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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 ( 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
LZMA SDK is written and placed in the public domain by Igor Pavlov.
Some code in LZMA SDK is based on public domain code from another developers:
1) PPMd var.H (2001): Dmitry Shkarin
2) SHA-256: Wei Dai (Crypto++ library)
LZMA SDK Contents
LZMA SDK includes:
- ANSI-C/C++/C#/Java source code for LZMA compressing and decompressing
- Compiled file->file LZMA compressing/decompressing program for Windows system
UNIX/Linux version
To compile C++ version of file->file LZMA encoding, go to directory
and call make to recompile it:
make -f makefile.gcc clean all
In some UNIX/Linux versions you must compile LZMA with static libraries.
To compile with static libraries, you can use
LIB = -lm -static
lzma.txt - LZMA SDK description (this file)
7zFormat.txt - 7z Format description
7zC.txt - 7z ANSI-C Decoder description
methods.txt - Compression method IDs for .7z
lzma.exe - Compiled file->file LZMA encoder/decoder for Windows
7zr.exe - 7-Zip with 7z/lzma/xz support.
history.txt - history of the LZMA SDK
Source code structure
C/ - C files
7zCrc*.* - CRC code
Alloc.* - Memory allocation functions
Bra*.* - Filters for x86, IA-64, ARM, ARM-Thumb, PowerPC and SPARC code
LzFind.* - Match finder for LZ (LZMA) encoders
LzFindMt.* - Match finder for LZ (LZMA) encoders for multithreading encoding
LzHash.h - Additional file for LZ match finder
LzmaDec.* - LZMA decoding
LzmaEnc.* - LZMA encoding
LzmaLib.* - LZMA Library for DLL calling
Types.h - Basic types for another .c files
Threads.* - The code for multithreading.
LzmaLib - LZMA Library (.DLL for Windows)
LzmaUtil - LZMA Utility (file->file LZMA encoder/decoder).
Archive - files related to archiving
7z - 7z ANSI-C Decoder
CPP/ -- 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
Archive - files related to archiving
Common - common files for archive handling
7z - 7z C++ Encoder/Decoder
Bundles - Modules that are bundles of other modules
Alone7z - 7zr.exe: Standalone version of 7z.exe that supports only 7z/LZMA/BCJ/BCJ2
LzmaCon - lzma.exe: LZMA compression/decompression
Format7zR - 7zr.dll: Reduced version of 7za.dll: extracting/compressing to 7z/LZMA/BCJ/BCJ2
Format7zExtractR - 7zxr.dll: Reduced version of 7zxa.dll: extracting from 7z/LZMA/BCJ/BCJ2.
UI - User Interface files
Client7z - Test application for 7za.dll, 7zr.dll, 7zxr.dll
Common - Common UI files
Console - Code for console archiver
CS/ - C# files
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
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.
7-Zip source code can be downloaded from 7-Zip's SourceForge page:
LZMA features
- Variable dictionary size (up to 1 GB)
- Estimated compressing speed: about 2 MB/s on 2 GHz CPU
- Estimated decompressing speed:
- 20-30 MB/s on 2 GHz Core 2 or AMD Athlon 64
- 1-2 MB/s on 200 MHz ARM, MIPS, PowerPC or other simple RISC
- Small memory requirements for decompressing (16 KB + DictionarySize)
- Small code size for decompressing: 5-8 KB
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 the 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
The 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 Intel's Core 2 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 parameter.
Also you can change the number of iterations. Example for 30 iterations:
LZMA b 30
Default number of iterations is 10.
-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
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
To increase the 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, ...).
You can increase the compression ratio for some data types, using
special filters before compressing. For example, it's possible to
increase the compression ratio on 5-10% for code for those CPU ISAs:
x86, IA-64, ARM, ARM-Thumb, PowerPC, SPARC.
You can find C source code of such filters in C/Bra*.* files
You can check the 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=arm -m1=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
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 (lc,lp, pb in encoded form)
1 4 Dictionary size (little endian)
5 8 Uncompressed size (little endian). -1 means unknown size
13 Compressed data
Please note that interfaces for ANSI-C code were changed in LZMA SDK 4.58.
If you want to use old interfaces you can download previous version of LZMA SDK
from site.
To use ANSI-C LZMA Decoder you need the following files:
1) LzmaDec.h + LzmaDec.c + Types.h
LzmaUtil/LzmaUtil.c is example application that uses these files.
Memory requirements for LZMA decoding
Stack usage of LZMA decoding function for local variables is not
larger than 200-400 bytes.
LZMA Decoder uses dictionary buffer and internal state structure.
Internal state structure consumes
state_size = (4 + (1.5 << (lc + lp))) KB
by default (lc=3, lp=0), state_size = 16 KB.
How To decompress data
LZMA Decoder (ANSI-C version) now supports 2 interfaces:
1) Single-call Decompressing
2) Multi-call State Decompressing (zlib-like interface)
You must use external allocator:
void *SzAlloc(void *p, size_t size) { p = p; return malloc(size); }
void SzFree(void *p, void *address) { p = p; free(address); }
ISzAlloc alloc = { SzAlloc, SzFree };
You can use p = p; operator to disable compiler warnings.
Single-call Decompressing
When to use: RAM->RAM decompressing
Compile files: LzmaDec.h + LzmaDec.c + Types.h
Compile defines: no defines
Memory Requirements:
- Input buffer: compressed size
- Output buffer: uncompressed size
- LZMA Internal Structures: state_size (16 KB for default settings)
int LzmaDecode(Byte *dest, SizeT *destLen, const Byte *src, SizeT *srcLen,
const Byte *propData, unsigned propSize, ELzmaFinishMode finishMode,
ELzmaStatus *status, ISzAlloc *alloc);
dest - output data
destLen - output data size
src - input data
srcLen - input data size
propData - LZMA properties (5 bytes)
propSize - size of propData buffer (5 bytes)
finishMode - It has meaning only if the decoding reaches output limit (*destLen).
LZMA_FINISH_ANY - Decode just destLen bytes.
LZMA_FINISH_END - Stream must be finished after (*destLen).
You can use LZMA_FINISH_END, when you know that
current output buffer covers last bytes of stream.
alloc - Memory allocator.
destLen - processed output size
srcLen - processed input size
SZ_ERROR_DATA - Data error
SZ_ERROR_MEM - Memory allocation error
SZ_ERROR_UNSUPPORTED - Unsupported properties
SZ_ERROR_INPUT_EOF - It needs more bytes in input buffer (src).
If LZMA decoder sees end_marker before reaching output limit, it returns OK result,
and output value of destLen will be less than output buffer size limit.
You can use multiple checks to test data integrity after full decompression:
1) Check Result and "status" variable.
2) Check that output(destLen) = uncompressedSize, if you know real uncompressedSize.
3) Check that output(srcLen) = compressedSize, if you know real compressedSize.
You must use correct finish mode in that case. */
Multi-call State Decompressing (zlib-like interface)
When to use: file->file decompressing
Compile files: LzmaDec.h + LzmaDec.c + Types.h
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: state_size (16 KB for default settings)
- LZMA dictionary (dictionary size is encoded in LZMA properties header)
1) read LZMA properties (5 bytes) and uncompressed size (8 bytes, little-endian) to header:
unsigned char header[LZMA_PROPS_SIZE + 8];
ReadFile(inFile, header, sizeof(header)
2) Allocate CLzmaDec structures (state + dictionary) using LZMA properties
CLzmaDec state;
res = LzmaDec_Allocate(&state, header, LZMA_PROPS_SIZE, &g_Alloc);
if (res != SZ_OK)
return res;
3) Init LzmaDec structure before any new LZMA stream. And call LzmaDec_DecodeToBuf in loop
for (;;)
int res = LzmaDec_DecodeToBuf(CLzmaDec *p, Byte *dest, SizeT *destLen,
const Byte *src, SizeT *srcLen, ELzmaFinishMode finishMode);
4) Free all allocated structures
LzmaDec_Free(&state, &g_Alloc);
For full code example, look at C/LzmaUtil/LzmaUtil.c code.
How To compress data
Compile files: LzmaEnc.h + LzmaEnc.c + Types.h +
LzFind.c + LzFind.h + LzFindMt.c + LzFindMt.h + LzHash.h
Memory Requirements:
- (dictSize * 11.5 + 6 MB) + state_size
Lzma Encoder can use two memory allocators:
1) alloc - for small arrays.
2) allocBig - for big arrays.
For example, you can use Large RAM Pages (2 MB) in allocBig allocator for
better compression speed. Note that Windows has bad implementation for
Large RAM Pages.
It's OK to use same allocator for alloc and allocBig.
Single-call Compression with callbacks
Check C/LzmaUtil/LzmaUtil.c as example,
When to use: file->file decompressing
1) you must implement callback structures for interfaces:
static void *SzAlloc(void *p, size_t size) { p = p; return MyAlloc(size); }
static void SzFree(void *p, void *address) { p = p; MyFree(address); }
static ISzAlloc g_Alloc = { SzAlloc, SzFree };
CFileSeqInStream inStream;
CFileSeqOutStream outStream;
inStream.funcTable.Read = MyRead;
inStream.file = inFile;
outStream.funcTable.Write = MyWrite;
outStream.file = outFile;
2) Create CLzmaEncHandle object;
CLzmaEncHandle enc;
enc = LzmaEnc_Create(&g_Alloc);
if (enc == 0)
return SZ_ERROR_MEM;
3) initialize CLzmaEncProps properties;
Then you can change some properties in that structure.
4) Send LZMA properties to LZMA Encoder
res = LzmaEnc_SetProps(enc, &props);
5) Write encoded properties to header
Byte header[LZMA_PROPS_SIZE + 8];
size_t headerSize = LZMA_PROPS_SIZE;
UInt64 fileSize;
int i;
res = LzmaEnc_WriteProperties(enc, header, &headerSize);
fileSize = MyGetFileLength(inFile);
for (i = 0; i < 8; i++)
header[headerSize++] = (Byte)(fileSize >> (8 * i));
MyWriteFileAndCheck(outFile, header, headerSize)
6) Call encoding function:
res = LzmaEnc_Encode(enc, &outStream.funcTable, &inStream.funcTable,
NULL, &g_Alloc, &g_Alloc);
7) Destroy LZMA Encoder Object
LzmaEnc_Destroy(enc, &g_Alloc, &g_Alloc);
If callback function return some error code, LzmaEnc_Encode also returns that code
or it can return the code like SZ_ERROR_READ, SZ_ERROR_WRITE or SZ_ERROR_PROGRESS.
Single-call RAM->RAM Compression
Single-call RAM->RAM Compression is similar to Compression with callbacks,
but you provide pointers to buffers instead of pointers to stream callbacks:
HRes LzmaEncode(Byte *dest, SizeT *destLen, const Byte *src, SizeT srcLen,
CLzmaEncProps *props, Byte *propsEncoded, SizeT *propsSize, int writeEndMark,
ICompressProgress *progress, ISzAlloc *alloc, ISzAlloc *allocBig);
Return code:
SZ_ERROR_MEM - Memory allocation error
SZ_ERROR_PARAM - Incorrect paramater
SZ_ERROR_OUTPUT_EOF - output buffer overflow
SZ_ERROR_THREAD - errors in multithreading functions (only for Mt version)
_LZMA_SIZE_OPT - Enable some optimizations in LZMA Decoder to get smaller executable code.
_LZMA_PROB32 - It can increase the speed on some 32-bit CPUs, but memory usage for
some structures 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_NO_SYSTEM_SIZE_T - Define it if you don't want to use size_t type.
_7ZIP_PPMD_SUPPPORT - Define it if you don't want to support PPMD method in AMSI-C .7z decoder.
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.
C++ LZMA code is just wrapper over ANSI-C code.
C++ Notes
If you use some C++ code folders in 7-Zip (for example, C++ code for .7z handling),
you must check that you correctly work with "new" operator.
7-Zip can be compiled with MSVC 6.0 that doesn't throw "exception" from "new" operator.
So 7-Zip uses "CPP\Common\NewHandler.cpp" that redefines "new" operator:
operator new(size_t size)
void *p = ::malloc(size);
if (p == 0)
throw CNewException();
return p;
If you use MSCV that throws exception for "new" operator, you can compile without
"NewHandler.cpp". So standard exception will be used. Actually some code of
7-Zip catches any exception in internal code and converts it to HRESULT code.
So you don't need to catch CNewException, if you call COM interfaces of 7-Zip.