7z ANSI-C Decoder 4.62 ---------------------- 7z ANSI-C provides 7z/LZMA decoding. 7z ANSI-C version is simplified version ported from C++ code. LZMA is default and general compression method of 7z format in 7-Zip compression program (www.7-zip.org). LZMA provides high compression ratio and very fast decompression. LICENSE ------- 7z ANSI-C Decoder is part of the LZMA SDK. LZMA SDK is written and placed in the public domain by Igor Pavlov. Files --------------------- 7zDecode.* - Low level 7z decoding 7zExtract.* - High level 7z decoding 7zHeader.* - .7z format constants 7zIn.* - .7z archive opening 7zItem.* - .7z structures 7zMain.c - Test application How To Use ---------- You must download 7-Zip program from www.7-zip.org. You can create .7z archive with 7z.exe or 7za.exe: 7za.exe a archive.7z *.htm -r -mx -m0fb=255 If you have big number of files in archive, and you need fast extracting, you can use partly-solid archives: 7za.exe a archive.7z *.htm -ms=512K -r -mx -m0fb=255 -m0d=512K In that example 7-Zip will use 512KB solid blocks. So it needs to decompress only 512KB for extracting one file from such archive. Limitations of current version of 7z ANSI-C Decoder --------------------------------------------------- - It reads only "FileName", "Size", "LastWriteTime" and "CRC" information for each file in archive. - It supports only LZMA and Copy (no compression) methods with BCJ or BCJ2 filters. - It converts original UTF-16 Unicode file names to UTF-8 Unicode file names. These limitations will be fixed in future versions. Using 7z ANSI-C Decoder Test application: ----------------------------------------- Usage: 7zDec : e: Extract files from archive l: List contents of archive t: Test integrity of archive Example: 7zDec l archive.7z lists contents of archive.7z 7zDec e archive.7z extracts files from archive.7z to current folder. How to use .7z Decoder ---------------------- Memory allocation ~~~~~~~~~~~~~~~~~ 7z Decoder uses two memory pools: 1) Temporary pool 2) Main pool Such scheme can allow you to avoid fragmentation of allocated blocks. Steps for using 7z decoder -------------------------- Use code at 7zMain.c as example. 1) Declare variables: inStream /* implements ILookInStream interface */ CSzArEx db; /* 7z archive database structure */ ISzAlloc allocImp; /* memory functions for main pool */ ISzAlloc allocTempImp; /* memory functions for temporary pool */ 2) call CrcGenerateTable(); function to initialize CRC structures. 3) call SzArEx_Init(&db); function to initialize db structures. 4) call SzArEx_Open(&db, inStream, &allocMain, &allocTemp) to open archive This function opens archive "inStream" and reads headers to "db". All items in "db" will be allocated with "allocMain" functions. SzArEx_Open function allocates and frees temporary structures by "allocTemp" functions. 5) List items or Extract items Listing code: ~~~~~~~~~~~~~ { UInt32 i; for (i = 0; i < db.db.NumFiles; i++) { CFileItem *f = db.db.Files + i; printf("%10d %s\n", (int)f->Size, f->Name); } } Extracting code: ~~~~~~~~~~~~~~~~ SZ_RESULT SzAr_Extract( CArchiveDatabaseEx *db, ILookInStream *inStream, UInt32 fileIndex, /* index of file */ UInt32 *blockIndex, /* index of solid block */ Byte **outBuffer, /* pointer to pointer to output buffer (allocated with allocMain) */ size_t *outBufferSize, /* buffer size for output buffer */ size_t *offset, /* offset of stream for required file in *outBuffer */ size_t *outSizeProcessed, /* size of file in *outBuffer */ ISzAlloc *allocMain, ISzAlloc *allocTemp); If you need to decompress more than one file, you can send these values from previous call: blockIndex, outBuffer, outBufferSize, You can consider "outBuffer" as cache of solid block. If your archive is solid, it will increase decompression speed. After decompressing you must free "outBuffer": allocImp.Free(outBuffer); 6) call SzArEx_Free(&db, allocImp.Free) to free allocated items in "db". Memory requirements for .7z decoding ------------------------------------ Memory usage for Archive opening: - Temporary pool: - Memory for uncompressed .7z headers - some other temporary blocks - Main pool: - Memory for database: Estimated size of one file structures in solid archive: - Size (4 or 8 Bytes) - CRC32 (4 bytes) - LastWriteTime (8 bytes) - Some file information (4 bytes) - File Name (variable length) + pointer + allocation structures Memory usage for archive Decompressing: - Temporary pool: - Memory for LZMA decompressing structures - Main pool: - Memory for decompressed solid block - Memory for temprorary buffers, if BCJ2 fileter is used. Usually these temprorary buffers can be about 15% of solid block size. 7z Decoder doesn't allocate memory for compressed blocks. Instead of this, you must allocate buffer with desired size before calling 7z Decoder. Use 7zMain.c as example. Defines ------- _SZ_ALLOC_DEBUG - define it if you want to debug alloc/free operations to stderr. --- http://www.7-zip.org http://www.7-zip.org/sdk.html http://www.7-zip.org/support.html