1 /* 2 Copyright 2011 Google Inc. All Rights Reserved. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 16 Author: lode.vandevenne@gmail.com (Lode Vandevenne) 17 Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala) 18 */ 19 20 /* 21 Several utilities, including: #defines to try different compression results, 22 basic deflate specification values and generic program options. 23 */ 24 25 #ifndef ZOPFLI_UTIL_H_ 26 #define ZOPFLI_UTIL_H_ 27 28 #include <string.h> 29 #include <stdlib.h> 30 31 /* Minimum and maximum length that can be encoded in deflate. */ 32 #define ZOPFLI_MAX_MATCH 258 33 #define ZOPFLI_MIN_MATCH 3 34 35 /* Number of distinct literal/length and distance symbols in DEFLATE */ 36 #define ZOPFLI_NUM_LL 288 37 #define ZOPFLI_NUM_D 32 38 39 /* 40 The window size for deflate. Must be a power of two. This should be 32768, the 41 maximum possible by the deflate spec. Anything less hurts compression more than 42 speed. 43 */ 44 #define ZOPFLI_WINDOW_SIZE 32768 45 46 /* 47 The window mask used to wrap indices into the window. This is why the 48 window size must be a power of two. 49 */ 50 #define ZOPFLI_WINDOW_MASK (ZOPFLI_WINDOW_SIZE - 1) 51 52 /* 53 A block structure of huge, non-smart, blocks to divide the input into, to allow 54 operating on huge files without exceeding memory, such as the 1GB wiki9 corpus. 55 The whole compression algorithm, including the smarter block splitting, will 56 be executed independently on each huge block. 57 Dividing into huge blocks hurts compression, but not much relative to the size. 58 Set it to 0 to disable master blocks. 59 */ 60 #define ZOPFLI_MASTER_BLOCK_SIZE 1000000 61 62 /* 63 Used to initialize costs for example 64 */ 65 #define ZOPFLI_LARGE_FLOAT 1e30 66 67 /* 68 For longest match cache. max 256. Uses huge amounts of memory but makes it 69 faster. Uses this many times three bytes per single byte of the input data. 70 This is so because longest match finding has to find the exact distance 71 that belongs to each length for the best lz77 strategy. 72 Good values: e.g. 5, 8. 73 */ 74 #define ZOPFLI_CACHE_LENGTH 8 75 76 /* 77 limit the max hash chain hits for this hash value. This has an effect only 78 on files where the hash value is the same very often. On these files, this 79 gives worse compression (the value should ideally be 32768, which is the 80 ZOPFLI_WINDOW_SIZE, while zlib uses 4096 even for best level), but makes it 81 faster on some specific files. 82 Good value: e.g. 8192. 83 */ 84 #define ZOPFLI_MAX_CHAIN_HITS 8192 85 86 /* 87 Whether to use the longest match cache for ZopfliFindLongestMatch. This cache 88 consumes a lot of memory but speeds it up. No effect on compression size. 89 */ 90 #define ZOPFLI_LONGEST_MATCH_CACHE 91 92 /* 93 Enable to remember amount of successive identical bytes in the hash chain for 94 finding longest match 95 required for ZOPFLI_HASH_SAME_HASH and ZOPFLI_SHORTCUT_LONG_REPETITIONS 96 This has no effect on the compression result, and enabling it increases speed. 97 */ 98 #define ZOPFLI_HASH_SAME 99 100 /* 101 Switch to a faster hash based on the info from ZOPFLI_HASH_SAME once the 102 best length so far is long enough. This is way faster for files with lots of 103 identical bytes, on which the compressor is otherwise too slow. Regular files 104 are unaffected or maybe a tiny bit slower. 105 This has no effect on the compression result, only on speed. 106 */ 107 #define ZOPFLI_HASH_SAME_HASH 108 109 /* 110 Enable this, to avoid slowness for files which are a repetition of the same 111 character more than a multiple of ZOPFLI_MAX_MATCH times. This should not affect 112 the compression result. 113 */ 114 #define ZOPFLI_SHORTCUT_LONG_REPETITIONS 115 116 /* 117 Whether to use lazy matching in the greedy LZ77 implementation. This gives a 118 better result of ZopfliLZ77Greedy, but the effect this has on the optimal LZ77 119 varies from file to file. 120 */ 121 #define ZOPFLI_LAZY_MATCHING 122 123 /* 124 Appends value to dynamically allocated memory, doubling its allocation size 125 whenever needed. 126 127 value: the value to append, type T 128 data: pointer to the dynamic array to append to, type T** 129 size: pointer to the size of the array to append to, type size_t*. This is the 130 size that you consider the array to be, not the internal allocation size. 131 Precondition: allocated size of data is at least a power of two greater than or 132 equal than *size. 133 */ 134 #ifdef __cplusplus /* C++ cannot assign void* from malloc to *data */ 135 #define ZOPFLI_APPEND_DATA(/* T */ value, /* T** */ data, /* size_t* */ size) {\ 136 if (!((*size) & ((*size) - 1))) {\ 137 /*double alloc size if it's a power of two*/\ 138 void** data_void = reinterpret_cast<void**>(data);\ 139 *data_void = (*size) == 0 ? malloc(sizeof(**data))\ 140 : realloc((*data), (*size) * 2 * sizeof(**data));\ 141 }\ 142 (*data)[(*size)] = (value);\ 143 (*size)++;\ 144 } 145 #else /* C gives problems with strict-aliasing rules for (void**) cast */ 146 #define ZOPFLI_APPEND_DATA(/* T */ value, /* T** */ data, /* size_t* */ size) {\ 147 if (!((*size) & ((*size) - 1))) {\ 148 /*double alloc size if it's a power of two*/\ 149 (*data) = (*size) == 0 ? malloc(sizeof(**data))\ 150 : realloc((*data), (*size) * 2 * sizeof(**data));\ 151 }\ 152 (*data)[(*size)] = (value);\ 153 (*size)++;\ 154 } 155 #endif 156 157 158 #endif /* ZOPFLI_UTIL_H_ */ 159