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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

◆ 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}
unsigned int(__cdecl typeof(jpeg_read_scanlines))(struct jpeg_decompress_struct *
Definition: typeof.h:31
unsigned short(__cdecl typeof(TIFFCurrentDirectory))(struct tiff *)
Definition: typeof.h:94
#define assert(x)
Definition: debug.h:53
MEM_STATIC U32 MEM_readLE32(const void *memPtr)
Definition: mem.h:346
size_t FSE_readNCount(short *normalizedCounter, unsigned *maxSVPtr, unsigned *tableLogPtr, const void *headerBuffer, size_t hbSize)
#define ERROR(name)
Definition: error_private.h:53
#define FSE_isError
Definition: fse_compress.c:35
GLuint GLuint GLsizei count
Definition: gl.h:1545
GLuint buffer
Definition: glext.h:5915
#define memcpy(s1, s2, n)
Definition: mkisofs.h:878
#define memset(x, y, z)
Definition: compat.h:39
Definition: dhcpd.h:62
#define max(a, b)
Definition: svc.c:63
unsigned char BYTE
Definition: xxhash.c:193
unsigned int U32
Definition: xxhash.c:195

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); }

◆ 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); }

◆ 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}
MEM_STATIC unsigned BIT_highbit32(U32 val)
Definition: bitstream.h:139
unsigned FSE_DTable
Definition: fse.h:233
size_t FSE_decompress_wksp(void *dst, size_t dstCapacity, const void *cSrc, size_t cSrcSize, FSE_DTable *workSpace, unsigned maxLog)
size_t total
GLdouble n
Definition: glext.h:7729
GLenum src
Definition: glext.h:6340

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