1/* ******************************************************************
2 * Huffman encoder, part of New Generation Entropy library
3 * Copyright (c) Meta Platforms, Inc. and affiliates.
4 *
5 * You can contact the author at :
6 * - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy
7 * - Public forum : https://groups.google.com/forum/#!forum/lz4c
8 *
9 * This source code is licensed under both the BSD-style license (found in the
10 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
11 * in the COPYING file in the root directory of this source tree).
12 * You may select, at your option, one of the above-listed licenses.
13****************************************************************** */
14
15/* **************************************************************
16* Compiler specifics
17****************************************************************/
18#ifdef _MSC_VER /* Visual Studio */
19# pragma warning(disable : 4127) /* disable: C4127: conditional expression is constant */
20#endif
21
22
23/* **************************************************************
24* Includes
25****************************************************************/
26#include "../common/zstd_deps.h" /* ZSTD_memcpy, ZSTD_memset */
27#include "../common/compiler.h"
28#include "../common/bitstream.h"
29#include "hist.h"
30#define FSE_STATIC_LINKING_ONLY /* FSE_optimalTableLog_internal */
31#include "../common/fse.h" /* header compression */
32#include "../common/huf.h"
33#include "../common/error_private.h"
34#include "../common/bits.h" /* ZSTD_highbit32 */
35
36
37/* **************************************************************
38* Error Management
39****************************************************************/
40#define HUF_isError ERR_isError
41#define HUF_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c) /* use only *after* variable declarations */
42
43
44/* **************************************************************
45* Required declarations
46****************************************************************/
47typedef struct nodeElt_s {
48 U32 count;
49 U16 parent;
50 BYTE byte;
51 BYTE nbBits;
52} nodeElt;
53
54
55/* **************************************************************
56* Debug Traces
57****************************************************************/
58
59#if DEBUGLEVEL >= 2
60
61static size_t showU32(const U32* arr, size_t size)
62{
63 size_t u;
64 for (u=0; u<size; u++) {
65 RAWLOG(6, " %u", arr[u]); (void)arr;
66 }
67 RAWLOG(6, " \n");
68 return size;
69}
70
71static size_t HUF_getNbBits(HUF_CElt elt);
72
73static size_t showCTableBits(const HUF_CElt* ctable, size_t size)
74{
75 size_t u;
76 for (u=0; u<size; u++) {
77 RAWLOG(6, " %zu", HUF_getNbBits(ctable[u])); (void)ctable;
78 }
79 RAWLOG(6, " \n");
80 return size;
81
82}
83
84static size_t showHNodeSymbols(const nodeElt* hnode, size_t size)
85{
86 size_t u;
87 for (u=0; u<size; u++) {
88 RAWLOG(6, " %u", hnode[u].byte); (void)hnode;
89 }
90 RAWLOG(6, " \n");
91 return size;
92}
93
94static size_t showHNodeBits(const nodeElt* hnode, size_t size)
95{
96 size_t u;
97 for (u=0; u<size; u++) {
98 RAWLOG(6, " %u", hnode[u].nbBits); (void)hnode;
99 }
100 RAWLOG(6, " \n");
101 return size;
102}
103
104#endif
105
106
107/* *******************************************************
108* HUF : Huffman block compression
109*********************************************************/
110#define HUF_WORKSPACE_MAX_ALIGNMENT 8
111
112static void* HUF_alignUpWorkspace(void* workspace, size_t* workspaceSizePtr, size_t align)
113{
114 size_t const mask = align - 1;
115 size_t const rem = (size_t)workspace & mask;
116 size_t const add = (align - rem) & mask;
117 BYTE* const aligned = (BYTE*)workspace + add;
118 assert((align & (align - 1)) == 0); /* pow 2 */
119 assert(align <= HUF_WORKSPACE_MAX_ALIGNMENT);
120 if (*workspaceSizePtr >= add) {
121 assert(add < align);
122 assert(((size_t)aligned & mask) == 0);
123 *workspaceSizePtr -= add;
124 return aligned;
125 } else {
126 *workspaceSizePtr = 0;
127 return NULL;
128 }
129}
130
131
132/* HUF_compressWeights() :
133 * Same as FSE_compress(), but dedicated to huff0's weights compression.
134 * The use case needs much less stack memory.
135 * Note : all elements within weightTable are supposed to be <= HUF_TABLELOG_MAX.
136 */
137#define MAX_FSE_TABLELOG_FOR_HUFF_HEADER 6
138
139typedef struct {
140 FSE_CTable CTable[FSE_CTABLE_SIZE_U32(MAX_FSE_TABLELOG_FOR_HUFF_HEADER, HUF_TABLELOG_MAX)];
141 U32 scratchBuffer[FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(HUF_TABLELOG_MAX, MAX_FSE_TABLELOG_FOR_HUFF_HEADER)];
142 unsigned count[HUF_TABLELOG_MAX+1];
143 S16 norm[HUF_TABLELOG_MAX+1];
144} HUF_CompressWeightsWksp;
145
146static size_t
147HUF_compressWeights(void* dst, size_t dstSize,
148 const void* weightTable, size_t wtSize,
149 void* workspace, size_t workspaceSize)
150{
151 BYTE* const ostart = (BYTE*) dst;
152 BYTE* op = ostart;
153 BYTE* const oend = ostart + dstSize;
154
155 unsigned maxSymbolValue = HUF_TABLELOG_MAX;
156 U32 tableLog = MAX_FSE_TABLELOG_FOR_HUFF_HEADER;
157 HUF_CompressWeightsWksp* wksp = (HUF_CompressWeightsWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32));
158
159 if (workspaceSize < sizeof(HUF_CompressWeightsWksp)) return ERROR(GENERIC);
160
161 /* init conditions */
162 if (wtSize <= 1) return 0; /* Not compressible */
163
164 /* Scan input and build symbol stats */
165 { unsigned const maxCount = HIST_count_simple(wksp->count, &maxSymbolValue, weightTable, wtSize); /* never fails */
166 if (maxCount == wtSize) return 1; /* only a single symbol in src : rle */
167 if (maxCount == 1) return 0; /* each symbol present maximum once => not compressible */
168 }
169
170 tableLog = FSE_optimalTableLog(tableLog, wtSize, maxSymbolValue);
171 CHECK_F( FSE_normalizeCount(wksp->norm, tableLog, wksp->count, wtSize, maxSymbolValue, /* useLowProbCount */ 0) );
172
173 /* Write table description header */
174 { CHECK_V_F(hSize, FSE_writeNCount(op, (size_t)(oend-op), wksp->norm, maxSymbolValue, tableLog) );
175 op += hSize;
176 }
177
178 /* Compress */
179 CHECK_F( FSE_buildCTable_wksp(wksp->CTable, wksp->norm, maxSymbolValue, tableLog, wksp->scratchBuffer, sizeof(wksp->scratchBuffer)) );
180 { CHECK_V_F(cSize, FSE_compress_usingCTable(op, (size_t)(oend - op), weightTable, wtSize, wksp->CTable) );
181 if (cSize == 0) return 0; /* not enough space for compressed data */
182 op += cSize;
183 }
184
185 return (size_t)(op-ostart);
186}
187
188static size_t HUF_getNbBits(HUF_CElt elt)
189{
190 return elt & 0xFF;
191}
192
193static size_t HUF_getNbBitsFast(HUF_CElt elt)
194{
195 return elt;
196}
197
198static size_t HUF_getValue(HUF_CElt elt)
199{
200 return elt & ~(size_t)0xFF;
201}
202
203static size_t HUF_getValueFast(HUF_CElt elt)
204{
205 return elt;
206}
207
208static void HUF_setNbBits(HUF_CElt* elt, size_t nbBits)
209{
210 assert(nbBits <= HUF_TABLELOG_ABSOLUTEMAX);
211 *elt = nbBits;
212}
213
214static void HUF_setValue(HUF_CElt* elt, size_t value)
215{
216 size_t const nbBits = HUF_getNbBits(*elt);
217 if (nbBits > 0) {
218 assert((value >> nbBits) == 0);
219 *elt |= value << (sizeof(HUF_CElt) * 8 - nbBits);
220 }
221}
222
223typedef struct {
224 HUF_CompressWeightsWksp wksp;
225 BYTE bitsToWeight[HUF_TABLELOG_MAX + 1]; /* precomputed conversion table */
226 BYTE huffWeight[HUF_SYMBOLVALUE_MAX];
227} HUF_WriteCTableWksp;
228
229size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize,
230 const HUF_CElt* CTable, unsigned maxSymbolValue, unsigned huffLog,
231 void* workspace, size_t workspaceSize)
232{
233 HUF_CElt const* const ct = CTable + 1;
234 BYTE* op = (BYTE*)dst;
235 U32 n;
236 HUF_WriteCTableWksp* wksp = (HUF_WriteCTableWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32));
237
238 HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE >= sizeof(HUF_WriteCTableWksp));
239
240 /* check conditions */
241 if (workspaceSize < sizeof(HUF_WriteCTableWksp)) return ERROR(GENERIC);
242 if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
243
244 /* convert to weight */
245 wksp->bitsToWeight[0] = 0;
246 for (n=1; n<huffLog+1; n++)
247 wksp->bitsToWeight[n] = (BYTE)(huffLog + 1 - n);
248 for (n=0; n<maxSymbolValue; n++)
249 wksp->huffWeight[n] = wksp->bitsToWeight[HUF_getNbBits(ct[n])];
250
251 /* attempt weights compression by FSE */
252 if (maxDstSize < 1) return ERROR(dstSize_tooSmall);
253 { CHECK_V_F(hSize, HUF_compressWeights(op+1, maxDstSize-1, wksp->huffWeight, maxSymbolValue, &wksp->wksp, sizeof(wksp->wksp)) );
254 if ((hSize>1) & (hSize < maxSymbolValue/2)) { /* FSE compressed */
255 op[0] = (BYTE)hSize;
256 return hSize+1;
257 } }
258
259 /* write raw values as 4-bits (max : 15) */
260 if (maxSymbolValue > (256-128)) return ERROR(GENERIC); /* should not happen : likely means source cannot be compressed */
261 if (((maxSymbolValue+1)/2) + 1 > maxDstSize) return ERROR(dstSize_tooSmall); /* not enough space within dst buffer */
262 op[0] = (BYTE)(128 /*special case*/ + (maxSymbolValue-1));
263 wksp->huffWeight[maxSymbolValue] = 0; /* to be sure it doesn't cause msan issue in final combination */
264 for (n=0; n<maxSymbolValue; n+=2)
265 op[(n/2)+1] = (BYTE)((wksp->huffWeight[n] << 4) + wksp->huffWeight[n+1]);
266 return ((maxSymbolValue+1)/2) + 1;
267}
268
269
270size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize, unsigned* hasZeroWeights)
271{
272 BYTE huffWeight[HUF_SYMBOLVALUE_MAX + 1]; /* init not required, even though some static analyzer may complain */
273 U32 rankVal[HUF_TABLELOG_ABSOLUTEMAX + 1]; /* large enough for values from 0 to 16 */
274 U32 tableLog = 0;
275 U32 nbSymbols = 0;
276 HUF_CElt* const ct = CTable + 1;
277
278 /* get symbol weights */
279 CHECK_V_F(readSize, HUF_readStats(huffWeight, HUF_SYMBOLVALUE_MAX+1, rankVal, &nbSymbols, &tableLog, src, srcSize));
280 *hasZeroWeights = (rankVal[0] > 0);
281
282 /* check result */
283 if (tableLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
284 if (nbSymbols > *maxSymbolValuePtr+1) return ERROR(maxSymbolValue_tooSmall);
285
286 CTable[0] = tableLog;
287
288 /* Prepare base value per rank */
289 { U32 n, nextRankStart = 0;
290 for (n=1; n<=tableLog; n++) {
291 U32 curr = nextRankStart;
292 nextRankStart += (rankVal[n] << (n-1));
293 rankVal[n] = curr;
294 } }
295
296 /* fill nbBits */
297 { U32 n; for (n=0; n<nbSymbols; n++) {
298 const U32 w = huffWeight[n];
299 HUF_setNbBits(ct + n, (BYTE)(tableLog + 1 - w) & -(w != 0));
300 } }
301
302 /* fill val */
303 { U16 nbPerRank[HUF_TABLELOG_MAX+2] = {0}; /* support w=0=>n=tableLog+1 */
304 U16 valPerRank[HUF_TABLELOG_MAX+2] = {0};
305 { U32 n; for (n=0; n<nbSymbols; n++) nbPerRank[HUF_getNbBits(ct[n])]++; }
306 /* determine stating value per rank */
307 valPerRank[tableLog+1] = 0; /* for w==0 */
308 { U16 min = 0;
309 U32 n; for (n=tableLog; n>0; n--) { /* start at n=tablelog <-> w=1 */
310 valPerRank[n] = min; /* get starting value within each rank */
311 min += nbPerRank[n];
312 min >>= 1;
313 } }
314 /* assign value within rank, symbol order */
315 { U32 n; for (n=0; n<nbSymbols; n++) HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++); }
316 }
317
318 *maxSymbolValuePtr = nbSymbols - 1;
319 return readSize;
320}
321
322U32 HUF_getNbBitsFromCTable(HUF_CElt const* CTable, U32 symbolValue)
323{
324 const HUF_CElt* const ct = CTable + 1;
325 assert(symbolValue <= HUF_SYMBOLVALUE_MAX);
326 return (U32)HUF_getNbBits(ct[symbolValue]);
327}
328
329
330/**
331 * HUF_setMaxHeight():
332 * Try to enforce @targetNbBits on the Huffman tree described in @huffNode.
333 *
334 * It attempts to convert all nodes with nbBits > @targetNbBits
335 * to employ @targetNbBits instead. Then it adjusts the tree
336 * so that it remains a valid canonical Huffman tree.
337 *
338 * @pre The sum of the ranks of each symbol == 2^largestBits,
339 * where largestBits == huffNode[lastNonNull].nbBits.
340 * @post The sum of the ranks of each symbol == 2^largestBits,
341 * where largestBits is the return value (expected <= targetNbBits).
342 *
343 * @param huffNode The Huffman tree modified in place to enforce targetNbBits.
344 * It's presumed sorted, from most frequent to rarest symbol.
345 * @param lastNonNull The symbol with the lowest count in the Huffman tree.
346 * @param targetNbBits The allowed number of bits, which the Huffman tree
347 * may not respect. After this function the Huffman tree will
348 * respect targetNbBits.
349 * @return The maximum number of bits of the Huffman tree after adjustment.
350 */
351static U32 HUF_setMaxHeight(nodeElt* huffNode, U32 lastNonNull, U32 targetNbBits)
352{
353 const U32 largestBits = huffNode[lastNonNull].nbBits;
354 /* early exit : no elt > targetNbBits, so the tree is already valid. */
355 if (largestBits <= targetNbBits) return largestBits;
356
357 DEBUGLOG(5, "HUF_setMaxHeight (targetNbBits = %u)", targetNbBits);
358
359 /* there are several too large elements (at least >= 2) */
360 { int totalCost = 0;
361 const U32 baseCost = 1 << (largestBits - targetNbBits);
362 int n = (int)lastNonNull;
363
364 /* Adjust any ranks > targetNbBits to targetNbBits.
365 * Compute totalCost, which is how far the sum of the ranks is
366 * we are over 2^largestBits after adjust the offending ranks.
367 */
368 while (huffNode[n].nbBits > targetNbBits) {
369 totalCost += baseCost - (1 << (largestBits - huffNode[n].nbBits));
370 huffNode[n].nbBits = (BYTE)targetNbBits;
371 n--;
372 }
373 /* n stops at huffNode[n].nbBits <= targetNbBits */
374 assert(huffNode[n].nbBits <= targetNbBits);
375 /* n end at index of smallest symbol using < targetNbBits */
376 while (huffNode[n].nbBits == targetNbBits) --n;
377
378 /* renorm totalCost from 2^largestBits to 2^targetNbBits
379 * note : totalCost is necessarily a multiple of baseCost */
380 assert(((U32)totalCost & (baseCost - 1)) == 0);
381 totalCost >>= (largestBits - targetNbBits);
382 assert(totalCost > 0);
383
384 /* repay normalized cost */
385 { U32 const noSymbol = 0xF0F0F0F0;
386 U32 rankLast[HUF_TABLELOG_MAX+2];
387
388 /* Get pos of last (smallest = lowest cum. count) symbol per rank */
389 ZSTD_memset(rankLast, 0xF0, sizeof(rankLast));
390 { U32 currentNbBits = targetNbBits;
391 int pos;
392 for (pos=n ; pos >= 0; pos--) {
393 if (huffNode[pos].nbBits >= currentNbBits) continue;
394 currentNbBits = huffNode[pos].nbBits; /* < targetNbBits */
395 rankLast[targetNbBits-currentNbBits] = (U32)pos;
396 } }
397
398 while (totalCost > 0) {
399 /* Try to reduce the next power of 2 above totalCost because we
400 * gain back half the rank.
401 */
402 U32 nBitsToDecrease = ZSTD_highbit32((U32)totalCost) + 1;
403 for ( ; nBitsToDecrease > 1; nBitsToDecrease--) {
404 U32 const highPos = rankLast[nBitsToDecrease];
405 U32 const lowPos = rankLast[nBitsToDecrease-1];
406 if (highPos == noSymbol) continue;
407 /* Decrease highPos if no symbols of lowPos or if it is
408 * not cheaper to remove 2 lowPos than highPos.
409 */
410 if (lowPos == noSymbol) break;
411 { U32 const highTotal = huffNode[highPos].count;
412 U32 const lowTotal = 2 * huffNode[lowPos].count;
413 if (highTotal <= lowTotal) break;
414 } }
415 /* only triggered when no more rank 1 symbol left => find closest one (note : there is necessarily at least one !) */
416 assert(rankLast[nBitsToDecrease] != noSymbol || nBitsToDecrease == 1);
417 /* HUF_MAX_TABLELOG test just to please gcc 5+; but it should not be necessary */
418 while ((nBitsToDecrease<=HUF_TABLELOG_MAX) && (rankLast[nBitsToDecrease] == noSymbol))
419 nBitsToDecrease++;
420 assert(rankLast[nBitsToDecrease] != noSymbol);
421 /* Increase the number of bits to gain back half the rank cost. */
422 totalCost -= 1 << (nBitsToDecrease-1);
423 huffNode[rankLast[nBitsToDecrease]].nbBits++;
424
425 /* Fix up the new rank.
426 * If the new rank was empty, this symbol is now its smallest.
427 * Otherwise, this symbol will be the largest in the new rank so no adjustment.
428 */
429 if (rankLast[nBitsToDecrease-1] == noSymbol)
430 rankLast[nBitsToDecrease-1] = rankLast[nBitsToDecrease];
431 /* Fix up the old rank.
432 * If the symbol was at position 0, meaning it was the highest weight symbol in the tree,
433 * it must be the only symbol in its rank, so the old rank now has no symbols.
434 * Otherwise, since the Huffman nodes are sorted by count, the previous position is now
435 * the smallest node in the rank. If the previous position belongs to a different rank,
436 * then the rank is now empty.
437 */
438 if (rankLast[nBitsToDecrease] == 0) /* special case, reached largest symbol */
439 rankLast[nBitsToDecrease] = noSymbol;
440 else {
441 rankLast[nBitsToDecrease]--;
442 if (huffNode[rankLast[nBitsToDecrease]].nbBits != targetNbBits-nBitsToDecrease)
443 rankLast[nBitsToDecrease] = noSymbol; /* this rank is now empty */
444 }
445 } /* while (totalCost > 0) */
446
447 /* If we've removed too much weight, then we have to add it back.
448 * To avoid overshooting again, we only adjust the smallest rank.
449 * We take the largest nodes from the lowest rank 0 and move them
450 * to rank 1. There's guaranteed to be enough rank 0 symbols because
451 * TODO.
452 */
453 while (totalCost < 0) { /* Sometimes, cost correction overshoot */
454 /* special case : no rank 1 symbol (using targetNbBits-1);
455 * let's create one from largest rank 0 (using targetNbBits).
456 */
457 if (rankLast[1] == noSymbol) {
458 while (huffNode[n].nbBits == targetNbBits) n--;
459 huffNode[n+1].nbBits--;
460 assert(n >= 0);
461 rankLast[1] = (U32)(n+1);
462 totalCost++;
463 continue;
464 }
465 huffNode[ rankLast[1] + 1 ].nbBits--;
466 rankLast[1]++;
467 totalCost ++;
468 }
469 } /* repay normalized cost */
470 } /* there are several too large elements (at least >= 2) */
471
472 return targetNbBits;
473}
474
475typedef struct {
476 U16 base;
477 U16 curr;
478} rankPos;
479
480typedef nodeElt huffNodeTable[2 * (HUF_SYMBOLVALUE_MAX + 1)];
481
482/* Number of buckets available for HUF_sort() */
483#define RANK_POSITION_TABLE_SIZE 192
484
485typedef struct {
486 huffNodeTable huffNodeTbl;
487 rankPos rankPosition[RANK_POSITION_TABLE_SIZE];
488} HUF_buildCTable_wksp_tables;
489
490/* RANK_POSITION_DISTINCT_COUNT_CUTOFF == Cutoff point in HUF_sort() buckets for which we use log2 bucketing.
491 * Strategy is to use as many buckets as possible for representing distinct
492 * counts while using the remainder to represent all "large" counts.
493 *
494 * To satisfy this requirement for 192 buckets, we can do the following:
495 * Let buckets 0-166 represent distinct counts of [0, 166]
496 * Let buckets 166 to 192 represent all remaining counts up to RANK_POSITION_MAX_COUNT_LOG using log2 bucketing.
497 */
498#define RANK_POSITION_MAX_COUNT_LOG 32
499#define RANK_POSITION_LOG_BUCKETS_BEGIN ((RANK_POSITION_TABLE_SIZE - 1) - RANK_POSITION_MAX_COUNT_LOG - 1 /* == 158 */)
500#define RANK_POSITION_DISTINCT_COUNT_CUTOFF (RANK_POSITION_LOG_BUCKETS_BEGIN + ZSTD_highbit32(RANK_POSITION_LOG_BUCKETS_BEGIN) /* == 166 */)
501
502/* Return the appropriate bucket index for a given count. See definition of
503 * RANK_POSITION_DISTINCT_COUNT_CUTOFF for explanation of bucketing strategy.
504 */
505static U32 HUF_getIndex(U32 const count) {
506 return (count < RANK_POSITION_DISTINCT_COUNT_CUTOFF)
507 ? count
508 : ZSTD_highbit32(count) + RANK_POSITION_LOG_BUCKETS_BEGIN;
509}
510
511/* Helper swap function for HUF_quickSortPartition() */
512static void HUF_swapNodes(nodeElt* a, nodeElt* b) {
513 nodeElt tmp = *a;
514 *a = *b;
515 *b = tmp;
516}
517
518/* Returns 0 if the huffNode array is not sorted by descending count */
519MEM_STATIC int HUF_isSorted(nodeElt huffNode[], U32 const maxSymbolValue1) {
520 U32 i;
521 for (i = 1; i < maxSymbolValue1; ++i) {
522 if (huffNode[i].count > huffNode[i-1].count) {
523 return 0;
524 }
525 }
526 return 1;
527}
528
529/* Insertion sort by descending order */
530HINT_INLINE void HUF_insertionSort(nodeElt huffNode[], int const low, int const high) {
531 int i;
532 int const size = high-low+1;
533 huffNode += low;
534 for (i = 1; i < size; ++i) {
535 nodeElt const key = huffNode[i];
536 int j = i - 1;
537 while (j >= 0 && huffNode[j].count < key.count) {
538 huffNode[j + 1] = huffNode[j];
539 j--;
540 }
541 huffNode[j + 1] = key;
542 }
543}
544
545/* Pivot helper function for quicksort. */
546static int HUF_quickSortPartition(nodeElt arr[], int const low, int const high) {
547 /* Simply select rightmost element as pivot. "Better" selectors like
548 * median-of-three don't experimentally appear to have any benefit.
549 */
550 U32 const pivot = arr[high].count;
551 int i = low - 1;
552 int j = low;
553 for ( ; j < high; j++) {
554 if (arr[j].count > pivot) {
555 i++;
556 HUF_swapNodes(&arr[i], &arr[j]);
557 }
558 }
559 HUF_swapNodes(&arr[i + 1], &arr[high]);
560 return i + 1;
561}
562
563/* Classic quicksort by descending with partially iterative calls
564 * to reduce worst case callstack size.
565 */
566static void HUF_simpleQuickSort(nodeElt arr[], int low, int high) {
567 int const kInsertionSortThreshold = 8;
568 if (high - low < kInsertionSortThreshold) {
569 HUF_insertionSort(arr, low, high);
570 return;
571 }
572 while (low < high) {
573 int const idx = HUF_quickSortPartition(arr, low, high);
574 if (idx - low < high - idx) {
575 HUF_simpleQuickSort(arr, low, idx - 1);
576 low = idx + 1;
577 } else {
578 HUF_simpleQuickSort(arr, idx + 1, high);
579 high = idx - 1;
580 }
581 }
582}
583
584/**
585 * HUF_sort():
586 * Sorts the symbols [0, maxSymbolValue] by count[symbol] in decreasing order.
587 * This is a typical bucket sorting strategy that uses either quicksort or insertion sort to sort each bucket.
588 *
589 * @param[out] huffNode Sorted symbols by decreasing count. Only members `.count` and `.byte` are filled.
590 * Must have (maxSymbolValue + 1) entries.
591 * @param[in] count Histogram of the symbols.
592 * @param[in] maxSymbolValue Maximum symbol value.
593 * @param rankPosition This is a scratch workspace. Must have RANK_POSITION_TABLE_SIZE entries.
594 */
595static void HUF_sort(nodeElt huffNode[], const unsigned count[], U32 const maxSymbolValue, rankPos rankPosition[]) {
596 U32 n;
597 U32 const maxSymbolValue1 = maxSymbolValue+1;
598
599 /* Compute base and set curr to base.
600 * For symbol s let lowerRank = HUF_getIndex(count[n]) and rank = lowerRank + 1.
601 * See HUF_getIndex to see bucketing strategy.
602 * We attribute each symbol to lowerRank's base value, because we want to know where
603 * each rank begins in the output, so for rank R we want to count ranks R+1 and above.
604 */
605 ZSTD_memset(rankPosition, 0, sizeof(*rankPosition) * RANK_POSITION_TABLE_SIZE);
606 for (n = 0; n < maxSymbolValue1; ++n) {
607 U32 lowerRank = HUF_getIndex(count[n]);
608 assert(lowerRank < RANK_POSITION_TABLE_SIZE - 1);
609 rankPosition[lowerRank].base++;
610 }
611
612 assert(rankPosition[RANK_POSITION_TABLE_SIZE - 1].base == 0);
613 /* Set up the rankPosition table */
614 for (n = RANK_POSITION_TABLE_SIZE - 1; n > 0; --n) {
615 rankPosition[n-1].base += rankPosition[n].base;
616 rankPosition[n-1].curr = rankPosition[n-1].base;
617 }
618
619 /* Insert each symbol into their appropriate bucket, setting up rankPosition table. */
620 for (n = 0; n < maxSymbolValue1; ++n) {
621 U32 const c = count[n];
622 U32 const r = HUF_getIndex(c) + 1;
623 U32 const pos = rankPosition[r].curr++;
624 assert(pos < maxSymbolValue1);
625 huffNode[pos].count = c;
626 huffNode[pos].byte = (BYTE)n;
627 }
628
629 /* Sort each bucket. */
630 for (n = RANK_POSITION_DISTINCT_COUNT_CUTOFF; n < RANK_POSITION_TABLE_SIZE - 1; ++n) {
631 int const bucketSize = rankPosition[n].curr - rankPosition[n].base;
632 U32 const bucketStartIdx = rankPosition[n].base;
633 if (bucketSize > 1) {
634 assert(bucketStartIdx < maxSymbolValue1);
635 HUF_simpleQuickSort(huffNode + bucketStartIdx, 0, bucketSize-1);
636 }
637 }
638
639 assert(HUF_isSorted(huffNode, maxSymbolValue1));
640}
641
642
643/** HUF_buildCTable_wksp() :
644 * Same as HUF_buildCTable(), but using externally allocated scratch buffer.
645 * `workSpace` must be aligned on 4-bytes boundaries, and be at least as large as sizeof(HUF_buildCTable_wksp_tables).
646 */
647#define STARTNODE (HUF_SYMBOLVALUE_MAX+1)
648
649/* HUF_buildTree():
650 * Takes the huffNode array sorted by HUF_sort() and builds an unlimited-depth Huffman tree.
651 *
652 * @param huffNode The array sorted by HUF_sort(). Builds the Huffman tree in this array.
653 * @param maxSymbolValue The maximum symbol value.
654 * @return The smallest node in the Huffman tree (by count).
655 */
656static int HUF_buildTree(nodeElt* huffNode, U32 maxSymbolValue)
657{
658 nodeElt* const huffNode0 = huffNode - 1;
659 int nonNullRank;
660 int lowS, lowN;
661 int nodeNb = STARTNODE;
662 int n, nodeRoot;
663 DEBUGLOG(5, "HUF_buildTree (alphabet size = %u)", maxSymbolValue + 1);
664 /* init for parents */
665 nonNullRank = (int)maxSymbolValue;
666 while(huffNode[nonNullRank].count == 0) nonNullRank--;
667 lowS = nonNullRank; nodeRoot = nodeNb + lowS - 1; lowN = nodeNb;
668 huffNode[nodeNb].count = huffNode[lowS].count + huffNode[lowS-1].count;
669 huffNode[lowS].parent = huffNode[lowS-1].parent = (U16)nodeNb;
670 nodeNb++; lowS-=2;
671 for (n=nodeNb; n<=nodeRoot; n++) huffNode[n].count = (U32)(1U<<30);
672 huffNode0[0].count = (U32)(1U<<31); /* fake entry, strong barrier */
673
674 /* create parents */
675 while (nodeNb <= nodeRoot) {
676 int const n1 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
677 int const n2 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
678 huffNode[nodeNb].count = huffNode[n1].count + huffNode[n2].count;
679 huffNode[n1].parent = huffNode[n2].parent = (U16)nodeNb;
680 nodeNb++;
681 }
682
683 /* distribute weights (unlimited tree height) */
684 huffNode[nodeRoot].nbBits = 0;
685 for (n=nodeRoot-1; n>=STARTNODE; n--)
686 huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;
687 for (n=0; n<=nonNullRank; n++)
688 huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;
689
690 DEBUGLOG(6, "Initial distribution of bits completed (%zu sorted symbols)", showHNodeBits(huffNode, maxSymbolValue+1));
691
692 return nonNullRank;
693}
694
695/**
696 * HUF_buildCTableFromTree():
697 * Build the CTable given the Huffman tree in huffNode.
698 *
699 * @param[out] CTable The output Huffman CTable.
700 * @param huffNode The Huffman tree.
701 * @param nonNullRank The last and smallest node in the Huffman tree.
702 * @param maxSymbolValue The maximum symbol value.
703 * @param maxNbBits The exact maximum number of bits used in the Huffman tree.
704 */
705static void HUF_buildCTableFromTree(HUF_CElt* CTable, nodeElt const* huffNode, int nonNullRank, U32 maxSymbolValue, U32 maxNbBits)
706{
707 HUF_CElt* const ct = CTable + 1;
708 /* fill result into ctable (val, nbBits) */
709 int n;
710 U16 nbPerRank[HUF_TABLELOG_MAX+1] = {0};
711 U16 valPerRank[HUF_TABLELOG_MAX+1] = {0};
712 int const alphabetSize = (int)(maxSymbolValue + 1);
713 for (n=0; n<=nonNullRank; n++)
714 nbPerRank[huffNode[n].nbBits]++;
715 /* determine starting value per rank */
716 { U16 min = 0;
717 for (n=(int)maxNbBits; n>0; n--) {
718 valPerRank[n] = min; /* get starting value within each rank */
719 min += nbPerRank[n];
720 min >>= 1;
721 } }
722 for (n=0; n<alphabetSize; n++)
723 HUF_setNbBits(ct + huffNode[n].byte, huffNode[n].nbBits); /* push nbBits per symbol, symbol order */
724 for (n=0; n<alphabetSize; n++)
725 HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++); /* assign value within rank, symbol order */
726 CTable[0] = maxNbBits;
727}
728
729size_t
730HUF_buildCTable_wksp(HUF_CElt* CTable, const unsigned* count, U32 maxSymbolValue, U32 maxNbBits,
731 void* workSpace, size_t wkspSize)
732{
733 HUF_buildCTable_wksp_tables* const wksp_tables =
734 (HUF_buildCTable_wksp_tables*)HUF_alignUpWorkspace(workSpace, &wkspSize, ZSTD_ALIGNOF(U32));
735 nodeElt* const huffNode0 = wksp_tables->huffNodeTbl;
736 nodeElt* const huffNode = huffNode0+1;
737 int nonNullRank;
738
739 HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE == sizeof(HUF_buildCTable_wksp_tables));
740
741 DEBUGLOG(5, "HUF_buildCTable_wksp (alphabet size = %u)", maxSymbolValue+1);
742
743 /* safety checks */
744 if (wkspSize < sizeof(HUF_buildCTable_wksp_tables))
745 return ERROR(workSpace_tooSmall);
746 if (maxNbBits == 0) maxNbBits = HUF_TABLELOG_DEFAULT;
747 if (maxSymbolValue > HUF_SYMBOLVALUE_MAX)
748 return ERROR(maxSymbolValue_tooLarge);
749 ZSTD_memset(huffNode0, 0, sizeof(huffNodeTable));
750
751 /* sort, decreasing order */
752 HUF_sort(huffNode, count, maxSymbolValue, wksp_tables->rankPosition);
753 DEBUGLOG(6, "sorted symbols completed (%zu symbols)", showHNodeSymbols(huffNode, maxSymbolValue+1));
754
755 /* build tree */
756 nonNullRank = HUF_buildTree(huffNode, maxSymbolValue);
757
758 /* determine and enforce maxTableLog */
759 maxNbBits = HUF_setMaxHeight(huffNode, (U32)nonNullRank, maxNbBits);
760 if (maxNbBits > HUF_TABLELOG_MAX) return ERROR(GENERIC); /* check fit into table */
761
762 HUF_buildCTableFromTree(CTable, huffNode, nonNullRank, maxSymbolValue, maxNbBits);
763
764 return maxNbBits;
765}
766
767size_t HUF_estimateCompressedSize(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue)
768{
769 HUF_CElt const* ct = CTable + 1;
770 size_t nbBits = 0;
771 int s;
772 for (s = 0; s <= (int)maxSymbolValue; ++s) {
773 nbBits += HUF_getNbBits(ct[s]) * count[s];
774 }
775 return nbBits >> 3;
776}
777
778int HUF_validateCTable(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue) {
779 HUF_CElt const* ct = CTable + 1;
780 int bad = 0;
781 int s;
782 for (s = 0; s <= (int)maxSymbolValue; ++s) {
783 bad |= (count[s] != 0) & (HUF_getNbBits(ct[s]) == 0);
784 }
785 return !bad;
786}
787
788size_t HUF_compressBound(size_t size) { return HUF_COMPRESSBOUND(size); }
789
790/** HUF_CStream_t:
791 * Huffman uses its own BIT_CStream_t implementation.
792 * There are three major differences from BIT_CStream_t:
793 * 1. HUF_addBits() takes a HUF_CElt (size_t) which is
794 * the pair (nbBits, value) in the format:
795 * format:
796 * - Bits [0, 4) = nbBits
797 * - Bits [4, 64 - nbBits) = 0
798 * - Bits [64 - nbBits, 64) = value
799 * 2. The bitContainer is built from the upper bits and
800 * right shifted. E.g. to add a new value of N bits
801 * you right shift the bitContainer by N, then or in
802 * the new value into the N upper bits.
803 * 3. The bitstream has two bit containers. You can add
804 * bits to the second container and merge them into
805 * the first container.
806 */
807
808#define HUF_BITS_IN_CONTAINER (sizeof(size_t) * 8)
809
810typedef struct {
811 size_t bitContainer[2];
812 size_t bitPos[2];
813
814 BYTE* startPtr;
815 BYTE* ptr;
816 BYTE* endPtr;
817} HUF_CStream_t;
818
819/**! HUF_initCStream():
820 * Initializes the bitstream.
821 * @returns 0 or an error code.
822 */
823static size_t HUF_initCStream(HUF_CStream_t* bitC,
824 void* startPtr, size_t dstCapacity)
825{
826 ZSTD_memset(bitC, 0, sizeof(*bitC));
827 bitC->startPtr = (BYTE*)startPtr;
828 bitC->ptr = bitC->startPtr;
829 bitC->endPtr = bitC->startPtr + dstCapacity - sizeof(bitC->bitContainer[0]);
830 if (dstCapacity <= sizeof(bitC->bitContainer[0])) return ERROR(dstSize_tooSmall);
831 return 0;
832}
833
834/*! HUF_addBits():
835 * Adds the symbol stored in HUF_CElt elt to the bitstream.
836 *
837 * @param elt The element we're adding. This is a (nbBits, value) pair.
838 * See the HUF_CStream_t docs for the format.
839 * @param idx Insert into the bitstream at this idx.
840 * @param kFast This is a template parameter. If the bitstream is guaranteed
841 * to have at least 4 unused bits after this call it may be 1,
842 * otherwise it must be 0. HUF_addBits() is faster when fast is set.
843 */
844FORCE_INLINE_TEMPLATE void HUF_addBits(HUF_CStream_t* bitC, HUF_CElt elt, int idx, int kFast)
845{
846 assert(idx <= 1);
847 assert(HUF_getNbBits(elt) <= HUF_TABLELOG_ABSOLUTEMAX);
848 /* This is efficient on x86-64 with BMI2 because shrx
849 * only reads the low 6 bits of the register. The compiler
850 * knows this and elides the mask. When fast is set,
851 * every operation can use the same value loaded from elt.
852 */
853 bitC->bitContainer[idx] >>= HUF_getNbBits(elt);
854 bitC->bitContainer[idx] |= kFast ? HUF_getValueFast(elt) : HUF_getValue(elt);
855 /* We only read the low 8 bits of bitC->bitPos[idx] so it
856 * doesn't matter that the high bits have noise from the value.
857 */
858 bitC->bitPos[idx] += HUF_getNbBitsFast(elt);
859 assert((bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER);
860 /* The last 4-bits of elt are dirty if fast is set,
861 * so we must not be overwriting bits that have already been
862 * inserted into the bit container.
863 */
864#if DEBUGLEVEL >= 1
865 {
866 size_t const nbBits = HUF_getNbBits(elt);
867 size_t const dirtyBits = nbBits == 0 ? 0 : ZSTD_highbit32((U32)nbBits) + 1;
868 (void)dirtyBits;
869 /* Middle bits are 0. */
870 assert(((elt >> dirtyBits) << (dirtyBits + nbBits)) == 0);
871 /* We didn't overwrite any bits in the bit container. */
872 assert(!kFast || (bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER);
873 (void)dirtyBits;
874 }
875#endif
876}
877
878FORCE_INLINE_TEMPLATE void HUF_zeroIndex1(HUF_CStream_t* bitC)
879{
880 bitC->bitContainer[1] = 0;
881 bitC->bitPos[1] = 0;
882}
883
884/*! HUF_mergeIndex1() :
885 * Merges the bit container @ index 1 into the bit container @ index 0
886 * and zeros the bit container @ index 1.
887 */
888FORCE_INLINE_TEMPLATE void HUF_mergeIndex1(HUF_CStream_t* bitC)
889{
890 assert((bitC->bitPos[1] & 0xFF) < HUF_BITS_IN_CONTAINER);
891 bitC->bitContainer[0] >>= (bitC->bitPos[1] & 0xFF);
892 bitC->bitContainer[0] |= bitC->bitContainer[1];
893 bitC->bitPos[0] += bitC->bitPos[1];
894 assert((bitC->bitPos[0] & 0xFF) <= HUF_BITS_IN_CONTAINER);
895}
896
897/*! HUF_flushBits() :
898* Flushes the bits in the bit container @ index 0.
899*
900* @post bitPos will be < 8.
901* @param kFast If kFast is set then we must know a-priori that
902* the bit container will not overflow.
903*/
904FORCE_INLINE_TEMPLATE void HUF_flushBits(HUF_CStream_t* bitC, int kFast)
905{
906 /* The upper bits of bitPos are noisy, so we must mask by 0xFF. */
907 size_t const nbBits = bitC->bitPos[0] & 0xFF;
908 size_t const nbBytes = nbBits >> 3;
909 /* The top nbBits bits of bitContainer are the ones we need. */
910 size_t const bitContainer = bitC->bitContainer[0] >> (HUF_BITS_IN_CONTAINER - nbBits);
911 /* Mask bitPos to account for the bytes we consumed. */
912 bitC->bitPos[0] &= 7;
913 assert(nbBits > 0);
914 assert(nbBits <= sizeof(bitC->bitContainer[0]) * 8);
915 assert(bitC->ptr <= bitC->endPtr);
916 MEM_writeLEST(bitC->ptr, bitContainer);
917 bitC->ptr += nbBytes;
918 assert(!kFast || bitC->ptr <= bitC->endPtr);
919 if (!kFast && bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr;
920 /* bitContainer doesn't need to be modified because the leftover
921 * bits are already the top bitPos bits. And we don't care about
922 * noise in the lower values.
923 */
924}
925
926/*! HUF_endMark()
927 * @returns The Huffman stream end mark: A 1-bit value = 1.
928 */
929static HUF_CElt HUF_endMark(void)
930{
931 HUF_CElt endMark;
932 HUF_setNbBits(&endMark, 1);
933 HUF_setValue(&endMark, 1);
934 return endMark;
935}
936
937/*! HUF_closeCStream() :
938 * @return Size of CStream, in bytes,
939 * or 0 if it could not fit into dstBuffer */
940static size_t HUF_closeCStream(HUF_CStream_t* bitC)
941{
942 HUF_addBits(bitC, HUF_endMark(), /* idx */ 0, /* kFast */ 0);
943 HUF_flushBits(bitC, /* kFast */ 0);
944 {
945 size_t const nbBits = bitC->bitPos[0] & 0xFF;
946 if (bitC->ptr >= bitC->endPtr) return 0; /* overflow detected */
947 return (size_t)(bitC->ptr - bitC->startPtr) + (nbBits > 0);
948 }
949}
950
951FORCE_INLINE_TEMPLATE void
952HUF_encodeSymbol(HUF_CStream_t* bitCPtr, U32 symbol, const HUF_CElt* CTable, int idx, int fast)
953{
954 HUF_addBits(bitCPtr, CTable[symbol], idx, fast);
955}
956
957FORCE_INLINE_TEMPLATE void
958HUF_compress1X_usingCTable_internal_body_loop(HUF_CStream_t* bitC,
959 const BYTE* ip, size_t srcSize,
960 const HUF_CElt* ct,
961 int kUnroll, int kFastFlush, int kLastFast)
962{
963 /* Join to kUnroll */
964 int n = (int)srcSize;
965 int rem = n % kUnroll;
966 if (rem > 0) {
967 for (; rem > 0; --rem) {
968 HUF_encodeSymbol(bitC, ip[--n], ct, 0, /* fast */ 0);
969 }
970 HUF_flushBits(bitC, kFastFlush);
971 }
972 assert(n % kUnroll == 0);
973
974 /* Join to 2 * kUnroll */
975 if (n % (2 * kUnroll)) {
976 int u;
977 for (u = 1; u < kUnroll; ++u) {
978 HUF_encodeSymbol(bitC, ip[n - u], ct, 0, 1);
979 }
980 HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, 0, kLastFast);
981 HUF_flushBits(bitC, kFastFlush);
982 n -= kUnroll;
983 }
984 assert(n % (2 * kUnroll) == 0);
985
986 for (; n>0; n-= 2 * kUnroll) {
987 /* Encode kUnroll symbols into the bitstream @ index 0. */
988 int u;
989 for (u = 1; u < kUnroll; ++u) {
990 HUF_encodeSymbol(bitC, ip[n - u], ct, /* idx */ 0, /* fast */ 1);
991 }
992 HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, /* idx */ 0, /* fast */ kLastFast);
993 HUF_flushBits(bitC, kFastFlush);
994 /* Encode kUnroll symbols into the bitstream @ index 1.
995 * This allows us to start filling the bit container
996 * without any data dependencies.
997 */
998 HUF_zeroIndex1(bitC);
999 for (u = 1; u < kUnroll; ++u) {
1000 HUF_encodeSymbol(bitC, ip[n - kUnroll - u], ct, /* idx */ 1, /* fast */ 1);
1001 }
1002 HUF_encodeSymbol(bitC, ip[n - kUnroll - kUnroll], ct, /* idx */ 1, /* fast */ kLastFast);
1003 /* Merge bitstream @ index 1 into the bitstream @ index 0 */
1004 HUF_mergeIndex1(bitC);
1005 HUF_flushBits(bitC, kFastFlush);
1006 }
1007 assert(n == 0);
1008
1009}
1010
1011/**
1012 * Returns a tight upper bound on the output space needed by Huffman
1013 * with 8 bytes buffer to handle over-writes. If the output is at least
1014 * this large we don't need to do bounds checks during Huffman encoding.
1015 */
1016static size_t HUF_tightCompressBound(size_t srcSize, size_t tableLog)
1017{
1018 return ((srcSize * tableLog) >> 3) + 8;
1019}
1020
1021
1022FORCE_INLINE_TEMPLATE size_t
1023HUF_compress1X_usingCTable_internal_body(void* dst, size_t dstSize,
1024 const void* src, size_t srcSize,
1025 const HUF_CElt* CTable)
1026{
1027 U32 const tableLog = (U32)CTable[0];
1028 HUF_CElt const* ct = CTable + 1;
1029 const BYTE* ip = (const BYTE*) src;
1030 BYTE* const ostart = (BYTE*)dst;
1031 BYTE* const oend = ostart + dstSize;
1032 BYTE* op = ostart;
1033 HUF_CStream_t bitC;
1034
1035 /* init */
1036 if (dstSize < 8) return 0; /* not enough space to compress */
1037 { size_t const initErr = HUF_initCStream(&bitC, op, (size_t)(oend-op));
1038 if (HUF_isError(initErr)) return 0; }
1039
1040 if (dstSize < HUF_tightCompressBound(srcSize, (size_t)tableLog) || tableLog > 11)
1041 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ MEM_32bits() ? 2 : 4, /* kFast */ 0, /* kLastFast */ 0);
1042 else {
1043 if (MEM_32bits()) {
1044 switch (tableLog) {
1045 case 11:
1046 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 0);
1047 break;
1048 case 10: ZSTD_FALLTHROUGH;
1049 case 9: ZSTD_FALLTHROUGH;
1050 case 8:
1051 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 1);
1052 break;
1053 case 7: ZSTD_FALLTHROUGH;
1054 default:
1055 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 3, /* kFastFlush */ 1, /* kLastFast */ 1);
1056 break;
1057 }
1058 } else {
1059 switch (tableLog) {
1060 case 11:
1061 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 0);
1062 break;
1063 case 10:
1064 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 1);
1065 break;
1066 case 9:
1067 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 6, /* kFastFlush */ 1, /* kLastFast */ 0);
1068 break;
1069 case 8:
1070 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 7, /* kFastFlush */ 1, /* kLastFast */ 0);
1071 break;
1072 case 7:
1073 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 8, /* kFastFlush */ 1, /* kLastFast */ 0);
1074 break;
1075 case 6: ZSTD_FALLTHROUGH;
1076 default:
1077 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 9, /* kFastFlush */ 1, /* kLastFast */ 1);
1078 break;
1079 }
1080 }
1081 }
1082 assert(bitC.ptr <= bitC.endPtr);
1083
1084 return HUF_closeCStream(&bitC);
1085}
1086
1087#if DYNAMIC_BMI2
1088
1089static BMI2_TARGET_ATTRIBUTE size_t
1090HUF_compress1X_usingCTable_internal_bmi2(void* dst, size_t dstSize,
1091 const void* src, size_t srcSize,
1092 const HUF_CElt* CTable)
1093{
1094 return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
1095}
1096
1097static size_t
1098HUF_compress1X_usingCTable_internal_default(void* dst, size_t dstSize,
1099 const void* src, size_t srcSize,
1100 const HUF_CElt* CTable)
1101{
1102 return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
1103}
1104
1105static size_t
1106HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize,
1107 const void* src, size_t srcSize,
1108 const HUF_CElt* CTable, const int flags)
1109{
1110 if (flags & HUF_flags_bmi2) {
1111 return HUF_compress1X_usingCTable_internal_bmi2(dst, dstSize, src, srcSize, CTable);
1112 }
1113 return HUF_compress1X_usingCTable_internal_default(dst, dstSize, src, srcSize, CTable);
1114}
1115
1116#else
1117
1118static size_t
1119HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize,
1120 const void* src, size_t srcSize,
1121 const HUF_CElt* CTable, const int flags)
1122{
1123 (void)flags;
1124 return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
1125}
1126
1127#endif
1128
1129size_t HUF_compress1X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags)
1130{
1131 return HUF_compress1X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, flags);
1132}
1133
1134static size_t
1135HUF_compress4X_usingCTable_internal(void* dst, size_t dstSize,
1136 const void* src, size_t srcSize,
1137 const HUF_CElt* CTable, int flags)
1138{
1139 size_t const segmentSize = (srcSize+3)/4; /* first 3 segments */
1140 const BYTE* ip = (const BYTE*) src;
1141 const BYTE* const iend = ip + srcSize;
1142 BYTE* const ostart = (BYTE*) dst;
1143 BYTE* const oend = ostart + dstSize;
1144 BYTE* op = ostart;
1145
1146 if (dstSize < 6 + 1 + 1 + 1 + 8) return 0; /* minimum space to compress successfully */
1147 if (srcSize < 12) return 0; /* no saving possible : too small input */
1148 op += 6; /* jumpTable */
1149
1150 assert(op <= oend);
1151 { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) );
1152 if (cSize == 0 || cSize > 65535) return 0;
1153 MEM_writeLE16(ostart, (U16)cSize);
1154 op += cSize;
1155 }
1156
1157 ip += segmentSize;
1158 assert(op <= oend);
1159 { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) );
1160 if (cSize == 0 || cSize > 65535) return 0;
1161 MEM_writeLE16(ostart+2, (U16)cSize);
1162 op += cSize;
1163 }
1164
1165 ip += segmentSize;
1166 assert(op <= oend);
1167 { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) );
1168 if (cSize == 0 || cSize > 65535) return 0;
1169 MEM_writeLE16(ostart+4, (U16)cSize);
1170 op += cSize;
1171 }
1172
1173 ip += segmentSize;
1174 assert(op <= oend);
1175 assert(ip <= iend);
1176 { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, (size_t)(iend-ip), CTable, flags) );
1177 if (cSize == 0 || cSize > 65535) return 0;
1178 op += cSize;
1179 }
1180
1181 return (size_t)(op-ostart);
1182}
1183
1184size_t HUF_compress4X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags)
1185{
1186 return HUF_compress4X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, flags);
1187}
1188
1189typedef enum { HUF_singleStream, HUF_fourStreams } HUF_nbStreams_e;
1190
1191static size_t HUF_compressCTable_internal(
1192 BYTE* const ostart, BYTE* op, BYTE* const oend,
1193 const void* src, size_t srcSize,
1194 HUF_nbStreams_e nbStreams, const HUF_CElt* CTable, const int flags)
1195{
1196 size_t const cSize = (nbStreams==HUF_singleStream) ?
1197 HUF_compress1X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, flags) :
1198 HUF_compress4X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, flags);
1199 if (HUF_isError(cSize)) { return cSize; }
1200 if (cSize==0) { return 0; } /* uncompressible */
1201 op += cSize;
1202 /* check compressibility */
1203 assert(op >= ostart);
1204 if ((size_t)(op-ostart) >= srcSize-1) { return 0; }
1205 return (size_t)(op-ostart);
1206}
1207
1208typedef struct {
1209 unsigned count[HUF_SYMBOLVALUE_MAX + 1];
1210 HUF_CElt CTable[HUF_CTABLE_SIZE_ST(HUF_SYMBOLVALUE_MAX)];
1211 union {
1212 HUF_buildCTable_wksp_tables buildCTable_wksp;
1213 HUF_WriteCTableWksp writeCTable_wksp;
1214 U32 hist_wksp[HIST_WKSP_SIZE_U32];
1215 } wksps;
1216} HUF_compress_tables_t;
1217
1218#define SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE 4096
1219#define SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO 10 /* Must be >= 2 */
1220
1221unsigned HUF_cardinality(const unsigned* count, unsigned maxSymbolValue)
1222{
1223 unsigned cardinality = 0;
1224 unsigned i;
1225
1226 for (i = 0; i < maxSymbolValue + 1; i++) {
1227 if (count[i] != 0) cardinality += 1;
1228 }
1229
1230 return cardinality;
1231}
1232
1233unsigned HUF_minTableLog(unsigned symbolCardinality)
1234{
1235 U32 minBitsSymbols = ZSTD_highbit32(symbolCardinality) + 1;
1236 return minBitsSymbols;
1237}
1238
1239unsigned HUF_optimalTableLog(
1240 unsigned maxTableLog,
1241 size_t srcSize,
1242 unsigned maxSymbolValue,
1243 void* workSpace, size_t wkspSize,
1244 HUF_CElt* table,
1245 const unsigned* count,
1246 int flags)
1247{
1248 assert(srcSize > 1); /* Not supported, RLE should be used instead */
1249 assert(wkspSize >= sizeof(HUF_buildCTable_wksp_tables));
1250
1251 if (!(flags & HUF_flags_optimalDepth)) {
1252 /* cheap evaluation, based on FSE */
1253 return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 1);
1254 }
1255
1256 { BYTE* dst = (BYTE*)workSpace + sizeof(HUF_WriteCTableWksp);
1257 size_t dstSize = wkspSize - sizeof(HUF_WriteCTableWksp);
1258 size_t maxBits, hSize, newSize;
1259 const unsigned symbolCardinality = HUF_cardinality(count, maxSymbolValue);
1260 const unsigned minTableLog = HUF_minTableLog(symbolCardinality);
1261 size_t optSize = ((size_t) ~0) - 1;
1262 unsigned optLog = maxTableLog, optLogGuess;
1263
1264 DEBUGLOG(6, "HUF_optimalTableLog: probing huf depth (srcSize=%zu)", srcSize);
1265
1266 /* Search until size increases */
1267 for (optLogGuess = minTableLog; optLogGuess <= maxTableLog; optLogGuess++) {
1268 DEBUGLOG(7, "checking for huffLog=%u", optLogGuess);
1269 maxBits = HUF_buildCTable_wksp(table, count, maxSymbolValue, optLogGuess, workSpace, wkspSize);
1270 if (ERR_isError(maxBits)) continue;
1271
1272 if (maxBits < optLogGuess && optLogGuess > minTableLog) break;
1273
1274 hSize = HUF_writeCTable_wksp(dst, dstSize, table, maxSymbolValue, (U32)maxBits, workSpace, wkspSize);
1275
1276 if (ERR_isError(hSize)) continue;
1277
1278 newSize = HUF_estimateCompressedSize(table, count, maxSymbolValue) + hSize;
1279
1280 if (newSize > optSize + 1) {
1281 break;
1282 }
1283
1284 if (newSize < optSize) {
1285 optSize = newSize;
1286 optLog = optLogGuess;
1287 }
1288 }
1289 assert(optLog <= HUF_TABLELOG_MAX);
1290 return optLog;
1291 }
1292}
1293
1294/* HUF_compress_internal() :
1295 * `workSpace_align4` must be aligned on 4-bytes boundaries,
1296 * and occupies the same space as a table of HUF_WORKSPACE_SIZE_U64 unsigned */
1297static size_t
1298HUF_compress_internal (void* dst, size_t dstSize,
1299 const void* src, size_t srcSize,
1300 unsigned maxSymbolValue, unsigned huffLog,
1301 HUF_nbStreams_e nbStreams,
1302 void* workSpace, size_t wkspSize,
1303 HUF_CElt* oldHufTable, HUF_repeat* repeat, int flags)
1304{
1305 HUF_compress_tables_t* const table = (HUF_compress_tables_t*)HUF_alignUpWorkspace(workSpace, &wkspSize, ZSTD_ALIGNOF(size_t));
1306 BYTE* const ostart = (BYTE*)dst;
1307 BYTE* const oend = ostart + dstSize;
1308 BYTE* op = ostart;
1309
1310 DEBUGLOG(5, "HUF_compress_internal (srcSize=%zu)", srcSize);
1311 HUF_STATIC_ASSERT(sizeof(*table) + HUF_WORKSPACE_MAX_ALIGNMENT <= HUF_WORKSPACE_SIZE);
1312
1313 /* checks & inits */
1314 if (wkspSize < sizeof(*table)) return ERROR(workSpace_tooSmall);
1315 if (!srcSize) return 0; /* Uncompressed */
1316 if (!dstSize) return 0; /* cannot fit anything within dst budget */
1317 if (srcSize > HUF_BLOCKSIZE_MAX) return ERROR(srcSize_wrong); /* current block size limit */
1318 if (huffLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
1319 if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
1320 if (!maxSymbolValue) maxSymbolValue = HUF_SYMBOLVALUE_MAX;
1321 if (!huffLog) huffLog = HUF_TABLELOG_DEFAULT;
1322
1323 /* Heuristic : If old table is valid, use it for small inputs */
1324 if ((flags & HUF_flags_preferRepeat) && repeat && *repeat == HUF_repeat_valid) {
1325 return HUF_compressCTable_internal(ostart, op, oend,
1326 src, srcSize,
1327 nbStreams, oldHufTable, flags);
1328 }
1329
1330 /* If uncompressible data is suspected, do a smaller sampling first */
1331 DEBUG_STATIC_ASSERT(SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO >= 2);
1332 if ((flags & HUF_flags_suspectUncompressible) && srcSize >= (SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE * SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO)) {
1333 size_t largestTotal = 0;
1334 DEBUGLOG(5, "input suspected incompressible : sampling to check");
1335 { unsigned maxSymbolValueBegin = maxSymbolValue;
1336 CHECK_V_F(largestBegin, HIST_count_simple (table->count, &maxSymbolValueBegin, (const BYTE*)src, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) );
1337 largestTotal += largestBegin;
1338 }
1339 { unsigned maxSymbolValueEnd = maxSymbolValue;
1340 CHECK_V_F(largestEnd, HIST_count_simple (table->count, &maxSymbolValueEnd, (const BYTE*)src + srcSize - SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) );
1341 largestTotal += largestEnd;
1342 }
1343 if (largestTotal <= ((2 * SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) >> 7)+4) return 0; /* heuristic : probably not compressible enough */
1344 }
1345
1346 /* Scan input and build symbol stats */
1347 { CHECK_V_F(largest, HIST_count_wksp (table->count, &maxSymbolValue, (const BYTE*)src, srcSize, table->wksps.hist_wksp, sizeof(table->wksps.hist_wksp)) );
1348 if (largest == srcSize) { *ostart = ((const BYTE*)src)[0]; return 1; } /* single symbol, rle */
1349 if (largest <= (srcSize >> 7)+4) return 0; /* heuristic : probably not compressible enough */
1350 }
1351 DEBUGLOG(6, "histogram detail completed (%zu symbols)", showU32(table->count, maxSymbolValue+1));
1352
1353 /* Check validity of previous table */
1354 if ( repeat
1355 && *repeat == HUF_repeat_check
1356 && !HUF_validateCTable(oldHufTable, table->count, maxSymbolValue)) {
1357 *repeat = HUF_repeat_none;
1358 }
1359 /* Heuristic : use existing table for small inputs */
1360 if ((flags & HUF_flags_preferRepeat) && repeat && *repeat != HUF_repeat_none) {
1361 return HUF_compressCTable_internal(ostart, op, oend,
1362 src, srcSize,
1363 nbStreams, oldHufTable, flags);
1364 }
1365
1366 /* Build Huffman Tree */
1367 huffLog = HUF_optimalTableLog(huffLog, srcSize, maxSymbolValue, &table->wksps, sizeof(table->wksps), table->CTable, table->count, flags);
1368 { size_t const maxBits = HUF_buildCTable_wksp(table->CTable, table->count,
1369 maxSymbolValue, huffLog,
1370 &table->wksps.buildCTable_wksp, sizeof(table->wksps.buildCTable_wksp));
1371 CHECK_F(maxBits);
1372 huffLog = (U32)maxBits;
1373 DEBUGLOG(6, "bit distribution completed (%zu symbols)", showCTableBits(table->CTable + 1, maxSymbolValue+1));
1374 }
1375 /* Zero unused symbols in CTable, so we can check it for validity */
1376 {
1377 size_t const ctableSize = HUF_CTABLE_SIZE_ST(maxSymbolValue);
1378 size_t const unusedSize = sizeof(table->CTable) - ctableSize * sizeof(HUF_CElt);
1379 ZSTD_memset(table->CTable + ctableSize, 0, unusedSize);
1380 }
1381
1382 /* Write table description header */
1383 { CHECK_V_F(hSize, HUF_writeCTable_wksp(op, dstSize, table->CTable, maxSymbolValue, huffLog,
1384 &table->wksps.writeCTable_wksp, sizeof(table->wksps.writeCTable_wksp)) );
1385 /* Check if using previous huffman table is beneficial */
1386 if (repeat && *repeat != HUF_repeat_none) {
1387 size_t const oldSize = HUF_estimateCompressedSize(oldHufTable, table->count, maxSymbolValue);
1388 size_t const newSize = HUF_estimateCompressedSize(table->CTable, table->count, maxSymbolValue);
1389 if (oldSize <= hSize + newSize || hSize + 12 >= srcSize) {
1390 return HUF_compressCTable_internal(ostart, op, oend,
1391 src, srcSize,
1392 nbStreams, oldHufTable, flags);
1393 } }
1394
1395 /* Use the new huffman table */
1396 if (hSize + 12ul >= srcSize) { return 0; }
1397 op += hSize;
1398 if (repeat) { *repeat = HUF_repeat_none; }
1399 if (oldHufTable)
1400 ZSTD_memcpy(oldHufTable, table->CTable, sizeof(table->CTable)); /* Save new table */
1401 }
1402 return HUF_compressCTable_internal(ostart, op, oend,
1403 src, srcSize,
1404 nbStreams, table->CTable, flags);
1405}
1406
1407size_t HUF_compress1X_repeat (void* dst, size_t dstSize,
1408 const void* src, size_t srcSize,
1409 unsigned maxSymbolValue, unsigned huffLog,
1410 void* workSpace, size_t wkspSize,
1411 HUF_CElt* hufTable, HUF_repeat* repeat, int flags)
1412{
1413 DEBUGLOG(5, "HUF_compress1X_repeat (srcSize = %zu)", srcSize);
1414 return HUF_compress_internal(dst, dstSize, src, srcSize,
1415 maxSymbolValue, huffLog, HUF_singleStream,
1416 workSpace, wkspSize, hufTable,
1417 repeat, flags);
1418}
1419
1420/* HUF_compress4X_repeat():
1421 * compress input using 4 streams.
1422 * consider skipping quickly
1423 * re-use an existing huffman compression table */
1424size_t HUF_compress4X_repeat (void* dst, size_t dstSize,
1425 const void* src, size_t srcSize,
1426 unsigned maxSymbolValue, unsigned huffLog,
1427 void* workSpace, size_t wkspSize,
1428 HUF_CElt* hufTable, HUF_repeat* repeat, int flags)
1429{
1430 DEBUGLOG(5, "HUF_compress4X_repeat (srcSize = %zu)", srcSize);
1431 return HUF_compress_internal(dst, dstSize, src, srcSize,
1432 maxSymbolValue, huffLog, HUF_fourStreams,
1433 workSpace, wkspSize,
1434 hufTable, repeat, flags);
1435}
1436