BaseTools/Source/C/LzmaCompress/Sdk/DOC/lzma-sdk.txt

   1 LZMA SDK 18.05
   2 --------------
   3
   4 LZMA SDK provides the documentation, samples, header files,
   5 libraries, and tools you need to develop applications that
   6 use 7z / LZMA / LZMA2 / XZ compression.
   7
   8 LZMA is an improved version of famous LZ77 compression algorithm.
   9 It was improved in way of maximum increasing of compression ratio,
  10 keeping high decompression speed and low memory requirements for
  11 decompressing.
  12
  13 LZMA2 is a LZMA based compression method. LZMA2 provides better
  14 multithreading support for compression than LZMA and some other improvements.
  15
  16 7z is a file format for data compression and file archiving.
  17 7z is a main file format for 7-Zip compression program (www.7-zip.org).
  18 7z format supports different compression methods: LZMA, LZMA2 and others.
  19 7z also supports AES-256 based encryption.
  20
  21 XZ is a file format for data compression that uses LZMA2 compression.
  22 XZ format provides additional features: SHA/CRC check, filters for
  23 improved compression ratio, splitting to blocks and streams,
  24
  25
  26
  27 LICENSE
  28 -------
  29
  30 LZMA SDK is written and placed in the public domain by Igor Pavlov.
  31
  32 Some code in LZMA SDK is based on public domain code from another developers:
  33   1) PPMd var.H (2001): Dmitry Shkarin
  34   2) SHA-256: Wei Dai (Crypto++ library)
  35
  36 Anyone is free to copy, modify, publish, use, compile, sell, or distribute the
  37 original LZMA SDK code, either in source code form or as a compiled binary, for
  38 any purpose, commercial or non-commercial, and by any means.
  39
  40 LZMA SDK code is compatible with open source licenses, for example, you can
  41 include it to GNU GPL or GNU LGPL code.
  42
  43
  44 LZMA SDK Contents
  45 -----------------
  46
  47   Source code:
  48
  49     - C / C++ / C# / Java   - LZMA compression and decompression
  50     - C / C++               - LZMA2 compression and decompression
  51     - C / C++               - XZ compression and decompression
  52     - C                     - 7z decompression
  53     -     C++               - 7z compression and decompression
  54     - C                     - small SFXs for installers (7z decompression)
  55     -     C++               - SFXs and SFXs for installers (7z decompression)
  56
  57   Precompiled binaries:
  58
  59     - console programs for lzma / 7z / xz compression and decompression
  60     - SFX modules for installers.
  61
  62
  63 UNIX/Linux version
  64 ------------------
  65 To compile C++ version of file->file LZMA encoding, go to directory
  66 CPP/7zip/Bundles/LzmaCon
  67 and call make to recompile it:
  68   make -f makefile.gcc clean all
  69
  70 In some UNIX/Linux versions you must compile LZMA with static libraries.
  71 To compile with static libraries, you can use
  72 LIB = -lm -static
  73
  74 Also you can use p7zip (port of 7-Zip for POSIX systems like Unix or Linux):
  75
  76   http://p7zip.sourceforge.net/
  77
  78
  79 Files
  80 -----
  81
  82 DOC/7zC.txt          - 7z ANSI-C Decoder description
  83 DOC/7zFormat.txt     - 7z Format description
  84 DOC/installer.txt    - information about 7-Zip for installers
  85 DOC/lzma.txt         - LZMA compression description
  86 DOC/lzma-sdk.txt     - LZMA SDK description (this file)
  87 DOC/lzma-history.txt - history of LZMA SDK
  88 DOC/lzma-specification.txt - Specification of LZMA
  89 DOC/Methods.txt      - Compression method IDs for .7z
  90
  91 bin/installer/   - example script to create installer that uses SFX module,
  92
  93 bin/7zdec.exe    - simplified 7z archive decoder
  94 bin/7zr.exe      - 7-Zip console program (reduced version)
  95 bin/x64/7zr.exe  - 7-Zip console program (reduced version) (x64 version)
  96 bin/lzma.exe     - file->file LZMA encoder/decoder for Windows
  97 bin/7zS2.sfx     - small SFX module for installers (GUI version)
  98 bin/7zS2con.sfx  - small SFX module for installers (Console version)
  99 bin/7zSD.sfx     - SFX module for installers.
 100
 101
 102 7zDec.exe
 103 ---------
 104 7zDec.exe is simplified 7z archive decoder.
 105 It supports only LZMA, LZMA2, and PPMd methods.
 106 7zDec decodes whole solid block from 7z archive to RAM.
 107 The RAM consumption can be high.
 108
 109
 110
 111
 112 Source code structure
 113 ---------------------
 114
 115
 116 Asm/ - asm files (optimized code for CRC calculation and Intel-AES encryption)
 117
 118 C/  - C files (compression / decompression and other)
 119   Util/
 120     7z       - 7z decoder program (decoding 7z files)
 121     Lzma     - LZMA program (file->file LZMA encoder/decoder).
 122     LzmaLib  - LZMA library (.DLL for Windows)
 123     SfxSetup - small SFX module for installers
 124
 125 CPP/ -- CPP files
 126
 127   Common  - common files for C++ projects
 128   Windows - common files for Windows related code
 129
 130   7zip    - files related to 7-Zip
 131
 132     Archive - files related to archiving
 133
 134       Common   - common files for archive handling
 135       7z       - 7z C++ Encoder/Decoder
 136
 137     Bundles  - Modules that are bundles of other modules (files)
 138
 139       Alone7z       - 7zr.exe: Standalone 7-Zip console program (reduced version)
 140       Format7zExtractR  - 7zxr.dll: Reduced version of 7z DLL: extracting from 7z/LZMA/BCJ/BCJ2.
 141       Format7zR         - 7zr.dll:  Reduced version of 7z DLL: extracting/compressing to 7z/LZMA/BCJ/BCJ2
 142       LzmaCon       - lzma.exe: LZMA compression/decompression
 143       LzmaSpec      - example code for LZMA Specification
 144       SFXCon        - 7zCon.sfx: Console 7z SFX module
 145       SFXSetup      - 7zS.sfx: 7z SFX module for installers
 146       SFXWin        - 7z.sfx: GUI 7z SFX module
 147
 148     Common   - common files for 7-Zip
 149
 150     Compress - files for compression/decompression
 151
 152     Crypto   - files for encryption / decompression
 153
 154     UI       - User Interface files
 155
 156       Client7z - Test application for 7za.dll, 7zr.dll, 7zxr.dll
 157       Common   - Common UI files
 158       Console  - Code for console program (7z.exe)
 159       Explorer    - Some code from 7-Zip Shell extension
 160       FileManager - Some GUI code from 7-Zip File Manager
 161       GUI         - Some GUI code from 7-Zip
 162
 163
 164 CS/ - C# files
 165   7zip
 166     Common   - some common files for 7-Zip
 167     Compress - files related to compression/decompression
 168       LZ     - files related to LZ (Lempel-Ziv) compression algorithm
 169       LZMA         - LZMA compression/decompression
 170       LzmaAlone    - file->file LZMA compression/decompression
 171       RangeCoder   - Range Coder (special code of compression/decompression)
 172
 173 Java/  - Java files
 174   SevenZip
 175     Compression    - files related to compression/decompression
 176       LZ           - files related to LZ (Lempel-Ziv) compression algorithm
 177       LZMA         - LZMA compression/decompression
 178       RangeCoder   - Range Coder (special code of compression/decompression)
 179
 180
 181 Note:
 182   Asm / C / C++ source code of LZMA SDK is part of 7-Zip's source code.
 183   7-Zip's source code can be downloaded from 7-Zip's SourceForge page:
 184
 185   http://sourceforge.net/projects/sevenzip/
 186
 187
 188
 189 LZMA features
 190 -------------
 191   - Variable dictionary size (up to 1 GB)
 192   - Estimated compressing speed: about 2 MB/s on 2 GHz CPU
 193   - Estimated decompressing speed:
 194       - 20-30 MB/s on modern 2 GHz cpu
 195       - 1-2 MB/s on 200 MHz simple RISC cpu: (ARM, MIPS, PowerPC)
 196   - Small memory requirements for decompressing (16 KB + DictionarySize)
 197   - Small code size for decompressing: 5-8 KB
 198
 199 LZMA decoder uses only integer operations and can be
 200 implemented in any modern 32-bit CPU (or on 16-bit CPU with some conditions).
 201
 202 Some critical operations that affect the speed of LZMA decompression:
 203   1) 32*16 bit integer multiply
 204   2) Mispredicted branches (penalty mostly depends from pipeline length)
 205   3) 32-bit shift and arithmetic operations
 206
 207 The speed of LZMA decompressing mostly depends from CPU speed.
 208 Memory speed has no big meaning. But if your CPU has small data cache,
 209 overall weight of memory speed will slightly increase.
 210
 211
 212 How To Use
 213 ----------
 214
 215 Using LZMA encoder/decoder executable
 216 --------------------------------------
 217
 218 Usage:  LZMA <e|d> inputFile outputFile [<switches>...]
 219
 220   e: encode file
 221
 222   d: decode file
 223
 224   b: Benchmark. There are two tests: compressing and decompressing
 225      with LZMA method. Benchmark shows rating in MIPS (million
 226      instructions per second). Rating value is calculated from
 227      measured speed and it is normalized with Intel's Core 2 results.
 228      Also Benchmark checks possible hardware errors (RAM
 229      errors in most cases). Benchmark uses these settings:
 230      (-a1, -d21, -fb32, -mfbt4). You can change only -d parameter.
 231      Also you can change the number of iterations. Example for 30 iterations:
 232        LZMA b 30
 233      Default number of iterations is 10.
 234
 235 <Switches>
 236
 237
 238   -a{N}:  set compression mode 0 = fast, 1 = normal
 239           default: 1 (normal)
 240
 241   d{N}:   Sets Dictionary size - [0, 30], default: 23 (8MB)
 242           The maximum value for dictionary size is 1 GB = 2^30 bytes.
 243           Dictionary size is calculated as DictionarySize = 2^N bytes.
 244           For decompressing file compressed by LZMA method with dictionary
 245           size D = 2^N you need about D bytes of memory (RAM).
 246
 247   -fb{N}: set number of fast bytes - [5, 273], default: 128
 248           Usually big number gives a little bit better compression ratio
 249           and slower compression process.
 250
 251   -lc{N}: set number of literal context bits - [0, 8], default: 3
 252           Sometimes lc=4 gives gain for big files.
 253
 254   -lp{N}: set number of literal pos bits - [0, 4], default: 0
 255           lp switch is intended for periodical data when period is
 256           equal 2^N. For example, for 32-bit (4 bytes)
 257           periodical data you can use lp=2. Often it's better to set lc0,
 258           if you change lp switch.
 259
 260   -pb{N}: set number of pos bits - [0, 4], default: 2
 261           pb switch is intended for periodical data
 262           when period is equal 2^N.
 263
 264   -mf{MF_ID}: set Match Finder. Default: bt4.
 265               Algorithms from hc* group doesn't provide good compression
 266               ratio, but they often works pretty fast in combination with
 267               fast mode (-a0).
 268
 269               Memory requirements depend from dictionary size
 270               (parameter "d" in table below).
 271
 272                MF_ID     Memory                   Description
 273
 274                 bt2    d *  9.5 + 4MB  Binary Tree with 2 bytes hashing.
 275                 bt3    d * 11.5 + 4MB  Binary Tree with 3 bytes hashing.
 276                 bt4    d * 11.5 + 4MB  Binary Tree with 4 bytes hashing.
 277                 hc4    d *  7.5 + 4MB  Hash Chain with 4 bytes hashing.
 278
 279   -eos:   write End Of Stream marker. By default LZMA doesn't write
 280           eos marker, since LZMA decoder knows uncompressed size
 281           stored in .lzma file header.
 282
 283   -si:    Read data from stdin (it will write End Of Stream marker).
 284   -so:    Write data to stdout
 285
 286
 287 Examples:
 288
 289 1) LZMA e file.bin file.lzma -d16 -lc0
 290
 291 compresses file.bin to file.lzma with 64 KB dictionary (2^16=64K)
 292 and 0 literal context bits. -lc0 allows to reduce memory requirements
 293 for decompression.
 294
 295
 296 2) LZMA e file.bin file.lzma -lc0 -lp2
 297
 298 compresses file.bin to file.lzma with settings suitable
 299 for 32-bit periodical data (for example, ARM or MIPS code).
 300
 301 3) LZMA d file.lzma file.bin
 302
 303 decompresses file.lzma to file.bin.
 304
 305
 306 Compression ratio hints
 307 -----------------------
 308
 309 Recommendations
 310 ---------------
 311
 312 To increase the compression ratio for LZMA compressing it's desirable
 313 to have aligned data (if it's possible) and also it's desirable to locate
 314 data in such order, where code is grouped in one place and data is
 315 grouped in other place (it's better than such mixing: code, data, code,
 316 data, ...).
 317
 318
 319 Filters
 320 -------
 321 You can increase the compression ratio for some data types, using
 322 special filters before compressing. For example, it's possible to
 323 increase the compression ratio on 5-10% for code for those CPU ISAs:
 324 x86, IA-64, ARM, ARM-Thumb, PowerPC, SPARC.
 325
 326 You can find C source code of such filters in C/Bra*.* files
 327
 328 You can check the compression ratio gain of these filters with such
 329 7-Zip commands (example for ARM code):
 330 No filter:
 331   7z a a1.7z a.bin -m0=lzma
 332
 333 With filter for little-endian ARM code:
 334   7z a a2.7z a.bin -m0=arm -m1=lzma
 335
 336 It works in such manner:
 337 Compressing    = Filter_encoding + LZMA_encoding
 338 Decompressing  = LZMA_decoding + Filter_decoding
 339
 340 Compressing and decompressing speed of such filters is very high,
 341 so it will not increase decompressing time too much.
 342 Moreover, it reduces decompression time for LZMA_decoding,
 343 since compression ratio with filtering is higher.
 344
 345 These filters convert CALL (calling procedure) instructions
 346 from relative offsets to absolute addresses, so such data becomes more
 347 compressible.
 348
 349 For some ISAs (for example, for MIPS) it's impossible to get gain from such filter.
 350
 351
 352
 353 ---
 354
 355 http://www.7-zip.org
 356 http://www.7-zip.org/sdk.html
 357 http://www.7-zip.org/support.html