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entropy_common.c
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1 /* ******************************************************************
2  * Common functions of New Generation Entropy library
3  * Copyright (c) 2016-2020, 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 size_t FSE_readNCount (short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
42  const void* headerBuffer, size_t hbSize)
43 {
44  const BYTE* const istart = (const BYTE*) headerBuffer;
45  const BYTE* const iend = istart + hbSize;
46  const BYTE* ip = istart;
47  int nbBits;
48  int remaining;
49  int threshold;
50  U32 bitStream;
51  int bitCount;
52  unsigned charnum = 0;
53  int previous0 = 0;
54 
55  if (hbSize < 4) {
56  /* This function only works when hbSize >= 4 */
57  char buffer[4];
58  memset(buffer, 0, sizeof(buffer));
59  memcpy(buffer, headerBuffer, hbSize);
60  { size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr,
61  buffer, sizeof(buffer));
62  if (FSE_isError(countSize)) return countSize;
63  if (countSize > hbSize) return ERROR(corruption_detected);
64  return countSize;
65  } }
66  assert(hbSize >= 4);
67 
68  /* init */
69  memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0])); /* all symbols not present in NCount have a frequency of 0 */
70  bitStream = MEM_readLE32(ip);
71  nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG; /* extract tableLog */
72  if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);
73  bitStream >>= 4;
74  bitCount = 4;
75  *tableLogPtr = nbBits;
76  remaining = (1<<nbBits)+1;
77  threshold = 1<<nbBits;
78  nbBits++;
79 
80  while ((remaining>1) & (charnum<=*maxSVPtr)) {
81  if (previous0) {
82  unsigned n0 = charnum;
83  while ((bitStream & 0xFFFF) == 0xFFFF) {
84  n0 += 24;
85  if (ip < iend-5) {
86  ip += 2;
87  bitStream = MEM_readLE32(ip) >> bitCount;
88  } else {
89  bitStream >>= 16;
90  bitCount += 16;
91  } }
92  while ((bitStream & 3) == 3) {
93  n0 += 3;
94  bitStream >>= 2;
95  bitCount += 2;
96  }
97  n0 += bitStream & 3;
98  bitCount += 2;
99  if (n0 > *maxSVPtr) return ERROR(maxSymbolValue_tooSmall);
100  while (charnum < n0) normalizedCounter[charnum++] = 0;
101  if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
102  assert((bitCount >> 3) <= 3); /* For first condition to work */
103  ip += bitCount>>3;
104  bitCount &= 7;
105  bitStream = MEM_readLE32(ip) >> bitCount;
106  } else {
107  bitStream >>= 2;
108  } }
109  { int const max = (2*threshold-1) - remaining;
110  int count;
111 
112  if ((bitStream & (threshold-1)) < (U32)max) {
113  count = bitStream & (threshold-1);
114  bitCount += nbBits-1;
115  } else {
116  count = bitStream & (2*threshold-1);
117  if (count >= threshold) count -= max;
118  bitCount += nbBits;
119  }
120 
121  count--; /* extra accuracy */
122  remaining -= count < 0 ? -count : count; /* -1 means +1 */
123  normalizedCounter[charnum++] = (short)count;
124  previous0 = !count;
125  while (remaining < threshold) {
126  nbBits--;
127  threshold >>= 1;
128  }
129 
130  if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
131  ip += bitCount>>3;
132  bitCount &= 7;
133  } else {
134  bitCount -= (int)(8 * (iend - 4 - ip));
135  ip = iend - 4;
136  }
137  bitStream = MEM_readLE32(ip) >> (bitCount & 31);
138  } } /* while ((remaining>1) & (charnum<=*maxSVPtr)) */
139  if (remaining != 1) return ERROR(corruption_detected);
140  if (bitCount > 32) return ERROR(corruption_detected);
141  *maxSVPtr = charnum-1;
142 
143  ip += (bitCount+7)>>3;
144  return ip-istart;
145 }
146 
147 
155 size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,
156  U32* nbSymbolsPtr, U32* tableLogPtr,
157  const void* src, size_t srcSize)
158 {
159  U32 weightTotal;
160  const BYTE* ip = (const BYTE*) src;
161  size_t iSize;
162  size_t oSize;
163 
164  if (!srcSize) return ERROR(srcSize_wrong);
165  iSize = ip[0];
166  /* memset(huffWeight, 0, hwSize); *//* is not necessary, even though some analyzer complain ... */
167 
168  if (iSize >= 128) { /* special header */
169  oSize = iSize - 127;
170  iSize = ((oSize+1)/2);
171  if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
172  if (oSize >= hwSize) return ERROR(corruption_detected);
173  ip += 1;
174  { U32 n;
175  for (n=0; n<oSize; n+=2) {
176  huffWeight[n] = ip[n/2] >> 4;
177  huffWeight[n+1] = ip[n/2] & 15;
178  } } }
179  else { /* header compressed with FSE (normal case) */
180  FSE_DTable fseWorkspace[FSE_DTABLE_SIZE_U32(6)]; /* 6 is max possible tableLog for HUF header (maybe even 5, to be tested) */
181  if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
182  oSize = FSE_decompress_wksp(huffWeight, hwSize-1, ip+1, iSize, fseWorkspace, 6); /* max (hwSize-1) values decoded, as last one is implied */
183  if (FSE_isError(oSize)) return oSize;
184  }
185 
186  /* collect weight stats */
187  memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
188  weightTotal = 0;
189  { U32 n; for (n=0; n<oSize; n++) {
190  if (huffWeight[n] >= HUF_TABLELOG_MAX) return ERROR(corruption_detected);
191  rankStats[huffWeight[n]]++;
192  weightTotal += (1 << huffWeight[n]) >> 1;
193  } }
194  if (weightTotal == 0) return ERROR(corruption_detected);
195 
196  /* get last non-null symbol weight (implied, total must be 2^n) */
197  { U32 const tableLog = BIT_highbit32(weightTotal) + 1;
198  if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
199  *tableLogPtr = tableLog;
200  /* determine last weight */
201  { U32 const total = 1 << tableLog;
202  U32 const rest = total - weightTotal;
203  U32 const verif = 1 << BIT_highbit32(rest);
204  U32 const lastWeight = BIT_highbit32(rest) + 1;
205  if (verif != rest) return ERROR(corruption_detected); /* last value must be a clean power of 2 */
206  huffWeight[oSize] = (BYTE)lastWeight;
207  rankStats[lastWeight]++;
208  } }
209 
210  /* check tree construction validity */
211  if ((rankStats[1] < 2) || (rankStats[1] & 1)) return ERROR(corruption_detected); /* by construction : at least 2 elts of rank 1, must be even */
212 
213  /* results */
214  *nbSymbolsPtr = (U32)(oSize+1);
215  return iSize+1;
216 }
#define max(a, b)
Definition: svc.c:63
#define ERROR(name)
Definition: error_private.h:53
size_t FSE_readNCount(short *normalizedCounter, unsigned *maxSVPtr, unsigned *tableLogPtr, const void *headerBuffer, size_t hbSize)
GLuint GLuint GLsizei count
Definition: gl.h:1545
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Definition: mem.h:346
GLdouble n
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#define assert(x)
Definition: debug.h:53
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ERR_STATIC const char * ERR_getErrorName(size_t code)
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MEM_STATIC unsigned BIT_highbit32(U32 val)
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ERR_STATIC unsigned ERR_isError(size_t code)
Definition: error_private.h:56
const char * FSE_getErrorName(size_t code)
Definition: dhcpd.h:61
#define FSE_VERSION_NUMBER
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GLenum src
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unsigned char BYTE
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const char * HUF_getErrorName(size_t code)
unsigned FSE_isError(size_t code)
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size_t FSE_decompress_wksp(void *dst, size_t dstCapacity, const void *cSrc, size_t cSrcSize, FSE_DTable *workSpace, unsigned maxLog)
#define memset(x, y, z)
Definition: compat.h:39
unsigned int U32
Definition: xxhash.c:195
size_t HUF_readStats(BYTE *huffWeight, size_t hwSize, U32 *rankStats, U32 *nbSymbolsPtr, U32 *tableLogPtr, const void *src, size_t srcSize)
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Definition: typeof.h:31