1 7z ANSI-C Decoder 9.35 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 can create .7z archive with 7z.exe, 7za.exe or 7zr.exe: 33 34 7z.exe a archive.7z *.htm -r -mx -m0fb=255 35 36 If you have big number of files in archive, and you need fast extracting, 37 you can use partly-solid archives: 38 39 7za.exe a archive.7z *.htm -ms=512K -r -mx -m0fb=255 -m0d=512K 40 41 In that example 7-Zip will use 512KB solid blocks. So it needs to decompress only 42 512KB for extracting one file from such archive. 43 44 45 Limitations of current version of 7z ANSI-C Decoder 46 --------------------------------------------------- 47 48 - It reads only "FileName", "Size", "LastWriteTime" and "CRC" information for each file in archive. 49 - It supports only LZMA and Copy (no compression) methods with BCJ or BCJ2 filters. 50 - It converts original UTF-16 Unicode file names to UTF-8 Unicode file names. 51 52 These limitations will be fixed in future versions. 53 54 55 Using 7z ANSI-C Decoder Test application: 56 ----------------------------------------- 57 58 Usage: 7zDec <command> <archive_name> 59 60 <Command>: 61 e: Extract files from archive 62 l: List contents of archive 63 t: Test integrity of archive 64 65 Example: 66 67 7zDec l archive.7z 68 69 lists contents of archive.7z 70 71 7zDec e archive.7z 72 73 extracts files from archive.7z to current folder. 74 75 76 How to use .7z Decoder 77 ---------------------- 78 79 Memory allocation 80 ~~~~~~~~~~~~~~~~~ 81 82 7z Decoder uses two memory pools: 83 1) Temporary pool 84 2) Main pool 85 Such scheme can allow you to avoid fragmentation of allocated blocks. 86 87 88 Steps for using 7z decoder 89 -------------------------- 90 91 Use code at 7zMain.c as example. 92 93 1) Declare variables: 94 inStream /* implements ILookInStream interface */ 95 CSzArEx db; /* 7z archive database structure */ 96 ISzAlloc allocImp; /* memory functions for main pool */ 97 ISzAlloc allocTempImp; /* memory functions for temporary pool */ 98 99 2) call CrcGenerateTable(); function to initialize CRC structures. 100 101 3) call SzArEx_Init(&db); function to initialize db structures. 102 103 4) call SzArEx_Open(&db, inStream, &allocMain, &allocTemp) to open archive 104 105 This function opens archive "inStream" and reads headers to "db". 106 All items in "db" will be allocated with "allocMain" functions. 107 SzArEx_Open function allocates and frees temporary structures by "allocTemp" functions. 108 109 5) List items or Extract items 110 111 Listing code: 112 ~~~~~~~~~~~~~ 113 114 Use SzArEx_GetFileNameUtf16 function. Look example code in C\Util\7z\7zMain.c file. 115 116 117 Extracting code: 118 ~~~~~~~~~~~~~~~~ 119 120 SZ_RESULT SzAr_Extract( 121 CArchiveDatabaseEx *db, 122 ILookInStream *inStream, 123 UInt32 fileIndex, /* index of file */ 124 UInt32 *blockIndex, /* index of solid block */ 125 Byte **outBuffer, /* pointer to pointer to output buffer (allocated with allocMain) */ 126 size_t *outBufferSize, /* buffer size for output buffer */ 127 size_t *offset, /* offset of stream for required file in *outBuffer */ 128 size_t *outSizeProcessed, /* size of file in *outBuffer */ 129 ISzAlloc *allocMain, 130 ISzAlloc *allocTemp); 131 132 If you need to decompress more than one file, you can send these values from previous call: 133 blockIndex, 134 outBuffer, 135 outBufferSize, 136 You can consider "outBuffer" as cache of solid block. If your archive is solid, 137 it will increase decompression speed. 138 139 After decompressing you must free "outBuffer": 140 allocImp.Free(outBuffer); 141 142 6) call SzArEx_Free(&db, allocImp.Free) to free allocated items in "db". 143 144 145 146 147 Memory requirements for .7z decoding 148 ------------------------------------ 149 150 Memory usage for Archive opening: 151 - Temporary pool: 152 - Memory for uncompressed .7z headers 153 - some other temporary blocks 154 - Main pool: 155 - Memory for database: 156 Estimated size of one file structures in solid archive: 157 - Size (4 or 8 Bytes) 158 - CRC32 (4 bytes) 159 - LastWriteTime (8 bytes) 160 - Some file information (4 bytes) 161 - File Name (variable length) + pointer + allocation structures 162 163 Memory usage for archive Decompressing: 164 - Temporary pool: 165 - Memory for LZMA decompressing structures 166 - Main pool: 167 - Memory for decompressed solid block 168 - Memory for temprorary buffers, if BCJ2 fileter is used. Usually these 169 temprorary buffers can be about 15% of solid block size. 170 171 172 7z Decoder doesn't allocate memory for compressed blocks. 173 Instead of this, you must allocate buffer with desired 174 size before calling 7z Decoder. Use 7zMain.c as example. 175 176 177 Defines 178 ------- 179 180 _SZ_ALLOC_DEBUG - define it if you want to debug alloc/free operations to stderr. 181 182 183 --- 184 185 http://www.7-zip.org 186 http://www.7-zip.org/sdk.html 187 http://www.7-zip.org/support.html 188
