1 7z ANSI-C Decoder 4.62 2 ---------------------- 3 4 7z ANSI-C provides 7z/LZMA decoding. 5 7z ANSI-C version is simplified version ported from C++ code. 6 7 LZMA is default and general compression method of 7z format 8 in 7-Zip compression program (www.7-zip.org). LZMA provides high 9 compression ratio and very fast decompression. 10 11 12 LICENSE 13 ------- 14 15 7z ANSI-C Decoder is part of the LZMA SDK. 16 LZMA SDK is written and placed in the public domain by Igor Pavlov. 17 18 Files 19 --------------------- 20 21 7zDecode.* - Low level 7z decoding 22 7zExtract.* - High level 7z decoding 23 7zHeader.* - .7z format constants 24 7zIn.* - .7z archive opening 25 7zItem.* - .7z structures 26 7zMain.c - Test application 27 28 29 How To Use 30 ---------- 31 32 You must download 7-Zip program from www.7-zip.org. 33 34 You can create .7z archive with 7z.exe or 7za.exe: 35 36 7za.exe a archive.7z *.htm -r -mx -m0fb=255 37 38 If you have big number of files in archive, and you need fast extracting, 39 you can use partly-solid archives: 40 41 7za.exe a archive.7z *.htm -ms=512K -r -mx -m0fb=255 -m0d=512K 42 43 In that example 7-Zip will use 512KB solid blocks. So it needs to decompress only 44 512KB for extracting one file from such archive. 45 46 47 Limitations of current version of 7z ANSI-C Decoder 48 --------------------------------------------------- 49 50 - It reads only "FileName", "Size", "LastWriteTime" and "CRC" information for each file in archive. 51 - It supports only LZMA and Copy (no compression) methods with BCJ or BCJ2 filters. 52 - It converts original UTF-16 Unicode file names to UTF-8 Unicode file names. 53 54 These limitations will be fixed in future versions. 55 56 57 Using 7z ANSI-C Decoder Test application: 58 ----------------------------------------- 59 60 Usage: 7zDec <command> <archive_name> 61 62 <Command>: 63 e: Extract files from archive 64 l: List contents of archive 65 t: Test integrity of archive 66 67 Example: 68 69 7zDec l archive.7z 70 71 lists contents of archive.7z 72 73 7zDec e archive.7z 74 75 extracts files from archive.7z to current folder. 76 77 78 How to use .7z Decoder 79 ---------------------- 80 81 Memory allocation 82 ~~~~~~~~~~~~~~~~~ 83 84 7z Decoder uses two memory pools: 85 1) Temporary pool 86 2) Main pool 87 Such scheme can allow you to avoid fragmentation of allocated blocks. 88 89 90 Steps for using 7z decoder 91 -------------------------- 92 93 Use code at 7zMain.c as example. 94 95 1) Declare variables: 96 inStream /* implements ILookInStream interface */ 97 CSzArEx db; /* 7z archive database structure */ 98 ISzAlloc allocImp; /* memory functions for main pool */ 99 ISzAlloc allocTempImp; /* memory functions for temporary pool */ 100 101 2) call CrcGenerateTable(); function to initialize CRC structures. 102 103 3) call SzArEx_Init(&db); function to initialize db structures. 104 105 4) call SzArEx_Open(&db, inStream, &allocMain, &allocTemp) to open archive 106 107 This function opens archive "inStream" and reads headers to "db". 108 All items in "db" will be allocated with "allocMain" functions. 109 SzArEx_Open function allocates and frees temporary structures by "allocTemp" functions. 110 111 5) List items or Extract items 112 113 Listing code: 114 ~~~~~~~~~~~~~ 115 { 116 UInt32 i; 117 for (i = 0; i < db.db.NumFiles; i++) 118 { 119 CFileItem *f = db.db.Files + i; 120 printf("%10d %s\n", (int)f->Size, f->Name); 121 } 122 } 123 124 Extracting code: 125 ~~~~~~~~~~~~~~~~ 126 127 SZ_RESULT SzAr_Extract( 128 CArchiveDatabaseEx *db, 129 ILookInStream *inStream, 130 UInt32 fileIndex, /* index of file */ 131 UInt32 *blockIndex, /* index of solid block */ 132 Byte **outBuffer, /* pointer to pointer to output buffer (allocated with allocMain) */ 133 size_t *outBufferSize, /* buffer size for output buffer */ 134 size_t *offset, /* offset of stream for required file in *outBuffer */ 135 size_t *outSizeProcessed, /* size of file in *outBuffer */ 136 ISzAlloc *allocMain, 137 ISzAlloc *allocTemp); 138 139 If you need to decompress more than one file, you can send these values from previous call: 140 blockIndex, 141 outBuffer, 142 outBufferSize, 143 You can consider "outBuffer" as cache of solid block. If your archive is solid, 144 it will increase decompression speed. 145 146 After decompressing you must free "outBuffer": 147 allocImp.Free(outBuffer); 148 149 6) call SzArEx_Free(&db, allocImp.Free) to free allocated items in "db". 150 151 152 153 154 Memory requirements for .7z decoding 155 ------------------------------------ 156 157 Memory usage for Archive opening: 158 - Temporary pool: 159 - Memory for uncompressed .7z headers 160 - some other temporary blocks 161 - Main pool: 162 - Memory for database: 163 Estimated size of one file structures in solid archive: 164 - Size (4 or 8 Bytes) 165 - CRC32 (4 bytes) 166 - LastWriteTime (8 bytes) 167 - Some file information (4 bytes) 168 - File Name (variable length) + pointer + allocation structures 169 170 Memory usage for archive Decompressing: 171 - Temporary pool: 172 - Memory for LZMA decompressing structures 173 - Main pool: 174 - Memory for decompressed solid block 175 - Memory for temprorary buffers, if BCJ2 fileter is used. Usually these 176 temprorary buffers can be about 15% of solid block size. 177 178 179 7z Decoder doesn't allocate memory for compressed blocks. 180 Instead of this, you must allocate buffer with desired 181 size before calling 7z Decoder. Use 7zMain.c as example. 182 183 184 Defines 185 ------- 186 187 _SZ_ALLOC_DEBUG - define it if you want to debug alloc/free operations to stderr. 188 189 190 --- 191 192 http://www.7-zip.org 193 http://www.7-zip.org/sdk.html 194 http://www.7-zip.org/support.html 195
