You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
188 lines
5.4 KiB
188 lines
5.4 KiB
![]()
4 years ago
|
7z ANSI-C Decoder 9.35
|
||
|
----------------------
|
||
|
|
||
|
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 can create .7z archive with 7z.exe, 7za.exe or 7zr.exe:
|
||
|
|
||
|
7z.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
|
||
|
----------------------
|
||
|
|
||
|
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:
|
||
|
~~~~~~~~~~~~~
|
||
|
|
||
|
Use SzArEx_GetFileNameUtf16 function. Look example code in C\Util\7z\7zMain.c file.
|
||
|
|
||
|
|
||
|
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
|