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    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