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1// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
2/* ******************************************************************
3 * FSE : Finite State Entropy decoder
4 * Copyright (c) Meta Platforms, Inc. and affiliates.
5 *
6 * You can contact the author at :
7 * - FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy
8 * - Public forum : https://groups.google.com/forum/#!forum/lz4c
9 *
10 * This source code is licensed under both the BSD-style license (found in the
11 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
12 * in the COPYING file in the root directory of this source tree).
13 * You may select, at your option, one of the above-listed licenses.
14****************************************************************** */
15
16
17/* **************************************************************
18* Includes
19****************************************************************/
20#include "debug.h" /* assert */
21#include "bitstream.h"
22#include "compiler.h"
23#define FSE_STATIC_LINKING_ONLY
24#include "fse.h"
25#include "error_private.h"
26#include "zstd_deps.h" /* ZSTD_memcpy */
27#include "bits.h" /* ZSTD_highbit32 */
28
29
30/* **************************************************************
31* Error Management
32****************************************************************/
33#define FSE_isError ERR_isError
34#define FSE_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c) /* use only *after* variable declarations */
35
36
37/* **************************************************************
38* Templates
39****************************************************************/
40/*
41 designed to be included
42 for type-specific functions (template emulation in C)
43 Objective is to write these functions only once, for improved maintenance
44*/
45
46/* safety checks */
47#ifndef FSE_FUNCTION_EXTENSION
48# error "FSE_FUNCTION_EXTENSION must be defined"
49#endif
50#ifndef FSE_FUNCTION_TYPE
51# error "FSE_FUNCTION_TYPE must be defined"
52#endif
53
54/* Function names */
55#define FSE_CAT(X,Y) X##Y
56#define FSE_FUNCTION_NAME(X,Y) FSE_CAT(X,Y)
57#define FSE_TYPE_NAME(X,Y) FSE_CAT(X,Y)
58
59static size_t FSE_buildDTable_internal(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize)
60{
61 void* const tdPtr = dt+1; /* because *dt is unsigned, 32-bits aligned on 32-bits */
62 FSE_DECODE_TYPE* const tableDecode = (FSE_DECODE_TYPE*) (tdPtr);
63 U16* symbolNext = (U16*)workSpace;
64 BYTE* spread = (BYTE*)(symbolNext + maxSymbolValue + 1);
65
66 U32 const maxSV1 = maxSymbolValue + 1;
67 U32 const tableSize = 1 << tableLog;
68 U32 highThreshold = tableSize-1;
69
70 /* Sanity Checks */
71 if (FSE_BUILD_DTABLE_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(maxSymbolValue_tooLarge);
72 if (maxSymbolValue > FSE_MAX_SYMBOL_VALUE) return ERROR(maxSymbolValue_tooLarge);
73 if (tableLog > FSE_MAX_TABLELOG) return ERROR(tableLog_tooLarge);
74
75 /* Init, lay down lowprob symbols */
76 { FSE_DTableHeader DTableH;
77 DTableH.tableLog = (U16)tableLog;
78 DTableH.fastMode = 1;
79 { S16 const largeLimit= (S16)(1 << (tableLog-1));
80 U32 s;
81 for (s=0; s<maxSV1; s++) {
82 if (normalizedCounter[s]==-1) {
83 tableDecode[highThreshold--].symbol = (FSE_FUNCTION_TYPE)s;
84 symbolNext[s] = 1;
85 } else {
86 if (normalizedCounter[s] >= largeLimit) DTableH.fastMode=0;
87 symbolNext[s] = (U16)normalizedCounter[s];
88 } } }
89 ZSTD_memcpy(dt, &DTableH, sizeof(DTableH));
90 }
91
92 /* Spread symbols */
93 if (highThreshold == tableSize - 1) {
94 size_t const tableMask = tableSize-1;
95 size_t const step = FSE_TABLESTEP(tableSize);
96 /* First lay down the symbols in order.
97 * We use a uint64_t to lay down 8 bytes at a time. This reduces branch
98 * misses since small blocks generally have small table logs, so nearly
99 * all symbols have counts <= 8. We ensure we have 8 bytes at the end of
100 * our buffer to handle the over-write.
101 */
102 { U64 const add = 0x0101010101010101ull;
103 size_t pos = 0;
104 U64 sv = 0;
105 U32 s;
106 for (s=0; s<maxSV1; ++s, sv += add) {
107 int i;
108 int const n = normalizedCounter[s];
109 MEM_write64(spread + pos, sv);
110 for (i = 8; i < n; i += 8) {
111 MEM_write64(spread + pos + i, sv);
112 }
113 pos += (size_t)n;
114 } }
115 /* Now we spread those positions across the table.
116 * The benefit of doing it in two stages is that we avoid the
117 * variable size inner loop, which caused lots of branch misses.
118 * Now we can run through all the positions without any branch misses.
119 * We unroll the loop twice, since that is what empirically worked best.
120 */
121 {
122 size_t position = 0;
123 size_t s;
124 size_t const unroll = 2;
125 assert(tableSize % unroll == 0); /* FSE_MIN_TABLELOG is 5 */
126 for (s = 0; s < (size_t)tableSize; s += unroll) {
127 size_t u;
128 for (u = 0; u < unroll; ++u) {
129 size_t const uPosition = (position + (u * step)) & tableMask;
130 tableDecode[uPosition].symbol = spread[s + u];
131 }
132 position = (position + (unroll * step)) & tableMask;
133 }
134 assert(position == 0);
135 }
136 } else {
137 U32 const tableMask = tableSize-1;
138 U32 const step = FSE_TABLESTEP(tableSize);
139 U32 s, position = 0;
140 for (s=0; s<maxSV1; s++) {
141 int i;
142 for (i=0; i<normalizedCounter[s]; i++) {
143 tableDecode[position].symbol = (FSE_FUNCTION_TYPE)s;
144 position = (position + step) & tableMask;
145 while (position > highThreshold) position = (position + step) & tableMask; /* lowprob area */
146 } }
147 if (position!=0) return ERROR(GENERIC); /* position must reach all cells once, otherwise normalizedCounter is incorrect */
148 }
149
150 /* Build Decoding table */
151 { U32 u;
152 for (u=0; u<tableSize; u++) {
153 FSE_FUNCTION_TYPE const symbol = (FSE_FUNCTION_TYPE)(tableDecode[u].symbol);
154 U32 const nextState = symbolNext[symbol]++;
155 tableDecode[u].nbBits = (BYTE) (tableLog - ZSTD_highbit32(nextState) );
156 tableDecode[u].newState = (U16) ( (nextState << tableDecode[u].nbBits) - tableSize);
157 } }
158
159 return 0;
160}
161
162size_t FSE_buildDTable_wksp(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize)
163{
164 return FSE_buildDTable_internal(dt, normalizedCounter, maxSymbolValue, tableLog, workSpace, wkspSize);
165}
166
167
168#ifndef FSE_COMMONDEFS_ONLY
169
170/*-*******************************************************
171* Decompression (Byte symbols)
172*********************************************************/
173
174FORCE_INLINE_TEMPLATE size_t FSE_decompress_usingDTable_generic(
175 void* dst, size_t maxDstSize,
176 const void* cSrc, size_t cSrcSize,
177 const FSE_DTable* dt, const unsigned fast)
178{
179 BYTE* const ostart = (BYTE*) dst;
180 BYTE* op = ostart;
181 BYTE* const omax = op + maxDstSize;
182 BYTE* const olimit = omax-3;
183
184 BIT_DStream_t bitD;
185 FSE_DState_t state1;
186 FSE_DState_t state2;
187
188 /* Init */
189 CHECK_F(BIT_initDStream(&bitD, cSrc, cSrcSize));
190
191 FSE_initDState(&state1, &bitD, dt);
192 FSE_initDState(&state2, &bitD, dt);
193
194 RETURN_ERROR_IF(BIT_reloadDStream(&bitD)==BIT_DStream_overflow, corruption_detected, "");
195
196#define FSE_GETSYMBOL(statePtr) fast ? FSE_decodeSymbolFast(statePtr, &bitD) : FSE_decodeSymbol(statePtr, &bitD)
197
198 /* 4 symbols per loop */
199 for ( ; (BIT_reloadDStream(&bitD)==BIT_DStream_unfinished) & (op<olimit) ; op+=4) {
200 op[0] = FSE_GETSYMBOL(&state1);
201
202 if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */
203 BIT_reloadDStream(&bitD);
204
205 op[1] = FSE_GETSYMBOL(&state2);
206
207 if (FSE_MAX_TABLELOG*4+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */
208 { if (BIT_reloadDStream(&bitD) > BIT_DStream_unfinished) { op+=2; break; } }
209
210 op[2] = FSE_GETSYMBOL(&state1);
211
212 if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */
213 BIT_reloadDStream(&bitD);
214
215 op[3] = FSE_GETSYMBOL(&state2);
216 }
217
218 /* tail */
219 /* note : BIT_reloadDStream(&bitD) >= FSE_DStream_partiallyFilled; Ends at exactly BIT_DStream_completed */
220 while (1) {
221 if (op>(omax-2)) return ERROR(dstSize_tooSmall);
222 *op++ = FSE_GETSYMBOL(&state1);
223 if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) {
224 *op++ = FSE_GETSYMBOL(&state2);
225 break;
226 }
227
228 if (op>(omax-2)) return ERROR(dstSize_tooSmall);
229 *op++ = FSE_GETSYMBOL(&state2);
230 if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) {
231 *op++ = FSE_GETSYMBOL(&state1);
232 break;
233 } }
234
235 assert(op >= ostart);
236 return (size_t)(op-ostart);
237}
238
239typedef struct {
240 short ncount[FSE_MAX_SYMBOL_VALUE + 1];
241} FSE_DecompressWksp;
242
243
244FORCE_INLINE_TEMPLATE size_t FSE_decompress_wksp_body(
245 void* dst, size_t dstCapacity,
246 const void* cSrc, size_t cSrcSize,
247 unsigned maxLog, void* workSpace, size_t wkspSize,
248 int bmi2)
249{
250 const BYTE* const istart = (const BYTE*)cSrc;
251 const BYTE* ip = istart;
252 unsigned tableLog;
253 unsigned maxSymbolValue = FSE_MAX_SYMBOL_VALUE;
254 FSE_DecompressWksp* const wksp = (FSE_DecompressWksp*)workSpace;
255 size_t const dtablePos = sizeof(FSE_DecompressWksp) / sizeof(FSE_DTable);
256 FSE_DTable* const dtable = (FSE_DTable*)workSpace + dtablePos;
257
258 FSE_STATIC_ASSERT((FSE_MAX_SYMBOL_VALUE + 1) % 2 == 0);
259 if (wkspSize < sizeof(*wksp)) return ERROR(GENERIC);
260
261 /* correct offset to dtable depends on this property */
262 FSE_STATIC_ASSERT(sizeof(FSE_DecompressWksp) % sizeof(FSE_DTable) == 0);
263
264 /* normal FSE decoding mode */
265 { size_t const NCountLength =
266 FSE_readNCount_bmi2(wksp->ncount, &maxSymbolValue, &tableLog, istart, cSrcSize, bmi2);
267 if (FSE_isError(NCountLength)) return NCountLength;
268 if (tableLog > maxLog) return ERROR(tableLog_tooLarge);
269 assert(NCountLength <= cSrcSize);
270 ip += NCountLength;
271 cSrcSize -= NCountLength;
272 }
273
274 if (FSE_DECOMPRESS_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(tableLog_tooLarge);
275 assert(sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog) <= wkspSize);
276 workSpace = (BYTE*)workSpace + sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog);
277 wkspSize -= sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog);
278
279 CHECK_F( FSE_buildDTable_internal(dtable, wksp->ncount, maxSymbolValue, tableLog, workSpace, wkspSize) );
280
281 {
282 const void* ptr = dtable;
283 const FSE_DTableHeader* DTableH = (const FSE_DTableHeader*)ptr;
284 const U32 fastMode = DTableH->fastMode;
285
286 /* select fast mode (static) */
287 if (fastMode) return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 1);
288 return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 0);
289 }
290}
291
292/* Avoids the FORCE_INLINE of the _body() function. */
293static size_t FSE_decompress_wksp_body_default(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize)
294{
295 return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 0);
296}
297
298#if DYNAMIC_BMI2
299BMI2_TARGET_ATTRIBUTE static size_t FSE_decompress_wksp_body_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize)
300{
301 return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 1);
302}
303#endif
304
305size_t FSE_decompress_wksp_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize, int bmi2)
306{
307#if DYNAMIC_BMI2
308 if (bmi2) {
309 return FSE_decompress_wksp_body_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
310 }
311#endif
312 (void)bmi2;
313 return FSE_decompress_wksp_body_default(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
314}
315
316#endif /* FSE_COMMONDEFS_ONLY */