1 // SPDX-License-Identifier: (GPL-2.0 or BSD-2-Clause)
2 /*
3 * Common functions of New Generation Entropy library
4 * Copyright (C) 2016, Yann Collet.
5 *
6 * You can contact the author at :
7 * - Source repository : https://github.com/Cyan4973/FiniteStateEntropy
8 */
9
10 /* *************************************
11 * Dependencies
12 ***************************************/
13 #include "error_private.h" /* ERR_*, ERROR */
14 #include "fse.h"
15 #include "huf.h"
16 #include "mem.h"
17
18 /*=== Version ===*/
FSE_versionNumber(void)19 unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }
20
21 /*=== Error Management ===*/
FSE_isError(size_t code)22 unsigned FSE_isError(size_t code) { return ERR_isError(code); }
23
HUF_isError(size_t code)24 unsigned HUF_isError(size_t code) { return ERR_isError(code); }
25
26 /*-**************************************************************
27 * FSE NCount encoding-decoding
28 ****************************************************************/
FSE_readNCount(short * normalizedCounter,unsigned * maxSVPtr,unsigned * tableLogPtr,const void * headerBuffer,size_t hbSize)29 size_t FSE_readNCount(short *normalizedCounter, unsigned *maxSVPtr, unsigned *tableLogPtr, const void *headerBuffer, size_t hbSize)
30 {
31 const BYTE *const istart = (const BYTE *)headerBuffer;
32 const BYTE *const iend = istart + hbSize;
33 const BYTE *ip = istart;
34 int nbBits;
35 int remaining;
36 int threshold;
37 U32 bitStream;
38 int bitCount;
39 unsigned charnum = 0;
40 int previous0 = 0;
41
42 if (hbSize < 4)
43 return ERROR(srcSize_wrong);
44 bitStream = ZSTD_readLE32(ip);
45 nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG; /* extract tableLog */
46 if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX)
47 return ERROR(tableLog_tooLarge);
48 bitStream >>= 4;
49 bitCount = 4;
50 *tableLogPtr = nbBits;
51 remaining = (1 << nbBits) + 1;
52 threshold = 1 << nbBits;
53 nbBits++;
54
55 while ((remaining > 1) & (charnum <= *maxSVPtr)) {
56 if (previous0) {
57 unsigned n0 = charnum;
58 while ((bitStream & 0xFFFF) == 0xFFFF) {
59 n0 += 24;
60 if (ip < iend - 5) {
61 ip += 2;
62 bitStream = ZSTD_readLE32(ip) >> bitCount;
63 } else {
64 bitStream >>= 16;
65 bitCount += 16;
66 }
67 }
68 while ((bitStream & 3) == 3) {
69 n0 += 3;
70 bitStream >>= 2;
71 bitCount += 2;
72 }
73 n0 += bitStream & 3;
74 bitCount += 2;
75 if (n0 > *maxSVPtr)
76 return ERROR(maxSymbolValue_tooSmall);
77 while (charnum < n0)
78 normalizedCounter[charnum++] = 0;
79 if ((ip <= iend - 7) || (ip + (bitCount >> 3) <= iend - 4)) {
80 ip += bitCount >> 3;
81 bitCount &= 7;
82 bitStream = ZSTD_readLE32(ip) >> bitCount;
83 } else {
84 bitStream >>= 2;
85 }
86 }
87 {
88 int const max = (2 * threshold - 1) - remaining;
89 int count;
90
91 if ((bitStream & (threshold - 1)) < (U32)max) {
92 count = bitStream & (threshold - 1);
93 bitCount += nbBits - 1;
94 } else {
95 count = bitStream & (2 * threshold - 1);
96 if (count >= threshold)
97 count -= max;
98 bitCount += nbBits;
99 }
100
101 count--; /* extra accuracy */
102 remaining -= count < 0 ? -count : count; /* -1 means +1 */
103 normalizedCounter[charnum++] = (short)count;
104 previous0 = !count;
105 while (remaining < threshold) {
106 nbBits--;
107 threshold >>= 1;
108 }
109
110 if ((ip <= iend - 7) || (ip + (bitCount >> 3) <= iend - 4)) {
111 ip += bitCount >> 3;
112 bitCount &= 7;
113 } else {
114 bitCount -= (int)(8 * (iend - 4 - ip));
115 ip = iend - 4;
116 }
117 bitStream = ZSTD_readLE32(ip) >> (bitCount & 31);
118 }
119 } /* while ((remaining>1) & (charnum<=*maxSVPtr)) */
120 if (remaining != 1)
121 return ERROR(corruption_detected);
122 if (bitCount > 32)
123 return ERROR(corruption_detected);
124 *maxSVPtr = charnum - 1;
125
126 ip += (bitCount + 7) >> 3;
127 return ip - istart;
128 }
129
130 /*! HUF_readStats() :
131 Read compact Huffman tree, saved by HUF_writeCTable().
132 `huffWeight` is destination buffer.
133 `rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
134 @return : size read from `src` , or an error Code .
135 Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
136 */
HUF_readStats_wksp(BYTE * huffWeight,size_t hwSize,U32 * rankStats,U32 * nbSymbolsPtr,U32 * tableLogPtr,const void * src,size_t srcSize,void * workspace,size_t workspaceSize)137 size_t HUF_readStats_wksp(BYTE *huffWeight, size_t hwSize, U32 *rankStats, U32 *nbSymbolsPtr, U32 *tableLogPtr, const void *src, size_t srcSize, void *workspace, size_t workspaceSize)
138 {
139 U32 weightTotal;
140 const BYTE *ip = (const BYTE *)src;
141 size_t iSize;
142 size_t oSize;
143
144 if (!srcSize)
145 return ERROR(srcSize_wrong);
146 iSize = ip[0];
147 /* memset(huffWeight, 0, hwSize); */ /* is not necessary, even though some analyzer complain ... */
148
149 if (iSize >= 128) { /* special header */
150 oSize = iSize - 127;
151 iSize = ((oSize + 1) / 2);
152 if (iSize + 1 > srcSize)
153 return ERROR(srcSize_wrong);
154 if (oSize >= hwSize)
155 return ERROR(corruption_detected);
156 ip += 1;
157 {
158 U32 n;
159 for (n = 0; n < oSize; n += 2) {
160 huffWeight[n] = ip[n / 2] >> 4;
161 huffWeight[n + 1] = ip[n / 2] & 15;
162 }
163 }
164 } else { /* header compressed with FSE (normal case) */
165 if (iSize + 1 > srcSize)
166 return ERROR(srcSize_wrong);
167 oSize = FSE_decompress_wksp(huffWeight, hwSize - 1, ip + 1, iSize, 6, workspace, workspaceSize); /* max (hwSize-1) values decoded, as last one is implied */
168 if (FSE_isError(oSize))
169 return oSize;
170 }
171
172 /* collect weight stats */
173 memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
174 weightTotal = 0;
175 {
176 U32 n;
177 for (n = 0; n < oSize; n++) {
178 if (huffWeight[n] >= HUF_TABLELOG_MAX)
179 return ERROR(corruption_detected);
180 rankStats[huffWeight[n]]++;
181 weightTotal += (1 << huffWeight[n]) >> 1;
182 }
183 }
184 if (weightTotal == 0)
185 return ERROR(corruption_detected);
186
187 /* get last non-null symbol weight (implied, total must be 2^n) */
188 {
189 U32 const tableLog = BIT_highbit32(weightTotal) + 1;
190 if (tableLog > HUF_TABLELOG_MAX)
191 return ERROR(corruption_detected);
192 *tableLogPtr = tableLog;
193 /* determine last weight */
194 {
195 U32 const total = 1 << tableLog;
196 U32 const rest = total - weightTotal;
197 U32 const verif = 1 << BIT_highbit32(rest);
198 U32 const lastWeight = BIT_highbit32(rest) + 1;
199 if (verif != rest)
200 return ERROR(corruption_detected); /* last value must be a clean power of 2 */
201 huffWeight[oSize] = (BYTE)lastWeight;
202 rankStats[lastWeight]++;
203 }
204 }
205
206 /* check tree construction validity */
207 if ((rankStats[1] < 2) || (rankStats[1] & 1))
208 return ERROR(corruption_detected); /* by construction : at least 2 elts of rank 1, must be even */
209
210 /* results */
211 *nbSymbolsPtr = (U32)(oSize + 1);
212 return iSize + 1;
213 }
214