xref: /linux/lib/zstd/compress/huf_compress.c (revision 2aa14b1a)
1 /* ******************************************************************
2  * Huffman encoder, part of New Generation Entropy library
3  * Copyright (c) Yann Collet, Facebook, Inc.
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 
19 
20 /* **************************************************************
21 *  Includes
22 ****************************************************************/
23 #include "../common/zstd_deps.h"     /* ZSTD_memcpy, ZSTD_memset */
24 #include "../common/compiler.h"
25 #include "../common/bitstream.h"
26 #include "hist.h"
27 #define FSE_STATIC_LINKING_ONLY   /* FSE_optimalTableLog_internal */
28 #include "../common/fse.h"        /* header compression */
29 #define HUF_STATIC_LINKING_ONLY
30 #include "../common/huf.h"
31 #include "../common/error_private.h"
32 
33 
34 /* **************************************************************
35 *  Error Management
36 ****************************************************************/
37 #define HUF_isError ERR_isError
38 #define HUF_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c)   /* use only *after* variable declarations */
39 
40 
41 /* **************************************************************
42 *  Utils
43 ****************************************************************/
HUF_optimalTableLog(unsigned maxTableLog,size_t srcSize,unsigned maxSymbolValue)44 unsigned HUF_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue)
45 {
46     return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 1);
47 }
48 
49 
50 /* *******************************************************
51 *  HUF : Huffman block compression
52 *********************************************************/
53 #define HUF_WORKSPACE_MAX_ALIGNMENT 8
54 
HUF_alignUpWorkspace(void * workspace,size_t * workspaceSizePtr,size_t align)55 static void* HUF_alignUpWorkspace(void* workspace, size_t* workspaceSizePtr, size_t align)
56 {
57     size_t const mask = align - 1;
58     size_t const rem = (size_t)workspace & mask;
59     size_t const add = (align - rem) & mask;
60     BYTE* const aligned = (BYTE*)workspace + add;
61     assert((align & (align - 1)) == 0); /* pow 2 */
62     assert(align <= HUF_WORKSPACE_MAX_ALIGNMENT);
63     if (*workspaceSizePtr >= add) {
64         assert(add < align);
65         assert(((size_t)aligned & mask) == 0);
66         *workspaceSizePtr -= add;
67         return aligned;
68     } else {
69         *workspaceSizePtr = 0;
70         return NULL;
71     }
72 }
73 
74 
75 /* HUF_compressWeights() :
76  * Same as FSE_compress(), but dedicated to huff0's weights compression.
77  * The use case needs much less stack memory.
78  * Note : all elements within weightTable are supposed to be <= HUF_TABLELOG_MAX.
79  */
80 #define MAX_FSE_TABLELOG_FOR_HUFF_HEADER 6
81 
82 typedef struct {
83     FSE_CTable CTable[FSE_CTABLE_SIZE_U32(MAX_FSE_TABLELOG_FOR_HUFF_HEADER, HUF_TABLELOG_MAX)];
84     U32 scratchBuffer[FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(HUF_TABLELOG_MAX, MAX_FSE_TABLELOG_FOR_HUFF_HEADER)];
85     unsigned count[HUF_TABLELOG_MAX+1];
86     S16 norm[HUF_TABLELOG_MAX+1];
87 } HUF_CompressWeightsWksp;
88 
HUF_compressWeights(void * dst,size_t dstSize,const void * weightTable,size_t wtSize,void * workspace,size_t workspaceSize)89 static size_t HUF_compressWeights(void* dst, size_t dstSize, const void* weightTable, size_t wtSize, void* workspace, size_t workspaceSize)
90 {
91     BYTE* const ostart = (BYTE*) dst;
92     BYTE* op = ostart;
93     BYTE* const oend = ostart + dstSize;
94 
95     unsigned maxSymbolValue = HUF_TABLELOG_MAX;
96     U32 tableLog = MAX_FSE_TABLELOG_FOR_HUFF_HEADER;
97     HUF_CompressWeightsWksp* wksp = (HUF_CompressWeightsWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32));
98 
99     if (workspaceSize < sizeof(HUF_CompressWeightsWksp)) return ERROR(GENERIC);
100 
101     /* init conditions */
102     if (wtSize <= 1) return 0;  /* Not compressible */
103 
104     /* Scan input and build symbol stats */
105     {   unsigned const maxCount = HIST_count_simple(wksp->count, &maxSymbolValue, weightTable, wtSize);   /* never fails */
106         if (maxCount == wtSize) return 1;   /* only a single symbol in src : rle */
107         if (maxCount == 1) return 0;        /* each symbol present maximum once => not compressible */
108     }
109 
110     tableLog = FSE_optimalTableLog(tableLog, wtSize, maxSymbolValue);
111     CHECK_F( FSE_normalizeCount(wksp->norm, tableLog, wksp->count, wtSize, maxSymbolValue, /* useLowProbCount */ 0) );
112 
113     /* Write table description header */
114     {   CHECK_V_F(hSize, FSE_writeNCount(op, (size_t)(oend-op), wksp->norm, maxSymbolValue, tableLog) );
115         op += hSize;
116     }
117 
118     /* Compress */
119     CHECK_F( FSE_buildCTable_wksp(wksp->CTable, wksp->norm, maxSymbolValue, tableLog, wksp->scratchBuffer, sizeof(wksp->scratchBuffer)) );
120     {   CHECK_V_F(cSize, FSE_compress_usingCTable(op, (size_t)(oend - op), weightTable, wtSize, wksp->CTable) );
121         if (cSize == 0) return 0;   /* not enough space for compressed data */
122         op += cSize;
123     }
124 
125     return (size_t)(op-ostart);
126 }
127 
HUF_getNbBits(HUF_CElt elt)128 static size_t HUF_getNbBits(HUF_CElt elt)
129 {
130     return elt & 0xFF;
131 }
132 
HUF_getNbBitsFast(HUF_CElt elt)133 static size_t HUF_getNbBitsFast(HUF_CElt elt)
134 {
135     return elt;
136 }
137 
HUF_getValue(HUF_CElt elt)138 static size_t HUF_getValue(HUF_CElt elt)
139 {
140     return elt & ~0xFF;
141 }
142 
HUF_getValueFast(HUF_CElt elt)143 static size_t HUF_getValueFast(HUF_CElt elt)
144 {
145     return elt;
146 }
147 
HUF_setNbBits(HUF_CElt * elt,size_t nbBits)148 static void HUF_setNbBits(HUF_CElt* elt, size_t nbBits)
149 {
150     assert(nbBits <= HUF_TABLELOG_ABSOLUTEMAX);
151     *elt = nbBits;
152 }
153 
HUF_setValue(HUF_CElt * elt,size_t value)154 static void HUF_setValue(HUF_CElt* elt, size_t value)
155 {
156     size_t const nbBits = HUF_getNbBits(*elt);
157     if (nbBits > 0) {
158         assert((value >> nbBits) == 0);
159         *elt |= value << (sizeof(HUF_CElt) * 8 - nbBits);
160     }
161 }
162 
163 typedef struct {
164     HUF_CompressWeightsWksp wksp;
165     BYTE bitsToWeight[HUF_TABLELOG_MAX + 1];   /* precomputed conversion table */
166     BYTE huffWeight[HUF_SYMBOLVALUE_MAX];
167 } HUF_WriteCTableWksp;
168 
HUF_writeCTable_wksp(void * dst,size_t maxDstSize,const HUF_CElt * CTable,unsigned maxSymbolValue,unsigned huffLog,void * workspace,size_t workspaceSize)169 size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize,
170                             const HUF_CElt* CTable, unsigned maxSymbolValue, unsigned huffLog,
171                             void* workspace, size_t workspaceSize)
172 {
173     HUF_CElt const* const ct = CTable + 1;
174     BYTE* op = (BYTE*)dst;
175     U32 n;
176     HUF_WriteCTableWksp* wksp = (HUF_WriteCTableWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32));
177 
178     /* check conditions */
179     if (workspaceSize < sizeof(HUF_WriteCTableWksp)) return ERROR(GENERIC);
180     if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
181 
182     /* convert to weight */
183     wksp->bitsToWeight[0] = 0;
184     for (n=1; n<huffLog+1; n++)
185         wksp->bitsToWeight[n] = (BYTE)(huffLog + 1 - n);
186     for (n=0; n<maxSymbolValue; n++)
187         wksp->huffWeight[n] = wksp->bitsToWeight[HUF_getNbBits(ct[n])];
188 
189     /* attempt weights compression by FSE */
190     if (maxDstSize < 1) return ERROR(dstSize_tooSmall);
191     {   CHECK_V_F(hSize, HUF_compressWeights(op+1, maxDstSize-1, wksp->huffWeight, maxSymbolValue, &wksp->wksp, sizeof(wksp->wksp)) );
192         if ((hSize>1) & (hSize < maxSymbolValue/2)) {   /* FSE compressed */
193             op[0] = (BYTE)hSize;
194             return hSize+1;
195     }   }
196 
197     /* write raw values as 4-bits (max : 15) */
198     if (maxSymbolValue > (256-128)) return ERROR(GENERIC);   /* should not happen : likely means source cannot be compressed */
199     if (((maxSymbolValue+1)/2) + 1 > maxDstSize) return ERROR(dstSize_tooSmall);   /* not enough space within dst buffer */
200     op[0] = (BYTE)(128 /*special case*/ + (maxSymbolValue-1));
201     wksp->huffWeight[maxSymbolValue] = 0;   /* to be sure it doesn't cause msan issue in final combination */
202     for (n=0; n<maxSymbolValue; n+=2)
203         op[(n/2)+1] = (BYTE)((wksp->huffWeight[n] << 4) + wksp->huffWeight[n+1]);
204     return ((maxSymbolValue+1)/2) + 1;
205 }
206 
207 /*! HUF_writeCTable() :
208     `CTable` : Huffman tree to save, using huf representation.
209     @return : size of saved CTable */
HUF_writeCTable(void * dst,size_t maxDstSize,const HUF_CElt * CTable,unsigned maxSymbolValue,unsigned huffLog)210 size_t HUF_writeCTable (void* dst, size_t maxDstSize,
211                         const HUF_CElt* CTable, unsigned maxSymbolValue, unsigned huffLog)
212 {
213     HUF_WriteCTableWksp wksp;
214     return HUF_writeCTable_wksp(dst, maxDstSize, CTable, maxSymbolValue, huffLog, &wksp, sizeof(wksp));
215 }
216 
217 
HUF_readCTable(HUF_CElt * CTable,unsigned * maxSymbolValuePtr,const void * src,size_t srcSize,unsigned * hasZeroWeights)218 size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize, unsigned* hasZeroWeights)
219 {
220     BYTE huffWeight[HUF_SYMBOLVALUE_MAX + 1];   /* init not required, even though some static analyzer may complain */
221     U32 rankVal[HUF_TABLELOG_ABSOLUTEMAX + 1];   /* large enough for values from 0 to 16 */
222     U32 tableLog = 0;
223     U32 nbSymbols = 0;
224     HUF_CElt* const ct = CTable + 1;
225 
226     /* get symbol weights */
227     CHECK_V_F(readSize, HUF_readStats(huffWeight, HUF_SYMBOLVALUE_MAX+1, rankVal, &nbSymbols, &tableLog, src, srcSize));
228     *hasZeroWeights = (rankVal[0] > 0);
229 
230     /* check result */
231     if (tableLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
232     if (nbSymbols > *maxSymbolValuePtr+1) return ERROR(maxSymbolValue_tooSmall);
233 
234     CTable[0] = tableLog;
235 
236     /* Prepare base value per rank */
237     {   U32 n, nextRankStart = 0;
238         for (n=1; n<=tableLog; n++) {
239             U32 curr = nextRankStart;
240             nextRankStart += (rankVal[n] << (n-1));
241             rankVal[n] = curr;
242     }   }
243 
244     /* fill nbBits */
245     {   U32 n; for (n=0; n<nbSymbols; n++) {
246             const U32 w = huffWeight[n];
247             HUF_setNbBits(ct + n, (BYTE)(tableLog + 1 - w) & -(w != 0));
248     }   }
249 
250     /* fill val */
251     {   U16 nbPerRank[HUF_TABLELOG_MAX+2]  = {0};  /* support w=0=>n=tableLog+1 */
252         U16 valPerRank[HUF_TABLELOG_MAX+2] = {0};
253         { U32 n; for (n=0; n<nbSymbols; n++) nbPerRank[HUF_getNbBits(ct[n])]++; }
254         /* determine stating value per rank */
255         valPerRank[tableLog+1] = 0;   /* for w==0 */
256         {   U16 min = 0;
257             U32 n; for (n=tableLog; n>0; n--) {  /* start at n=tablelog <-> w=1 */
258                 valPerRank[n] = min;     /* get starting value within each rank */
259                 min += nbPerRank[n];
260                 min >>= 1;
261         }   }
262         /* assign value within rank, symbol order */
263         { U32 n; for (n=0; n<nbSymbols; n++) HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++); }
264     }
265 
266     *maxSymbolValuePtr = nbSymbols - 1;
267     return readSize;
268 }
269 
HUF_getNbBitsFromCTable(HUF_CElt const * CTable,U32 symbolValue)270 U32 HUF_getNbBitsFromCTable(HUF_CElt const* CTable, U32 symbolValue)
271 {
272     const HUF_CElt* ct = CTable + 1;
273     assert(symbolValue <= HUF_SYMBOLVALUE_MAX);
274     return (U32)HUF_getNbBits(ct[symbolValue]);
275 }
276 
277 
278 typedef struct nodeElt_s {
279     U32 count;
280     U16 parent;
281     BYTE byte;
282     BYTE nbBits;
283 } nodeElt;
284 
285 /*
286  * HUF_setMaxHeight():
287  * Enforces maxNbBits on the Huffman tree described in huffNode.
288  *
289  * It sets all nodes with nbBits > maxNbBits to be maxNbBits. Then it adjusts
290  * the tree to so that it is a valid canonical Huffman tree.
291  *
292  * @pre               The sum of the ranks of each symbol == 2^largestBits,
293  *                    where largestBits == huffNode[lastNonNull].nbBits.
294  * @post              The sum of the ranks of each symbol == 2^largestBits,
295  *                    where largestBits is the return value <= maxNbBits.
296  *
297  * @param huffNode    The Huffman tree modified in place to enforce maxNbBits.
298  * @param lastNonNull The symbol with the lowest count in the Huffman tree.
299  * @param maxNbBits   The maximum allowed number of bits, which the Huffman tree
300  *                    may not respect. After this function the Huffman tree will
301  *                    respect maxNbBits.
302  * @return            The maximum number of bits of the Huffman tree after adjustment,
303  *                    necessarily no more than maxNbBits.
304  */
HUF_setMaxHeight(nodeElt * huffNode,U32 lastNonNull,U32 maxNbBits)305 static U32 HUF_setMaxHeight(nodeElt* huffNode, U32 lastNonNull, U32 maxNbBits)
306 {
307     const U32 largestBits = huffNode[lastNonNull].nbBits;
308     /* early exit : no elt > maxNbBits, so the tree is already valid. */
309     if (largestBits <= maxNbBits) return largestBits;
310 
311     /* there are several too large elements (at least >= 2) */
312     {   int totalCost = 0;
313         const U32 baseCost = 1 << (largestBits - maxNbBits);
314         int n = (int)lastNonNull;
315 
316         /* Adjust any ranks > maxNbBits to maxNbBits.
317          * Compute totalCost, which is how far the sum of the ranks is
318          * we are over 2^largestBits after adjust the offending ranks.
319          */
320         while (huffNode[n].nbBits > maxNbBits) {
321             totalCost += baseCost - (1 << (largestBits - huffNode[n].nbBits));
322             huffNode[n].nbBits = (BYTE)maxNbBits;
323             n--;
324         }
325         /* n stops at huffNode[n].nbBits <= maxNbBits */
326         assert(huffNode[n].nbBits <= maxNbBits);
327         /* n end at index of smallest symbol using < maxNbBits */
328         while (huffNode[n].nbBits == maxNbBits) --n;
329 
330         /* renorm totalCost from 2^largestBits to 2^maxNbBits
331          * note : totalCost is necessarily a multiple of baseCost */
332         assert((totalCost & (baseCost - 1)) == 0);
333         totalCost >>= (largestBits - maxNbBits);
334         assert(totalCost > 0);
335 
336         /* repay normalized cost */
337         {   U32 const noSymbol = 0xF0F0F0F0;
338             U32 rankLast[HUF_TABLELOG_MAX+2];
339 
340             /* Get pos of last (smallest = lowest cum. count) symbol per rank */
341             ZSTD_memset(rankLast, 0xF0, sizeof(rankLast));
342             {   U32 currentNbBits = maxNbBits;
343                 int pos;
344                 for (pos=n ; pos >= 0; pos--) {
345                     if (huffNode[pos].nbBits >= currentNbBits) continue;
346                     currentNbBits = huffNode[pos].nbBits;   /* < maxNbBits */
347                     rankLast[maxNbBits-currentNbBits] = (U32)pos;
348             }   }
349 
350             while (totalCost > 0) {
351                 /* Try to reduce the next power of 2 above totalCost because we
352                  * gain back half the rank.
353                  */
354                 U32 nBitsToDecrease = BIT_highbit32((U32)totalCost) + 1;
355                 for ( ; nBitsToDecrease > 1; nBitsToDecrease--) {
356                     U32 const highPos = rankLast[nBitsToDecrease];
357                     U32 const lowPos = rankLast[nBitsToDecrease-1];
358                     if (highPos == noSymbol) continue;
359                     /* Decrease highPos if no symbols of lowPos or if it is
360                      * not cheaper to remove 2 lowPos than highPos.
361                      */
362                     if (lowPos == noSymbol) break;
363                     {   U32 const highTotal = huffNode[highPos].count;
364                         U32 const lowTotal = 2 * huffNode[lowPos].count;
365                         if (highTotal <= lowTotal) break;
366                 }   }
367                 /* only triggered when no more rank 1 symbol left => find closest one (note : there is necessarily at least one !) */
368                 assert(rankLast[nBitsToDecrease] != noSymbol || nBitsToDecrease == 1);
369                 /* HUF_MAX_TABLELOG test just to please gcc 5+; but it should not be necessary */
370                 while ((nBitsToDecrease<=HUF_TABLELOG_MAX) && (rankLast[nBitsToDecrease] == noSymbol))
371                     nBitsToDecrease++;
372                 assert(rankLast[nBitsToDecrease] != noSymbol);
373                 /* Increase the number of bits to gain back half the rank cost. */
374                 totalCost -= 1 << (nBitsToDecrease-1);
375                 huffNode[rankLast[nBitsToDecrease]].nbBits++;
376 
377                 /* Fix up the new rank.
378                  * If the new rank was empty, this symbol is now its smallest.
379                  * Otherwise, this symbol will be the largest in the new rank so no adjustment.
380                  */
381                 if (rankLast[nBitsToDecrease-1] == noSymbol)
382                     rankLast[nBitsToDecrease-1] = rankLast[nBitsToDecrease];
383                 /* Fix up the old rank.
384                  * If the symbol was at position 0, meaning it was the highest weight symbol in the tree,
385                  * it must be the only symbol in its rank, so the old rank now has no symbols.
386                  * Otherwise, since the Huffman nodes are sorted by count, the previous position is now
387                  * the smallest node in the rank. If the previous position belongs to a different rank,
388                  * then the rank is now empty.
389                  */
390                 if (rankLast[nBitsToDecrease] == 0)    /* special case, reached largest symbol */
391                     rankLast[nBitsToDecrease] = noSymbol;
392                 else {
393                     rankLast[nBitsToDecrease]--;
394                     if (huffNode[rankLast[nBitsToDecrease]].nbBits != maxNbBits-nBitsToDecrease)
395                         rankLast[nBitsToDecrease] = noSymbol;   /* this rank is now empty */
396                 }
397             }   /* while (totalCost > 0) */
398 
399             /* If we've removed too much weight, then we have to add it back.
400              * To avoid overshooting again, we only adjust the smallest rank.
401              * We take the largest nodes from the lowest rank 0 and move them
402              * to rank 1. There's guaranteed to be enough rank 0 symbols because
403              * TODO.
404              */
405             while (totalCost < 0) {  /* Sometimes, cost correction overshoot */
406                 /* special case : no rank 1 symbol (using maxNbBits-1);
407                  * let's create one from largest rank 0 (using maxNbBits).
408                  */
409                 if (rankLast[1] == noSymbol) {
410                     while (huffNode[n].nbBits == maxNbBits) n--;
411                     huffNode[n+1].nbBits--;
412                     assert(n >= 0);
413                     rankLast[1] = (U32)(n+1);
414                     totalCost++;
415                     continue;
416                 }
417                 huffNode[ rankLast[1] + 1 ].nbBits--;
418                 rankLast[1]++;
419                 totalCost ++;
420             }
421         }   /* repay normalized cost */
422     }   /* there are several too large elements (at least >= 2) */
423 
424     return maxNbBits;
425 }
426 
427 typedef struct {
428     U16 base;
429     U16 curr;
430 } rankPos;
431 
432 typedef nodeElt huffNodeTable[HUF_CTABLE_WORKSPACE_SIZE_U32];
433 
434 /* Number of buckets available for HUF_sort() */
435 #define RANK_POSITION_TABLE_SIZE 192
436 
437 typedef struct {
438   huffNodeTable huffNodeTbl;
439   rankPos rankPosition[RANK_POSITION_TABLE_SIZE];
440 } HUF_buildCTable_wksp_tables;
441 
442 /* RANK_POSITION_DISTINCT_COUNT_CUTOFF == Cutoff point in HUF_sort() buckets for which we use log2 bucketing.
443  * Strategy is to use as many buckets as possible for representing distinct
444  * counts while using the remainder to represent all "large" counts.
445  *
446  * To satisfy this requirement for 192 buckets, we can do the following:
447  * Let buckets 0-166 represent distinct counts of [0, 166]
448  * Let buckets 166 to 192 represent all remaining counts up to RANK_POSITION_MAX_COUNT_LOG using log2 bucketing.
449  */
450 #define RANK_POSITION_MAX_COUNT_LOG 32
451 #define RANK_POSITION_LOG_BUCKETS_BEGIN (RANK_POSITION_TABLE_SIZE - 1) - RANK_POSITION_MAX_COUNT_LOG - 1 /* == 158 */
452 #define RANK_POSITION_DISTINCT_COUNT_CUTOFF RANK_POSITION_LOG_BUCKETS_BEGIN + BIT_highbit32(RANK_POSITION_LOG_BUCKETS_BEGIN) /* == 166 */
453 
454 /* Return the appropriate bucket index for a given count. See definition of
455  * RANK_POSITION_DISTINCT_COUNT_CUTOFF for explanation of bucketing strategy.
456  */
HUF_getIndex(U32 const count)457 static U32 HUF_getIndex(U32 const count) {
458     return (count < RANK_POSITION_DISTINCT_COUNT_CUTOFF)
459         ? count
460         : BIT_highbit32(count) + RANK_POSITION_LOG_BUCKETS_BEGIN;
461 }
462 
463 /* Helper swap function for HUF_quickSortPartition() */
HUF_swapNodes(nodeElt * a,nodeElt * b)464 static void HUF_swapNodes(nodeElt* a, nodeElt* b) {
465 	nodeElt tmp = *a;
466 	*a = *b;
467 	*b = tmp;
468 }
469 
470 /* Returns 0 if the huffNode array is not sorted by descending count */
HUF_isSorted(nodeElt huffNode[],U32 const maxSymbolValue1)471 MEM_STATIC int HUF_isSorted(nodeElt huffNode[], U32 const maxSymbolValue1) {
472     U32 i;
473     for (i = 1; i < maxSymbolValue1; ++i) {
474         if (huffNode[i].count > huffNode[i-1].count) {
475             return 0;
476         }
477     }
478     return 1;
479 }
480 
481 /* Insertion sort by descending order */
HUF_insertionSort(nodeElt huffNode[],int const low,int const high)482 HINT_INLINE void HUF_insertionSort(nodeElt huffNode[], int const low, int const high) {
483     int i;
484     int const size = high-low+1;
485     huffNode += low;
486     for (i = 1; i < size; ++i) {
487         nodeElt const key = huffNode[i];
488         int j = i - 1;
489         while (j >= 0 && huffNode[j].count < key.count) {
490             huffNode[j + 1] = huffNode[j];
491             j--;
492         }
493         huffNode[j + 1] = key;
494     }
495 }
496 
497 /* Pivot helper function for quicksort. */
HUF_quickSortPartition(nodeElt arr[],int const low,int const high)498 static int HUF_quickSortPartition(nodeElt arr[], int const low, int const high) {
499     /* Simply select rightmost element as pivot. "Better" selectors like
500      * median-of-three don't experimentally appear to have any benefit.
501      */
502     U32 const pivot = arr[high].count;
503     int i = low - 1;
504     int j = low;
505     for ( ; j < high; j++) {
506         if (arr[j].count > pivot) {
507             i++;
508             HUF_swapNodes(&arr[i], &arr[j]);
509         }
510     }
511     HUF_swapNodes(&arr[i + 1], &arr[high]);
512     return i + 1;
513 }
514 
515 /* Classic quicksort by descending with partially iterative calls
516  * to reduce worst case callstack size.
517  */
HUF_simpleQuickSort(nodeElt arr[],int low,int high)518 static void HUF_simpleQuickSort(nodeElt arr[], int low, int high) {
519     int const kInsertionSortThreshold = 8;
520     if (high - low < kInsertionSortThreshold) {
521         HUF_insertionSort(arr, low, high);
522         return;
523     }
524     while (low < high) {
525         int const idx = HUF_quickSortPartition(arr, low, high);
526         if (idx - low < high - idx) {
527             HUF_simpleQuickSort(arr, low, idx - 1);
528             low = idx + 1;
529         } else {
530             HUF_simpleQuickSort(arr, idx + 1, high);
531             high = idx - 1;
532         }
533     }
534 }
535 
536 /*
537  * HUF_sort():
538  * Sorts the symbols [0, maxSymbolValue] by count[symbol] in decreasing order.
539  * This is a typical bucket sorting strategy that uses either quicksort or insertion sort to sort each bucket.
540  *
541  * @param[out] huffNode       Sorted symbols by decreasing count. Only members `.count` and `.byte` are filled.
542  *                            Must have (maxSymbolValue + 1) entries.
543  * @param[in]  count          Histogram of the symbols.
544  * @param[in]  maxSymbolValue Maximum symbol value.
545  * @param      rankPosition   This is a scratch workspace. Must have RANK_POSITION_TABLE_SIZE entries.
546  */
HUF_sort(nodeElt huffNode[],const unsigned count[],U32 const maxSymbolValue,rankPos rankPosition[])547 static void HUF_sort(nodeElt huffNode[], const unsigned count[], U32 const maxSymbolValue, rankPos rankPosition[]) {
548     U32 n;
549     U32 const maxSymbolValue1 = maxSymbolValue+1;
550 
551     /* Compute base and set curr to base.
552      * For symbol s let lowerRank = HUF_getIndex(count[n]) and rank = lowerRank + 1.
553      * See HUF_getIndex to see bucketing strategy.
554      * We attribute each symbol to lowerRank's base value, because we want to know where
555      * each rank begins in the output, so for rank R we want to count ranks R+1 and above.
556      */
557     ZSTD_memset(rankPosition, 0, sizeof(*rankPosition) * RANK_POSITION_TABLE_SIZE);
558     for (n = 0; n < maxSymbolValue1; ++n) {
559         U32 lowerRank = HUF_getIndex(count[n]);
560         assert(lowerRank < RANK_POSITION_TABLE_SIZE - 1);
561         rankPosition[lowerRank].base++;
562     }
563 
564     assert(rankPosition[RANK_POSITION_TABLE_SIZE - 1].base == 0);
565     /* Set up the rankPosition table */
566     for (n = RANK_POSITION_TABLE_SIZE - 1; n > 0; --n) {
567         rankPosition[n-1].base += rankPosition[n].base;
568         rankPosition[n-1].curr = rankPosition[n-1].base;
569     }
570 
571     /* Insert each symbol into their appropriate bucket, setting up rankPosition table. */
572     for (n = 0; n < maxSymbolValue1; ++n) {
573         U32 const c = count[n];
574         U32 const r = HUF_getIndex(c) + 1;
575         U32 const pos = rankPosition[r].curr++;
576         assert(pos < maxSymbolValue1);
577         huffNode[pos].count = c;
578         huffNode[pos].byte  = (BYTE)n;
579     }
580 
581     /* Sort each bucket. */
582     for (n = RANK_POSITION_DISTINCT_COUNT_CUTOFF; n < RANK_POSITION_TABLE_SIZE - 1; ++n) {
583         U32 const bucketSize = rankPosition[n].curr-rankPosition[n].base;
584         U32 const bucketStartIdx = rankPosition[n].base;
585         if (bucketSize > 1) {
586             assert(bucketStartIdx < maxSymbolValue1);
587             HUF_simpleQuickSort(huffNode + bucketStartIdx, 0, bucketSize-1);
588         }
589     }
590 
591     assert(HUF_isSorted(huffNode, maxSymbolValue1));
592 }
593 
594 /* HUF_buildCTable_wksp() :
595  *  Same as HUF_buildCTable(), but using externally allocated scratch buffer.
596  *  `workSpace` must be aligned on 4-bytes boundaries, and be at least as large as sizeof(HUF_buildCTable_wksp_tables).
597  */
598 #define STARTNODE (HUF_SYMBOLVALUE_MAX+1)
599 
600 /* HUF_buildTree():
601  * Takes the huffNode array sorted by HUF_sort() and builds an unlimited-depth Huffman tree.
602  *
603  * @param huffNode        The array sorted by HUF_sort(). Builds the Huffman tree in this array.
604  * @param maxSymbolValue  The maximum symbol value.
605  * @return                The smallest node in the Huffman tree (by count).
606  */
HUF_buildTree(nodeElt * huffNode,U32 maxSymbolValue)607 static int HUF_buildTree(nodeElt* huffNode, U32 maxSymbolValue)
608 {
609     nodeElt* const huffNode0 = huffNode - 1;
610     int nonNullRank;
611     int lowS, lowN;
612     int nodeNb = STARTNODE;
613     int n, nodeRoot;
614     /* init for parents */
615     nonNullRank = (int)maxSymbolValue;
616     while(huffNode[nonNullRank].count == 0) nonNullRank--;
617     lowS = nonNullRank; nodeRoot = nodeNb + lowS - 1; lowN = nodeNb;
618     huffNode[nodeNb].count = huffNode[lowS].count + huffNode[lowS-1].count;
619     huffNode[lowS].parent = huffNode[lowS-1].parent = (U16)nodeNb;
620     nodeNb++; lowS-=2;
621     for (n=nodeNb; n<=nodeRoot; n++) huffNode[n].count = (U32)(1U<<30);
622     huffNode0[0].count = (U32)(1U<<31);  /* fake entry, strong barrier */
623 
624     /* create parents */
625     while (nodeNb <= nodeRoot) {
626         int const n1 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
627         int const n2 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
628         huffNode[nodeNb].count = huffNode[n1].count + huffNode[n2].count;
629         huffNode[n1].parent = huffNode[n2].parent = (U16)nodeNb;
630         nodeNb++;
631     }
632 
633     /* distribute weights (unlimited tree height) */
634     huffNode[nodeRoot].nbBits = 0;
635     for (n=nodeRoot-1; n>=STARTNODE; n--)
636         huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;
637     for (n=0; n<=nonNullRank; n++)
638         huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;
639 
640     return nonNullRank;
641 }
642 
643 /*
644  * HUF_buildCTableFromTree():
645  * Build the CTable given the Huffman tree in huffNode.
646  *
647  * @param[out] CTable         The output Huffman CTable.
648  * @param      huffNode       The Huffman tree.
649  * @param      nonNullRank    The last and smallest node in the Huffman tree.
650  * @param      maxSymbolValue The maximum symbol value.
651  * @param      maxNbBits      The exact maximum number of bits used in the Huffman tree.
652  */
HUF_buildCTableFromTree(HUF_CElt * CTable,nodeElt const * huffNode,int nonNullRank,U32 maxSymbolValue,U32 maxNbBits)653 static void HUF_buildCTableFromTree(HUF_CElt* CTable, nodeElt const* huffNode, int nonNullRank, U32 maxSymbolValue, U32 maxNbBits)
654 {
655     HUF_CElt* const ct = CTable + 1;
656     /* fill result into ctable (val, nbBits) */
657     int n;
658     U16 nbPerRank[HUF_TABLELOG_MAX+1] = {0};
659     U16 valPerRank[HUF_TABLELOG_MAX+1] = {0};
660     int const alphabetSize = (int)(maxSymbolValue + 1);
661     for (n=0; n<=nonNullRank; n++)
662         nbPerRank[huffNode[n].nbBits]++;
663     /* determine starting value per rank */
664     {   U16 min = 0;
665         for (n=(int)maxNbBits; n>0; n--) {
666             valPerRank[n] = min;      /* get starting value within each rank */
667             min += nbPerRank[n];
668             min >>= 1;
669     }   }
670     for (n=0; n<alphabetSize; n++)
671         HUF_setNbBits(ct + huffNode[n].byte, huffNode[n].nbBits);   /* push nbBits per symbol, symbol order */
672     for (n=0; n<alphabetSize; n++)
673         HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++);   /* assign value within rank, symbol order */
674     CTable[0] = maxNbBits;
675 }
676 
HUF_buildCTable_wksp(HUF_CElt * CTable,const unsigned * count,U32 maxSymbolValue,U32 maxNbBits,void * workSpace,size_t wkspSize)677 size_t HUF_buildCTable_wksp (HUF_CElt* CTable, const unsigned* count, U32 maxSymbolValue, U32 maxNbBits, void* workSpace, size_t wkspSize)
678 {
679     HUF_buildCTable_wksp_tables* const wksp_tables = (HUF_buildCTable_wksp_tables*)HUF_alignUpWorkspace(workSpace, &wkspSize, ZSTD_ALIGNOF(U32));
680     nodeElt* const huffNode0 = wksp_tables->huffNodeTbl;
681     nodeElt* const huffNode = huffNode0+1;
682     int nonNullRank;
683 
684     /* safety checks */
685     if (wkspSize < sizeof(HUF_buildCTable_wksp_tables))
686       return ERROR(workSpace_tooSmall);
687     if (maxNbBits == 0) maxNbBits = HUF_TABLELOG_DEFAULT;
688     if (maxSymbolValue > HUF_SYMBOLVALUE_MAX)
689       return ERROR(maxSymbolValue_tooLarge);
690     ZSTD_memset(huffNode0, 0, sizeof(huffNodeTable));
691 
692     /* sort, decreasing order */
693     HUF_sort(huffNode, count, maxSymbolValue, wksp_tables->rankPosition);
694 
695     /* build tree */
696     nonNullRank = HUF_buildTree(huffNode, maxSymbolValue);
697 
698     /* enforce maxTableLog */
699     maxNbBits = HUF_setMaxHeight(huffNode, (U32)nonNullRank, maxNbBits);
700     if (maxNbBits > HUF_TABLELOG_MAX) return ERROR(GENERIC);   /* check fit into table */
701 
702     HUF_buildCTableFromTree(CTable, huffNode, nonNullRank, maxSymbolValue, maxNbBits);
703 
704     return maxNbBits;
705 }
706 
HUF_estimateCompressedSize(const HUF_CElt * CTable,const unsigned * count,unsigned maxSymbolValue)707 size_t HUF_estimateCompressedSize(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue)
708 {
709     HUF_CElt const* ct = CTable + 1;
710     size_t nbBits = 0;
711     int s;
712     for (s = 0; s <= (int)maxSymbolValue; ++s) {
713         nbBits += HUF_getNbBits(ct[s]) * count[s];
714     }
715     return nbBits >> 3;
716 }
717 
HUF_validateCTable(const HUF_CElt * CTable,const unsigned * count,unsigned maxSymbolValue)718 int HUF_validateCTable(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue) {
719   HUF_CElt const* ct = CTable + 1;
720   int bad = 0;
721   int s;
722   for (s = 0; s <= (int)maxSymbolValue; ++s) {
723     bad |= (count[s] != 0) & (HUF_getNbBits(ct[s]) == 0);
724   }
725   return !bad;
726 }
727 
HUF_compressBound(size_t size)728 size_t HUF_compressBound(size_t size) { return HUF_COMPRESSBOUND(size); }
729 
730 /* HUF_CStream_t:
731  * Huffman uses its own BIT_CStream_t implementation.
732  * There are three major differences from BIT_CStream_t:
733  *   1. HUF_addBits() takes a HUF_CElt (size_t) which is
734  *      the pair (nbBits, value) in the format:
735  *      format:
736  *        - Bits [0, 4)            = nbBits
737  *        - Bits [4, 64 - nbBits)  = 0
738  *        - Bits [64 - nbBits, 64) = value
739  *   2. The bitContainer is built from the upper bits and
740  *      right shifted. E.g. to add a new value of N bits
741  *      you right shift the bitContainer by N, then or in
742  *      the new value into the N upper bits.
743  *   3. The bitstream has two bit containers. You can add
744  *      bits to the second container and merge them into
745  *      the first container.
746  */
747 
748 #define HUF_BITS_IN_CONTAINER (sizeof(size_t) * 8)
749 
750 typedef struct {
751     size_t bitContainer[2];
752     size_t bitPos[2];
753 
754     BYTE* startPtr;
755     BYTE* ptr;
756     BYTE* endPtr;
757 } HUF_CStream_t;
758 
759 /*! HUF_initCStream():
760  * Initializes the bitstream.
761  * @returns 0 or an error code.
762  */
HUF_initCStream(HUF_CStream_t * bitC,void * startPtr,size_t dstCapacity)763 static size_t HUF_initCStream(HUF_CStream_t* bitC,
764                                   void* startPtr, size_t dstCapacity)
765 {
766     ZSTD_memset(bitC, 0, sizeof(*bitC));
767     bitC->startPtr = (BYTE*)startPtr;
768     bitC->ptr = bitC->startPtr;
769     bitC->endPtr = bitC->startPtr + dstCapacity - sizeof(bitC->bitContainer[0]);
770     if (dstCapacity <= sizeof(bitC->bitContainer[0])) return ERROR(dstSize_tooSmall);
771     return 0;
772 }
773 
774 /*! HUF_addBits():
775  * Adds the symbol stored in HUF_CElt elt to the bitstream.
776  *
777  * @param elt   The element we're adding. This is a (nbBits, value) pair.
778  *              See the HUF_CStream_t docs for the format.
779  * @param idx   Insert into the bitstream at this idx.
780  * @param kFast This is a template parameter. If the bitstream is guaranteed
781  *              to have at least 4 unused bits after this call it may be 1,
782  *              otherwise it must be 0. HUF_addBits() is faster when fast is set.
783  */
HUF_addBits(HUF_CStream_t * bitC,HUF_CElt elt,int idx,int kFast)784 FORCE_INLINE_TEMPLATE void HUF_addBits(HUF_CStream_t* bitC, HUF_CElt elt, int idx, int kFast)
785 {
786     assert(idx <= 1);
787     assert(HUF_getNbBits(elt) <= HUF_TABLELOG_ABSOLUTEMAX);
788     /* This is efficient on x86-64 with BMI2 because shrx
789      * only reads the low 6 bits of the register. The compiler
790      * knows this and elides the mask. When fast is set,
791      * every operation can use the same value loaded from elt.
792      */
793     bitC->bitContainer[idx] >>= HUF_getNbBits(elt);
794     bitC->bitContainer[idx] |= kFast ? HUF_getValueFast(elt) : HUF_getValue(elt);
795     /* We only read the low 8 bits of bitC->bitPos[idx] so it
796      * doesn't matter that the high bits have noise from the value.
797      */
798     bitC->bitPos[idx] += HUF_getNbBitsFast(elt);
799     assert((bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER);
800     /* The last 4-bits of elt are dirty if fast is set,
801      * so we must not be overwriting bits that have already been
802      * inserted into the bit container.
803      */
804 #if DEBUGLEVEL >= 1
805     {
806         size_t const nbBits = HUF_getNbBits(elt);
807         size_t const dirtyBits = nbBits == 0 ? 0 : BIT_highbit32((U32)nbBits) + 1;
808         (void)dirtyBits;
809         /* Middle bits are 0. */
810         assert(((elt >> dirtyBits) << (dirtyBits + nbBits)) == 0);
811         /* We didn't overwrite any bits in the bit container. */
812         assert(!kFast || (bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER);
813         (void)dirtyBits;
814     }
815 #endif
816 }
817 
HUF_zeroIndex1(HUF_CStream_t * bitC)818 FORCE_INLINE_TEMPLATE void HUF_zeroIndex1(HUF_CStream_t* bitC)
819 {
820     bitC->bitContainer[1] = 0;
821     bitC->bitPos[1] = 0;
822 }
823 
824 /*! HUF_mergeIndex1() :
825  * Merges the bit container @ index 1 into the bit container @ index 0
826  * and zeros the bit container @ index 1.
827  */
HUF_mergeIndex1(HUF_CStream_t * bitC)828 FORCE_INLINE_TEMPLATE void HUF_mergeIndex1(HUF_CStream_t* bitC)
829 {
830     assert((bitC->bitPos[1] & 0xFF) < HUF_BITS_IN_CONTAINER);
831     bitC->bitContainer[0] >>= (bitC->bitPos[1] & 0xFF);
832     bitC->bitContainer[0] |= bitC->bitContainer[1];
833     bitC->bitPos[0] += bitC->bitPos[1];
834     assert((bitC->bitPos[0] & 0xFF) <= HUF_BITS_IN_CONTAINER);
835 }
836 
837 /*! HUF_flushBits() :
838 * Flushes the bits in the bit container @ index 0.
839 *
840 * @post bitPos will be < 8.
841 * @param kFast If kFast is set then we must know a-priori that
842 *              the bit container will not overflow.
843 */
HUF_flushBits(HUF_CStream_t * bitC,int kFast)844 FORCE_INLINE_TEMPLATE void HUF_flushBits(HUF_CStream_t* bitC, int kFast)
845 {
846     /* The upper bits of bitPos are noisy, so we must mask by 0xFF. */
847     size_t const nbBits = bitC->bitPos[0] & 0xFF;
848     size_t const nbBytes = nbBits >> 3;
849     /* The top nbBits bits of bitContainer are the ones we need. */
850     size_t const bitContainer = bitC->bitContainer[0] >> (HUF_BITS_IN_CONTAINER - nbBits);
851     /* Mask bitPos to account for the bytes we consumed. */
852     bitC->bitPos[0] &= 7;
853     assert(nbBits > 0);
854     assert(nbBits <= sizeof(bitC->bitContainer[0]) * 8);
855     assert(bitC->ptr <= bitC->endPtr);
856     MEM_writeLEST(bitC->ptr, bitContainer);
857     bitC->ptr += nbBytes;
858     assert(!kFast || bitC->ptr <= bitC->endPtr);
859     if (!kFast && bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr;
860     /* bitContainer doesn't need to be modified because the leftover
861      * bits are already the top bitPos bits. And we don't care about
862      * noise in the lower values.
863      */
864 }
865 
866 /*! HUF_endMark()
867  * @returns The Huffman stream end mark: A 1-bit value = 1.
868  */
HUF_endMark(void)869 static HUF_CElt HUF_endMark(void)
870 {
871     HUF_CElt endMark;
872     HUF_setNbBits(&endMark, 1);
873     HUF_setValue(&endMark, 1);
874     return endMark;
875 }
876 
877 /*! HUF_closeCStream() :
878  *  @return Size of CStream, in bytes,
879  *          or 0 if it could not fit into dstBuffer */
HUF_closeCStream(HUF_CStream_t * bitC)880 static size_t HUF_closeCStream(HUF_CStream_t* bitC)
881 {
882     HUF_addBits(bitC, HUF_endMark(), /* idx */ 0, /* kFast */ 0);
883     HUF_flushBits(bitC, /* kFast */ 0);
884     {
885         size_t const nbBits = bitC->bitPos[0] & 0xFF;
886         if (bitC->ptr >= bitC->endPtr) return 0; /* overflow detected */
887         return (bitC->ptr - bitC->startPtr) + (nbBits > 0);
888     }
889 }
890 
891 FORCE_INLINE_TEMPLATE void
HUF_encodeSymbol(HUF_CStream_t * bitCPtr,U32 symbol,const HUF_CElt * CTable,int idx,int fast)892 HUF_encodeSymbol(HUF_CStream_t* bitCPtr, U32 symbol, const HUF_CElt* CTable, int idx, int fast)
893 {
894     HUF_addBits(bitCPtr, CTable[symbol], idx, fast);
895 }
896 
897 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)898 HUF_compress1X_usingCTable_internal_body_loop(HUF_CStream_t* bitC,
899                                    const BYTE* ip, size_t srcSize,
900                                    const HUF_CElt* ct,
901                                    int kUnroll, int kFastFlush, int kLastFast)
902 {
903     /* Join to kUnroll */
904     int n = (int)srcSize;
905     int rem = n % kUnroll;
906     if (rem > 0) {
907         for (; rem > 0; --rem) {
908             HUF_encodeSymbol(bitC, ip[--n], ct, 0, /* fast */ 0);
909         }
910         HUF_flushBits(bitC, kFastFlush);
911     }
912     assert(n % kUnroll == 0);
913 
914     /* Join to 2 * kUnroll */
915     if (n % (2 * kUnroll)) {
916         int u;
917         for (u = 1; u < kUnroll; ++u) {
918             HUF_encodeSymbol(bitC, ip[n - u], ct, 0, 1);
919         }
920         HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, 0, kLastFast);
921         HUF_flushBits(bitC, kFastFlush);
922         n -= kUnroll;
923     }
924     assert(n % (2 * kUnroll) == 0);
925 
926     for (; n>0; n-= 2 * kUnroll) {
927         /* Encode kUnroll symbols into the bitstream @ index 0. */
928         int u;
929         for (u = 1; u < kUnroll; ++u) {
930             HUF_encodeSymbol(bitC, ip[n - u], ct, /* idx */ 0, /* fast */ 1);
931         }
932         HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, /* idx */ 0, /* fast */ kLastFast);
933         HUF_flushBits(bitC, kFastFlush);
934         /* Encode kUnroll symbols into the bitstream @ index 1.
935          * This allows us to start filling the bit container
936          * without any data dependencies.
937          */
938         HUF_zeroIndex1(bitC);
939         for (u = 1; u < kUnroll; ++u) {
940             HUF_encodeSymbol(bitC, ip[n - kUnroll - u], ct, /* idx */ 1, /* fast */ 1);
941         }
942         HUF_encodeSymbol(bitC, ip[n - kUnroll - kUnroll], ct, /* idx */ 1, /* fast */ kLastFast);
943         /* Merge bitstream @ index 1 into the bitstream @ index 0 */
944         HUF_mergeIndex1(bitC);
945         HUF_flushBits(bitC, kFastFlush);
946     }
947     assert(n == 0);
948 
949 }
950 
951 /*
952  * Returns a tight upper bound on the output space needed by Huffman
953  * with 8 bytes buffer to handle over-writes. If the output is at least
954  * this large we don't need to do bounds checks during Huffman encoding.
955  */
HUF_tightCompressBound(size_t srcSize,size_t tableLog)956 static size_t HUF_tightCompressBound(size_t srcSize, size_t tableLog)
957 {
958     return ((srcSize * tableLog) >> 3) + 8;
959 }
960 
961 
962 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)963 HUF_compress1X_usingCTable_internal_body(void* dst, size_t dstSize,
964                                    const void* src, size_t srcSize,
965                                    const HUF_CElt* CTable)
966 {
967     U32 const tableLog = (U32)CTable[0];
968     HUF_CElt const* ct = CTable + 1;
969     const BYTE* ip = (const BYTE*) src;
970     BYTE* const ostart = (BYTE*)dst;
971     BYTE* const oend = ostart + dstSize;
972     BYTE* op = ostart;
973     HUF_CStream_t bitC;
974 
975     /* init */
976     if (dstSize < 8) return 0;   /* not enough space to compress */
977     { size_t const initErr = HUF_initCStream(&bitC, op, (size_t)(oend-op));
978       if (HUF_isError(initErr)) return 0; }
979 
980     if (dstSize < HUF_tightCompressBound(srcSize, (size_t)tableLog) || tableLog > 11)
981         HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ MEM_32bits() ? 2 : 4, /* kFast */ 0, /* kLastFast */ 0);
982     else {
983         if (MEM_32bits()) {
984             switch (tableLog) {
985             case 11:
986                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 0);
987                 break;
988             case 10: ZSTD_FALLTHROUGH;
989             case 9: ZSTD_FALLTHROUGH;
990             case 8:
991                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 1);
992                 break;
993             case 7: ZSTD_FALLTHROUGH;
994             default:
995                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 3, /* kFastFlush */ 1, /* kLastFast */ 1);
996                 break;
997             }
998         } else {
999             switch (tableLog) {
1000             case 11:
1001                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 0);
1002                 break;
1003             case 10:
1004                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 1);
1005                 break;
1006             case 9:
1007                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 6, /* kFastFlush */ 1, /* kLastFast */ 0);
1008                 break;
1009             case 8:
1010                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 7, /* kFastFlush */ 1, /* kLastFast */ 0);
1011                 break;
1012             case 7:
1013                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 8, /* kFastFlush */ 1, /* kLastFast */ 0);
1014                 break;
1015             case 6: ZSTD_FALLTHROUGH;
1016             default:
1017                 HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 9, /* kFastFlush */ 1, /* kLastFast */ 1);
1018                 break;
1019             }
1020         }
1021     }
1022     assert(bitC.ptr <= bitC.endPtr);
1023 
1024     return HUF_closeCStream(&bitC);
1025 }
1026 
1027 #if DYNAMIC_BMI2
1028 
1029 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)1030 HUF_compress1X_usingCTable_internal_bmi2(void* dst, size_t dstSize,
1031                                    const void* src, size_t srcSize,
1032                                    const HUF_CElt* CTable)
1033 {
1034     return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
1035 }
1036 
1037 static size_t
HUF_compress1X_usingCTable_internal_default(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable)1038 HUF_compress1X_usingCTable_internal_default(void* dst, size_t dstSize,
1039                                       const void* src, size_t srcSize,
1040                                       const HUF_CElt* CTable)
1041 {
1042     return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
1043 }
1044 
1045 static size_t
HUF_compress1X_usingCTable_internal(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable,const int bmi2)1046 HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize,
1047                               const void* src, size_t srcSize,
1048                               const HUF_CElt* CTable, const int bmi2)
1049 {
1050     if (bmi2) {
1051         return HUF_compress1X_usingCTable_internal_bmi2(dst, dstSize, src, srcSize, CTable);
1052     }
1053     return HUF_compress1X_usingCTable_internal_default(dst, dstSize, src, srcSize, CTable);
1054 }
1055 
1056 #else
1057 
1058 static size_t
HUF_compress1X_usingCTable_internal(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable,const int bmi2)1059 HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize,
1060                               const void* src, size_t srcSize,
1061                               const HUF_CElt* CTable, const int bmi2)
1062 {
1063     (void)bmi2;
1064     return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable);
1065 }
1066 
1067 #endif
1068 
HUF_compress1X_usingCTable(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable)1069 size_t HUF_compress1X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable)
1070 {
1071     return HUF_compress1X_usingCTable_bmi2(dst, dstSize, src, srcSize, CTable, /* bmi2 */ 0);
1072 }
1073 
HUF_compress1X_usingCTable_bmi2(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable,int bmi2)1074 size_t HUF_compress1X_usingCTable_bmi2(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int bmi2)
1075 {
1076     return HUF_compress1X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, bmi2);
1077 }
1078 
1079 static size_t
HUF_compress4X_usingCTable_internal(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable,int bmi2)1080 HUF_compress4X_usingCTable_internal(void* dst, size_t dstSize,
1081                               const void* src, size_t srcSize,
1082                               const HUF_CElt* CTable, int bmi2)
1083 {
1084     size_t const segmentSize = (srcSize+3)/4;   /* first 3 segments */
1085     const BYTE* ip = (const BYTE*) src;
1086     const BYTE* const iend = ip + srcSize;
1087     BYTE* const ostart = (BYTE*) dst;
1088     BYTE* const oend = ostart + dstSize;
1089     BYTE* op = ostart;
1090 
1091     if (dstSize < 6 + 1 + 1 + 1 + 8) return 0;   /* minimum space to compress successfully */
1092     if (srcSize < 12) return 0;   /* no saving possible : too small input */
1093     op += 6;   /* jumpTable */
1094 
1095     assert(op <= oend);
1096     {   CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, bmi2) );
1097         if (cSize == 0 || cSize > 65535) return 0;
1098         MEM_writeLE16(ostart, (U16)cSize);
1099         op += cSize;
1100     }
1101 
1102     ip += segmentSize;
1103     assert(op <= oend);
1104     {   CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, bmi2) );
1105         if (cSize == 0 || cSize > 65535) return 0;
1106         MEM_writeLE16(ostart+2, (U16)cSize);
1107         op += cSize;
1108     }
1109 
1110     ip += segmentSize;
1111     assert(op <= oend);
1112     {   CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, bmi2) );
1113         if (cSize == 0 || cSize > 65535) return 0;
1114         MEM_writeLE16(ostart+4, (U16)cSize);
1115         op += cSize;
1116     }
1117 
1118     ip += segmentSize;
1119     assert(op <= oend);
1120     assert(ip <= iend);
1121     {   CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, (size_t)(iend-ip), CTable, bmi2) );
1122         if (cSize == 0 || cSize > 65535) return 0;
1123         op += cSize;
1124     }
1125 
1126     return (size_t)(op-ostart);
1127 }
1128 
HUF_compress4X_usingCTable(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable)1129 size_t HUF_compress4X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable)
1130 {
1131     return HUF_compress4X_usingCTable_bmi2(dst, dstSize, src, srcSize, CTable, /* bmi2 */ 0);
1132 }
1133 
HUF_compress4X_usingCTable_bmi2(void * dst,size_t dstSize,const void * src,size_t srcSize,const HUF_CElt * CTable,int bmi2)1134 size_t HUF_compress4X_usingCTable_bmi2(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int bmi2)
1135 {
1136     return HUF_compress4X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, bmi2);
1137 }
1138 
1139 typedef enum { HUF_singleStream, HUF_fourStreams } HUF_nbStreams_e;
1140 
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 bmi2)1141 static size_t HUF_compressCTable_internal(
1142                 BYTE* const ostart, BYTE* op, BYTE* const oend,
1143                 const void* src, size_t srcSize,
1144                 HUF_nbStreams_e nbStreams, const HUF_CElt* CTable, const int bmi2)
1145 {
1146     size_t const cSize = (nbStreams==HUF_singleStream) ?
1147                          HUF_compress1X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, bmi2) :
1148                          HUF_compress4X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, bmi2);
1149     if (HUF_isError(cSize)) { return cSize; }
1150     if (cSize==0) { return 0; }   /* uncompressible */
1151     op += cSize;
1152     /* check compressibility */
1153     assert(op >= ostart);
1154     if ((size_t)(op-ostart) >= srcSize-1) { return 0; }
1155     return (size_t)(op-ostart);
1156 }
1157 
1158 typedef struct {
1159     unsigned count[HUF_SYMBOLVALUE_MAX + 1];
1160     HUF_CElt CTable[HUF_CTABLE_SIZE_ST(HUF_SYMBOLVALUE_MAX)];
1161     union {
1162         HUF_buildCTable_wksp_tables buildCTable_wksp;
1163         HUF_WriteCTableWksp writeCTable_wksp;
1164         U32 hist_wksp[HIST_WKSP_SIZE_U32];
1165     } wksps;
1166 } HUF_compress_tables_t;
1167 
1168 #define SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE 4096
1169 #define SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO 10  /* Must be >= 2 */
1170 
1171 /* HUF_compress_internal() :
1172  * `workSpace_align4` must be aligned on 4-bytes boundaries,
1173  * and occupies the same space as a table of HUF_WORKSPACE_SIZE_U64 unsigned */
1174 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 preferRepeat,const int bmi2,unsigned suspectUncompressible)1175 HUF_compress_internal (void* dst, size_t dstSize,
1176                  const void* src, size_t srcSize,
1177                        unsigned maxSymbolValue, unsigned huffLog,
1178                        HUF_nbStreams_e nbStreams,
1179                        void* workSpace, size_t wkspSize,
1180                        HUF_CElt* oldHufTable, HUF_repeat* repeat, int preferRepeat,
1181                  const int bmi2, unsigned suspectUncompressible)
1182 {
1183     HUF_compress_tables_t* const table = (HUF_compress_tables_t*)HUF_alignUpWorkspace(workSpace, &wkspSize, ZSTD_ALIGNOF(size_t));
1184     BYTE* const ostart = (BYTE*)dst;
1185     BYTE* const oend = ostart + dstSize;
1186     BYTE* op = ostart;
1187 
1188     HUF_STATIC_ASSERT(sizeof(*table) + HUF_WORKSPACE_MAX_ALIGNMENT <= HUF_WORKSPACE_SIZE);
1189 
1190     /* checks & inits */
1191     if (wkspSize < sizeof(*table)) return ERROR(workSpace_tooSmall);
1192     if (!srcSize) return 0;  /* Uncompressed */
1193     if (!dstSize) return 0;  /* cannot fit anything within dst budget */
1194     if (srcSize > HUF_BLOCKSIZE_MAX) return ERROR(srcSize_wrong);   /* current block size limit */
1195     if (huffLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
1196     if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
1197     if (!maxSymbolValue) maxSymbolValue = HUF_SYMBOLVALUE_MAX;
1198     if (!huffLog) huffLog = HUF_TABLELOG_DEFAULT;
1199 
1200     /* Heuristic : If old table is valid, use it for small inputs */
1201     if (preferRepeat && repeat && *repeat == HUF_repeat_valid) {
1202         return HUF_compressCTable_internal(ostart, op, oend,
1203                                            src, srcSize,
1204                                            nbStreams, oldHufTable, bmi2);
1205     }
1206 
1207     /* If uncompressible data is suspected, do a smaller sampling first */
1208     DEBUG_STATIC_ASSERT(SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO >= 2);
1209     if (suspectUncompressible && srcSize >= (SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE * SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO)) {
1210         size_t largestTotal = 0;
1211         {   unsigned maxSymbolValueBegin = maxSymbolValue;
1212             CHECK_V_F(largestBegin, HIST_count_simple (table->count, &maxSymbolValueBegin, (const BYTE*)src, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) );
1213             largestTotal += largestBegin;
1214         }
1215         {   unsigned maxSymbolValueEnd = maxSymbolValue;
1216             CHECK_V_F(largestEnd, HIST_count_simple (table->count, &maxSymbolValueEnd, (const BYTE*)src + srcSize - SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) );
1217             largestTotal += largestEnd;
1218         }
1219         if (largestTotal <= ((2 * SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) >> 7)+4) return 0;   /* heuristic : probably not compressible enough */
1220     }
1221 
1222     /* Scan input and build symbol stats */
1223     {   CHECK_V_F(largest, HIST_count_wksp (table->count, &maxSymbolValue, (const BYTE*)src, srcSize, table->wksps.hist_wksp, sizeof(table->wksps.hist_wksp)) );
1224         if (largest == srcSize) { *ostart = ((const BYTE*)src)[0]; return 1; }   /* single symbol, rle */
1225         if (largest <= (srcSize >> 7)+4) return 0;   /* heuristic : probably not compressible enough */
1226     }
1227 
1228     /* Check validity of previous table */
1229     if ( repeat
1230       && *repeat == HUF_repeat_check
1231       && !HUF_validateCTable(oldHufTable, table->count, maxSymbolValue)) {
1232         *repeat = HUF_repeat_none;
1233     }
1234     /* Heuristic : use existing table for small inputs */
1235     if (preferRepeat && repeat && *repeat != HUF_repeat_none) {
1236         return HUF_compressCTable_internal(ostart, op, oend,
1237                                            src, srcSize,
1238                                            nbStreams, oldHufTable, bmi2);
1239     }
1240 
1241     /* Build Huffman Tree */
1242     huffLog = HUF_optimalTableLog(huffLog, srcSize, maxSymbolValue);
1243     {   size_t const maxBits = HUF_buildCTable_wksp(table->CTable, table->count,
1244                                             maxSymbolValue, huffLog,
1245                                             &table->wksps.buildCTable_wksp, sizeof(table->wksps.buildCTable_wksp));
1246         CHECK_F(maxBits);
1247         huffLog = (U32)maxBits;
1248     }
1249     /* Zero unused symbols in CTable, so we can check it for validity */
1250     {
1251         size_t const ctableSize = HUF_CTABLE_SIZE_ST(maxSymbolValue);
1252         size_t const unusedSize = sizeof(table->CTable) - ctableSize * sizeof(HUF_CElt);
1253         ZSTD_memset(table->CTable + ctableSize, 0, unusedSize);
1254     }
1255 
1256     /* Write table description header */
1257     {   CHECK_V_F(hSize, HUF_writeCTable_wksp(op, dstSize, table->CTable, maxSymbolValue, huffLog,
1258                                               &table->wksps.writeCTable_wksp, sizeof(table->wksps.writeCTable_wksp)) );
1259         /* Check if using previous huffman table is beneficial */
1260         if (repeat && *repeat != HUF_repeat_none) {
1261             size_t const oldSize = HUF_estimateCompressedSize(oldHufTable, table->count, maxSymbolValue);
1262             size_t const newSize = HUF_estimateCompressedSize(table->CTable, table->count, maxSymbolValue);
1263             if (oldSize <= hSize + newSize || hSize + 12 >= srcSize) {
1264                 return HUF_compressCTable_internal(ostart, op, oend,
1265                                                    src, srcSize,
1266                                                    nbStreams, oldHufTable, bmi2);
1267         }   }
1268 
1269         /* Use the new huffman table */
1270         if (hSize + 12ul >= srcSize) { return 0; }
1271         op += hSize;
1272         if (repeat) { *repeat = HUF_repeat_none; }
1273         if (oldHufTable)
1274             ZSTD_memcpy(oldHufTable, table->CTable, sizeof(table->CTable));  /* Save new table */
1275     }
1276     return HUF_compressCTable_internal(ostart, op, oend,
1277                                        src, srcSize,
1278                                        nbStreams, table->CTable, bmi2);
1279 }
1280 
1281 
HUF_compress1X_wksp(void * dst,size_t dstSize,const void * src,size_t srcSize,unsigned maxSymbolValue,unsigned huffLog,void * workSpace,size_t wkspSize)1282 size_t HUF_compress1X_wksp (void* dst, size_t dstSize,
1283                       const void* src, size_t srcSize,
1284                       unsigned maxSymbolValue, unsigned huffLog,
1285                       void* workSpace, size_t wkspSize)
1286 {
1287     return HUF_compress_internal(dst, dstSize, src, srcSize,
1288                                  maxSymbolValue, huffLog, HUF_singleStream,
1289                                  workSpace, wkspSize,
1290                                  NULL, NULL, 0, 0 /*bmi2*/, 0);
1291 }
1292 
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 preferRepeat,int bmi2,unsigned suspectUncompressible)1293 size_t HUF_compress1X_repeat (void* dst, size_t dstSize,
1294                       const void* src, size_t srcSize,
1295                       unsigned maxSymbolValue, unsigned huffLog,
1296                       void* workSpace, size_t wkspSize,
1297                       HUF_CElt* hufTable, HUF_repeat* repeat, int preferRepeat,
1298                       int bmi2, unsigned suspectUncompressible)
1299 {
1300     return HUF_compress_internal(dst, dstSize, src, srcSize,
1301                                  maxSymbolValue, huffLog, HUF_singleStream,
1302                                  workSpace, wkspSize, hufTable,
1303                                  repeat, preferRepeat, bmi2, suspectUncompressible);
1304 }
1305 
1306 /* HUF_compress4X_repeat():
1307  * compress input using 4 streams.
1308  * provide workspace to generate compression tables */
HUF_compress4X_wksp(void * dst,size_t dstSize,const void * src,size_t srcSize,unsigned maxSymbolValue,unsigned huffLog,void * workSpace,size_t wkspSize)1309 size_t HUF_compress4X_wksp (void* dst, size_t dstSize,
1310                       const void* src, size_t srcSize,
1311                       unsigned maxSymbolValue, unsigned huffLog,
1312                       void* workSpace, size_t wkspSize)
1313 {
1314     return HUF_compress_internal(dst, dstSize, src, srcSize,
1315                                  maxSymbolValue, huffLog, HUF_fourStreams,
1316                                  workSpace, wkspSize,
1317                                  NULL, NULL, 0, 0 /*bmi2*/, 0);
1318 }
1319 
1320 /* HUF_compress4X_repeat():
1321  * compress input using 4 streams.
1322  * consider skipping quickly
1323  * re-use an existing huffman compression table */
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 preferRepeat,int bmi2,unsigned suspectUncompressible)1324 size_t HUF_compress4X_repeat (void* dst, size_t dstSize,
1325                       const void* src, size_t srcSize,
1326                       unsigned maxSymbolValue, unsigned huffLog,
1327                       void* workSpace, size_t wkspSize,
1328                       HUF_CElt* hufTable, HUF_repeat* repeat, int preferRepeat, int bmi2, unsigned suspectUncompressible)
1329 {
1330     return HUF_compress_internal(dst, dstSize, src, srcSize,
1331                                  maxSymbolValue, huffLog, HUF_fourStreams,
1332                                  workSpace, wkspSize,
1333                                  hufTable, repeat, preferRepeat, bmi2, suspectUncompressible);
1334 }
1335 
1336