1 /* ******************************************************************
2  * hist : Histogram functions
3  * part of Finite State Entropy project
4  * Copyright (c) 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 --- */
HIST_isError(size_t code)24 unsigned HIST_isError(size_t code) { return ERR_isError(code); }
25 
26 /*-**************************************************************
27  *  Histogram functions
28  ****************************************************************/
HIST_count_simple(unsigned * count,unsigned * maxSymbolValuePtr,const void * src,size_t srcSize)29 unsigned 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     ZSTD_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 
56 typedef 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` must be a U32 table of size >= HIST_WKSP_SIZE_U32.
64  * @return : largest histogram frequency,
65  *           or an error code (notably when histogram's alphabet is larger than *maxSymbolValuePtr) */
HIST_count_parallel_wksp(unsigned * count,unsigned * maxSymbolValuePtr,const void * source,size_t sourceSize,HIST_checkInput_e check,U32 * const workSpace)66 static 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     size_t const countSize = (*maxSymbolValuePtr + 1) * sizeof(*count);
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     /* safety checks */
82     assert(*maxSymbolValuePtr <= 255);
83     if (!sourceSize) {
84         ZSTD_memset(count, 0, countSize);
85         *maxSymbolValuePtr = 0;
86         return 0;
87     }
88     ZSTD_memset(workSpace, 0, 4*256*sizeof(unsigned));
89 
90     /* by stripes of 16 bytes */
91     {   U32 cached = MEM_read32(ip); ip += 4;
92         while (ip < iend-15) {
93             U32 c = cached; cached = MEM_read32(ip); ip += 4;
94             Counting1[(BYTE) c     ]++;
95             Counting2[(BYTE)(c>>8) ]++;
96             Counting3[(BYTE)(c>>16)]++;
97             Counting4[       c>>24 ]++;
98             c = cached; cached = MEM_read32(ip); ip += 4;
99             Counting1[(BYTE) c     ]++;
100             Counting2[(BYTE)(c>>8) ]++;
101             Counting3[(BYTE)(c>>16)]++;
102             Counting4[       c>>24 ]++;
103             c = cached; cached = MEM_read32(ip); ip += 4;
104             Counting1[(BYTE) c     ]++;
105             Counting2[(BYTE)(c>>8) ]++;
106             Counting3[(BYTE)(c>>16)]++;
107             Counting4[       c>>24 ]++;
108             c = cached; cached = MEM_read32(ip); ip += 4;
109             Counting1[(BYTE) c     ]++;
110             Counting2[(BYTE)(c>>8) ]++;
111             Counting3[(BYTE)(c>>16)]++;
112             Counting4[       c>>24 ]++;
113         }
114         ip-=4;
115     }
116 
117     /* finish last symbols */
118     while (ip<iend) Counting1[*ip++]++;
119 
120     {   U32 s;
121         for (s=0; s<256; s++) {
122             Counting1[s] += Counting2[s] + Counting3[s] + Counting4[s];
123             if (Counting1[s] > max) max = Counting1[s];
124     }   }
125 
126     {   unsigned maxSymbolValue = 255;
127         while (!Counting1[maxSymbolValue]) maxSymbolValue--;
128         if (check && maxSymbolValue > *maxSymbolValuePtr) return ERROR(maxSymbolValue_tooSmall);
129         *maxSymbolValuePtr = maxSymbolValue;
130         ZSTD_memmove(count, Counting1, countSize);   /* in case count & Counting1 are overlapping */
131     }
132     return (size_t)max;
133 }
134 
135 /* HIST_countFast_wksp() :
136  * Same as HIST_countFast(), but using an externally provided scratch buffer.
137  * `workSpace` is a writable buffer which must be 4-bytes aligned,
138  * `workSpaceSize` must be >= HIST_WKSP_SIZE
139  */
HIST_countFast_wksp(unsigned * count,unsigned * maxSymbolValuePtr,const void * source,size_t sourceSize,void * workSpace,size_t workSpaceSize)140 size_t HIST_countFast_wksp(unsigned* count, unsigned* maxSymbolValuePtr,
141                           const void* source, size_t sourceSize,
142                           void* workSpace, size_t workSpaceSize)
143 {
144     if (sourceSize < 1500) /* heuristic threshold */
145         return HIST_count_simple(count, maxSymbolValuePtr, source, sourceSize);
146     if ((size_t)workSpace & 3) return ERROR(GENERIC);  /* must be aligned on 4-bytes boundaries */
147     if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall);
148     return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, trustInput, (U32*)workSpace);
149 }
150 
151 /* HIST_count_wksp() :
152  * Same as HIST_count(), but using an externally provided scratch buffer.
153  * `workSpace` size must be table of >= HIST_WKSP_SIZE_U32 unsigned */
HIST_count_wksp(unsigned * count,unsigned * maxSymbolValuePtr,const void * source,size_t sourceSize,void * workSpace,size_t workSpaceSize)154 size_t HIST_count_wksp(unsigned* count, unsigned* maxSymbolValuePtr,
155                        const void* source, size_t sourceSize,
156                        void* workSpace, size_t workSpaceSize)
157 {
158     if ((size_t)workSpace & 3) return ERROR(GENERIC);  /* must be aligned on 4-bytes boundaries */
159     if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall);
160     if (*maxSymbolValuePtr < 255)
161         return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, checkMaxSymbolValue, (U32*)workSpace);
162     *maxSymbolValuePtr = 255;
163     return HIST_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, workSpace, workSpaceSize);
164 }
165 
166