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   ===*/
27unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }
28
29
30/*===   Error Management   ===*/
31unsigned FSE_isError(size_t code) { return ERR_isError(code); }
32const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); }
33
34unsigned HUF_isError(size_t code) { return ERR_isError(code); }
35const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); }
36
37
38/*-**************************************************************
39*  FSE NCount encoding-decoding
40****************************************************************/
41static 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
58FORCE_INLINE_TEMPLATE
59size_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. */
207static 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
215BMI2_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
223size_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
236size_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*/
251size_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
259FORCE_INLINE_TEMPLATE size_t
260HUF_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. */
326static 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
335static 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
344size_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