update libchdr

[pcsx_rearmed.git] / deps / libchdr / deps / lzma-22.01 / 7zC.txt

7z ANSI-C Decoder 9.35\r
----------------------\r
\r
7z ANSI-C provides 7z/LZMA decoding.\r
7z ANSI-C version is simplified version ported from C++ code.\r
\r
LZMA is default and general compression method of 7z format\r
in 7-Zip compression program (www.7-zip.org). LZMA provides high \r
compression ratio and very fast decompression.\r
\r
\r
LICENSE\r
-------\r
\r
7z ANSI-C Decoder is part of the LZMA SDK.\r
LZMA SDK is written and placed in the public domain by Igor Pavlov.\r
\r
Files\r
---------------------\r
\r
7zDecode.*   - Low level 7z decoding\r
7zExtract.*  - High level 7z decoding\r
7zHeader.*   - .7z format constants\r
7zIn.*       - .7z archive opening\r
7zItem.*     - .7z structures\r
7zMain.c     - Test application\r
\r
\r
How To Use\r
----------\r
\r
You can create .7z archive with 7z.exe, 7za.exe or 7zr.exe:\r
\r
  7z.exe a archive.7z *.htm -r -mx -m0fb=255\r
\r
If you have big number of files in archive, and you need fast extracting, \r
you can use partly-solid archives:\r
  \r
  7za.exe a archive.7z *.htm -ms=512K -r -mx -m0fb=255 -m0d=512K\r
\r
In that example 7-Zip will use 512KB solid blocks. So it needs to decompress only \r
512KB for extracting one file from such archive.\r
\r
\r
Limitations of current version of 7z ANSI-C Decoder\r
---------------------------------------------------\r
\r
 - It reads only "FileName", "Size", "LastWriteTime" and "CRC" information for each file in archive.\r
 - It supports only LZMA and Copy (no compression) methods with BCJ or BCJ2 filters.\r
 - It converts original UTF-16 Unicode file names to UTF-8 Unicode file names.\r
 \r
These limitations will be fixed in future versions.\r
\r
\r
Using 7z ANSI-C Decoder Test application:\r
-----------------------------------------\r
\r
Usage: 7zDec <command> <archive_name>\r
\r
<Command>:\r
  e: Extract files from archive\r
  l: List contents of archive\r
  t: Test integrity of archive\r
\r
Example: \r
\r
  7zDec l archive.7z\r
\r
lists contents of archive.7z\r
\r
  7zDec e archive.7z\r
\r
extracts files from archive.7z to current folder.\r
\r
\r
How to use .7z Decoder\r
----------------------\r
\r
Memory allocation\r
~~~~~~~~~~~~~~~~~\r
\r
7z Decoder uses two memory pools:\r
1) Temporary pool\r
2) Main pool\r
Such scheme can allow you to avoid fragmentation of allocated blocks.\r
\r
\r
Steps for using 7z decoder\r
--------------------------\r
\r
Use code at 7zMain.c as example.\r
\r
1) Declare variables:\r
  inStream                 /* implements ILookInStream interface */\r
  CSzArEx db;              /* 7z archive database structure */\r
  ISzAlloc allocImp;       /* memory functions for main pool */\r
  ISzAlloc allocTempImp;   /* memory functions for temporary pool */\r
\r
2) call CrcGenerateTable(); function to initialize CRC structures.\r
\r
3) call SzArEx_Init(&db); function to initialize db structures.\r
\r
4) call SzArEx_Open(&db, inStream, &allocMain, &allocTemp) to open archive\r
\r
This function opens archive "inStream" and reads headers to "db".\r
All items in "db" will be allocated with "allocMain" functions.\r
SzArEx_Open function allocates and frees temporary structures by "allocTemp" functions.\r
\r
5) List items or Extract items\r
\r
  Listing code:\r
  ~~~~~~~~~~~~~\r
\r
    Use SzArEx_GetFileNameUtf16 function. Look example code in C\Util\7z\7zMain.c file. \r
    \r
\r
  Extracting code:\r
  ~~~~~~~~~~~~~~~~\r
\r
  SZ_RESULT SzAr_Extract(\r
    CArchiveDatabaseEx *db,\r
    ILookInStream *inStream, \r
    UInt32 fileIndex,         /* index of file */\r
    UInt32 *blockIndex,       /* index of solid block */\r
    Byte **outBuffer,         /* pointer to pointer to output buffer (allocated with allocMain) */\r
    size_t *outBufferSize,    /* buffer size for output buffer */\r
    size_t *offset,           /* offset of stream for required file in *outBuffer */\r
    size_t *outSizeProcessed, /* size of file in *outBuffer */\r
    ISzAlloc *allocMain,\r
    ISzAlloc *allocTemp);\r
\r
  If you need to decompress more than one file, you can send these values from previous call:\r
    blockIndex, \r
    outBuffer, \r
    outBufferSize,\r
  You can consider "outBuffer" as cache of solid block. If your archive is solid, \r
  it will increase decompression speed.\r
\r
  After decompressing you must free "outBuffer":\r
  allocImp.Free(outBuffer);\r
\r
6) call SzArEx_Free(&db, allocImp.Free) to free allocated items in "db".\r
\r
\r
\r
\r
Memory requirements for .7z decoding \r
------------------------------------\r
\r
Memory usage for Archive opening:\r
  - Temporary pool:\r
     - Memory for uncompressed .7z headers\r
     - some other temporary blocks\r
  - Main pool:\r
     - Memory for database: \r
       Estimated size of one file structures in solid archive:\r
         - Size (4 or 8 Bytes)\r
         - CRC32 (4 bytes)\r
         - LastWriteTime (8 bytes)\r
         - Some file information (4 bytes)\r
         - File Name (variable length) + pointer + allocation structures\r
\r
Memory usage for archive Decompressing:\r
  - Temporary pool:\r
     - Memory for LZMA decompressing structures\r
  - Main pool:\r
     - Memory for decompressed solid block\r
     - Memory for temprorary buffers, if BCJ2 fileter is used. Usually these \r
       temprorary buffers can be about 15% of solid block size. \r
  \r
\r
7z Decoder doesn't allocate memory for compressed blocks. \r
Instead of this, you must allocate buffer with desired \r
size before calling 7z Decoder. Use 7zMain.c as example.\r
\r
\r
Defines\r
-------\r
\r
_SZ_ALLOC_DEBUG   - define it if you want to debug alloc/free operations to stderr.\r
\r
\r
---\r
\r
http://www.7-zip.org\r
http://www.7-zip.org/sdk.html\r
http://www.7-zip.org/support.html\r