17z ANSI-C Decoder 4.62 2---------------------- 3 47z ANSI-C provides 7z/LZMA decoding. 57z ANSI-C version is simplified version ported from C++ code. 6 7LZMA is default and general compression method of 7z format 8in 7-Zip compression program (www.7-zip.org). LZMA provides high 9compression ratio and very fast decompression. 10 11 12LICENSE 13------- 14 157z ANSI-C Decoder is part of the LZMA SDK. 16LZMA SDK is written and placed in the public domain by Igor Pavlov. 17 18Files 19--------------------- 20 217zDecode.* - Low level 7z decoding 227zExtract.* - High level 7z decoding 237zHeader.* - .7z format constants 247zIn.* - .7z archive opening 257zItem.* - .7z structures 267zMain.c - Test application 27 28 29How To Use 30---------- 31 32You must download 7-Zip program from www.7-zip.org. 33 34You can create .7z archive with 7z.exe or 7za.exe: 35 36 7za.exe a archive.7z *.htm -r -mx -m0fb=255 37 38If you have big number of files in archive, and you need fast extracting, 39you can use partly-solid archives: 40 41 7za.exe a archive.7z *.htm -ms=512K -r -mx -m0fb=255 -m0d=512K 42 43In that example 7-Zip will use 512KB solid blocks. So it needs to decompress only 44512KB for extracting one file from such archive. 45 46 47Limitations 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 54These limitations will be fixed in future versions. 55 56 57Using 7z ANSI-C Decoder Test application: 58----------------------------------------- 59 60Usage: 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 67Example: 68 69 7zDec l archive.7z 70 71lists contents of archive.7z 72 73 7zDec e archive.7z 74 75extracts files from archive.7z to current folder. 76 77 78How to use .7z Decoder 79---------------------- 80 81Memory allocation 82~~~~~~~~~~~~~~~~~ 83 847z Decoder uses two memory pools: 851) Temporary pool 862) Main pool 87Such scheme can allow you to avoid fragmentation of allocated blocks. 88 89 90Steps for using 7z decoder 91-------------------------- 92 93Use code at 7zMain.c as example. 94 951) 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 1012) call CrcGenerateTable(); function to initialize CRC structures. 102 1033) call SzArEx_Init(&db); function to initialize db structures. 104 1054) call SzArEx_Open(&db, inStream, &allocMain, &allocTemp) to open archive 106 107This function opens archive "inStream" and reads headers to "db". 108All items in "db" will be allocated with "allocMain" functions. 109SzArEx_Open function allocates and frees temporary structures by "allocTemp" functions. 110 1115) 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 1496) call SzArEx_Free(&db, allocImp.Free) to free allocated items in "db". 150 151 152 153 154Memory requirements for .7z decoding 155------------------------------------ 156 157Memory 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 170Memory 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 1797z Decoder doesn't allocate memory for compressed blocks. 180Instead of this, you must allocate buffer with desired 181size before calling 7z Decoder. Use 7zMain.c as example. 182 183 184Defines 185------- 186 187_SZ_ALLOC_DEBUG - define it if you want to debug alloc/free operations to stderr. 188 189 190--- 191 192http://www.7-zip.org 193http://www.7-zip.org/sdk.html 194http://www.7-zip.org/support.html 195