src/lzma/7zC.txt
changeset 972 254427fc42ab
parent 917 d299a58a274f
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lzma/7zC.txt	Fri Mar 27 15:10:42 2009 -0400
@@ -0,0 +1,237 @@
+7z ANSI-C Decoder 4.48
+----------------------
+
+7z ANSI-C Decoder 4.48 Copyright (C) 1999-2006 Igor Pavlov
+
+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
+-------
+
+Read lzma.txt for information about license.
+
+
+Files
+---------------------
+
+7zAlloc.*    - Allocate and Free
+7zBuffer.*   - Buffer structure
+7zCrc.*      - CRC32 code
+7zDecode.*   - Low level memory->memory decoding
+7zExtract.*  - High level stream->memory decoding
+7zHeader.*   - .7z format constants
+7zIn.*       - .7z archive opening
+7zItem.*     - .7z structures
+7zMain.c     - Test application
+7zMethodID.* - MethodID structure
+7zTypes.h    - Base types and constants
+
+
+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 <command> <archive_name>
+
+<Command>:
+  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
+----------------------
+
+.7z Decoder can be compiled in one of two modes:
+
+1) Default mode. In that mode 7z Decoder will read full compressed 
+   block to RAM before decompressing.
+  
+2) Mode with defined _LZMA_IN_CB. In that mode 7z Decoder can read
+   compressed block by parts. And you can specify desired buffer size. 
+   So memory requirements can be reduced. But decompressing speed will 
+   be 5-10% lower and code size is slightly larger.
+
+   
+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 ISzInStream interface */
+  CArchiveDatabaseEx db;       /* 7z archive database structure */
+  ISzAlloc allocImp;           /* memory functions for main pool */
+  ISzAlloc allocTempImp;       /* memory functions for temporary pool */
+
+2) call InitCrcTable(); function to initialize CRC structures.
+
+3) call SzArDbExInit(&db); function to initialize db structures.
+
+4) call SzArchiveOpen(inStream, &db, &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.
+SzArchiveOpen function allocates and frees temporary structures by "allocTemp" functions.
+
+5) List items or Extract items
+
+  Listing code:
+  ~~~~~~~~~~~~~
+    {
+      UInt32 i;
+      for (i = 0; i < db.Database.NumFiles; i++)
+      {
+        CFileItem *f = db.Database.Files + i;
+        printf("%10d  %s\n", (int)f->Size, f->Name);
+      }
+    }
+
+  Extracting code:
+  ~~~~~~~~~~~~~~~~
+
+  SZ_RESULT SzExtract(
+    ISzInStream *inStream, 
+    CArchiveDatabaseEx *db,
+    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 SzArDbExFree(&db, allocImp.Free) to free allocated items in "db".
+
+
+
+
+Memory requirements for .7z decoding 
+------------------------------------
+
+Memory usage for Archive opening:
+  - Temporary pool:
+     - Memory for compressed .7z headers (if _LZMA_IN_CB is not defined)
+     - 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 compressed solid block (if _LZMA_IN_CB is not defined)
+     - 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. 
+  
+
+If _LZMA_IN_CB is defined, 7z Decoder will not allocate memory for 
+compressed blocks. Instead of this, you must allocate buffer with desired 
+size before calling 7z Decoder. Use 7zMain.c as example.
+
+
+
+EXIT codes
+-----------
+
+7z Decoder functions can return one of the following codes:
+
+#define SZ_OK (0)
+#define SZE_DATA_ERROR (1)
+#define SZE_OUTOFMEMORY (2)
+#define SZE_CRC_ERROR (3)
+
+#define SZE_NOTIMPL (4)
+#define SZE_FAIL (5)
+
+#define SZE_ARCHIVE_ERROR (6)
+
+
+
+LZMA Defines
+------------
+
+_LZMA_IN_CB       - Use special callback mode for input stream to reduce memory requirements
+
+_SZ_FILE_SIZE_32  - define it if you need only support for files smaller than 4 GB
+_SZ_NO_INT_64     - define it if your compiler doesn't support long long int or __int64.
+
+_LZMA_PROB32      - it can increase LZMA decompressing speed on some 32-bit CPUs.
+
+_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/support.html