lzma.txt

LZMA SDK 4.43
-------------

LZMA SDK   Copyright (C) 1999-2006 Igor Pavlov

LZMA SDK provides the documentation, samples, header files, libraries,
and tools you need to develop applications that use LZMA compression.

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.

LZMA is an improved version of famous LZ77 compression algorithm.
It was improved in way of maximum increasing of compression ratio,
keeping high decompression speed and low memory requirements for
decompressing.



LICENSE
-------

LZMA SDK is available under any of the following licenses:

1) GNU Lesser General Public License (GNU LGPL)
2) Common Public License (CPL)
3) Simplified license for unmodified code (read SPECIAL EXCEPTION)
4) Proprietary license

It means that you can select one of these four options and follow rules of that license.


1,2) GNU LGPL and CPL licenses are pretty similar and both these
licenses are classified as
 - "Free software licenses" at http://www.gnu.org/
 - "OSI-approved" at http://www.opensource.org/


3) SPECIAL EXCEPTION

Igor Pavlov, as the author of this code, expressly permits you
to statically or dynamically link your code (or bind by name)
to the files from LZMA SDK without subjecting your linked
code to the terms of the CPL or GNU LGPL.
Any modifications or additions to files from LZMA SDK, however,
are subject to the GNU LGPL or CPL terms.

SPECIAL EXCEPTION allows you to use LZMA SDK in applications with closed code,
while you keep LZMA SDK code unmodified.


SPECIAL EXCEPTION #2: Igor Pavlov, as the author of this code, expressly permits
you to use this code under the same terms and conditions contained in the License
Agreement you have for any previous version of LZMA SDK developed by Igor Pavlov.

SPECIAL EXCEPTION #2 allows owners of proprietary licenses to use latest version
of LZMA SDK as update for previous versions.


SPECIAL EXCEPTION #3: Igor Pavlov, as the author of this code, expressly permits
you to use code of the following files:
BranchTypes.h, LzmaTypes.h, LzmaTest.c, LzmaStateTest.c, LzmaAlone.cpp,
LzmaAlone.cs, LzmaAlone.java
as public domain code.


4) Proprietary license

LZMA SDK also can be available under a proprietary license which
can include:

1) Right to modify code without subjecting modified code to the
terms of the CPL or GNU LGPL
2) Technical support for code

To request such proprietary license or any additional consultations,
send email message from that page:
http://www.7-zip.org/support.html


You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

You should have received a copy of the Common Public License
along with this library.


LZMA SDK Contents
-----------------

LZMA SDK includes:

  - C++ source code of LZMA compressing and decompressing
  - ANSI-C compatible source code for LZMA decompressing
  - C# source code for LZMA compressing and decompressing
  - Java source code for LZMA compressing and decompressing
  - Compiled file->file LZMA compressing/decompressing program for Windows system

ANSI-C LZMA decompression code was ported from original C++ sources to C.
Also it was simplified and optimized for code size.
But it is fully compatible with LZMA from 7-Zip.


UNIX/Linux version
------------------
To compile C++ version of file->file LZMA, go to directory
C/7zip/Compress/LZMA_Alone
and type "make" or "make clean all" to recompile all.

In some UNIX/Linux versions you must compile LZMA with static libraries.
To compile with static libraries, change string in makefile
LIB = -lm
to string
LIB = -lm -static


Files
---------------------
C        - C / CPP source code
CS       - C# source code
Java     - Java source code
lzma.txt - LZMA SDK description (this file)
7zFormat.txt - 7z Format description
7zC.txt  - 7z ANSI-C Decoder description (this file)
methods.txt  - Compression method IDs for .7z
LGPL.txt - GNU Lesser General Public License
CPL.html - Common Public License
lzma.exe - Compiled file->file LZMA encoder/decoder for Windows
history.txt - history of the LZMA SDK


Source code structure
---------------------

C  - C / CPP files
  Common  - common files for C++ projects
  Windows - common files for Windows related code
  7zip    - files related to 7-Zip Project
    Common   - common files for 7-Zip
    Compress - files related to compression/decompression
      LZ     - files related to LZ (Lempel-Ziv) compression algorithm
        BinTree    - Binary Tree Match Finder for LZ algorithm
        HashChain  - Hash Chain Match Finder for LZ algorithm
        Patricia   - Patricia Match Finder for LZ algorithm
      RangeCoder   - Range Coder (special code of compression/decompression)
      LZMA         - LZMA compression/decompression on C++
      LZMA_Alone   - file->file LZMA compression/decompression
      LZMA_C       - ANSI-C compatible LZMA decompressor
        LzmaDecode.h  - interface for LZMA decoding on ANSI-C
        LzmaDecode.c      - LZMA decoding on ANSI-C (new fastest version)
        LzmaDecodeSize.c  - LZMA decoding on ANSI-C (old size-optimized version)
        LzmaTest.c        - test application that decodes LZMA encoded file
        LzmaTypes.h       - basic types for LZMA Decoder
        LzmaStateDecode.h - interface for LZMA decoding (State version)
        LzmaStateDecode.c - LZMA decoding on ANSI-C (State version)
        LzmaStateTest.c   - test application (State version)
      Branch       - Filters for x86, IA-64, ARM, ARM-Thumb, PowerPC and SPARC code
    Archive - files related to archiving
      7z_C     - 7z ANSI-C Decoder

CS - C# files
  7zip
    Common   - some common files for 7-Zip
    Compress - files related to compression/decompression
      LZ     - files related to LZ (Lempel-Ziv) compression algorithm
      LZMA         - LZMA compression/decompression
      LzmaAlone    - file->file LZMA compression/decompression
      RangeCoder   - Range Coder (special code of compression/decompression)

Java  - Java files
  SevenZip
    Compression    - files related to compression/decompression
      LZ           - files related to LZ (Lempel-Ziv) compression algorithm
      LZMA         - LZMA compression/decompression
      RangeCoder   - Range Coder (special code of compression/decompression)

C/C++ source code of LZMA SDK is part of 7-Zip project.

You can find ANSI-C LZMA decompressing code at folder
  C/7zip/Compress/LZMA_C
7-Zip doesn't use that ANSI-C LZMA code and that code was developed
specially for this SDK. And files from LZMA_C do not need files from
other directories of SDK for compiling.

7-Zip source code can be downloaded from 7-Zip's SourceForge page:

  http://sourceforge.net/projects/sevenzip/


LZMA features
-------------
  - Variable dictionary size (up to 1 GB)
  - Estimated compressing speed: about 1 MB/s on 1 GHz CPU
  - Estimated decompressing speed:
      - 8-12 MB/s on 1 GHz Intel Pentium 3 or AMD Athlon
      - 500-1000 KB/s on 100 MHz ARM, MIPS, PowerPC or other simple RISC
  - Small memory requirements for decompressing (8-32 KB + DictionarySize)
  - Small code size for decompressing: 2-8 KB (depending from
    speed optimizations)

LZMA decoder uses only integer operations and can be
implemented in any modern 32-bit CPU (or on 16-bit CPU with some conditions).

Some critical operations that affect to speed of LZMA decompression:
  1) 32*16 bit integer multiply
  2) Misspredicted branches (penalty mostly depends from pipeline length)
  3) 32-bit shift and arithmetic operations

Speed of LZMA decompressing mostly depends from CPU speed.
Memory speed has no big meaning. But if your CPU has small data cache,
overall weight of memory speed will slightly increase.


How To Use
----------

Using LZMA encoder/decoder executable
--------------------------------------

Usage:  LZMA <e|d> inputFile outputFile [<switches>...]

  e: encode file

  d: decode file

  b: Benchmark. There are two tests: compressing and decompressing
     with LZMA method. Benchmark shows rating in MIPS (million
     instructions per second). Rating value is calculated from
     measured speed and it is normalized with AMD Athlon 64 X2 CPU
     results. Also Benchmark checks possible hardware errors (RAM
     errors in most cases). Benchmark uses these settings:
     (-a1, -d21, -fb32, -mfbt4). You can change only -d. Also you
     can change number of iterations. Example for 30 iterations:
        LZMA b 30
     Default number of iterations is 10.

<Switches>


  -a{N}:  set compression mode 0 = fast, 1 = normal
          default: 1 (normal)

  d{N}:   Sets Dictionary size - [0, 30], default: 23 (8MB)
          The maximum value for dictionary size is 1 GB = 2^30 bytes.
          Dictionary size is calculated as DictionarySize = 2^N bytes.
          For decompressing file compressed by LZMA method with dictionary
          size D = 2^N you need about D bytes of memory (RAM).

  -fb{N}: set number of fast bytes - [5, 273], default: 128
          Usually big number gives a little bit better compression ratio
          and slower compression process.

  -lc{N}: set number of literal context bits - [0, 8], default: 3
          Sometimes lc=4 gives gain for big files.

  -lp{N}: set number of literal pos bits - [0, 4], default: 0
          lp switch is intended for periodical data when period is
          equal 2^N. For example, for 32-bit (4 bytes)
          periodical data you can use lp=2. Often it's better to set lc0,
          if you change lp switch.

  -pb{N}: set number of pos bits - [0, 4], default: 2
          pb switch is intended for periodical data
          when period is equal 2^N.

  -mf{MF_ID}: set Match Finder. Default: bt4.
              Algorithms from hc* group doesn't provide good compression
              ratio, but they often works pretty fast in combination with
              fast mode (-a0).

              Memory requirements depend from dictionary size
              (parameter "d" in table below).

               MF_ID     Memory                   Description

                bt2    d *  9.5 + 4MB  Binary Tree with 2 bytes hashing.
                bt3    d * 11.5 + 4MB  Binary Tree with 3 bytes hashing.
                bt4    d * 11.5 + 4MB  Binary Tree with 4 bytes hashing.
                hc4    d *  7.5 + 4MB  Hash Chain with 4 bytes hashing.

  -eos:   write End Of Stream marker. By default LZMA doesn't write
          eos marker, since LZMA decoder knows uncompressed size
          stored in .lzma file header.

  -si:    Read data from stdin (it will write End Of Stream marker).
  -so:    Write data to stdout


Examples:

1) LZMA e file.bin file.lzma -d16 -lc0

compresses file.bin to file.lzma with 64 KB dictionary (2^16=64K)
and 0 literal context bits. -lc0 allows to reduce memory requirements
for decompression.


2) LZMA e file.bin file.lzma -lc0 -lp2

compresses file.bin to file.lzma with settings suitable
for 32-bit periodical data (for example, ARM or MIPS code).

3) LZMA d file.lzma file.bin

decompresses file.lzma to file.bin.


Compression ratio hints
-----------------------

Recommendations
---------------

To increase compression ratio for LZMA compressing it's desirable
to have aligned data (if it's possible) and also it's desirable to locate
data in such order, where code is grouped in one place and data is
grouped in other place (it's better than such mixing: code, data, code,
data, ...).


Using Filters
-------------
You can increase compression ratio for some data types, using
special filters before compressing. For example, it's possible to
increase compression ratio on 5-10% for code for those CPU ISAs:
x86, IA-64, ARM, ARM-Thumb, PowerPC, SPARC.

You can find C/C++ source code of such filters in folder "7zip/Compress/Branch"

You can check compression ratio gain of these filters with such
7-Zip commands (example for ARM code):
No filter:
  7z a a1.7z a.bin -m0=lzma

With filter for little-endian ARM code:
  7z a a2.7z a.bin -m0=bc_arm -m1=lzma

With filter for big-endian ARM code (using additional Swap4 filter):
  7z a a3.7z a.bin -m0=swap4 -m1=bc_arm -m2=lzma

It works in such manner:
Compressing    = Filter_encoding + LZMA_encoding
Decompressing  = LZMA_decoding + Filter_decoding

Compressing and decompressing speed of such filters is very high,
so it will not increase decompressing time too much.
Moreover, it reduces decompression time for LZMA_decoding,
since compression ratio with filtering is higher.

These filters convert CALL (calling procedure) instructions
from relative offsets to absolute addresses, so such data becomes more
compressible. Source code of these CALL filters is pretty simple
(about 20 lines of C++), so you can convert it from C++ version yourself.

For some ISAs (for example, for MIPS) it's impossible to get gain from such filter.


LZMA compressed file format
---------------------------
Offset Size Description
  0     1   Special LZMA properties for compressed data
  1     4   Dictionary size (little endian)
  5     8   Uncompressed size (little endian). -1 means unknown size
 13         Compressed data


ANSI-C LZMA Decoder
~~~~~~~~~~~~~~~~~~~

To compile ANSI-C LZMA Decoder you can use one of the following files sets:
1) LzmaDecode.h + LzmaDecode.c + LzmaTest.c  (fastest version)
2) LzmaDecode.h + LzmaDecodeSize.c + LzmaTest.c  (old size-optimized version)
3) LzmaStateDecode.h + LzmaStateDecode.c + LzmaStateTest.c  (zlib-like interface)


Memory requirements for LZMA decoding
-------------------------------------

LZMA decoder doesn't allocate memory itself, so you must
allocate memory and send it to LZMA.

Stack usage of LZMA decoding function for local variables is not
larger than 200 bytes.

How To decompress data
----------------------

LZMA Decoder (ANSI-C version) now supports 5 interfaces:
1) Single-call Decompressing
2) Single-call Decompressing with input stream callback
3) Multi-call Decompressing with output buffer
4) Multi-call Decompressing with input callback and output buffer
5) Multi-call State Decompressing (zlib-like interface)

Variant-5 is similar to Variant-4, but Variant-5 doesn't use callback functions.

Decompressing steps
-------------------

1) read LZMA properties (5 bytes):
   unsigned char properties[LZMA_PROPERTIES_SIZE];

2) read uncompressed size (8 bytes, little-endian)

3) Decode properties:

  CLzmaDecoderState state;  /* it's 24-140 bytes structure, if int is 32-bit */

  if (LzmaDecodeProperties(&state.Properties, properties, LZMA_PROPERTIES_SIZE) != LZMA_RESULT_OK)
    return PrintError(rs, "Incorrect stream properties");

4) Allocate memory block for internal Structures:

  state.Probs = (CProb *)malloc(LzmaGetNumProbs(&state.Properties) * sizeof(CProb));
  if (state.Probs == 0)
    return PrintError(rs, kCantAllocateMessage);

  LZMA decoder uses array of CProb variables as internal structure.
  By default, CProb is unsigned_short. But you can define _LZMA_PROB32 to make
  it unsigned_int. It can increase speed on some 32-bit CPUs, but memory
  usage will be doubled in that case.


5) Main Decompressing

You must use one of the following interfaces:

5.1 Single-call Decompressing
-----------------------------
When to use: RAM->RAM decompressing
Compile files: LzmaDecode.h, LzmaDecode.c
Compile defines: no defines
Memory Requirements:
  - Input buffer: compressed size
  - Output buffer: uncompressed size
  - LZMA Internal Structures (~16 KB for default settings)

Interface:
  int res = LzmaDecode(&state,
      inStream, compressedSize, &inProcessed,
      outStream, outSize, &outProcessed);


5.2 Single-call Decompressing with input stream callback
--------------------------------------------------------
When to use: File->RAM or Flash->RAM decompressing.
Compile files: LzmaDecode.h, LzmaDecode.c
Compile defines: _LZMA_IN_CB
Memory Requirements:
  - Buffer for input stream: any size (for example, 16 KB)
  - Output buffer: uncompressed size
  - LZMA Internal Structures (~16 KB for default settings)

Interface:
  typedef struct _CBuffer
  {
    ILzmaInCallback InCallback;
    FILE *File;
    unsigned char Buffer[kInBufferSize];
  } CBuffer;

  int LzmaReadCompressed(void *object, const unsigned char **buffer, SizeT *size)
  {
    CBuffer *bo = (CBuffer *)object;
    *buffer = bo->Buffer;
    *size = MyReadFile(bo->File, bo->Buffer, kInBufferSize);
    return LZMA_RESULT_OK;
  }

  CBuffer g_InBuffer;

  g_InBuffer.File = inFile;
  g_InBuffer.InCallback.Read = LzmaReadCompressed;
  int res = LzmaDecode(&state,
      &g_InBuffer.InCallback,
      outStream, outSize, &outProcessed);


5.3 Multi-call decompressing with output buffer
-----------------------------------------------
When to use: RAM->File decompressing
Compile files: LzmaDecode.h, LzmaDecode.c
Compile defines: _LZMA_OUT_READ
Memory Requirements:
 - Input buffer: compressed size
 - Buffer for output stream: any size (for example, 16 KB)
 - LZMA Internal Structures (~16 KB for default settings)
 - LZMA dictionary (dictionary size is encoded in stream properties)

Interface:

  state.Dictionary = (unsigned char *)malloc(state.Properties.DictionarySize);

  LzmaDecoderInit(&state);
  do
  {
    LzmaDecode(&state,
      inBuffer, inAvail, &inProcessed,
      g_OutBuffer, outAvail, &outProcessed);
    inAvail -= inProcessed;
    inBuffer += inProcessed;
  }
  while you need more bytes

  see LzmaTest.c for more details.


5.4 Multi-call decompressing with input callback and output buffer
------------------------------------------------------------------
When to use: File->File decompressing
Compile files: LzmaDecode.h, LzmaDecode.c
Compile defines: _LZMA_IN_CB, _LZMA_OUT_READ
Memory Requirements:
 - Buffer for input stream: any size (for example, 16 KB)
 - Buffer for output stream: any size (for example, 16 KB)
 - LZMA Internal Structures (~16 KB for default settings)
 - LZMA dictionary (dictionary size is encoded in stream properties)

Interface:

  state.Dictionary = (unsigned char *)malloc(state.Properties.DictionarySize);

  LzmaDecoderInit(&state);
  do
  {
    LzmaDecode(&state,
      &bo.InCallback,
      g_OutBuffer, outAvail, &outProcessed);
  }
  while you need more bytes

  see LzmaTest.c for more details:


5.5 Multi-call State Decompressing (zlib-like interface)
------------------------------------------------------------------
When to use: file->file decompressing
Compile files: LzmaStateDecode.h, LzmaStateDecode.c
Compile defines:
Memory Requirements:
 - Buffer for input stream: any size (for example, 16 KB)
 - Buffer for output stream: any size (for example, 16 KB)
 - LZMA Internal Structures (~16 KB for default settings)
 - LZMA dictionary (dictionary size is encoded in stream properties)

Interface:

  state.Dictionary = (unsigned char *)malloc(state.Properties.DictionarySize);


  LzmaDecoderInit(&state);
  do
  {
    res = LzmaDecode(&state,
      inBuffer, inAvail, &inProcessed,
      g_OutBuffer, outAvail, &outProcessed,
      finishDecoding);
    inAvail -= inProcessed;
    inBuffer += inProcessed;
  }
  while you need more bytes

  see LzmaStateTest.c for more details:


6) Free all allocated blocks


Note
----
LzmaDecodeSize.c is size-optimized version of LzmaDecode.c.
But compiled code of LzmaDecodeSize.c can be larger than
compiled code of LzmaDecode.c. So it's better to use
LzmaDecode.c in most cases.


EXIT codes
-----------

LZMA decoder can return one of the following codes:

#define LZMA_RESULT_OK 0
#define LZMA_RESULT_DATA_ERROR 1

If you use callback function for input data and you return some
error code, LZMA Decoder also returns that code.



LZMA Defines
------------

_LZMA_IN_CB    - Use callback for input data

_LZMA_OUT_READ - Use read function for output data

_LZMA_LOC_OPT  - Enable local speed optimizations inside code.
                 _LZMA_LOC_OPT is only for LzmaDecodeSize.c (size-optimized version).
                 _LZMA_LOC_OPT doesn't affect LzmaDecode.c (speed-optimized version)
                 and LzmaStateDecode.c

_LZMA_PROB32   - It can increase speed on some 32-bit CPUs,
                 but memory usage will be doubled in that case

_LZMA_UINT32_IS_ULONG  - Define it if int is 16-bit on your compiler
                         and long is 32-bit.

_LZMA_SYSTEM_SIZE_T  - Define it if you want to use system's size_t.
                       You can use it to enable 64-bit sizes supporting



C++ LZMA Encoder/Decoder
~~~~~~~~~~~~~~~~~~~~~~~~
C++ LZMA code use COM-like interfaces. So if you want to use it,
you can study basics of COM/OLE.

By default, LZMA Encoder contains all Match Finders.
But for compressing it's enough to have just one of them.
So for reducing size of compressing code you can define:
  #define COMPRESS_MF_BT
  #define COMPRESS_MF_BT4
and it will use only bt4 match finder.


---

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http://www.7-zip.org/support.html