repo sync | baa3858 | 2013-07-26 17:53:31 -0700 | [diff] [blame] | 1 | 7z ANSI-C Decoder 4.62
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| 2 | ----------------------
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| 3 |
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| 4 | 7z ANSI-C provides 7z/LZMA decoding.
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| 5 | 7z ANSI-C version is simplified version ported from C++ code.
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| 6 |
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| 7 | LZMA is default and general compression method of 7z format
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| 8 | in 7-Zip compression program (www.7-zip.org). LZMA provides high
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| 9 | compression ratio and very fast decompression.
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| 10 |
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| 11 |
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| 12 | LICENSE
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| 13 | -------
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| 14 |
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| 15 | 7z ANSI-C Decoder is part of the LZMA SDK.
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| 16 | LZMA SDK is written and placed in the public domain by Igor Pavlov.
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| 17 |
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| 18 | Files
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| 19 | ---------------------
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| 20 |
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| 21 | 7zDecode.* - Low level 7z decoding
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| 22 | 7zExtract.* - High level 7z decoding
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| 23 | 7zHeader.* - .7z format constants
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| 24 | 7zIn.* - .7z archive opening
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| 25 | 7zItem.* - .7z structures
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| 26 | 7zMain.c - Test application
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| 27 |
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| 28 |
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| 29 | How To Use
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| 30 | ----------
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| 31 |
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| 32 | You must download 7-Zip program from www.7-zip.org.
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| 33 |
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| 34 | You can create .7z archive with 7z.exe or 7za.exe:
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| 35 |
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| 36 | 7za.exe a archive.7z *.htm -r -mx -m0fb=255
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| 37 |
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| 38 | If you have big number of files in archive, and you need fast extracting,
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| 39 | you can use partly-solid archives:
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| 40 |
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| 41 | 7za.exe a archive.7z *.htm -ms=512K -r -mx -m0fb=255 -m0d=512K
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| 42 |
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| 43 | In that example 7-Zip will use 512KB solid blocks. So it needs to decompress only
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| 44 | 512KB for extracting one file from such archive.
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| 45 |
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| 46 |
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| 47 | Limitations of current version of 7z ANSI-C Decoder
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| 48 | ---------------------------------------------------
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| 49 |
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| 50 | - It reads only "FileName", "Size", "LastWriteTime" and "CRC" information for each file in archive.
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| 51 | - It supports only LZMA and Copy (no compression) methods with BCJ or BCJ2 filters.
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| 52 | - It converts original UTF-16 Unicode file names to UTF-8 Unicode file names.
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| 53 |
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| 54 | These limitations will be fixed in future versions.
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| 55 |
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| 56 |
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| 57 | Using 7z ANSI-C Decoder Test application:
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| 58 | -----------------------------------------
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| 59 |
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| 60 | Usage: 7zDec <command> <archive_name>
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| 61 |
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| 62 | <Command>:
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| 63 | e: Extract files from archive
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| 64 | l: List contents of archive
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| 65 | t: Test integrity of archive
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| 66 |
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| 67 | Example:
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| 68 |
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| 69 | 7zDec l archive.7z
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| 70 |
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| 71 | lists contents of archive.7z
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| 72 |
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| 73 | 7zDec e archive.7z
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| 74 |
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| 75 | extracts files from archive.7z to current folder.
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| 76 |
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| 77 |
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| 78 | How to use .7z Decoder
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| 79 | ----------------------
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| 80 |
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| 81 | Memory allocation
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| 82 | ~~~~~~~~~~~~~~~~~
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| 83 |
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| 84 | 7z Decoder uses two memory pools:
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| 85 | 1) Temporary pool
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| 86 | 2) Main pool
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| 87 | Such scheme can allow you to avoid fragmentation of allocated blocks.
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| 88 |
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| 89 |
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| 90 | Steps for using 7z decoder
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| 91 | --------------------------
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| 92 |
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| 93 | Use code at 7zMain.c as example.
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| 94 |
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| 95 | 1) Declare variables:
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| 96 | inStream /* implements ILookInStream interface */
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| 97 | CSzArEx db; /* 7z archive database structure */
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| 98 | ISzAlloc allocImp; /* memory functions for main pool */
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| 99 | ISzAlloc allocTempImp; /* memory functions for temporary pool */
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| 100 |
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| 101 | 2) call CrcGenerateTable(); function to initialize CRC structures.
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| 102 |
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| 103 | 3) call SzArEx_Init(&db); function to initialize db structures.
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| 104 |
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| 105 | 4) call SzArEx_Open(&db, inStream, &allocMain, &allocTemp) to open archive
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| 106 |
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| 107 | This function opens archive "inStream" and reads headers to "db".
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| 108 | All items in "db" will be allocated with "allocMain" functions.
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| 109 | SzArEx_Open function allocates and frees temporary structures by "allocTemp" functions.
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| 110 |
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| 111 | 5) List items or Extract items
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| 112 |
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| 113 | Listing code:
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| 114 | ~~~~~~~~~~~~~
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| 115 | {
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| 116 | UInt32 i;
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| 117 | for (i = 0; i < db.db.NumFiles; i++)
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| 118 | {
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| 119 | CFileItem *f = db.db.Files + i;
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| 120 | printf("%10d %s\n", (int)f->Size, f->Name);
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| 121 | }
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| 122 | }
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| 123 |
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| 124 | Extracting code:
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| 125 | ~~~~~~~~~~~~~~~~
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| 126 |
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| 127 | SZ_RESULT SzAr_Extract(
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| 128 | CArchiveDatabaseEx *db,
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| 129 | ILookInStream *inStream,
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| 130 | UInt32 fileIndex, /* index of file */
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| 131 | UInt32 *blockIndex, /* index of solid block */
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| 132 | Byte **outBuffer, /* pointer to pointer to output buffer (allocated with allocMain) */
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| 133 | size_t *outBufferSize, /* buffer size for output buffer */
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| 134 | size_t *offset, /* offset of stream for required file in *outBuffer */
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| 135 | size_t *outSizeProcessed, /* size of file in *outBuffer */
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| 136 | ISzAlloc *allocMain,
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| 137 | ISzAlloc *allocTemp);
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| 138 |
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| 139 | If you need to decompress more than one file, you can send these values from previous call:
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| 140 | blockIndex,
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| 141 | outBuffer,
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| 142 | outBufferSize,
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| 143 | You can consider "outBuffer" as cache of solid block. If your archive is solid,
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| 144 | it will increase decompression speed.
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| 145 |
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| 146 | After decompressing you must free "outBuffer":
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| 147 | allocImp.Free(outBuffer);
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| 148 |
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| 149 | 6) call SzArEx_Free(&db, allocImp.Free) to free allocated items in "db".
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| 150 |
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| 151 |
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| 152 |
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| 153 |
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| 154 | Memory requirements for .7z decoding
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| 155 | ------------------------------------
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| 156 |
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| 157 | Memory usage for Archive opening:
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| 158 | - Temporary pool:
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| 159 | - Memory for uncompressed .7z headers
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| 160 | - some other temporary blocks
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| 161 | - Main pool:
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| 162 | - Memory for database:
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| 163 | Estimated size of one file structures in solid archive:
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| 164 | - Size (4 or 8 Bytes)
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| 165 | - CRC32 (4 bytes)
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| 166 | - LastWriteTime (8 bytes)
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| 167 | - Some file information (4 bytes)
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| 168 | - File Name (variable length) + pointer + allocation structures
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| 169 |
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| 170 | Memory usage for archive Decompressing:
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| 171 | - Temporary pool:
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| 172 | - Memory for LZMA decompressing structures
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| 173 | - Main pool:
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| 174 | - Memory for decompressed solid block
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| 175 | - Memory for temprorary buffers, if BCJ2 fileter is used. Usually these
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| 176 | temprorary buffers can be about 15% of solid block size.
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| 177 |
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| 178 |
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| 179 | 7z Decoder doesn't allocate memory for compressed blocks.
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| 180 | Instead of this, you must allocate buffer with desired
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| 181 | size before calling 7z Decoder. Use 7zMain.c as example.
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| 182 |
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| 183 |
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| 184 | Defines
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| 185 | -------
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| 186 |
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| 187 | _SZ_ALLOC_DEBUG - define it if you want to debug alloc/free operations to stderr.
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| 188 |
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| 189 |
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| 190 | ---
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| 191 |
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| 192 | http://www.7-zip.org
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| 193 | http://www.7-zip.org/sdk.html
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| 194 | http://www.7-zip.org/support.html
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