1 /*
2 * Copyright (c) Yann Collet, Facebook, Inc.
3 * All rights reserved.
4 *
5 * This source code is licensed under both the BSD-style license (found in the
6 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
7 * in the COPYING file in the root directory of this source tree).
8 * You may select, at your option, one of the above-listed licenses.
9 */
10
11 /*-*************************************
12 * Dependencies
13 ***************************************/
14 #include "zstd_compress_literals.h"
15
ZSTD_noCompressLiterals(void * dst,size_t dstCapacity,const void * src,size_t srcSize)16 size_t ZSTD_noCompressLiterals (void* dst, size_t dstCapacity, const void* src, size_t srcSize)
17 {
18 BYTE* const ostart = (BYTE*)dst;
19 U32 const flSize = 1 + (srcSize>31) + (srcSize>4095);
20
21 RETURN_ERROR_IF(srcSize + flSize > dstCapacity, dstSize_tooSmall, "");
22
23 switch(flSize)
24 {
25 case 1: /* 2 - 1 - 5 */
26 ostart[0] = (BYTE)((U32)set_basic + (srcSize<<3));
27 break;
28 case 2: /* 2 - 2 - 12 */
29 MEM_writeLE16(ostart, (U16)((U32)set_basic + (1<<2) + (srcSize<<4)));
30 break;
31 case 3: /* 2 - 2 - 20 */
32 MEM_writeLE32(ostart, (U32)((U32)set_basic + (3<<2) + (srcSize<<4)));
33 break;
34 default: /* not necessary : flSize is {1,2,3} */
35 assert(0);
36 }
37
38 ZSTD_memcpy(ostart + flSize, src, srcSize);
39 DEBUGLOG(5, "Raw literals: %u -> %u", (U32)srcSize, (U32)(srcSize + flSize));
40 return srcSize + flSize;
41 }
42
ZSTD_compressRleLiteralsBlock(void * dst,size_t dstCapacity,const void * src,size_t srcSize)43 size_t ZSTD_compressRleLiteralsBlock (void* dst, size_t dstCapacity, const void* src, size_t srcSize)
44 {
45 BYTE* const ostart = (BYTE*)dst;
46 U32 const flSize = 1 + (srcSize>31) + (srcSize>4095);
47
48 (void)dstCapacity; /* dstCapacity already guaranteed to be >=4, hence large enough */
49
50 switch(flSize)
51 {
52 case 1: /* 2 - 1 - 5 */
53 ostart[0] = (BYTE)((U32)set_rle + (srcSize<<3));
54 break;
55 case 2: /* 2 - 2 - 12 */
56 MEM_writeLE16(ostart, (U16)((U32)set_rle + (1<<2) + (srcSize<<4)));
57 break;
58 case 3: /* 2 - 2 - 20 */
59 MEM_writeLE32(ostart, (U32)((U32)set_rle + (3<<2) + (srcSize<<4)));
60 break;
61 default: /* not necessary : flSize is {1,2,3} */
62 assert(0);
63 }
64
65 ostart[flSize] = *(const BYTE*)src;
66 DEBUGLOG(5, "RLE literals: %u -> %u", (U32)srcSize, (U32)flSize + 1);
67 return flSize+1;
68 }
69
ZSTD_compressLiterals(ZSTD_hufCTables_t const * prevHuf,ZSTD_hufCTables_t * nextHuf,ZSTD_strategy strategy,int disableLiteralCompression,void * dst,size_t dstCapacity,const void * src,size_t srcSize,void * entropyWorkspace,size_t entropyWorkspaceSize,const int bmi2,unsigned suspectUncompressible)70 size_t ZSTD_compressLiterals (ZSTD_hufCTables_t const* prevHuf,
71 ZSTD_hufCTables_t* nextHuf,
72 ZSTD_strategy strategy, int disableLiteralCompression,
73 void* dst, size_t dstCapacity,
74 const void* src, size_t srcSize,
75 void* entropyWorkspace, size_t entropyWorkspaceSize,
76 const int bmi2,
77 unsigned suspectUncompressible)
78 {
79 size_t const minGain = ZSTD_minGain(srcSize, strategy);
80 size_t const lhSize = 3 + (srcSize >= 1 KB) + (srcSize >= 16 KB);
81 BYTE* const ostart = (BYTE*)dst;
82 U32 singleStream = srcSize < 256;
83 symbolEncodingType_e hType = set_compressed;
84 size_t cLitSize;
85
86 DEBUGLOG(5,"ZSTD_compressLiterals (disableLiteralCompression=%i srcSize=%u)",
87 disableLiteralCompression, (U32)srcSize);
88
89 /* Prepare nextEntropy assuming reusing the existing table */
90 ZSTD_memcpy(nextHuf, prevHuf, sizeof(*prevHuf));
91
92 if (disableLiteralCompression)
93 return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize);
94
95 /* small ? don't even attempt compression (speed opt) */
96 # define COMPRESS_LITERALS_SIZE_MIN 63
97 { size_t const minLitSize = (prevHuf->repeatMode == HUF_repeat_valid) ? 6 : COMPRESS_LITERALS_SIZE_MIN;
98 if (srcSize <= minLitSize) return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize);
99 }
100
101 RETURN_ERROR_IF(dstCapacity < lhSize+1, dstSize_tooSmall, "not enough space for compression");
102 { HUF_repeat repeat = prevHuf->repeatMode;
103 int const preferRepeat = strategy < ZSTD_lazy ? srcSize <= 1024 : 0;
104 if (repeat == HUF_repeat_valid && lhSize == 3) singleStream = 1;
105 cLitSize = singleStream ?
106 HUF_compress1X_repeat(
107 ostart+lhSize, dstCapacity-lhSize, src, srcSize,
108 HUF_SYMBOLVALUE_MAX, HUF_TABLELOG_DEFAULT, entropyWorkspace, entropyWorkspaceSize,
109 (HUF_CElt*)nextHuf->CTable, &repeat, preferRepeat, bmi2, suspectUncompressible) :
110 HUF_compress4X_repeat(
111 ostart+lhSize, dstCapacity-lhSize, src, srcSize,
112 HUF_SYMBOLVALUE_MAX, HUF_TABLELOG_DEFAULT, entropyWorkspace, entropyWorkspaceSize,
113 (HUF_CElt*)nextHuf->CTable, &repeat, preferRepeat, bmi2, suspectUncompressible);
114 if (repeat != HUF_repeat_none) {
115 /* reused the existing table */
116 DEBUGLOG(5, "Reusing previous huffman table");
117 hType = set_repeat;
118 }
119 }
120
121 if ((cLitSize==0) || (cLitSize >= srcSize - minGain) || ERR_isError(cLitSize)) {
122 ZSTD_memcpy(nextHuf, prevHuf, sizeof(*prevHuf));
123 return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize);
124 }
125 if (cLitSize==1) {
126 ZSTD_memcpy(nextHuf, prevHuf, sizeof(*prevHuf));
127 return ZSTD_compressRleLiteralsBlock(dst, dstCapacity, src, srcSize);
128 }
129
130 if (hType == set_compressed) {
131 /* using a newly constructed table */
132 nextHuf->repeatMode = HUF_repeat_check;
133 }
134
135 /* Build header */
136 switch(lhSize)
137 {
138 case 3: /* 2 - 2 - 10 - 10 */
139 { U32 const lhc = hType + ((!singleStream) << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<14);
140 MEM_writeLE24(ostart, lhc);
141 break;
142 }
143 case 4: /* 2 - 2 - 14 - 14 */
144 { U32 const lhc = hType + (2 << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<18);
145 MEM_writeLE32(ostart, lhc);
146 break;
147 }
148 case 5: /* 2 - 2 - 18 - 18 */
149 { U32 const lhc = hType + (3 << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<22);
150 MEM_writeLE32(ostart, lhc);
151 ostart[4] = (BYTE)(cLitSize >> 10);
152 break;
153 }
154 default: /* not possible : lhSize is {3,4,5} */
155 assert(0);
156 }
157 DEBUGLOG(5, "Compressed literals: %u -> %u", (U32)srcSize, (U32)(lhSize+cLitSize));
158 return lhSize+cLitSize;
159 }
160