1/*
2 * Copyright (c) 2016-2020, 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
16size_t ZSTD_noCompressLiterals (void* dst, size_t dstCapacity, const void* src, size_t srcSize)
17{
18    BYTE* const ostart = (BYTE* const)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    memcpy(ostart + flSize, src, srcSize);
39    DEBUGLOG(5, "Raw literals: %u -> %u", (U32)srcSize, (U32)(srcSize + flSize));
40    return srcSize + flSize;
41}
42
43size_t ZSTD_compressRleLiteralsBlock (void* dst, size_t dstCapacity, const void* src, size_t srcSize)
44{
45    BYTE* const ostart = (BYTE* const)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
70size_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{
78    size_t const minGain = ZSTD_minGain(srcSize, strategy);
79    size_t const lhSize = 3 + (srcSize >= 1 KB) + (srcSize >= 16 KB);
80    BYTE*  const ostart = (BYTE*)dst;
81    U32 singleStream = srcSize < 256;
82    symbolEncodingType_e hType = set_compressed;
83    size_t cLitSize;
84
85    DEBUGLOG(5,"ZSTD_compressLiterals (disableLiteralCompression=%i srcSize=%u)",
86                disableLiteralCompression, (U32)srcSize);
87
88    /* Prepare nextEntropy assuming reusing the existing table */
89    memcpy(nextHuf, prevHuf, sizeof(*prevHuf));
90
91    if (disableLiteralCompression)
92        return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize);
93
94    /* small ? don't even attempt compression (speed opt) */
95#   define COMPRESS_LITERALS_SIZE_MIN 63
96    {   size_t const minLitSize = (prevHuf->repeatMode == HUF_repeat_valid) ? 6 : COMPRESS_LITERALS_SIZE_MIN;
97        if (srcSize <= minLitSize) return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize);
98    }
99
100    RETURN_ERROR_IF(dstCapacity < lhSize+1, dstSize_tooSmall, "not enough space for compression");
101    {   HUF_repeat repeat = prevHuf->repeatMode;
102        int const preferRepeat = strategy < ZSTD_lazy ? srcSize <= 1024 : 0;
103        if (repeat == HUF_repeat_valid && lhSize == 3) singleStream = 1;
104        cLitSize = singleStream ?
105            HUF_compress1X_repeat(
106                ostart+lhSize, dstCapacity-lhSize, src, srcSize,
107                HUF_SYMBOLVALUE_MAX, HUF_TABLELOG_DEFAULT, entropyWorkspace, entropyWorkspaceSize,
108                (HUF_CElt*)nextHuf->CTable, &repeat, preferRepeat, bmi2) :
109            HUF_compress4X_repeat(
110                ostart+lhSize, dstCapacity-lhSize, src, srcSize,
111                HUF_SYMBOLVALUE_MAX, HUF_TABLELOG_DEFAULT, entropyWorkspace, entropyWorkspaceSize,
112                (HUF_CElt*)nextHuf->CTable, &repeat, preferRepeat, bmi2);
113        if (repeat != HUF_repeat_none) {
114            /* reused the existing table */
115            DEBUGLOG(5, "Reusing previous huffman table");
116            hType = set_repeat;
117        }
118    }
119
120    if ((cLitSize==0) | (cLitSize >= srcSize - minGain) | ERR_isError(cLitSize)) {
121        memcpy(nextHuf, prevHuf, sizeof(*prevHuf));
122        return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize);
123    }
124    if (cLitSize==1) {
125        memcpy(nextHuf, prevHuf, sizeof(*prevHuf));
126        return ZSTD_compressRleLiteralsBlock(dst, dstCapacity, src, srcSize);
127    }
128
129    if (hType == set_compressed) {
130        /* using a newly constructed table */
131        nextHuf->repeatMode = HUF_repeat_check;
132    }
133
134    /* Build header */
135    switch(lhSize)
136    {
137    case 3: /* 2 - 2 - 10 - 10 */
138        {   U32 const lhc = hType + ((!singleStream) << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<14);
139            MEM_writeLE24(ostart, lhc);
140            break;
141        }
142    case 4: /* 2 - 2 - 14 - 14 */
143        {   U32 const lhc = hType + (2 << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<18);
144            MEM_writeLE32(ostart, lhc);
145            break;
146        }
147    case 5: /* 2 - 2 - 18 - 18 */
148        {   U32 const lhc = hType + (3 << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<22);
149            MEM_writeLE32(ostart, lhc);
150            ostart[4] = (BYTE)(cLitSize >> 10);
151            break;
152        }
153    default:  /* not possible : lhSize is {3,4,5} */
154        assert(0);
155    }
156    DEBUGLOG(5, "Compressed literals: %u -> %u", (U32)srcSize, (U32)(lhSize+cLitSize));
157    return lhSize+cLitSize;
158}
159