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// SPDX-License-Identifier: (GPL-2.0 or BSD-2-Clause)
/*
* Common functions of New Generation Entropy library
* Copyright (C) 2016, Yann Collet.
*
* You can contact the author at :
* - Source repository : https://github.com/Cyan4973/FiniteStateEntropy
*/
/* *************************************
* Dependencies
***************************************/
#include "error_private.h" /* ERR_*, ERROR */
#include "fse.h"
#include "huf.h"
#include "mem.h"
/*=== Version ===*/
unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }
/*=== Error Management ===*/
unsigned FSE_isError(size_t code) { return ERR_isError(code); }
unsigned HUF_isError(size_t code) { return ERR_isError(code); }
/*-**************************************************************
* FSE NCount encoding-decoding
****************************************************************/
size_t FSE_readNCount(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;
int previous0 = 0;
if (hbSize < 4)
return ERROR(srcSize_wrong);
bitStream = ZSTD_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++;
while ((remaining > 1) & (charnum <= *maxSVPtr)) {
if (previous0) {
unsigned n0 = charnum;
while ((bitStream & 0xFFFF) == 0xFFFF) {
n0 += 24;
if (ip < iend - 5) {
ip += 2;
bitStream = ZSTD_readLE32(ip) >> bitCount;
} else {
bitStream >>= 16;
bitCount += 16;
}
}
while ((bitStream & 3) == 3) {
n0 += 3;
bitStream >>= 2;
bitCount += 2;
}
n0 += bitStream & 3;
bitCount += 2;
if (n0 > *maxSVPtr)
return ERROR(maxSymbolValue_tooSmall);
while (charnum < n0)
normalizedCounter[charnum++] = 0;
if ((ip <= iend - 7) || (ip + (bitCount >> 3) <= iend - 4)) {
ip += bitCount >> 3;
bitCount &= 7;
bitStream = ZSTD_readLE32(ip) >> bitCount;
} else {
bitStream >>= 2;
}
}
{
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 */
remaining -= count < 0 ? -count : count; /* -1 means +1 */
normalizedCounter[charnum++] = (short)count;
previous0 = !count;
while (remaining < threshold) {
nbBits--;
threshold >>= 1;
}
if ((ip <= iend - 7) || (ip + (bitCount >> 3) <= iend - 4)) {
ip += bitCount >> 3;
bitCount &= 7;
} else {
bitCount -= (int)(8 * (iend - 4 - ip));
ip = iend - 4;
}
bitStream = ZSTD_readLE32(ip) >> (bitCount & 31);
}
} /* while ((remaining>1) & (charnum<=*maxSVPtr)) */
if (remaining != 1)
return ERROR(corruption_detected);
if (bitCount > 32)
return ERROR(corruption_detected);
*maxSVPtr = charnum - 1;
ip += (bitCount + 7) >> 3;
return ip - istart;
}
/*! 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_wksp(BYTE *huffWeight, size_t hwSize, U32 *rankStats, U32 *nbSymbolsPtr, U32 *tableLogPtr, const void *src, size_t srcSize, void *workspace, size_t workspaceSize)
{
U32 weightTotal;
const BYTE *ip = (const BYTE *)src;
size_t iSize;
size_t oSize;
if (!srcSize)
return ERROR(srcSize_wrong);
iSize = ip[0];
/* 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);
oSize = FSE_decompress_wksp(huffWeight, hwSize - 1, ip + 1, iSize, 6, workspace, workspaceSize); /* max (hwSize-1) values decoded, as last one is implied */
if (FSE_isError(oSize))
return oSize;
}
/* collect weight stats */
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 = BIT_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 << BIT_highbit32(rest);
U32 const lastWeight = BIT_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;
}
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