1/* ******************************************************************
2 * hist : Histogram functions
3 * part of Finite State Entropy project
4 * Copyright (c) 2013-2020, Yann Collet, Facebook, Inc.
5 *
6 *  You can contact the author at :
7 *  - FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy
8 *  - Public forum : https://groups.google.com/forum/#!forum/lz4c
9 *
10 * This source code is licensed under both the BSD-style license (found in the
11 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
12 * in the COPYING file in the root directory of this source tree).
13 * You may select, at your option, one of the above-listed licenses.
14****************************************************************** */
15
16/* --- dependencies --- */
17#include "../common/mem.h"             /* U32, BYTE, etc. */
18#include "../common/debug.h"           /* assert, DEBUGLOG */
19#include "../common/error_private.h"   /* ERROR */
20#include "hist.h"
21
22
23/* --- Error management --- */
24unsigned HIST_isError(size_t code) { return ERR_isError(code); }
25
26/*-**************************************************************
27 *  Histogram functions
28 ****************************************************************/
29unsigned HIST_count_simple(unsigned* count, unsigned* maxSymbolValuePtr,
30                           const void* src, size_t srcSize)
31{
32    const BYTE* ip = (const BYTE*)src;
33    const BYTE* const end = ip + srcSize;
34    unsigned maxSymbolValue = *maxSymbolValuePtr;
35    unsigned largestCount=0;
36
37    memset(count, 0, (maxSymbolValue+1) * sizeof(*count));
38    if (srcSize==0) { *maxSymbolValuePtr = 0; return 0; }
39
40    while (ip<end) {
41        assert(*ip <= maxSymbolValue);
42        count[*ip++]++;
43    }
44
45    while (!count[maxSymbolValue]) maxSymbolValue--;
46    *maxSymbolValuePtr = maxSymbolValue;
47
48    {   U32 s;
49        for (s=0; s<=maxSymbolValue; s++)
50            if (count[s] > largestCount) largestCount = count[s];
51    }
52
53    return largestCount;
54}
55
56typedef enum { trustInput, checkMaxSymbolValue } HIST_checkInput_e;
57
58/* HIST_count_parallel_wksp() :
59 * store histogram into 4 intermediate tables, recombined at the end.
60 * this design makes better use of OoO cpus,
61 * and is noticeably faster when some values are heavily repeated.
62 * But it needs some additional workspace for intermediate tables.
63 * `workSpace` size must be a table of size >= HIST_WKSP_SIZE_U32.
64 * @return : largest histogram frequency,
65 *           or an error code (notably when histogram would be larger than *maxSymbolValuePtr). */
66static size_t HIST_count_parallel_wksp(
67                                unsigned* count, unsigned* maxSymbolValuePtr,
68                                const void* source, size_t sourceSize,
69                                HIST_checkInput_e check,
70                                U32* const workSpace)
71{
72    const BYTE* ip = (const BYTE*)source;
73    const BYTE* const iend = ip+sourceSize;
74    unsigned maxSymbolValue = *maxSymbolValuePtr;
75    unsigned max=0;
76    U32* const Counting1 = workSpace;
77    U32* const Counting2 = Counting1 + 256;
78    U32* const Counting3 = Counting2 + 256;
79    U32* const Counting4 = Counting3 + 256;
80
81    memset(workSpace, 0, 4*256*sizeof(unsigned));
82
83    /* safety checks */
84    if (!sourceSize) {
85        memset(count, 0, maxSymbolValue + 1);
86        *maxSymbolValuePtr = 0;
87        return 0;
88    }
89    if (!maxSymbolValue) maxSymbolValue = 255;            /* 0 == default */
90
91    /* by stripes of 16 bytes */
92    {   U32 cached = MEM_read32(ip); ip += 4;
93        while (ip < iend-15) {
94            U32 c = cached; cached = MEM_read32(ip); ip += 4;
95            Counting1[(BYTE) c     ]++;
96            Counting2[(BYTE)(c>>8) ]++;
97            Counting3[(BYTE)(c>>16)]++;
98            Counting4[       c>>24 ]++;
99            c = cached; cached = MEM_read32(ip); ip += 4;
100            Counting1[(BYTE) c     ]++;
101            Counting2[(BYTE)(c>>8) ]++;
102            Counting3[(BYTE)(c>>16)]++;
103            Counting4[       c>>24 ]++;
104            c = cached; cached = MEM_read32(ip); ip += 4;
105            Counting1[(BYTE) c     ]++;
106            Counting2[(BYTE)(c>>8) ]++;
107            Counting3[(BYTE)(c>>16)]++;
108            Counting4[       c>>24 ]++;
109            c = cached; cached = MEM_read32(ip); ip += 4;
110            Counting1[(BYTE) c     ]++;
111            Counting2[(BYTE)(c>>8) ]++;
112            Counting3[(BYTE)(c>>16)]++;
113            Counting4[       c>>24 ]++;
114        }
115        ip-=4;
116    }
117
118    /* finish last symbols */
119    while (ip<iend) Counting1[*ip++]++;
120
121    if (check) {   /* verify stats will fit into destination table */
122        U32 s; for (s=255; s>maxSymbolValue; s--) {
123            Counting1[s] += Counting2[s] + Counting3[s] + Counting4[s];
124            if (Counting1[s]) return ERROR(maxSymbolValue_tooSmall);
125    }   }
126
127    {   U32 s;
128        if (maxSymbolValue > 255) maxSymbolValue = 255;
129        for (s=0; s<=maxSymbolValue; s++) {
130            count[s] = Counting1[s] + Counting2[s] + Counting3[s] + Counting4[s];
131            if (count[s] > max) max = count[s];
132    }   }
133
134    while (!count[maxSymbolValue]) maxSymbolValue--;
135    *maxSymbolValuePtr = maxSymbolValue;
136    return (size_t)max;
137}
138
139/* HIST_countFast_wksp() :
140 * Same as HIST_countFast(), but using an externally provided scratch buffer.
141 * `workSpace` is a writable buffer which must be 4-bytes aligned,
142 * `workSpaceSize` must be >= HIST_WKSP_SIZE
143 */
144size_t HIST_countFast_wksp(unsigned* count, unsigned* maxSymbolValuePtr,
145                          const void* source, size_t sourceSize,
146                          void* workSpace, size_t workSpaceSize)
147{
148    if (sourceSize < 1500) /* heuristic threshold */
149        return HIST_count_simple(count, maxSymbolValuePtr, source, sourceSize);
150    if ((size_t)workSpace & 3) return ERROR(GENERIC);  /* must be aligned on 4-bytes boundaries */
151    if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall);
152    return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, trustInput, (U32*)workSpace);
153}
154
155/* fast variant (unsafe : won't check if src contains values beyond count[] limit) */
156size_t HIST_countFast(unsigned* count, unsigned* maxSymbolValuePtr,
157                     const void* source, size_t sourceSize)
158{
159    unsigned tmpCounters[HIST_WKSP_SIZE_U32];
160    return HIST_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, tmpCounters, sizeof(tmpCounters));
161}
162
163/* HIST_count_wksp() :
164 * Same as HIST_count(), but using an externally provided scratch buffer.
165 * `workSpace` size must be table of >= HIST_WKSP_SIZE_U32 unsigned */
166size_t HIST_count_wksp(unsigned* count, unsigned* maxSymbolValuePtr,
167                       const void* source, size_t sourceSize,
168                       void* workSpace, size_t workSpaceSize)
169{
170    if ((size_t)workSpace & 3) return ERROR(GENERIC);  /* must be aligned on 4-bytes boundaries */
171    if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall);
172    if (*maxSymbolValuePtr < 255)
173        return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, checkMaxSymbolValue, (U32*)workSpace);
174    *maxSymbolValuePtr = 255;
175    return HIST_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, workSpace, workSpaceSize);
176}
177
178size_t HIST_count(unsigned* count, unsigned* maxSymbolValuePtr,
179                 const void* src, size_t srcSize)
180{
181    unsigned tmpCounters[HIST_WKSP_SIZE_U32];
182    return HIST_count_wksp(count, maxSymbolValuePtr, src, srcSize, tmpCounters, sizeof(tmpCounters));
183}
184