize){    return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 0);} #if DYNAMIC_BMI2static BMI2_TARGET_ATTRIBUTE size_t HUF_readStats_body_bmi2(BYTE* huffWeight, size_t hwSize, U32* rankStats,                     U32* nbSymbolsPtr, U32* tableLogPtr,                     const void* src, size_t srcSize,                     void* workSpace, size_t wkspSize){    return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 1);}#endif size_t HUF_readStats_wksp(BYTE* huffWeight, size_t hwSize, U32* rankStats,                     U32* nbSymbolsPtr, U32* tableLogPtr,                     const void* src, size_t srcSize,                     void* workSpace, size_t wkspSize,                     int flags){#if DYNAMIC_BMI2    if (flags & HUF_flags_bmi2) {        return HUF_readStats_body_bmi2(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);    }#endif    (void)flags;    return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);}