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entropy_common.c File Reference
#include "mem.h"
#include "error_private.h"
#include "fse.h"
#include "huf.h"
Include dependency graph for entropy_common.c:

Go to the source code of this file.

Macros

#define FSE_STATIC_LINKING_ONLY   /* FSE_MIN_TABLELOG */
 
#define HUF_STATIC_LINKING_ONLY   /* HUF_TABLELOG_ABSOLUTEMAX */
 

Functions

unsigned FSE_versionNumber (void)
 
unsigned FSE_isError (size_t code)
 
const charFSE_getErrorName (size_t code)
 
unsigned HUF_isError (size_t code)
 
const charHUF_getErrorName (size_t code)
 
size_t FSE_readNCount (short *normalizedCounter, unsigned *maxSVPtr, unsigned *tableLogPtr, const void *headerBuffer, size_t hbSize)
 
size_t HUF_readStats (BYTE *huffWeight, size_t hwSize, U32 *rankStats, U32 *nbSymbolsPtr, U32 *tableLogPtr, const void *src, size_t srcSize)
 

Macro Definition Documentation

◆ FSE_STATIC_LINKING_ONLY

#define FSE_STATIC_LINKING_ONLY   /* FSE_MIN_TABLELOG */

Definition at line 20 of file entropy_common.c.

◆ HUF_STATIC_LINKING_ONLY

#define HUF_STATIC_LINKING_ONLY   /* HUF_TABLELOG_ABSOLUTEMAX */

Definition at line 22 of file entropy_common.c.

Function Documentation

◆ FSE_getErrorName()

const char* FSE_getErrorName ( size_t  code)

Definition at line 32 of file entropy_common.c.

32 { return ERR_getErrorName(code); }
ERR_STATIC const char * ERR_getErrorName(size_t code)
Definition: error_private.h:71
Definition: inflate.c:139

◆ FSE_isError()

unsigned FSE_isError ( size_t  code)

Definition at line 31 of file entropy_common.c.

31 { return ERR_isError(code); }
ERR_STATIC unsigned ERR_isError(size_t code)
Definition: error_private.h:56
Definition: inflate.c:139

Referenced by FSE_readNCount(), and HUF_readStats().

◆ FSE_readNCount()

size_t FSE_readNCount ( short normalizedCounter,
unsigned maxSymbolValuePtr,
unsigned tableLogPtr,
const void rBuffer,
size_t  rBuffSize 
)

Tutorial :

The first step is to count all symbols. FSE_count() does this job very fast. Result will be saved into 'count', a table of unsigned int, which must be already allocated, and have 'maxSymbolValuePtr[0]+1' cells. 'src' is a table of bytes of size 'srcSize'. All values within 'src' MUST be <= maxSymbolValuePtr[0] maxSymbolValuePtr[0] will be updated, with its real value (necessarily <= original value) FSE_count() will return the number of occurrence of the most frequent symbol. This can be used to know if there is a single symbol within 'src', and to quickly evaluate its compressibility. If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).

The next step is to normalize the frequencies. FSE_normalizeCount() will ensure that sum of frequencies is == 2 ^'tableLog'. It also guarantees a minimum of 1 to any Symbol with frequency >= 1. You can use 'tableLog'==0 to mean "use default tableLog value". If you are unsure of which tableLog value to use, you can ask FSE_optimalTableLog(), which will provide the optimal valid tableLog given sourceSize, maxSymbolValue, and a user-defined maximum (0 means "default").

The result of FSE_normalizeCount() will be saved into a table, called 'normalizedCounter', which is a table of signed short. 'normalizedCounter' must be already allocated, and have at least 'maxSymbolValue+1' cells. The return value is tableLog if everything proceeded as expected. It is 0 if there is a single symbol within distribution. If there is an error (ex: invalid tableLog value), the function will return an ErrorCode (which can be tested using FSE_isError()).

'normalizedCounter' can be saved in a compact manner to a memory area using FSE_writeNCount(). 'buffer' must be already allocated. For guaranteed success, buffer size must be at least FSE_headerBound(). The result of the function is the number of bytes written into 'buffer'. If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError(); ex : buffer size too small).

'normalizedCounter' can then be used to create the compression table 'CTable'. The space required by 'CTable' must be already allocated, using FSE_createCTable(). You can then use FSE_buildCTable() to fill 'CTable'. If there is an error, both functions will return an ErrorCode (which can be tested using FSE_isError()).

'CTable' can then be used to compress 'src', with FSE_compress_usingCTable(). Similar to FSE_count(), the convention is that 'src' is assumed to be a table of char of size 'srcSize' The function returns the size of compressed data (without header), necessarily <= dstCapacity. If it returns '0', compressed data could not fit into 'dst'. If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).

FSE_readNCount(): Read compactly saved 'normalizedCounter' from 'rBuffer'.

Returns
: size read from 'rBuffer', or an errorCode, which can be tested using FSE_isError(). maxSymbolValuePtr[0] and tableLogPtr[0] will also be updated with their respective values

Definition at line 41 of file entropy_common.c.

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 }
#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
MEM_STATIC U32 MEM_readLE32(const void *memPtr)
Definition: mem.h:346
#define assert(x)
Definition: debug.h:53
GLuint buffer
Definition: glext.h:5915
unsigned short(__cdecl typeof(TIFFCurrentDirectory))(struct tiff *)
Definition: typeof.h:94
Definition: dhcpd.h:61
#define memcpy(s1, s2, n)
Definition: mkisofs.h:878
unsigned char BYTE
Definition: xxhash.c:193
unsigned FSE_isError(size_t code)
#define memset(x, y, z)
Definition: compat.h:39
unsigned int U32
Definition: xxhash.c:195
unsigned int(__cdecl typeof(jpeg_read_scanlines))(struct jpeg_decompress_struct *
Definition: typeof.h:31

Referenced by FSE_decompress_wksp(), FSE_readNCount(), ZSTD_loadCEntropy(), and ZSTD_loadDEntropy().

◆ FSE_versionNumber()

unsigned FSE_versionNumber ( void  )

library version number; to be used when checking dll version

Definition at line 27 of file entropy_common.c.

27 { return FSE_VERSION_NUMBER; }
#define FSE_VERSION_NUMBER
Definition: fse.h:52

◆ HUF_getErrorName()

const char* HUF_getErrorName ( size_t  code)

provides error code string (useful for debugging)

Definition at line 35 of file entropy_common.c.

35 { return ERR_getErrorName(code); }
ERR_STATIC const char * ERR_getErrorName(size_t code)
Definition: error_private.h:71
Definition: inflate.c:139

◆ HUF_isError()

unsigned HUF_isError ( size_t  code)

tells if a return value is an error code

Definition at line 34 of file entropy_common.c.

34 { return ERR_isError(code); }
ERR_STATIC unsigned ERR_isError(size_t code)
Definition: error_private.h:56
Definition: inflate.c:139

◆ HUF_readStats()

size_t HUF_readStats ( BYTE huffWeight,
size_t  hwSize,
U32 rankStats,
U32 nbSymbolsPtr,
U32 tableLogPtr,
const void src,
size_t  srcSize 
)

HUF_readStats() : Read compact Huffman tree, saved by HUF_writeCTable(). huffWeight is destination buffer. rankStats is assumed to be a table of at least HUF_TABLELOG_MAX U32.

Returns
: size read from src , or an error Code . Note : Needed by HUF_readCTable() and HUF_readDTableX?() .

Definition at line 155 of file entropy_common.c.

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 ERROR(name)
Definition: error_private.h:53
GLdouble n
Definition: glext.h:7729
unsigned FSE_DTable
Definition: fse.h:233
MEM_STATIC unsigned BIT_highbit32(U32 val)
Definition: bitstream.h:139
Definition: dhcpd.h:61
GLenum src
Definition: glext.h:6340
unsigned char BYTE
Definition: xxhash.c:193
unsigned FSE_isError(size_t code)
size_t total
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

Referenced by HUF_readCTable(), HUF_readDTableX1_wksp(), and HUF_readDTableX2_wksp().