xref: /openbmc/linux/lib/zstd/common/entropy_common.c (revision 8ffd3d5e)
1 /* ******************************************************************
2  * Common functions 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 *  Dependencies
17 ***************************************/
18 #include "mem.h"
19 #include "error_private.h"       /* ERR_*, ERROR */
20 #define FSE_STATIC_LINKING_ONLY  /* FSE_MIN_TABLELOG */
21 #include "fse.h"
22 #define HUF_STATIC_LINKING_ONLY  /* HUF_TABLELOG_ABSOLUTEMAX */
23 #include "huf.h"
24 
25 
26 /*===   Version   ===*/
27 unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }
28 
29 
30 /*===   Error Management   ===*/
31 unsigned FSE_isError(size_t code) { return ERR_isError(code); }
32 const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); }
33 
34 unsigned HUF_isError(size_t code) { return ERR_isError(code); }
35 const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); }
36 
37 
38 /*-**************************************************************
39 *  FSE NCount encoding-decoding
40 ****************************************************************/
41 static U32 FSE_ctz(U32 val)
42 {
43     assert(val != 0);
44     {
45 #   if (__GNUC__ >= 3)   /* GCC Intrinsic */
46         return __builtin_ctz(val);
47 #   else   /* Software version */
48         U32 count = 0;
49         while ((val & 1) == 0) {
50             val >>= 1;
51             ++count;
52         }
53         return count;
54 #   endif
55     }
56 }
57 
58 FORCE_INLINE_TEMPLATE
59 size_t FSE_readNCount_body(short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
60                            const void* headerBuffer, size_t hbSize)
61 {
62     const BYTE* const istart = (const BYTE*) headerBuffer;
63     const BYTE* const iend = istart + hbSize;
64     const BYTE* ip = istart;
65     int nbBits;
66     int remaining;
67     int threshold;
68     U32 bitStream;
69     int bitCount;
70     unsigned charnum = 0;
71     unsigned const maxSV1 = *maxSVPtr + 1;
72     int previous0 = 0;
73 
74     if (hbSize < 8) {
75         /* This function only works when hbSize >= 8 */
76         char buffer[8] = {0};
77         ZSTD_memcpy(buffer, headerBuffer, hbSize);
78         {   size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr,
79                                                     buffer, sizeof(buffer));
80             if (FSE_isError(countSize)) return countSize;
81             if (countSize > hbSize) return ERROR(corruption_detected);
82             return countSize;
83     }   }
84     assert(hbSize >= 8);
85 
86     /* init */
87     ZSTD_memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0]));   /* all symbols not present in NCount have a frequency of 0 */
88     bitStream = MEM_readLE32(ip);
89     nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG;   /* extract tableLog */
90     if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);
91     bitStream >>= 4;
92     bitCount = 4;
93     *tableLogPtr = nbBits;
94     remaining = (1<<nbBits)+1;
95     threshold = 1<<nbBits;
96     nbBits++;
97 
98     for (;;) {
99         if (previous0) {
100             /* Count the number of repeats. Each time the
101              * 2-bit repeat code is 0b11 there is another
102              * repeat.
103              * Avoid UB by setting the high bit to 1.
104              */
105             int repeats = FSE_ctz(~bitStream | 0x80000000) >> 1;
106             while (repeats >= 12) {
107                 charnum += 3 * 12;
108                 if (LIKELY(ip <= iend-7)) {
109                     ip += 3;
110                 } else {
111                     bitCount -= (int)(8 * (iend - 7 - ip));
112                     bitCount &= 31;
113                     ip = iend - 4;
114                 }
115                 bitStream = MEM_readLE32(ip) >> bitCount;
116                 repeats = FSE_ctz(~bitStream | 0x80000000) >> 1;
117             }
118             charnum += 3 * repeats;
119             bitStream >>= 2 * repeats;
120             bitCount += 2 * repeats;
121 
122             /* Add the final repeat which isn't 0b11. */
123             assert((bitStream & 3) < 3);
124             charnum += bitStream & 3;
125             bitCount += 2;
126 
127             /* This is an error, but break and return an error
128              * at the end, because returning out of a loop makes
129              * it harder for the compiler to optimize.
130              */
131             if (charnum >= maxSV1) break;
132 
133             /* We don't need to set the normalized count to 0
134              * because we already memset the whole buffer to 0.
135              */
136 
137             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
138                 assert((bitCount >> 3) <= 3); /* For first condition to work */
139                 ip += bitCount>>3;
140                 bitCount &= 7;
141             } else {
142                 bitCount -= (int)(8 * (iend - 4 - ip));
143                 bitCount &= 31;
144                 ip = iend - 4;
145             }
146             bitStream = MEM_readLE32(ip) >> bitCount;
147         }
148         {
149             int const max = (2*threshold-1) - remaining;
150             int count;
151 
152             if ((bitStream & (threshold-1)) < (U32)max) {
153                 count = bitStream & (threshold-1);
154                 bitCount += nbBits-1;
155             } else {
156                 count = bitStream & (2*threshold-1);
157                 if (count >= threshold) count -= max;
158                 bitCount += nbBits;
159             }
160 
161             count--;   /* extra accuracy */
162             /* When it matters (small blocks), this is a
163              * predictable branch, because we don't use -1.
164              */
165             if (count >= 0) {
166                 remaining -= count;
167             } else {
168                 assert(count == -1);
169                 remaining += count;
170             }
171             normalizedCounter[charnum++] = (short)count;
172             previous0 = !count;
173 
174             assert(threshold > 1);
175             if (remaining < threshold) {
176                 /* This branch can be folded into the
177                  * threshold update condition because we
178                  * know that threshold > 1.
179                  */
180                 if (remaining <= 1) break;
181                 nbBits = BIT_highbit32(remaining) + 1;
182                 threshold = 1 << (nbBits - 1);
183             }
184             if (charnum >= maxSV1) break;
185 
186             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
187                 ip += bitCount>>3;
188                 bitCount &= 7;
189             } else {
190                 bitCount -= (int)(8 * (iend - 4 - ip));
191                 bitCount &= 31;
192                 ip = iend - 4;
193             }
194             bitStream = MEM_readLE32(ip) >> bitCount;
195     }   }
196     if (remaining != 1) return ERROR(corruption_detected);
197     /* Only possible when there are too many zeros. */
198     if (charnum > maxSV1) return ERROR(maxSymbolValue_tooSmall);
199     if (bitCount > 32) return ERROR(corruption_detected);
200     *maxSVPtr = charnum-1;
201 
202     ip += (bitCount+7)>>3;
203     return ip-istart;
204 }
205 
206 /* Avoids the FORCE_INLINE of the _body() function. */
207 static size_t FSE_readNCount_body_default(
208         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
209         const void* headerBuffer, size_t hbSize)
210 {
211     return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
212 }
213 
214 #if DYNAMIC_BMI2
215 BMI2_TARGET_ATTRIBUTE static size_t FSE_readNCount_body_bmi2(
216         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
217         const void* headerBuffer, size_t hbSize)
218 {
219     return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
220 }
221 #endif
222 
223 size_t FSE_readNCount_bmi2(
224         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
225         const void* headerBuffer, size_t hbSize, int bmi2)
226 {
227 #if DYNAMIC_BMI2
228     if (bmi2) {
229         return FSE_readNCount_body_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
230     }
231 #endif
232     (void)bmi2;
233     return FSE_readNCount_body_default(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
234 }
235 
236 size_t FSE_readNCount(
237         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
238         const void* headerBuffer, size_t hbSize)
239 {
240     return FSE_readNCount_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize, /* bmi2 */ 0);
241 }
242 
243 
244 /*! HUF_readStats() :
245     Read compact Huffman tree, saved by HUF_writeCTable().
246     `huffWeight` is destination buffer.
247     `rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
248     @return : size read from `src` , or an error Code .
249     Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
250 */
251 size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,
252                      U32* nbSymbolsPtr, U32* tableLogPtr,
253                      const void* src, size_t srcSize)
254 {
255     U32 wksp[HUF_READ_STATS_WORKSPACE_SIZE_U32];
256     return HUF_readStats_wksp(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, wksp, sizeof(wksp), /* bmi2 */ 0);
257 }
258 
259 FORCE_INLINE_TEMPLATE size_t
260 HUF_readStats_body(BYTE* huffWeight, size_t hwSize, U32* rankStats,
261                    U32* nbSymbolsPtr, U32* tableLogPtr,
262                    const void* src, size_t srcSize,
263                    void* workSpace, size_t wkspSize,
264                    int bmi2)
265 {
266     U32 weightTotal;
267     const BYTE* ip = (const BYTE*) src;
268     size_t iSize;
269     size_t oSize;
270 
271     if (!srcSize) return ERROR(srcSize_wrong);
272     iSize = ip[0];
273     /* ZSTD_memset(huffWeight, 0, hwSize);   *//* is not necessary, even though some analyzer complain ... */
274 
275     if (iSize >= 128) {  /* special header */
276         oSize = iSize - 127;
277         iSize = ((oSize+1)/2);
278         if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
279         if (oSize >= hwSize) return ERROR(corruption_detected);
280         ip += 1;
281         {   U32 n;
282             for (n=0; n<oSize; n+=2) {
283                 huffWeight[n]   = ip[n/2] >> 4;
284                 huffWeight[n+1] = ip[n/2] & 15;
285     }   }   }
286     else  {   /* header compressed with FSE (normal case) */
287         if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
288         /* max (hwSize-1) values decoded, as last one is implied */
289         oSize = FSE_decompress_wksp_bmi2(huffWeight, hwSize-1, ip+1, iSize, 6, workSpace, wkspSize, bmi2);
290         if (FSE_isError(oSize)) return oSize;
291     }
292 
293     /* collect weight stats */
294     ZSTD_memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
295     weightTotal = 0;
296     {   U32 n; for (n=0; n<oSize; n++) {
297             if (huffWeight[n] > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
298             rankStats[huffWeight[n]]++;
299             weightTotal += (1 << huffWeight[n]) >> 1;
300     }   }
301     if (weightTotal == 0) return ERROR(corruption_detected);
302 
303     /* get last non-null symbol weight (implied, total must be 2^n) */
304     {   U32 const tableLog = BIT_highbit32(weightTotal) + 1;
305         if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
306         *tableLogPtr = tableLog;
307         /* determine last weight */
308         {   U32 const total = 1 << tableLog;
309             U32 const rest = total - weightTotal;
310             U32 const verif = 1 << BIT_highbit32(rest);
311             U32 const lastWeight = BIT_highbit32(rest) + 1;
312             if (verif != rest) return ERROR(corruption_detected);    /* last value must be a clean power of 2 */
313             huffWeight[oSize] = (BYTE)lastWeight;
314             rankStats[lastWeight]++;
315     }   }
316 
317     /* check tree construction validity */
318     if ((rankStats[1] < 2) || (rankStats[1] & 1)) return ERROR(corruption_detected);   /* by construction : at least 2 elts of rank 1, must be even */
319 
320     /* results */
321     *nbSymbolsPtr = (U32)(oSize+1);
322     return iSize+1;
323 }
324 
325 /* Avoids the FORCE_INLINE of the _body() function. */
326 static size_t HUF_readStats_body_default(BYTE* huffWeight, size_t hwSize, U32* rankStats,
327                      U32* nbSymbolsPtr, U32* tableLogPtr,
328                      const void* src, size_t srcSize,
329                      void* workSpace, size_t wkspSize)
330 {
331     return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 0);
332 }
333 
334 #if DYNAMIC_BMI2
335 static BMI2_TARGET_ATTRIBUTE size_t HUF_readStats_body_bmi2(BYTE* huffWeight, size_t hwSize, U32* rankStats,
336                      U32* nbSymbolsPtr, U32* tableLogPtr,
337                      const void* src, size_t srcSize,
338                      void* workSpace, size_t wkspSize)
339 {
340     return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 1);
341 }
342 #endif
343 
344 size_t HUF_readStats_wksp(BYTE* huffWeight, size_t hwSize, U32* rankStats,
345                      U32* nbSymbolsPtr, U32* tableLogPtr,
346                      const void* src, size_t srcSize,
347                      void* workSpace, size_t wkspSize,
348                      int bmi2)
349 {
350 #if DYNAMIC_BMI2
351     if (bmi2) {
352         return HUF_readStats_body_bmi2(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
353     }
354 #endif
355     (void)bmi2;
356     return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
357 }
358