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godot/thirdparty/zstd/compress/huf_compress.c

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/* ******************************************************************
* Huffman encoder, part 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.
****************************************************************** */
/* **************************************************************
* Compiler specifics
****************************************************************/
#ifdef _MSC_VER /* Visual Studio */
# pragma warning(disable : 4127) /* disable: C4127: conditional expression is constant */
#endif
/* **************************************************************
* Includes
****************************************************************/
#include "../common/zstd_deps.h" /* ZSTD_memcpy, ZSTD_memset */
#include "../common/compiler.h"
#include "../common/bitstream.h"
#include "hist.h"
#define FSE_STATIC_LINKING_ONLY /* FSE_optimalTableLog_internal */
#include "../common/fse.h" /* header compression */
#include "../common/huf.h"
#include "../common/error_private.h"
#include "../common/bits.h" /* ZSTD_highbit32 */
/* **************************************************************
* Error Management
****************************************************************/
#define HUF_isError ERR_isError
#define HUF_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c) /* use only *after* variable declarations */
/* **************************************************************
* Required declarations
****************************************************************/
typedef struct nodeElt_s {
U32 count;
U16 parent;
BYTE byte;
BYTE nbBits;
} nodeElt;
/* **************************************************************
* Debug Traces
****************************************************************/
#if DEBUGLEVEL >= 2
static size_t showU32(const U32* arr, size_t size)
{
size_t u;
for (u=0; u<size; u++) {
RAWLOG(6, " %u", arr[u]); (void)arr;
}
RAWLOG(6, " \n");
return size;
}
static size_t HUF_getNbBits(HUF_CElt elt);
static size_t showCTableBits(const HUF_CElt* ctable, size_t size)
{
size_t u;
for (u=0; u<size; u++) {
RAWLOG(6, " %zu", HUF_getNbBits(ctable[u])); (void)ctable;
}
RAWLOG(6, " \n");
return size;
}
static size_t showHNodeSymbols(const nodeElt* hnode, size_t size)
{
size_t u;
for (u=0; u<size; u++) {
RAWLOG(6, " %u", hnode[u].byte); (void)hnode;
}
RAWLOG(6, " \n");
return size;
}
static size_t showHNodeBits(const nodeElt* hnode, size_t size)
{
size_t u;
for (u=0; u<size; u++) {
RAWLOG(6, " %u", hnode[u].nbBits); (void)hnode;
}
RAWLOG(6, " \n");
return size;
}
#endif
/* *******************************************************
* HUF : Huffman block compression
*********************************************************/
#define HUF_WORKSPACE_MAX_ALIGNMENT 8
static void* HUF_alignUpWorkspace(void* workspace, size_t* workspaceSizePtr, size_t align)
{
size_t const mask = align - 1;
size_t const rem = (size_t)workspace & mask;
size_t const add = (align - rem) & mask;
BYTE* const aligned = (BYTE*)workspace + add;
assert((align & (align - 1)) == 0); /* pow 2 */
assert(align <= HUF_WORKSPACE_MAX_ALIGNMENT);
if (*workspaceSizePtr >= add) {
assert(add < align);
assert(((size_t)aligned & mask) == 0);
*workspaceSizePtr -= add;
return aligned;
} else {
*workspaceSizePtr = 0;
return NULL;
}
}
/* HUF_compressWeights() :
* Same as FSE_compress(), but dedicated to huff0's weights compression.
* The use case needs much less stack memory.
* Note : all elements within weightTable are supposed to be <= HUF_TABLELOG_MAX.
*/
#define MAX_FSE_TABLELOG_FOR_HUFF_HEADER 6
typedef struct {
FSE_CTable CTable[FSE_CTABLE_SIZE_U32(MAX_FSE_TABLELOG_FOR_HUFF_HEADER, HUF_TABLELOG_MAX)];
U32 scratchBuffer[FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(HUF_TABLELOG_MAX, MAX_FSE_TABLELOG_FOR_HUFF_HEADER)];
unsigned count[HUF_TABLELOG_MAX+1];
S16 norm[HUF_TABLELOG_MAX+1];
} HUF_CompressWeightsWksp;
static size_t
HUF_compressWeights(void* dst, size_t dstSize,
const void* weightTable, size_t wtSize,
void* workspace, size_t workspaceSize)
{
BYTE* const ostart = (BYTE*) dst;
BYTE* op = ostart;
BYTE* const oend = ostart + dstSize;
unsigned maxSymbolValue = HUF_TABLELOG_MAX;
U32 tableLog = MAX_FSE_TABLELOG_FOR_HUFF_HEADER;
HUF_CompressWeightsWksp* wksp = (HUF_CompressWeightsWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32));
if (workspaceSize < sizeof(HUF_CompressWeightsWksp)) return ERROR(GENERIC);
/* init conditions */
if (wtSize <= 1) return 0; /* Not compressible */
/* Scan input and build symbol stats */
{ unsigned const maxCount = HIST_count_simple(wksp->count, &maxSymbolValue, weightTable, wtSize); /* never fails */
if (maxCount == wtSize) return 1; /* only a single symbol in src : rle */
if (maxCount == 1) return 0; /* each symbol present maximum once => not compressible */
}
tableLog = FSE_optimalTableLog(tableLog, wtSize, maxSymbolValue);
CHECK_F( FSE_normalizeCount(wksp->norm, tableLog, wksp->count, wtSize, maxSymbolValue, /* useLowProbCount */ 0) );
/* Write table description header */
{ CHECK_V_F(hSize, FSE_writeNCount(op, (size_t)(oend-op), wksp->norm, maxSymbolValue, tableLog) );
op += hSize;
}
/* Compress */
CHECK_F( FSE_buildCTable_wksp(wksp->CTable, wksp->norm, maxSymbolValue, tableLog, wksp->scratchBuffer, sizeof(wksp->scratchBuffer)) );
{ CHECK_V_F(cSize, FSE_compress_usingCTable(op, (size_t)(oend - op), weightTable, wtSize, wksp->CTable) );
if (cSize == 0) return 0; /* not enough space for compressed data */
op += cSize;
}
return (size_t)(op-ostart);
}
static size_t HUF_getNbBits(HUF_CElt elt)
{
return elt & 0xFF;
}
static size_t HUF_getNbBitsFast(HUF_CElt elt)
{
return elt;
}
static size_t HUF_getValue(HUF_CElt elt)
{
return elt & ~(size_t)0xFF;
}
static size_t HUF_getValueFast(HUF_CElt elt)
{
return elt;
}
static void HUF_setNbBits(HUF_CElt* elt, size_t nbBits)
{
assert(nbBits <= HUF_TABLELOG_ABSOLUTEMAX);
*elt = nbBits;
}
static void HUF_setValue(HUF_CElt* elt, size_t value)
{
size_t const nbBits = HUF_getNbBits(*elt);
if (nbBits > 0) {
assert((value >> nbBits) == 0);
*elt |= value << (sizeof(HUF_CElt) * 8 - nbBits);
}
}
HUF_CTableHeader HUF_readCTableHeader(HUF_CElt const* ctable)
{
HUF_CTableHeader header;
ZSTD_memcpy(&header, ctable, sizeof(header));
return header;
}
static void HUF_writeCTableHeader(HUF_CElt* ctable, U32 tableLog, U32 maxSymbolValue)
{
HUF_CTableHeader header;
HUF_STATIC_ASSERT(sizeof(ctable[0]) == sizeof(header));
ZSTD_memset(&header, 0, sizeof(header));
assert(tableLog < 256);
header.tableLog = (BYTE)tableLog;
assert(maxSymbolValue < 256);
header.maxSymbolValue = (BYTE)maxSymbolValue;
ZSTD_memcpy(ctable, &header, sizeof(header));
}
typedef struct {
HUF_CompressWeightsWksp wksp;
BYTE bitsToWeight[HUF_TABLELOG_MAX + 1]; /* precomputed conversion table */
BYTE huffWeight[HUF_SYMBOLVALUE_MAX];
} HUF_WriteCTableWksp;
size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize,
const HUF_CElt* CTable, unsigned maxSymbolValue, unsigned huffLog,
void* workspace, size_t workspaceSize)
{
HUF_CElt const* const ct = CTable + 1;
BYTE* op = (BYTE*)dst;
U32 n;
HUF_WriteCTableWksp* wksp = (HUF_WriteCTableWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32));
HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE >= sizeof(HUF_WriteCTableWksp));
assert(HUF_readCTableHeader(CTable).maxSymbolValue == maxSymbolValue);
assert(HUF_readCTableHeader(CTable).tableLog == huffLog);
/* check conditions */
if (workspaceSize < sizeof(HUF_WriteCTableWksp)) return ERROR(GENERIC);
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
/* convert to weight */
wksp->bitsToWeight[0] = 0;
for (n=1; n<huffLog+1; n++)
wksp->bitsToWeight[n] = (BYTE)(huffLog + 1 - n);
for (n=0; n<maxSymbolValue; n++)
wksp->huffWeight[n] = wksp->bitsToWeight[HUF_getNbBits(ct[n])];
/* attempt weights compression by FSE */
if (maxDstSize < 1) return ERROR(dstSize_tooSmall);
{ CHECK_V_F(hSize, HUF_compressWeights(op+1, maxDstSize-1, wksp->huffWeight, maxSymbolValue, &wksp->wksp, sizeof(wksp->wksp)) );
if ((hSize>1) & (hSize < maxSymbolValue/2)) { /* FSE compressed */
op[0] = (BYTE)hSize;
return hSize+1;
} }
/* write raw values as 4-bits (max : 15) */
if (maxSymbolValue > (256-128)) return ERROR(GENERIC); /* should not happen : likely means source cannot be compressed */
if (((maxSymbolValue+1)/2) + 1 > maxDstSize) return ERROR(dstSize_tooSmall); /* not enough space within dst buffer */
op[0] = (BYTE)(128 /*special case*/ + (maxSymbolValue-1));
wksp->huffWeight[maxSymbolValue] = 0; /* to be sure it doesn't cause msan issue in final combination */
for (n=0; n<maxSymbolValue; n+=2)
op[(n/2)+1] = (BYTE)((wksp->huffWeight[n] << 4) + wksp->huffWeight[n+1]);
return ((maxSymbolValue+1)/2) + 1;
}
size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize, unsigned* hasZeroWeights)
{
BYTE huffWeight[HUF_SYMBOLVALUE_MAX + 1]; /* init not required, even though some static analyzer may complain */
U32 rankVal[HUF_TABLELOG_ABSOLUTEMAX + 1]; /* large enough for values from 0 to 16 */
U32 tableLog = 0;
U32 nbSymbols = 0;
HUF_CElt* const ct = CTable + 1;
/* get symbol weights */
CHECK_V_F(readSize, HUF_readStats(huffWeight, HUF_SYMBOLVALUE_MAX+1, rankVal, &nbSymbols, &tableLog, src, srcSize));
*hasZeroWeights = (rankVal[0] > 0);
/* check result */
if (tableLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
if (nbSymbols > *maxSymbolValuePtr+1) return ERROR(maxSymbolValue_tooSmall);
*maxSymbolValuePtr = nbSymbols - 1;
HUF_writeCTableHeader(CTable, tableLog, *maxSymbolValuePtr);
/* Prepare base value per rank */
{ U32 n, nextRankStart = 0;
for (n=1; n<=tableLog; n++) {
U32 curr = nextRankStart;
nextRankStart += (rankVal[n] << (n-1));
rankVal[n] = curr;
} }
/* fill nbBits */
{ U32 n; for (n=0; n<nbSymbols; n++) {
const U32 w = huffWeight[n];
HUF_setNbBits(ct + n, (BYTE)(tableLog + 1 - w) & -(w != 0));
} }
/* fill val */
{ U16 nbPerRank[HUF_TABLELOG_MAX+2] = {0}; /* support w=0=>n=tableLog+1 */
U16 valPerRank[HUF_TABLELOG_MAX+2] = {0};
{ U32 n; for (n=0; n<nbSymbols; n++) nbPerRank[HUF_getNbBits(ct[n])]++; }
/* determine stating value per rank */
valPerRank[tableLog+1] = 0; /* for w==0 */
{ U16 min = 0;
U32 n; for (n=tableLog; n>0; n--) { /* start at n=tablelog <-> w=1 */
valPerRank[n] = min; /* get starting value within each rank */
min += nbPerRank[n];
min >>= 1;
} }
/* assign value within rank, symbol order */
{ U32 n; for (n=0; n<nbSymbols; n++) HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++); }
}
return readSize;
}
U32 HUF_getNbBitsFromCTable(HUF_CElt const* CTable, U32 symbolValue)
{
const HUF_CElt* const ct = CTable + 1;
assert(symbolValue <= HUF_SYMBOLVALUE_MAX);
if (symbolValue > HUF_readCTableHeader(CTable).maxSymbolValue)
return 0;
return (U32)HUF_getNbBits(ct[symbolValue]);
}
/**
* HUF_setMaxHeight():
* Try to enforce @targetNbBits on the Huffman tree described in @huffNode.
*
* It attempts to convert all nodes with nbBits > @targetNbBits
* to employ @targetNbBits instead. Then it adjusts the tree
* so that it remains a valid canonical Huffman tree.
*
* @pre The sum of the ranks of each symbol == 2^largestBits,
* where largestBits == huffNode[lastNonNull].nbBits.
* @post The sum of the ranks of each symbol == 2^largestBits,
* where largestBits is the return value (expected <= targetNbBits).
*
* @param huffNode The Huffman tree modified in place to enforce targetNbBits.
* It's presumed sorted, from most frequent to rarest symbol.
* @param lastNonNull The symbol with the lowest count in the Huffman tree.
* @param targetNbBits The allowed number of bits, which the Huffman tree
* may not respect. After this function the Huffman tree will
* respect targetNbBits.
* @return The maximum number of bits of the Huffman tree after adjustment.
*/
static U32 HUF_setMaxHeight(nodeElt* huffNode, U32 lastNonNull, U32 targetNbBits)
{
const U32 largestBits = huffNode[lastNonNull].nbBits;
/* early exit : no elt > targetNbBits, so the tree is already valid. */
if (largestBits <= targetNbBits) return largestBits;
DEBUGLOG(5, "HUF_setMaxHeight (targetNbBits = %u)", targetNbBits);
/* there are several too large elements (at least >= 2) */
{ int totalCost = 0;
const U32 baseCost = 1 << (largestBits - targetNbBits);
int n = (int)lastNonNull;
/* Adjust any ranks > targetNbBits to targetNbBits.
* Compute totalCost, which is how far the sum of the ranks is
* we are over 2^largestBits after adjust the offending ranks.
*/
while (huffNode[n].nbBits > targetNbBits) {
totalCost += baseCost - (1 << (largestBits - huffNode[n].nbBits));
huffNode[n].nbBits = (BYTE)targetNbBits;
n--;
}
/* n stops at huffNode[n].nbBits <= targetNbBits */
assert(huffNode[n].nbBits <= targetNbBits);
/* n end at index of smallest symbol using < targetNbBits */
while (huffNode[n].nbBits == targetNbBits) --n;
/* renorm totalCost from 2^largestBits to 2^targetNbBits
* note : totalCost is necessarily a multiple of baseCost */
assert(((U32)totalCost & (baseCost - 1)) == 0);
totalCost >>= (largestBits - targetNbBits);
assert(totalCost > 0);
/* repay normalized cost */
{ U32 const noSymbol = 0xF0F0F0F0;
U32 rankLast[HUF_TABLELOG_MAX+2];
/* Get pos of last (smallest = lowest cum. count) symbol per rank */
ZSTD_memset(rankLast, 0xF0, sizeof(rankLast));
{ U32 currentNbBits = targetNbBits;
int pos;
for (pos=n ; pos >= 0; pos--) {
if (huffNode[pos].nbBits >= currentNbBits) continue;
currentNbBits = huffNode[pos].nbBits; /* < targetNbBits */
rankLast[targetNbBits-currentNbBits] = (U32)pos;
} }
while (totalCost > 0) {
/* Try to reduce the next power of 2 above totalCost because we
* gain back half the rank.
*/
U32 nBitsToDecrease = ZSTD_highbit32((U32)totalCost) + 1;
for ( ; nBitsToDecrease > 1; nBitsToDecrease--) {
U32 const highPos = rankLast[nBitsToDecrease];
U32 const lowPos = rankLast[nBitsToDecrease-1];
if (highPos == noSymbol) continue;
/* Decrease highPos if no symbols of lowPos or if it is
* not cheaper to remove 2 lowPos than highPos.
*/
if (lowPos == noSymbol) break;
{ U32 const highTotal = huffNode[highPos].count;
U32 const lowTotal = 2 * huffNode[lowPos].count;
if (highTotal <= lowTotal) break;
} }
/* only triggered when no more rank 1 symbol left => find closest one (note : there is necessarily at least one !) */
assert(rankLast[nBitsToDecrease] != noSymbol || nBitsToDecrease == 1);
/* HUF_MAX_TABLELOG test just to please gcc 5+; but it should not be necessary */
while ((nBitsToDecrease<=HUF_TABLELOG_MAX) && (rankLast[nBitsToDecrease] == noSymbol))
nBitsToDecrease++;
assert(rankLast[nBitsToDecrease] != noSymbol);
/* Increase the number of bits to gain back half the rank cost. */
totalCost -= 1 << (nBitsToDecrease-1);
huffNode[rankLast[nBitsToDecrease]].nbBits++;
/* Fix up the new rank.
* If the new rank was empty, this symbol is now its smallest.
* Otherwise, this symbol will be the largest in the new rank so no adjustment.
*/
if (rankLast[nBitsToDecrease-1] == noSymbol)
rankLast[nBitsToDecrease-1] = rankLast[nBitsToDecrease];
/* Fix up the old rank.
* If the symbol was at position 0, meaning it was the highest weight symbol in the tree,
* it must be the only symbol in its rank, so the old rank now has no symbols.
* Otherwise, since the Huffman nodes are sorted by count, the previous position is now
* the smallest node in the rank. If the previous position belongs to a different rank,
* then the rank is now empty.
*/
if (rankLast[nBitsToDecrease] == 0) /* special case, reached largest symbol */
rankLast[nBitsToDecrease] = noSymbol;
else {
rankLast[nBitsToDecrease]--;
if (huffNode[rankLast[nBitsToDecrease]].nbBits != targetNbBits-nBitsToDecrease)
rankLast[nBitsToDecrease] = noSymbol; /* this rank is now empty */
}
} /* while (totalCost > 0) */
/* If we've removed too much weight, then we have to add it back.
* To avoid overshooting again, we only adjust the smallest rank.
* We take the largest nodes from the lowest rank 0 and move them
* to rank 1. There's guaranteed to be enough rank 0 symbols because
* TODO.
*/
while (totalCost < 0) { /* Sometimes, cost correction overshoot */
/* special case : no rank 1 symbol (using targetNbBits-1);
* let's create one from largest rank 0 (using targetNbBits).
*/
if (rankLast[1] == noSymbol) {
while (huffNode[n].nbBits == targetNbBits) n--;
huffNode[n+1].nbBits--;
assert(n >= 0);
rankLast[1] = (U32)(n+1);
totalCost++;
continue;
}
huffNode[ rankLast[1] + 1 ].nbBits--;
rankLast[1]++;
totalCost ++;
}
} /* repay normalized cost */
} /* there are several too large elements (at least >= 2) */
return targetNbBits;
}
typedef struct {
U16 base;
U16 curr;
} rankPos;
typedef nodeElt huffNodeTable[2 * (HUF_SYMBOLVALUE_MAX + 1)];
/* Number of buckets available for HUF_sort() */
#define RANK_POSITION_TABLE_SIZE 192
typedef struct {
huffNodeTable huffNodeTbl;
rankPos rankPosition[RANK_POSITION_TABLE_SIZE];
} HUF_buildCTable_wksp_tables;
/* RANK_POSITION_DISTINCT_COUNT_CUTOFF == Cutoff point in HUF_sort() buckets for which we use log2 bucketing.
* Strategy is to use as many buckets as possible for representing distinct
* counts while using the remainder to represent all "large" counts.
*
* To satisfy this requirement for 192 buckets, we can do the following:
* Let buckets 0-166 represent distinct counts of [0, 166]
* Let buckets 166 to 192 represent all remaining counts up to RANK_POSITION_MAX_COUNT_LOG using log2 bucketing.
*/
#define RANK_POSITION_MAX_COUNT_LOG 32
#define RANK_POSITION_LOG_BUCKETS_BEGIN ((RANK_POSITION_TABLE_SIZE - 1) - RANK_POSITION_MAX_COUNT_LOG - 1 /* == 158 */)
#define RANK_POSITION_DISTINCT_COUNT_CUTOFF (RANK_POSITION_LOG_BUCKETS_BEGIN + ZSTD_highbit32(RANK_POSITION_LOG_BUCKETS_BEGIN) /* == 166 */)
/* Return the appropriate bucket index for a given count. See definition of
* RANK_POSITION_DISTINCT_COUNT_CUTOFF for explanation of bucketing strategy.
*/
static U32 HUF_getIndex(U32 const count) {
return (count < RANK_POSITION_DISTINCT_COUNT_CUTOFF)
? count
: ZSTD_highbit32(count) + RANK_POSITION_LOG_BUCKETS_BEGIN;
}
/* Helper swap function for HUF_quickSortPartition() */
static void HUF_swapNodes(nodeElt* a, nodeElt* b) {
nodeElt tmp = *a;
*a = *b;
*b = tmp;
}
/* Returns 0 if the huffNode array is not sorted by descending count */
MEM_STATIC int HUF_isSorted(nodeElt huffNode[], U32 const maxSymbolValue1) {
U32 i;
for (i = 1; i < maxSymbolValue1; ++i) {
if (huffNode[i].count > huffNode[i-1].count) {
return 0;
}
}
return 1;
}
/* Insertion sort by descending order */
HINT_INLINE void HUF_insertionSort(nodeElt huffNode[], int const low, int const high) {
int i;
int const size = high-low+1;
huffNode += low;
for (i = 1; i < size; ++i) {
nodeElt const key = huffNode[i];
int j = i - 1;
while (j >= 0 && huffNode[j].count < key.count) {
huffNode[j + 1] = huffNode[j];
j--;
}
huffNode[j + 1] = key;
}
}
/* Pivot helper function for quicksort. */
static int HUF_quickSortPartition(nodeElt arr[], int const low, int const high) {
/* Simply select rightmost element as pivot. "Better" selectors like
* median-of-three don't experimentally appear to have any benefit.
*/
U32 const pivot = arr[high].count;
int i = low - 1;
int j = low;
for ( ; j < high; j++) {
if (arr[j].count > pivot) {
i++;
HUF_swapNodes(&arr[i], &arr[j]);
}
}
HUF_swapNodes(&arr[i + 1], &arr[high]);
return i + 1;
}
/* Classic quicksort by descending with partially iterative calls
* to reduce worst case callstack size.
*/
static void HUF_simpleQuickSort(nodeElt arr[], int low, int high) {
int const kInsertionSortThreshold = 8;
if (high - low < kInsertionSortThreshold) {
HUF_insertionSort(arr, low, high);
return;
}
while (low < high) {
int const idx = HUF_quickSortPartition(arr, low, high);
if (idx - low < high - idx) {
HUF_simpleQuickSort(arr, low, idx - 1);
low = idx + 1;
} else {
HUF_simpleQuickSort(arr, idx + 1, high);
high = idx - 1;
}
}
}
/**
* HUF_sort():
* Sorts the symbols [0, maxSymbolValue] by count[symbol] in decreasing order.
* This is a typical bucket sorting strategy that uses either quicksort or insertion sort to sort each bucket.
*
* @param[out] huffNode Sorted symbols by decreasing count. Only members `.count` and `.byte` are filled.
* Must have (maxSymbolValue + 1) entries.
* @param[in] count Histogram of the symbols.
* @param[in] maxSymbolValue Maximum symbol value.
* @param rankPosition This is a scratch workspace. Must have RANK_POSITION_TABLE_SIZE entries.
*/
static void HUF_sort(nodeElt huffNode[], const unsigned count[], U32 const maxSymbolValue, rankPos rankPosition[]) {
U32 n;
U32 const maxSymbolValue1 = maxSymbolValue+1;
/* Compute base and set curr to base.
* For symbol s let lowerRank = HUF_getIndex(count[n]) and rank = lowerRank + 1.
* See HUF_getIndex to see bucketing strategy.
* We attribute each symbol to lowerRank's base value, because we want to know where
* each rank begins in the output, so for rank R we want to count ranks R+1 and above.
*/
ZSTD_memset(rankPosition, 0, sizeof(*rankPosition) * RANK_POSITION_TABLE_SIZE);
for (n = 0; n < maxSymbolValue1; ++n) {
U32 lowerRank = HUF_getIndex(count[n]);
assert(lowerRank < RANK_POSITION_TABLE_SIZE - 1);
rankPosition[lowerRank].base++;
}
assert(rankPosition[RANK_POSITION_TABLE_SIZE - 1].base == 0);
/* Set up the rankPosition table */
for (n = RANK_POSITION_TABLE_SIZE - 1; n > 0; --n) {
rankPosition[n-1].base += rankPosition[n].base;
rankPosition[n-1].curr = rankPosition[n-1].base;
}
/* Insert each symbol into their appropriate bucket, setting up rankPosition table. */
for (n = 0; n < maxSymbolValue1; ++n) {
U32 const c = count[n];
U32 const r = HUF_getIndex(c) + 1;
U32 const pos = rankPosition[r].curr++;
assert(pos < maxSymbolValue1);
huffNode[pos].count = c;
huffNode[pos].byte = (BYTE)n;
}
/* Sort each bucket. */
for (n = RANK_POSITION_DISTINCT_COUNT_CUTOFF; n < RANK_POSITION_TABLE_SIZE - 1; ++n) {
int const bucketSize = rankPosition[n].curr - rankPosition[n].base;
U32 const bucketStartIdx = rankPosition[n].base;
if (bucketSize > 1) {
assert(bucketStartIdx < maxSymbolValue1);
HUF_simpleQuickSort(huffNode + bucketStartIdx, 0, bucketSize-1);
}
}
assert(HUF_isSorted(huffNode, maxSymbolValue1));
}
/** HUF_buildCTable_wksp() :
* Same as HUF_buildCTable(), but using externally allocated scratch buffer.
* `workSpace` must be aligned on 4-bytes boundaries, and be at least as large as sizeof(HUF_buildCTable_wksp_tables).
*/
#define STARTNODE (HUF_SYMBOLVALUE_MAX+1)
/* HUF_buildTree():
* Takes the huffNode array sorted by HUF_sort() and builds an unlimited-depth Huffman tree.
*
* @param huffNode The array sorted by HUF_sort(). Builds the Huffman tree in this array.
* @param maxSymbolValue The maximum symbol value.
* @return The smallest node in the Huffman tree (by count).
*/
static int HUF_buildTree(nodeElt* huffNode, U32 maxSymbolValue)
{
nodeElt* const huffNode0 = huffNode - 1;
int nonNullRank;
int lowS, lowN;
int nodeNb = STARTNODE;
int n, nodeRoot;
DEBUGLOG(5, "HUF_buildTree (alphabet size = %u)", maxSymbolValue + 1);
/* init for parents */
nonNullRank = (int)maxSymbolValue;
while(huffNode[nonNullRank].count == 0) nonNullRank--;
lowS = nonNullRank; nodeRoot = nodeNb + lowS - 1; lowN = nodeNb;
huffNode[nodeNb].count = huffNode[lowS].count + huffNode[lowS-1].count;
huffNode[lowS].parent = huffNode[lowS-1].parent = (U16)nodeNb;
nodeNb++; lowS-=2;
for (n=nodeNb; n<=nodeRoot; n++) huffNode[n].count = (U32)(1U<<30);
huffNode0[0].count = (U32)(1U<<31); /* fake entry, strong barrier */
/* create parents */
while (nodeNb <= nodeRoot) {
int const n1 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
int const n2 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
huffNode[nodeNb].count = huffNode[n1].count + huffNode[n2].count;
huffNode[n1].parent = huffNode[n2].parent = (U16)nodeNb;
nodeNb++;
}
/* distribute weights (unlimited tree height) */
huffNode[nodeRoot].nbBits = 0;
for (n=nodeRoot-1; n>=STARTNODE; n--)
huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;
for (n=0; n<=nonNullRank; n++)
huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;
DEBUGLOG(6, "Initial distribution of bits completed (%zu sorted symbols)", showHNodeBits(huffNode, maxSymbolValue+1));
return nonNullRank;
}
/**
* HUF_buildCTableFromTree():
* Build the CTable given the Huffman tree in huffNode.
*
* @param[out] CTable The output Huffman CTable.
* @param huffNode The Huffman tree.
* @param nonNullRank The last and smallest node in the Huffman tree.
* @param maxSymbolValue The maximum symbol value.
* @param maxNbBits The exact maximum number of bits used in the Huffman tree.
*/
static void HUF_buildCTableFromTree(HUF_CElt* CTable, nodeElt const* huffNode, int nonNullRank, U32 maxSymbolValue, U32 maxNbBits)
{
HUF_CElt* const ct = CTable + 1;
/* fill result into ctable (val, nbBits) */
int n;
U16 nbPerRank[HUF_TABLELOG_MAX+1] = {0};
U16 valPerRank[HUF_TABLELOG_MAX+1] = {0};
int const alphabetSize = (int)(maxSymbolValue + 1);
for (n=0; n<=nonNullRank; n++)
nbPerRank[huffNode[n].nbBits]++;
/* determine starting value per rank */
{ U16 min = 0;
for (n=(int)maxNbBits; n>0; n--) {
valPerRank[n] = min; /* get starting value within each rank */
min += nbPerRank[n];
min >>= 1;
} }
for (n=0; n<alphabetSize; n++)
HUF_setNbBits(ct + huffNode[n].byte, huffNode[n].nbBits); /* push nbBits per symbol, symbol order */
for (n=0; n<alphabetSize; n++)
HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++); /* assign value within rank, symbol order */
HUF_writeCTableHeader(CTable, maxNbBits, maxSymbolValue);
}
size_t
HUF_buildCTable_wksp(HUF_CElt* CTable, const unsigned* count, U32 maxSymbolValue, U32 maxNbBits,
void* workSpace, size_t wkspSize)
{
HUF_buildCTable_wksp_tables* const wksp_tables =
(HUF_buildCTable_wksp_tables*)HUF_alignUpWorkspace(workSpace, &wkspSize, ZSTD_ALIGNOF(U32));
nodeElt* const huffNode0 = wksp_tables->huffNodeTbl;
nodeElt* const huffNode = huffNode0+1;
int nonNullRank;
HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE == sizeof(HUF_buildCTable_wksp_tables));
DEBUGLOG(5, "HUF_buildCTable_wksp (alphabet size = %u)", maxSymbolValue+1);
/* safety checks */
if (wkspSize < sizeof(HUF_buildCTable_wksp_tables))
return ERROR(workSpace_tooSmall);
if (maxNbBits == 0) maxNbBits = HUF_TABLELOG_DEFAULT;
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX)
return ERROR(maxSymbolValue_tooLarge);
ZSTD_memset(huffNode0, 0, sizeof(huffNodeTable));
/* sort, decreasing order */
HUF_sort(huffNode, count, maxSymbolValue, wksp_tables->rankPosition);
DEBUGLOG(6, "sorted symbols completed (%zu symbols)", showHNodeSymbols(huffNode, maxSymbolValue+1));
/* build tree */
nonNullRank = HUF_buildTree(huffNode, maxSymbolValue);
/* determine and enforce maxTableLog */
maxNbBits = HUF_setMaxHeight(huffNode, (U32)nonNullRank, maxNbBits);
if (maxNbBits > HUF_TABLELOG_MAX) return ERROR(GENERIC); /* check fit into table */
HUF_buildCTableFromTree(CTable, huffNode, nonNullRank, maxSymbolValue, maxNbBits);
return maxNbBits;
}
size_t HUF_estimateCompressedSize(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue)
{
HUF_CElt const* ct = CTable + 1;
size_t nbBits = 0;
int s;
for (s = 0; s <= (int)maxSymbolValue; ++s) {
nbBits += HUF_getNbBits(ct[s]) * count[s];
}
return nbBits >> 3;
}
int HUF_validateCTable(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue) {
HUF_CTableHeader header = HUF_readCTableHeader(CTable);
HUF_CElt const* ct = CTable + 1;
int bad = 0;
int s;
assert(header.tableLog <= HUF_TABLELOG_ABSOLUTEMAX);
if (header.maxSymbolValue < maxSymbolValue)
return 0;
for (s = 0; s <= (int)maxSymbolValue; ++s) {
bad |= (count[s] != 0) & (HUF_getNbBits(ct[s]) == 0);
}
return !bad;
}
size_t HUF_compressBound(size_t size) { return HUF_COMPRESSBOUND(size); }
/** HUF_CStream_t:
* Huffman uses its own BIT_CStream_t implementation.
* There are three major differences from BIT_CStream_t:
* 1. HUF_addBits() takes a HUF_CElt (size_t) which is
* the pair (nbBits, value) in the format:
* format:
* - Bits [0, 4) = nbBits
* - Bits [4, 64 - nbBits) = 0
* - Bits [64 - nbBits, 64) = value
* 2. The bitContainer is built from the upper bits and
* right shifted. E.g. to add a new value of N bits
* you right shift the bitContainer by N, then or in
* the new value into the N upper bits.
* 3. The bitstream has two bit containers. You can add
* bits to the second container and merge them into
* the first container.
*/
#define HUF_BITS_IN_CONTAINER (sizeof(size_t) * 8)
typedef struct {
size_t bitContainer[2];
size_t bitPos[2];
BYTE* startPtr;
BYTE* ptr;
BYTE* endPtr;
} HUF_CStream_t;
/**! HUF_initCStream():
* Initializes the bitstream.
* @returns 0 or an error code.
*/
static size_t HUF_initCStream(HUF_CStream_t* bitC,
void* startPtr, size_t dstCapacity)
{
ZSTD_memset(bitC, 0, sizeof(*bitC));
bitC->startPtr = (BYTE*)startPtr;
bitC->ptr = bitC->startPtr;
bitC->endPtr = bitC->startPtr + dstCapacity - sizeof(bitC->bitContainer[0]);
if (dstCapacity <= sizeof(bitC->bitContainer[0])) return ERROR(dstSize_tooSmall);
return 0;
}
/*! HUF_addBits():
* Adds the symbol stored in HUF_CElt elt to the bitstream.
*
* @param elt The element we're adding. This is a (nbBits, value) pair.
* See the HUF_CStream_t docs for the format.
* @param idx Insert into the bitstream at this idx.
* @param kFast This is a template parameter. If the bitstream is guaranteed
* to have at least 4 unused bits after this call it may be 1,
* otherwise it must be 0. HUF_addBits() is faster when fast is set.
*/
FORCE_INLINE_TEMPLATE void HUF_addBits(HUF_CStream_t* bitC, HUF_CElt elt, int idx, int kFast)
{
assert(idx <= 1);
assert(HUF_getNbBits(elt) <= HUF_TABLELOG_ABSOLUTEMAX);
/* This is efficient on x86-64 with BMI2 because shrx
* only reads the low 6 bits of the register. The compiler
* knows this and elides the mask. When fast is set,
* every operation can use the same value loaded from elt.
*/
bitC->bitContainer[idx] >>= HUF_getNbBits(elt);
bitC->bitContainer[idx] |= kFast ? HUF_getValueFast(elt) : HUF_getValue(elt);
/* We only read the low 8 bits of bitC->bitPos[idx] so it
* doesn't matter that the high bits have noise from the value.
*/
bitC->bitPos[idx] += HUF_getNbBitsFast(elt);
assert((bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER);
/* The last 4-bits of elt are dirty if fast is set,
* so we must not be overwriting bits that have already been
* inserted into the bit container.
*/
#if DEBUGLEVEL >= 1
{
size_t const nbBits = HUF_getNbBits(elt);
size_t const dirtyBits = nbBits == 0 ? 0 : ZSTD_highbit32((U32)nbBits) + 1;
(void)dirtyBits;
/* Middle bits are 0. */
assert(((elt >> dirtyBits) << (dirtyBits + nbBits)) == 0);
/* We didn't overwrite any bits in the bit container. */
assert(!kFast || (bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER);
(void)dirtyBits;
}
#endif
}
FORCE_INLINE_TEMPLATE void HUF_zeroIndex1(HUF_CStream_t* bitC)
{
bitC->bitContainer[1] = 0;
bitC->bitPos[1] = 0;
}
/*! HUF_mergeIndex1() :
* Merges the bit container @ index 1 into the bit container @ index 0
* and zeros the bit container @ index 1.
*/
FORCE_INLINE_TEMPLATE void HUF_mergeIndex1(HUF_CStream_t* bitC)
{
assert((bitC->bitPos[1] & 0xFF) < HUF_BITS_IN_CONTAINER);
bitC->bitContainer[0] >>= (bitC->bitPos[1] & 0xFF);
bitC->bitContainer[0] |= bitC->bitContainer[1];
bitC->bitPos[0] += bitC->bitPos[1];
assert((bitC->bitPos[0] & 0xFF) <= HUF_BITS_IN_CONTAINER);
}
/*! HUF_flushBits() :
* Flushes the bits in the bit container @ index 0.
*
* @post bitPos will be < 8.
* @param kFast If kFast is set then we must know a-priori that
* the bit container will not overflow.
*/
FORCE_INLINE_TEMPLATE void HUF_flushBits(HUF_CStream_t* bitC, int kFast)
{
/* The upper bits of bitPos are noisy, so we must mask by 0xFF. */
size_t const nbBits = bitC->bitPos[0] & 0xFF;
size_t const nbBytes = nbBits >> 3;
/* The top nbBits bits of bitContainer are the ones we need. */
size_t const bitContainer = bitC->bitContainer[0] >> (HUF_BITS_IN_CONTAINER - nbBits);
/* Mask bitPos to account for the bytes we consumed. */
bitC->bitPos[0] &= 7;
assert(nbBits > 0);
assert(nbBits <= sizeof(bitC->bitContainer[0]) * 8);
assert(bitC->ptr <= bitC->endPtr);
MEM_writeLEST(bitC->ptr, bitContainer);
bitC->ptr += nbBytes;
assert(!kFast || bitC->ptr <= bitC->endPtr);
if (!kFast && bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr;
/* bitContainer doesn't need to be modified because the leftover
* bits are already the top bitPos bits. And we don't care about
* noise in the lower values.
*/
}
/*! HUF_endMark()
* @returns The Huffman stream end mark: A 1-bit value = 1.
*/
static HUF_CElt HUF_endMark(void)
{
HUF_CElt endMark;
HUF_setNbBits(&endMark, 1);
HUF_setValue(&endMark, 1);
return endMark;
}
/*! HUF_closeCStream() :
* @return Size of CStream, in bytes,
* or 0 if it could not fit into dstBuffer */
static size_t HUF_closeCStream(HUF_CStream_t* bitC)
{
HUF_addBits(bitC, HUF_endMark(), /* idx */ 0, /* kFast */ 0);
HUF_flushBits(bitC, /* kFast */ 0);
{
size_t const nbBits = bitC->bitPos[0] & 0xFF;
if (bitC->ptr >= bitC->endPtr) return 0; /* overflow detected */
return (size_t)(bitC->ptr - bitC->startPtr) + (nbBits > 0);
}
}
FORCE_INLINE_TEMPLATE void
HUF_encodeSymbol(HUF_CStream_t* bitCPtr, U32 symbol, const HUF_CElt* CTable, int idx, int fast)
{
HUF_addBits(bitCPtr, CTable[symbol], idx, fast);
}
FORCE_INLINE_TEMPLATE void
HUF_compress1X_usingCTable_internal_body_loop(HUF_CStream_t* bitC,
const BYTE* ip, size_t srcSize,
const HUF_CElt* ct,
int kUnroll, int kFastFlush, int kLastFast)
{
/* Join to kUnroll */
int n = (int)srcSize;
int rem = n % kUnroll;
if (rem > 0) {
for (; rem > 0; --rem) {
HUF_encodeSymbol(bitC, ip[--n], ct, 0, /* fast */ 0);
}
HUF_flushBits(bitC, kFastFlush);
}
assert(n % kUnroll == 0);
/* Join to 2 * kUnroll */
if (n % (2 * kUnroll)) {
int u;
for (u = 1; u < kUnroll; ++u) {
HUF_encodeSymbol(bitC, ip[n - u], ct, 0, 1);
}
HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, 0, kLastFast);
HUF_flushBits(bitC, kFastFlush);
n -= kUnroll;
}
assert(n % (2 * kUnroll) == 0);
for (; n>0; n-= 2 * kUnroll) {
/* Encode kUnroll symbols into the bitstream @ index 0. */
int u;
for (u = 1; u < kUnroll; ++u) {
HUF_encodeSymbol(bitC, ip[n - u], ct, /* idx */ 0, /* fast */ 1);
}
HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, /* idx */ 0, /* fast */ kLastFast);
HUF_flushBits(bitC, kFastFlush);
/* Encode kUnroll symbols into the bitstream @ index 1.
* This allows us to start filling the bit container
* without any data dependencies.
*/
HUF_zeroIndex1(bitC);
for (u = 1; u < kUnroll; ++u) {
HUF_encodeSymbol(bitC, ip[n - kUnroll - u], ct, /* idx */ 1, /* fast */ 1);
}
HUF_encodeSymbol(bitC, ip[n - kUnroll - kUnroll], ct, /* idx */ 1, /* fast */ kLastFast);
/* Merge bitstream @ index 1 into the bitstream @ index 0 */
HUF_mergeIndex1(bitC);
HUF_flushBits(bitC, kFastFlush);
}
assert(n == 0);
}
/**
* Returns a tight upper bound on the output space needed by Huffman
* with 8 bytes buffer to handle over-writes. If the output is at least
* this large we don't need to do bounds checks during Huffman encoding.
*/
static size_t HUF_tightCompressBound(size_t srcSize, size_t tableLog)
{
return ((srcSize * tableLog) >> 3) + 8;
}
FORCE_INLINE_TEMPLATE size_t
HUF_compress1X_usingCTable_internal_body(void* dst, size_t dstSize,
const void* src, size_t srcSize,
const HUF_CElt* CTable)
{
U32 const tableLog = HUF_readCTableHeader(CTable).tableLog;
HUF_CElt const* ct = CTable + 1;
const BYTE* ip = (const BYTE*) src;
BYTE* const ostart = (BYTE*)dst;
BYTE* const oend = ostart + dstSize;
HUF_CStream_t bitC;
/* init */
if (dstSize < 8) return 0; /* not enough space to compress */
{ BYTE* op = ostart;
size_t const initErr = HUF_initCStream(&bitC, op, (size_t)(oend-op));
if (HUF_isError(initErr)) return 0; }
if (dstSize < HUF_tightCompressBound(srcSize, (size_t)tableLog) || tableLog > 11)
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ MEM_32bits() ? 2 : 4, /* kFast */ 0, /* kLastFast */ 0);
else {
if (MEM_32bits()) {
switch (tableLog) {
case 11:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 0);
break;
case 10: ZSTD_FALLTHROUGH;
case 9: ZSTD_FALLTHROUGH;
case 8:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 1);
break;
case 7: ZSTD_FALLTHROUGH;
default:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 3, /* kFastFlush */ 1, /* kLastFast */ 1);
break;
}
} else {
switch (tableLog) {
case 11:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 0);
break;
case 10:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 1);
break;
case 9:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 6, /* kFastFlush */ 1, /* kLastFast */ 0);
break;
case 8:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 7, /* kFastFlush */ 1, /* kLastFast */ 0);
break;
case 7:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 8, /* kFastFlush */ 1, /* kLastFast */ 0);
break;
case 6: ZSTD_FALLTHROUGH;
default:
HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 9, /* kFastFlush */ 1, /* kLastFast */ 1);
break;
}
}
}
assert(bitC.ptr <= bitC.endPtr);
return HUF_closeCStream(&bitC);
}
#if DYNAMIC_BMI2
static BMI2_TARGET_ATTRIBUTE size_t
HUF_compress1X_usingCTable_internal_bmi2(void* dst, size_t dstSize,
const void* src, size_t srcSize,
const HUF_CElt* CTable)
{
return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
}
static size_t
HUF_compress1X_usingCTable_internal_default(void* dst, size_t dstSize,
const void* src, size_t srcSize,
const HUF_CElt* CTable)
{
return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
}
static size_t
HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize,
const void* src, size_t srcSize,
const HUF_CElt* CTable, const int flags)
{
if (flags & HUF_flags_bmi2) {
return HUF_compress1X_usingCTable_internal_bmi2(dst, dstSize, src, srcSize, CTable);
}
return HUF_compress1X_usingCTable_internal_default(dst, dstSize, src, srcSize, CTable);
}
#else
static size_t
HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize,
const void* src, size_t srcSize,
const HUF_CElt* CTable, const int flags)
{
(void)flags;
return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
}
#endif
size_t HUF_compress1X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags)
{
return HUF_compress1X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, flags);
}
static size_t
HUF_compress4X_usingCTable_internal(void* dst, size_t dstSize,
const void* src, size_t srcSize,
const HUF_CElt* CTable, int flags)
{
size_t const segmentSize = (srcSize+3)/4; /* first 3 segments */
const BYTE* ip = (const BYTE*) src;
const BYTE* const iend = ip + srcSize;
BYTE* const ostart = (BYTE*) dst;
BYTE* const oend = ostart + dstSize;
BYTE* op = ostart;
if (dstSize < 6 + 1 + 1 + 1 + 8) return 0; /* minimum space to compress successfully */
if (srcSize < 12) return 0; /* no saving possible : too small input */
op += 6; /* jumpTable */
assert(op <= oend);
{ CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) );
if (cSize == 0 || cSize > 65535) return 0;
MEM_writeLE16(ostart, (U16)cSize);
op += cSize;
}
ip += segmentSize;
assert(op <= oend);
{ CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) );
if (cSize == 0 || cSize > 65535) return 0;
MEM_writeLE16(ostart+2, (U16)cSize);
op += cSize;
}
ip += segmentSize;
assert(op <= oend);
{ CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) );
if (cSize == 0 || cSize > 65535) return 0;
MEM_writeLE16(ostart+4, (U16)cSize);
op += cSize;
}
ip += segmentSize;
assert(op <= oend);
assert(ip <= iend);
{ CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, (size_t)(iend-ip), CTable, flags) );
if (cSize == 0 || cSize > 65535) return 0;
op += cSize;
}
return (size_t)(op-ostart);
}
size_t HUF_compress4X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags)
{
return HUF_compress4X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, flags);
}
typedef enum { HUF_singleStream, HUF_fourStreams } HUF_nbStreams_e;
static size_t HUF_compressCTable_internal(
BYTE* const ostart, BYTE* op, BYTE* const oend,
const void* src, size_t srcSize,
HUF_nbStreams_e nbStreams, const HUF_CElt* CTable, const int flags)
{
size_t const cSize = (nbStreams==HUF_singleStream) ?
HUF_compress1X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, flags) :
HUF_compress4X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, flags);
if (HUF_isError(cSize)) { return cSize; }
if (cSize==0) { return 0; } /* uncompressible */
op += cSize;
/* check compressibility */
assert(op >= ostart);
if ((size_t)(op-ostart) >= srcSize-1) { return 0; }
return (size_t)(op-ostart);
}
typedef struct {
unsigned count[HUF_SYMBOLVALUE_MAX + 1];
HUF_CElt CTable[HUF_CTABLE_SIZE_ST(HUF_SYMBOLVALUE_MAX)];
union {
HUF_buildCTable_wksp_tables buildCTable_wksp;
HUF_WriteCTableWksp writeCTable_wksp;
U32 hist_wksp[HIST_WKSP_SIZE_U32];
} wksps;
} HUF_compress_tables_t;
#define SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE 4096
#define SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO 10 /* Must be >= 2 */
unsigned HUF_cardinality(const unsigned* count, unsigned maxSymbolValue)
{
unsigned cardinality = 0;
unsigned i;
for (i = 0; i < maxSymbolValue + 1; i++) {
if (count[i] != 0) cardinality += 1;
}
return cardinality;
}
unsigned HUF_minTableLog(unsigned symbolCardinality)
{
U32 minBitsSymbols = ZSTD_highbit32(symbolCardinality) + 1;
return minBitsSymbols;
}
unsigned HUF_optimalTableLog(
unsigned maxTableLog,
size_t srcSize,
unsigned maxSymbolValue,
void* workSpace, size_t wkspSize,
HUF_CElt* table,
const unsigned* count,
int flags)
{
assert(srcSize > 1); /* Not supported, RLE should be used instead */
assert(wkspSize >= sizeof(HUF_buildCTable_wksp_tables));
if (!(flags & HUF_flags_optimalDepth)) {
/* cheap evaluation, based on FSE */
return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 1);
}
{ BYTE* dst = (BYTE*)workSpace + sizeof(HUF_WriteCTableWksp);
size_t dstSize = wkspSize - sizeof(HUF_WriteCTableWksp);
size_t hSize, newSize;
const unsigned symbolCardinality = HUF_cardinality(count, maxSymbolValue);
const unsigned minTableLog = HUF_minTableLog(symbolCardinality);
size_t optSize = ((size_t) ~0) - 1;
unsigned optLog = maxTableLog, optLogGuess;
DEBUGLOG(6, "HUF_optimalTableLog: probing huf depth (srcSize=%zu)", srcSize);
/* Search until size increases */
for (optLogGuess = minTableLog; optLogGuess <= maxTableLog; optLogGuess++) {
DEBUGLOG(7, "checking for huffLog=%u", optLogGuess);
{ size_t maxBits = HUF_buildCTable_wksp(table, count, maxSymbolValue, optLogGuess, workSpace, wkspSize);
if (ERR_isError(maxBits)) continue;
if (maxBits < optLogGuess && optLogGuess > minTableLog) break;
hSize = HUF_writeCTable_wksp(dst, dstSize, table, maxSymbolValue, (U32)maxBits, workSpace, wkspSize);
}
if (ERR_isError(hSize)) continue;
newSize = HUF_estimateCompressedSize(table, count, maxSymbolValue) + hSize;
if (newSize > optSize + 1) {
break;
}
if (newSize < optSize) {
optSize = newSize;
optLog = optLogGuess;
}
}
assert(optLog <= HUF_TABLELOG_MAX);
return optLog;
}
}
/* HUF_compress_internal() :
* `workSpace_align4` must be aligned on 4-bytes boundaries,
* and occupies the same space as a table of HUF_WORKSPACE_SIZE_U64 unsigned */
static size_t
HUF_compress_internal (void* dst, size_t dstSize,
const void* src, size_t srcSize,
unsigned maxSymbolValue, unsigned huffLog,
HUF_nbStreams_e nbStreams,
void* workSpace, size_t wkspSize,
HUF_CElt* oldHufTable, HUF_repeat* repeat, int flags)
{
HUF_compress_tables_t* const table = (HUF_compress_tables_t*)HUF_alignUpWorkspace(workSpace, &wkspSize, ZSTD_ALIGNOF(size_t));
BYTE* const ostart = (BYTE*)dst;
BYTE* const oend = ostart + dstSize;
BYTE* op = ostart;
DEBUGLOG(5, "HUF_compress_internal (srcSize=%zu)", srcSize);
HUF_STATIC_ASSERT(sizeof(*table) + HUF_WORKSPACE_MAX_ALIGNMENT <= HUF_WORKSPACE_SIZE);
/* checks & inits */
if (wkspSize < sizeof(*table)) return ERROR(workSpace_tooSmall);
if (!srcSize) return 0; /* Uncompressed */
if (!dstSize) return 0; /* cannot fit anything within dst budget */
if (srcSize > HUF_BLOCKSIZE_MAX) return ERROR(srcSize_wrong); /* current block size limit */
if (huffLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
if (!maxSymbolValue) maxSymbolValue = HUF_SYMBOLVALUE_MAX;
if (!huffLog) huffLog = HUF_TABLELOG_DEFAULT;
/* Heuristic : If old table is valid, use it for small inputs */
if ((flags & HUF_flags_preferRepeat) && repeat && *repeat == HUF_repeat_valid) {
return HUF_compressCTable_internal(ostart, op, oend,
src, srcSize,
nbStreams, oldHufTable, flags);
}
/* If uncompressible data is suspected, do a smaller sampling first */
DEBUG_STATIC_ASSERT(SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO >= 2);
if ((flags & HUF_flags_suspectUncompressible) && srcSize >= (SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE * SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO)) {
size_t largestTotal = 0;
DEBUGLOG(5, "input suspected incompressible : sampling to check");
{ unsigned maxSymbolValueBegin = maxSymbolValue;
CHECK_V_F(largestBegin, HIST_count_simple (table->count, &maxSymbolValueBegin, (const BYTE*)src, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) );
largestTotal += largestBegin;
}
{ unsigned maxSymbolValueEnd = maxSymbolValue;
CHECK_V_F(largestEnd, HIST_count_simple (table->count, &maxSymbolValueEnd, (const BYTE*)src + srcSize - SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) );
largestTotal += largestEnd;
}
if (largestTotal <= ((2 * SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) >> 7)+4) return 0; /* heuristic : probably not compressible enough */
}
/* Scan input and build symbol stats */
{ CHECK_V_F(largest, HIST_count_wksp (table->count, &maxSymbolValue, (const BYTE*)src, srcSize, table->wksps.hist_wksp, sizeof(table->wksps.hist_wksp)) );
if (largest == srcSize) { *ostart = ((const BYTE*)src)[0]; return 1; } /* single symbol, rle */
if (largest <= (srcSize >> 7)+4) return 0; /* heuristic : probably not compressible enough */
}
DEBUGLOG(6, "histogram detail completed (%zu symbols)", showU32(table->count, maxSymbolValue+1));
/* Check validity of previous table */
if ( repeat
&& *repeat == HUF_repeat_check
&& !HUF_validateCTable(oldHufTable, table->count, maxSymbolValue)) {
*repeat = HUF_repeat_none;
}
/* Heuristic : use existing table for small inputs */
if ((flags & HUF_flags_preferRepeat) && repeat && *repeat != HUF_repeat_none) {
return HUF_compressCTable_internal(ostart, op, oend,
src, srcSize,
nbStreams, oldHufTable, flags);
}
/* Build Huffman Tree */
huffLog = HUF_optimalTableLog(huffLog, srcSize, maxSymbolValue, &table->wksps, sizeof(table->wksps), table->CTable, table->count, flags);
{ size_t const maxBits = HUF_buildCTable_wksp(table->CTable, table->count,
maxSymbolValue, huffLog,
&table->wksps.buildCTable_wksp, sizeof(table->wksps.buildCTable_wksp));
CHECK_F(maxBits);
huffLog = (U32)maxBits;
DEBUGLOG(6, "bit distribution completed (%zu symbols)", showCTableBits(table->CTable + 1, maxSymbolValue+1));
}
/* Write table description header */
{ CHECK_V_F(hSize, HUF_writeCTable_wksp(op, dstSize, table->CTable, maxSymbolValue, huffLog,
&table->wksps.writeCTable_wksp, sizeof(table->wksps.writeCTable_wksp)) );
/* Check if using previous huffman table is beneficial */
if (repeat && *repeat != HUF_repeat_none) {
size_t const oldSize = HUF_estimateCompressedSize(oldHufTable, table->count, maxSymbolValue);
size_t const newSize = HUF_estimateCompressedSize(table->CTable, table->count, maxSymbolValue);
if (oldSize <= hSize + newSize || hSize + 12 >= srcSize) {
return HUF_compressCTable_internal(ostart, op, oend,
src, srcSize,
nbStreams, oldHufTable, flags);
} }
/* Use the new huffman table */
if (hSize + 12ul >= srcSize) { return 0; }
op += hSize;
if (repeat) { *repeat = HUF_repeat_none; }
if (oldHufTable)
ZSTD_memcpy(oldHufTable, table->CTable, sizeof(table->CTable)); /* Save new table */
}
return HUF_compressCTable_internal(ostart, op, oend,
src, srcSize,
nbStreams, table->CTable, flags);
}
size_t HUF_compress1X_repeat (void* dst, size_t dstSize,
const void* src, size_t srcSize,
unsigned maxSymbolValue, unsigned huffLog,
void* workSpace, size_t wkspSize,
HUF_CElt* hufTable, HUF_repeat* repeat, int flags)
{
DEBUGLOG(5, "HUF_compress1X_repeat (srcSize = %zu)", srcSize);
return HUF_compress_internal(dst, dstSize, src, srcSize,
maxSymbolValue, huffLog, HUF_singleStream,
workSpace, wkspSize, hufTable,
repeat, flags);
}
/* HUF_compress4X_repeat():
* compress input using 4 streams.
* consider skipping quickly
* reuse an existing huffman compression table */
size_t HUF_compress4X_repeat (void* dst, size_t dstSize,
const void* src, size_t srcSize,
unsigned maxSymbolValue, unsigned huffLog,
void* workSpace, size_t wkspSize,
HUF_CElt* hufTable, HUF_repeat* repeat, int flags)
{
DEBUGLOG(5, "HUF_compress4X_repeat (srcSize = %zu)", srcSize);
return HUF_compress_internal(dst, dstSize, src, srcSize,
maxSymbolValue, huffLog, HUF_fourStreams,
workSpace, wkspSize,
hufTable, repeat, flags);
}
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