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217 lines
8.4 KiB
C
217 lines
8.4 KiB
C
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/* ******************************************************************
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* Common functions of New Generation Entropy library
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* Copyright (c) 2016-2020, Yann Collet, Facebook, Inc.
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*
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* You can contact the author at :
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* - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy
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* - Public forum : https://groups.google.com/forum/#!forum/lz4c
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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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/* *************************************
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* Dependencies
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***************************************/
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#include "mem.h"
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#include "error_private.h" /* ERR_*, ERROR */
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#define FSE_STATIC_LINKING_ONLY /* FSE_MIN_TABLELOG */
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#include "fse.h"
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#define HUF_STATIC_LINKING_ONLY /* HUF_TABLELOG_ABSOLUTEMAX */
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#include "huf.h"
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/*=== Version ===*/
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unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }
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/*=== Error Management ===*/
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unsigned FSE_isError(size_t code) { return ERR_isError(code); }
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const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); }
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unsigned HUF_isError(size_t code) { return ERR_isError(code); }
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const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); }
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/*-**************************************************************
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* FSE NCount encoding-decoding
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****************************************************************/
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size_t FSE_readNCount (short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
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const void* headerBuffer, size_t hbSize)
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{
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const BYTE* const istart = (const BYTE*) headerBuffer;
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const BYTE* const iend = istart + hbSize;
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const BYTE* ip = istart;
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int nbBits;
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int remaining;
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int threshold;
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U32 bitStream;
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int bitCount;
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unsigned charnum = 0;
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int previous0 = 0;
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if (hbSize < 4) {
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/* This function only works when hbSize >= 4 */
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char buffer[4];
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memset(buffer, 0, sizeof(buffer));
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memcpy(buffer, headerBuffer, hbSize);
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{ size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr,
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buffer, sizeof(buffer));
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if (FSE_isError(countSize)) return countSize;
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if (countSize > hbSize) return ERROR(corruption_detected);
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return countSize;
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} }
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assert(hbSize >= 4);
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/* init */
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memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0])); /* all symbols not present in NCount have a frequency of 0 */
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bitStream = MEM_readLE32(ip);
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nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG; /* extract tableLog */
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if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);
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bitStream >>= 4;
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bitCount = 4;
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*tableLogPtr = nbBits;
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remaining = (1<<nbBits)+1;
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threshold = 1<<nbBits;
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nbBits++;
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while ((remaining>1) & (charnum<=*maxSVPtr)) {
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if (previous0) {
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unsigned n0 = charnum;
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while ((bitStream & 0xFFFF) == 0xFFFF) {
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n0 += 24;
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if (ip < iend-5) {
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ip += 2;
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bitStream = MEM_readLE32(ip) >> bitCount;
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} else {
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bitStream >>= 16;
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bitCount += 16;
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} }
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while ((bitStream & 3) == 3) {
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n0 += 3;
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bitStream >>= 2;
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bitCount += 2;
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}
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n0 += bitStream & 3;
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bitCount += 2;
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if (n0 > *maxSVPtr) return ERROR(maxSymbolValue_tooSmall);
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while (charnum < n0) normalizedCounter[charnum++] = 0;
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if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
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assert((bitCount >> 3) <= 3); /* For first condition to work */
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ip += bitCount>>3;
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bitCount &= 7;
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bitStream = MEM_readLE32(ip) >> bitCount;
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} else {
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bitStream >>= 2;
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} }
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{ int const max = (2*threshold-1) - remaining;
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int count;
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if ((bitStream & (threshold-1)) < (U32)max) {
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count = bitStream & (threshold-1);
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bitCount += nbBits-1;
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} else {
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count = bitStream & (2*threshold-1);
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if (count >= threshold) count -= max;
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bitCount += nbBits;
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}
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count--; /* extra accuracy */
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remaining -= count < 0 ? -count : count; /* -1 means +1 */
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normalizedCounter[charnum++] = (short)count;
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previous0 = !count;
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while (remaining < threshold) {
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nbBits--;
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threshold >>= 1;
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}
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if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
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ip += bitCount>>3;
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bitCount &= 7;
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} else {
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bitCount -= (int)(8 * (iend - 4 - ip));
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ip = iend - 4;
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}
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bitStream = MEM_readLE32(ip) >> (bitCount & 31);
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} } /* while ((remaining>1) & (charnum<=*maxSVPtr)) */
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if (remaining != 1) return ERROR(corruption_detected);
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if (bitCount > 32) return ERROR(corruption_detected);
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*maxSVPtr = charnum-1;
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ip += (bitCount+7)>>3;
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return ip-istart;
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}
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/*! HUF_readStats() :
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Read compact Huffman tree, saved by HUF_writeCTable().
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`huffWeight` is destination buffer.
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`rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
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@return : size read from `src` , or an error Code .
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Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
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*/
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size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,
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U32* nbSymbolsPtr, U32* tableLogPtr,
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const void* src, size_t srcSize)
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{
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U32 weightTotal;
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const BYTE* ip = (const BYTE*) src;
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size_t iSize;
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size_t oSize;
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if (!srcSize) return ERROR(srcSize_wrong);
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iSize = ip[0];
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/* memset(huffWeight, 0, hwSize); *//* is not necessary, even though some analyzer complain ... */
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if (iSize >= 128) { /* special header */
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oSize = iSize - 127;
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iSize = ((oSize+1)/2);
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if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
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if (oSize >= hwSize) return ERROR(corruption_detected);
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ip += 1;
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{ U32 n;
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for (n=0; n<oSize; n+=2) {
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huffWeight[n] = ip[n/2] >> 4;
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huffWeight[n+1] = ip[n/2] & 15;
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} } }
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else { /* header compressed with FSE (normal case) */
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FSE_DTable fseWorkspace[FSE_DTABLE_SIZE_U32(6)]; /* 6 is max possible tableLog for HUF header (maybe even 5, to be tested) */
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if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
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oSize = FSE_decompress_wksp(huffWeight, hwSize-1, ip+1, iSize, fseWorkspace, 6); /* max (hwSize-1) values decoded, as last one is implied */
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if (FSE_isError(oSize)) return oSize;
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}
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/* collect weight stats */
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memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
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weightTotal = 0;
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{ U32 n; for (n=0; n<oSize; n++) {
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if (huffWeight[n] >= HUF_TABLELOG_MAX) return ERROR(corruption_detected);
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rankStats[huffWeight[n]]++;
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weightTotal += (1 << huffWeight[n]) >> 1;
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} }
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if (weightTotal == 0) return ERROR(corruption_detected);
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/* get last non-null symbol weight (implied, total must be 2^n) */
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{ U32 const tableLog = BIT_highbit32(weightTotal) + 1;
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if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
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*tableLogPtr = tableLog;
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/* determine last weight */
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{ U32 const total = 1 << tableLog;
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U32 const rest = total - weightTotal;
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U32 const verif = 1 << BIT_highbit32(rest);
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U32 const lastWeight = BIT_highbit32(rest) + 1;
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if (verif != rest) return ERROR(corruption_detected); /* last value must be a clean power of 2 */
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huffWeight[oSize] = (BYTE)lastWeight;
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rankStats[lastWeight]++;
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} }
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/* check tree construction validity */
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if ((rankStats[1] < 2) || (rankStats[1] & 1)) return ERROR(corruption_detected); /* by construction : at least 2 elts of rank 1, must be even */
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/* results */
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*nbSymbolsPtr = (U32)(oSize+1);
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return iSize+1;
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}
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