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3 <title> |
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4 zlib general purpose compression library version 1.1.4 |
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7 <body bgcolor="White" text="Black" vlink="Red" alink="Navy" link="Red"> |
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8 <!-- background="zlibbg.gif" --> |
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9 |
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10 <h1> zlib 1.1.4 Manual </h1> |
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11 <hr> |
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12 <a name="Contents"><h2>Contents</h2> |
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13 <ol type="I"> |
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14 <li> <a href="#Prologue">Prologue</a> |
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15 <li> <a href="#Introduction">Introduction</a> |
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16 <li> <a href="#Utility functions">Utility functions</a> |
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17 <li> <a href="#Basic functions">Basic functions</a> |
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18 <li> <a href="#Advanced functions">Advanced functions</a> |
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19 <li> <a href="#Constants">Constants</a> |
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20 <li> <a href="#struct z_stream_s">struct z_stream_s</a> |
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21 <li> <a href="#Checksum functions">Checksum functions</a> |
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22 <li> <a href="#Misc">Misc</a> |
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23 </ol> |
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24 <hr> |
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25 <a name="Prologue"><h2> Prologue </h2> |
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26 'zlib' general purpose compression library version 1.1.4, March 11th, 2002 |
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27 <p> |
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28 Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler |
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29 <p> |
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30 This software is provided 'as-is', without any express or implied |
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31 warranty. In no event will the authors be held liable for any damages |
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32 arising from the use of this software. |
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33 <p> |
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34 Permission is granted to anyone to use this software for any purpose, |
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35 including commercial applications, and to alter it and redistribute it |
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36 freely, subject to the following restrictions: |
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37 <ol> |
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38 <li> The origin of this software must not be misrepresented ; you must not |
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39 claim that you wrote the original software. If you use this software |
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40 in a product, an acknowledgment in the product documentation would be |
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41 appreciated but is not required. |
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42 <li> Altered source versions must be plainly marked as such, and must not be |
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43 misrepresented as being the original software. |
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44 <li> This notice may not be removed or altered from any source distribution. |
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45 </ol> |
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46 |
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47 <dl> |
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48 <dt>Jean-loup Gailly |
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49 <dd><a href="mailto:jloup@gzip.org">jloup@gzip.org</a> |
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50 <dt>Mark Adler |
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51 <dd><a href="mailto:madler@alumni.caltech.edu">madler@alumni.caltech.edu</a> |
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52 </dl> |
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53 |
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54 The data format used by the zlib library is described by RFCs (Request for |
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55 Comments) 1950 to 1952 in the files |
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56 <a href="ftp://ds.internic.net/rfc/rfc1950.txt"> |
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57 ftp://ds.internic.net/rfc/rfc1950.txt </a> |
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58 (zlib format), |
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59 <a href="ftp://ds.internic.net/rfc/rfc1951.txt"> |
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60 rfc1951.txt </a> |
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61 (<a href="#deflate">deflate</a> format) and |
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62 <a href="ftp://ds.internic.net/rfc/rfc1952.txt"> |
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63 rfc1952.txt </a> |
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64 (gzip format). |
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65 <p> |
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66 This manual is converted from zlib.h by |
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67 <a href="mailto:piaip@csie.ntu.edu.tw"> piaip </a> |
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68 <p> |
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69 Visit <a href="http://ftp.cdrom.com/pub/infozip/zlib/"> |
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70 http://ftp.cdrom.com/pub/infozip/zlib/</a> |
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71 for the official zlib web page. |
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72 <p> |
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73 |
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74 <hr> |
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75 <a name="Introduction"><h2> Introduction </h2> |
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76 The 'zlib' compression library provides in-memory compression and |
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77 decompression functions, including integrity checks of the uncompressed |
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78 data. This version of the library supports only one compression method |
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79 (deflation) but other algorithms will be added later and will have the same |
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80 stream interface. |
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81 <p> |
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82 |
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83 Compression can be done in a single step if the buffers are large |
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84 enough (for example if an input file is mmap'ed), or can be done by |
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85 repeated calls of the compression function. In the latter case, the |
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86 application must provide more input and/or consume the output |
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87 (providing more output space) before each call. |
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88 <p> |
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89 |
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90 The library also supports reading and writing files in gzip (.gz) format |
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91 with an interface similar to that of stdio. |
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92 <p> |
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93 |
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94 The library does not install any signal handler. The decoder checks |
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95 the consistency of the compressed data, so the library should never |
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96 crash even in case of corrupted input. |
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97 <p> |
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98 |
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99 <hr> |
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100 <a name="Utility functions"><h2> Utility functions </h2> |
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101 The following utility functions are implemented on top of the |
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102 <a href="#Basic functions">basic stream-oriented functions</a>. |
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103 To simplify the interface, some |
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104 default options are assumed (compression level and memory usage, |
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105 standard memory allocation functions). The source code of these |
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106 utility functions can easily be modified if you need special options. |
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107 <h3> Function list </h3> |
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108 <ul> |
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109 <li> int <a href="#compress">compress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen); |
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110 <li> int <a href="#compress2">compress2</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen, int level); |
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111 <li> int <a href="#uncompress">uncompress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen); |
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112 <li> typedef voidp gzFile; |
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113 <li> gzFile <a href="#gzopen">gzopen</a> (const char *path, const char *mode); |
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114 <li> gzFile <a href="#gzdopen">gzdopen</a> (int fd, const char *mode); |
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115 <li> int <a href="#gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy); |
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116 <li> int <a href="#gzread">gzread</a> (gzFile file, voidp buf, unsigned len); |
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117 <li> int <a href="#gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len); |
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118 <li> int VA <a href="#gzprintf">gzprintf</a> (gzFile file, const char *format, ...); |
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119 <li> int <a href="#gzputs">gzputs</a> (gzFile file, const char *s); |
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120 <li> char * <a href="#gzgets">gzgets</a> (gzFile file, char *buf, int len); |
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121 <li> int <a href="#gzputc">gzputc</a> (gzFile file, int c); |
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122 <li> int <a href="#gzgetc">gzgetc</a> (gzFile file); |
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123 <li> int <a href="#gzflush">gzflush</a> (gzFile file, int flush); |
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124 <li> z_off_t <a href="#gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence); |
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125 <li> z_off_t <a href="#gztell">gztell</a> (gzFile file); |
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126 <li> int <a href="#gzrewind">gzrewind</a> (gzFile file); |
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127 <li> int <a href="#gzeof">gzeof</a> (gzFile file); |
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128 <li> int <a href="#gzclose">gzclose</a> (gzFile file); |
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129 <li> const char * <a href="#gzerror">gzerror</a> (gzFile file, int *errnum); |
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130 </ul> |
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131 <h3> Function description </h3> |
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132 <dl> |
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133 <font color="Blue"><dt> int <a name="compress">compress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);</font> |
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134 <dd> |
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135 Compresses the source buffer into the destination buffer. sourceLen is |
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136 the byte length of the source buffer. Upon entry, destLen is the total |
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137 size of the destination buffer, which must be at least 0.1% larger than |
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138 sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the |
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139 compressed buffer.<p> |
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140 This function can be used to <a href="#compress">compress</a> a whole file at once if the |
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141 input file is mmap'ed.<p> |
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142 <a href="#compress">compress</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not |
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143 enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output |
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144 buffer.<p> |
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145 |
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146 <font color="Blue"><dt> int <a name="compress2">compress2</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen, int level);</font> |
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147 <dd> |
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148 Compresses the source buffer into the destination buffer. The level |
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149 parameter has the same meaning as in <a href="#deflateInit">deflateInit</a>. sourceLen is the byte |
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150 length of the source buffer. Upon entry, destLen is the total size of the |
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151 destination buffer, which must be at least 0.1% larger than sourceLen plus |
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152 12 bytes. Upon exit, destLen is the actual size of the compressed buffer. |
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153 <p> |
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154 |
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155 <a href="#compress2">compress2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough |
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156 memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output buffer, |
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157 <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the level parameter is invalid. |
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158 <p> |
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159 |
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160 <font color="Blue"><dt> int <a name="uncompress">uncompress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);</font> |
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161 <dd> |
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162 Decompresses the source buffer into the destination buffer. sourceLen is |
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163 the byte length of the source buffer. Upon entry, destLen is the total |
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164 size of the destination buffer, which must be large enough to hold the |
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165 entire uncompressed data. (The size of the uncompressed data must have |
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166 been saved previously by the compressor and transmitted to the decompressor |
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167 by some mechanism outside the scope of this compression library.) |
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168 Upon exit, destLen is the actual size of the compressed buffer. <p> |
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169 This function can be used to decompress a whole file at once if the |
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170 input file is mmap'ed. |
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171 <p> |
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172 |
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173 <a href="#uncompress">uncompress</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not |
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174 enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output |
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175 buffer, or <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was corrupted. |
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176 <p> |
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177 |
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178 <dt> typedef voidp gzFile; |
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179 <dd> <p> |
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180 |
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181 <font color="Blue"><dt> gzFile <a name="gzopen">gzopen</a> (const char *path, const char *mode);</font> |
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182 <dd> |
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183 Opens a gzip (.gz) file for reading or writing. The mode parameter |
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184 is as in fopen ("rb" or "wb") but can also include a compression level |
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185 ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for |
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186 Huffman only compression as in "wb1h". (See the description |
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187 of <a href="#deflateInit2">deflateInit2</a> for more information about the strategy parameter.) |
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188 <p> |
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189 |
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190 <a href="#gzopen">gzopen</a> can be used to read a file which is not in gzip format ; in this |
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191 case <a href="#gzread">gzread</a> will directly read from the file without decompression. |
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192 <p> |
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193 |
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194 <a href="#gzopen">gzopen</a> returns NULL if the file could not be opened or if there was |
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195 insufficient memory to allocate the (de)compression <a href="#state">state</a> ; errno |
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196 can be checked to distinguish the two cases (if errno is zero, the |
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197 zlib error is <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a>). |
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198 <p> |
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199 |
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200 <font color="Blue"><dt> gzFile <a name="gzdopen">gzdopen</a> (int fd, const char *mode);</font> |
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201 <dd> |
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202 <a href="#gzdopen">gzdopen</a>() associates a gzFile with the file descriptor fd. File |
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203 descriptors are obtained from calls like open, dup, creat, pipe or |
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204 fileno (in the file has been previously opened with fopen). |
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205 The mode parameter is as in <a href="#gzopen">gzopen</a>. |
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206 <p> |
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207 The next call of <a href="#gzclose">gzclose</a> on the returned gzFile will also close the |
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208 file descriptor fd, just like fclose(fdopen(fd), mode) closes the file |
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209 descriptor fd. If you want to keep fd open, use <a href="#gzdopen">gzdopen</a>(dup(fd), mode). |
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210 <p> |
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211 <a href="#gzdopen">gzdopen</a> returns NULL if there was insufficient memory to allocate |
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212 the (de)compression <a href="#state">state</a>. |
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213 <p> |
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214 |
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215 <font color="Blue"><dt> int <a name="gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);</font> |
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216 <dd> |
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217 Dynamically update the compression level or strategy. See the description |
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218 of <a href="#deflateInit2">deflateInit2</a> for the meaning of these parameters. |
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219 <p> |
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220 <a href="#gzsetparams">gzsetparams</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the file was not |
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221 opened for writing. |
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222 <p> |
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223 |
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224 <font color="Blue"><dt> int <a name="gzread">gzread</a> (gzFile file, voidp buf, unsigned len);</font> |
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225 <dd> |
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226 Reads the given number of uncompressed bytes from the compressed file. |
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227 If the input file was not in gzip format, <a href="#gzread">gzread</a> copies the given number |
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228 of bytes into the buffer. |
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229 <p> |
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230 <a href="#gzread">gzread</a> returns the number of uncompressed bytes actually read (0 for |
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231 end of file, -1 for error). |
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232 <p> |
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233 |
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234 <font color="Blue"><dt> int <a name="gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);</font> |
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235 <dd> |
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236 Writes the given number of uncompressed bytes into the compressed file. |
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237 <a href="#gzwrite">gzwrite</a> returns the number of uncompressed bytes actually written |
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238 (0 in case of error). |
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239 <p> |
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240 |
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241 <font color="Blue"><dt> int VA <a name="gzprintf">gzprintf</a> (gzFile file, const char *format, ...);</font> |
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242 <dd> |
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243 Converts, formats, and writes the args to the compressed file under |
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244 control of the format string, as in fprintf. <a href="#gzprintf">gzprintf</a> returns the number of |
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245 uncompressed bytes actually written (0 in case of error). |
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246 <p> |
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247 |
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248 <font color="Blue"><dt> int <a name="gzputs">gzputs</a> (gzFile file, const char *s);</font> |
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249 <dd> |
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250 Writes the given null-terminated string to the compressed file, excluding |
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251 the terminating null character. |
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252 <p> |
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253 <a href="#gzputs">gzputs</a> returns the number of characters written, or -1 in case of error. |
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254 <p> |
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255 |
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256 <font color="Blue"><dt> char * <a name="gzgets">gzgets</a> (gzFile file, char *buf, int len);</font> |
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257 <dd> |
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258 Reads bytes from the compressed file until len-1 characters are read, or |
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259 a newline character is read and transferred to buf, or an end-of-file |
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260 condition is encountered. The string is then terminated with a null |
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261 character. |
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262 <p> |
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263 <a href="#gzgets">gzgets</a> returns buf, or <a href="#Z_NULL">Z_NULL</a> in case of error. |
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264 <p> |
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265 |
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266 <font color="Blue"><dt> int <a name="gzputc">gzputc</a> (gzFile file, int c);</font> |
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267 <dd> |
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268 Writes c, converted to an unsigned char, into the compressed file. |
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269 <a href="#gzputc">gzputc</a> returns the value that was written, or -1 in case of error. |
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270 <p> |
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271 |
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272 <font color="Blue"><dt> int <a name="gzgetc">gzgetc</a> (gzFile file);</font> |
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273 <dd> |
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274 Reads one byte from the compressed file. <a href="#gzgetc">gzgetc</a> returns this byte |
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275 or -1 in case of end of file or error. |
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276 <p> |
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277 |
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278 <font color="Blue"><dt> int <a name="gzflush">gzflush</a> (gzFile file, int flush);</font> |
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279 <dd> |
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280 Flushes all pending output into the compressed file. The parameter |
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281 flush is as in the <a href="#deflate">deflate</a>() function. The return value is the zlib |
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282 error number (see function <a href="#gzerror">gzerror</a> below). <a href="#gzflush">gzflush</a> returns <a href="#Z_OK">Z_OK</a> if |
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283 the flush parameter is <a href="#Z_FINISH">Z_FINISH</a> and all output could be flushed. |
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284 <p> |
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285 <a href="#gzflush">gzflush</a> should be called only when strictly necessary because it can |
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286 degrade compression. |
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287 <p> |
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288 |
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289 <font color="Blue"><dt> z_off_t <a name="gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);</font> |
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290 <dd> |
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291 Sets the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the |
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292 given compressed file. The offset represents a number of bytes in the |
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293 uncompressed data stream. The whence parameter is defined as in lseek(2); |
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294 the value SEEK_END is not supported. |
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295 <p> |
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296 If the file is opened for reading, this function is emulated but can be |
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297 extremely slow. If the file is opened for writing, only forward seeks are |
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298 supported ; <a href="#gzseek">gzseek</a> then compresses a sequence of zeroes up to the new |
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299 starting position. |
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300 <p> |
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301 <a href="#gzseek">gzseek</a> returns the resulting offset location as measured in bytes from |
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302 the beginning of the uncompressed stream, or -1 in case of error, in |
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303 particular if the file is opened for writing and the new starting position |
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304 would be before the current position. |
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305 <p> |
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306 |
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307 <font color="Blue"><dt> int <a name="gzrewind">gzrewind</a> (gzFile file);</font> |
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308 <dd> |
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309 Rewinds the given file. This function is supported only for reading. |
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310 <p> |
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311 <a href="#gzrewind">gzrewind</a>(file) is equivalent to (int)<a href="#gzseek">gzseek</a>(file, 0L, SEEK_SET) |
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312 <p> |
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313 |
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314 <font color="Blue"><dt> z_off_t <a name="gztell">gztell</a> (gzFile file);</font> |
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315 <dd> |
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316 Returns the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the |
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317 given compressed file. This position represents a number of bytes in the |
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318 uncompressed data stream. |
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319 <p> |
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320 |
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321 <a href="#gztell">gztell</a>(file) is equivalent to <a href="#gzseek">gzseek</a>(file, 0L, SEEK_CUR) |
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322 <p> |
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323 |
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324 <font color="Blue"><dt> int <a name="gzeof">gzeof</a> (gzFile file);</font> |
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325 <dd> |
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326 Returns 1 when EOF has previously been detected reading the given |
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327 input stream, otherwise zero. |
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328 <p> |
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329 |
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330 <font color="Blue"><dt> int <a name="gzclose">gzclose</a> (gzFile file);</font> |
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331 <dd> |
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332 Flushes all pending output if necessary, closes the compressed file |
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333 and deallocates all the (de)compression <a href="#state">state</a>. The return value is the zlib |
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334 error number (see function <a href="#gzerror">gzerror</a> below). |
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335 <p> |
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336 |
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337 <font color="Blue"><dt> const char * <a name="gzerror">gzerror</a> (gzFile file, int *errnum);</font> |
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338 <dd> |
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339 Returns the error message for the last error which occurred on the |
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340 given compressed file. errnum is set to zlib error number. If an |
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341 error occurred in the file system and not in the compression library, |
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342 errnum is set to <a href="#Z_ERRNO">Z_ERRNO</a> and the application may consult errno |
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343 to get the exact error code. |
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344 <p> |
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345 </dl> |
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346 <hr> |
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347 <a name="Basic functions"><h2> Basic functions </h2> |
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348 <h3> Function list </h3> |
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349 <ul> |
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350 <li> const char * <a href="#zlibVersion">zlibVersion</a> (void); |
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351 <li> int <a href="#deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level); |
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352 <li> int <a href="#deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush); |
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353 <li> int <a href="#deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm); |
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354 <li> int <a href="#inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm); |
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355 <li> int <a href="#inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush); |
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356 <li> int <a href="#inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm); |
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357 </ul> |
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358 |
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359 <h3> Function description </h3> |
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360 <dl> |
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361 <font color="Blue"><dt> const char * <a name="zlibVersion">zlibVersion</a> (void);</font> |
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362 <dd> The application can compare <a href="#zlibVersion">zlibVersion</a> and ZLIB_VERSION for consistency. |
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363 If the first character differs, the library code actually used is |
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364 not compatible with the zlib.h header file used by the application. |
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365 This check is automatically made by <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a>. |
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366 <p> |
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367 |
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368 <font color="Blue"><dt> int <a name="deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);</font> |
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369 <dd> |
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370 Initializes the internal stream <a href="#state">state</a> for compression. The fields |
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371 <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by the caller. |
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372 If <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> are set to <a href="#Z_NULL">Z_NULL</a>, <a href="#deflateInit">deflateInit</a> updates them to |
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373 use default allocation functions. |
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374 <p> |
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375 |
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376 The compression level must be <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a>, or between 0 and 9: |
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377 1 gives best speed, 9 gives best compression, 0 gives no compression at |
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378 all (the input data is simply copied a block at a time). |
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379 <p> |
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380 |
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381 <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> requests a default compromise between speed and |
|
382 compression (currently equivalent to level 6). |
|
383 <p> |
|
384 |
|
385 <a href="#deflateInit">deflateInit</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not |
|
386 enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if level is not a valid compression level, |
|
387 <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version (<a href="#zlib_version">zlib_version</a>) is incompatible |
|
388 with the version assumed by the caller (ZLIB_VERSION). |
|
389 <a href="#msg">msg</a> is set to null if there is no error message. <a href="#deflateInit">deflateInit</a> does not |
|
390 perform any compression: this will be done by <a href="#deflate">deflate</a>(). |
|
391 <p> |
|
392 |
|
393 <font color="Blue"><dt> int <a name="deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font> |
|
394 <dd> |
|
395 <a href="#deflate">deflate</a> compresses as much data as possible, and stops when the input |
|
396 buffer becomes empty or the output buffer becomes full. It may introduce some |
|
397 output latency (reading input without producing any output) except when |
|
398 forced to flush.<p> |
|
399 |
|
400 The detailed semantics are as follows. <a href="#deflate">deflate</a> performs one or both of the |
|
401 following actions: |
|
402 |
|
403 <ul> |
|
404 <li> Compress more input starting at <a href="#next_in">next_in</a> and update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> |
|
405 accordingly. If not all input can be processed (because there is not |
|
406 enough room in the output buffer), <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> are updated and |
|
407 processing will resume at this point for the next call of <a href="#deflate">deflate</a>(). |
|
408 |
|
409 <li> |
|
410 Provide more output starting at <a href="#next_out">next_out</a> and update <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> |
|
411 accordingly. This action is forced if the parameter flush is non zero. |
|
412 Forcing flush frequently degrades the compression ratio, so this parameter |
|
413 should be set only when necessary (in interactive applications). |
|
414 Some output may be provided even if flush is not set. |
|
415 </ul> <p> |
|
416 |
|
417 Before the call of <a href="#deflate">deflate</a>(), the application should ensure that at least |
|
418 one of the actions is possible, by providing more input and/or consuming |
|
419 more output, and updating <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> accordingly ; <a href="#avail_out">avail_out</a> |
|
420 should never be zero before the call. The application can consume the |
|
421 compressed output when it wants, for example when the output buffer is full |
|
422 (<a href="#avail_out">avail_out</a> == 0), or after each call of <a href="#deflate">deflate</a>(). If <a href="#deflate">deflate</a> returns <a href="#Z_OK">Z_OK</a> |
|
423 and with zero <a href="#avail_out">avail_out</a>, it must be called again after making room in the |
|
424 output buffer because there might be more output pending. |
|
425 <p> |
|
426 |
|
427 If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, all pending output is |
|
428 flushed to the output buffer and the output is aligned on a byte boundary, so |
|
429 that the decompressor can get all input data available so far. (In particular |
|
430 <a href="#avail_in">avail_in</a> is zero after the call if enough output space has been provided |
|
431 before the call.) Flushing may degrade compression for some compression |
|
432 algorithms and so it should be used only when necessary. |
|
433 <p> |
|
434 |
|
435 If flush is set to <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>, all output is flushed as with |
|
436 <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, and the compression <a href="#state">state</a> is reset so that decompression can |
|
437 restart from this point if previous compressed data has been damaged or if |
|
438 random access is desired. Using <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a> too often can seriously degrade |
|
439 the compression. |
|
440 <p> |
|
441 |
|
442 If <a href="#deflate">deflate</a> returns with <a href="#avail_out">avail_out</a> == 0, this function must be called again |
|
443 with the same value of the flush parameter and more output space (updated |
|
444 <a href="#avail_out">avail_out</a>), until the flush is complete (<a href="#deflate">deflate</a> returns with non-zero |
|
445 <a href="#avail_out">avail_out</a>). |
|
446 <p> |
|
447 |
|
448 If the parameter flush is set to <a href="#Z_FINISH">Z_FINISH</a>, pending input is processed, |
|
449 pending output is flushed and <a href="#deflate">deflate</a> returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> if there |
|
450 was enough output space ; if <a href="#deflate">deflate</a> returns with <a href="#Z_OK">Z_OK</a>, this function must be |
|
451 called again with <a href="#Z_FINISH">Z_FINISH</a> and more output space (updated <a href="#avail_out">avail_out</a>) but no |
|
452 more input data, until it returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> or an error. After |
|
453 <a href="#deflate">deflate</a> has returned <a href="#Z_STREAM_END">Z_STREAM_END</a>, the only possible operations on the |
|
454 stream are <a href="#deflateReset">deflateReset</a> or <a href="#deflateEnd">deflateEnd</a>. |
|
455 <p> |
|
456 |
|
457 <a href="#Z_FINISH">Z_FINISH</a> can be used immediately after <a href="#deflateInit">deflateInit</a> if all the compression |
|
458 is to be done in a single step. In this case, <a href="#avail_out">avail_out</a> must be at least |
|
459 0.1% larger than <a href="#avail_in">avail_in</a> plus 12 bytes. If <a href="#deflate">deflate</a> does not return |
|
460 <a href="#Z_STREAM_END">Z_STREAM_END</a>, then it must be called again as described above. |
|
461 <p> |
|
462 |
|
463 <a href="#deflate">deflate</a>() sets strm-> <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all input read |
|
464 so far (that is, <a href="#total_in">total_in</a> bytes). |
|
465 <p> |
|
466 |
|
467 <a href="#deflate">deflate</a>() may update <a href="#data_type">data_type</a> if it can make a good guess about |
|
468 the input data type (<a href="#Z_ASCII">Z_ASCII</a> or <a href="#Z_BINARY">Z_BINARY</a>). In doubt, the data is considered |
|
469 binary. This field is only for information purposes and does not affect |
|
470 the compression algorithm in any manner. |
|
471 <p> |
|
472 |
|
473 <a href="#deflate">deflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input |
|
474 processed or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if all input has been |
|
475 consumed and all output has been produced (only when flush is set to |
|
476 <a href="#Z_FINISH">Z_FINISH</a>), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream <a href="#state">state</a> was inconsistent (for example |
|
477 if <a href="#next_in">next_in</a> or <a href="#next_out">next_out</a> was NULL), <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible |
|
478 (for example <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> was zero). |
|
479 <p> |
|
480 |
|
481 <font color="Blue"><dt> int <a name="deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
|
482 <dd> |
|
483 All dynamically allocated data structures for this stream are freed. |
|
484 This function discards any unprocessed input and does not flush any |
|
485 pending output. |
|
486 <p> |
|
487 |
|
488 <a href="#deflateEnd">deflateEnd</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the |
|
489 stream <a href="#state">state</a> was inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the stream was freed |
|
490 prematurely (some input or output was discarded). In the error case, |
|
491 <a href="#msg">msg</a> may be set but then points to a static string (which must not be |
|
492 deallocated). |
|
493 <p> |
|
494 |
|
495 <font color="Blue"><dt> int <a name="inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
|
496 <dd> |
|
497 Initializes the internal stream <a href="#state">state</a> for decompression. The fields |
|
498 <a href="#next_in">next_in</a>, <a href="#avail_in">avail_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by |
|
499 the caller. If <a href="#next_in">next_in</a> is not <a href="#Z_NULL">Z_NULL</a> and <a href="#avail_in">avail_in</a> is large enough (the exact |
|
500 value depends on the compression method), <a href="#inflateInit">inflateInit</a> determines the |
|
501 compression method from the zlib header and allocates all data structures |
|
502 accordingly ; otherwise the allocation will be deferred to the first call of |
|
503 <a href="#inflate">inflate</a>. If <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> are set to <a href="#Z_NULL">Z_NULL</a>, <a href="#inflateInit">inflateInit</a> updates them to |
|
504 use default allocation functions. |
|
505 <p> |
|
506 |
|
507 <a href="#inflateInit">inflateInit</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough |
|
508 memory, <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version is incompatible with the |
|
509 version assumed by the caller. <a href="#msg">msg</a> is set to null if there is no error |
|
510 message. <a href="#inflateInit">inflateInit</a> does not perform any decompression apart from reading |
|
511 the zlib header if present: this will be done by <a href="#inflate">inflate</a>(). (So <a href="#next_in">next_in</a> and |
|
512 <a href="#avail_in">avail_in</a> may be modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.) |
|
513 <p> |
|
514 |
|
515 <font color="Blue"><dt> int <a name="inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font> |
|
516 <dd> |
|
517 <a href="#inflate">inflate</a> decompresses as much data as possible, and stops when the input |
|
518 buffer becomes empty or the output buffer becomes full. It may some |
|
519 introduce some output latency (reading input without producing any output) |
|
520 except when forced to flush. |
|
521 <p> |
|
522 |
|
523 The detailed semantics are as follows. <a href="#inflate">inflate</a> performs one or both of the |
|
524 following actions: |
|
525 |
|
526 <ul> |
|
527 <li> Decompress more input starting at <a href="#next_in">next_in</a> and update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> |
|
528 accordingly. If not all input can be processed (because there is not |
|
529 enough room in the output buffer), <a href="#next_in">next_in</a> is updated and processing |
|
530 will resume at this point for the next call of <a href="#inflate">inflate</a>(). |
|
531 |
|
532 <li> Provide more output starting at <a href="#next_out">next_out</a> and update <a href="#next_out">next_out</a> and |
|
533 <a href="#avail_out">avail_out</a> accordingly. <a href="#inflate">inflate</a>() provides as much output as possible, |
|
534 until there is no more input data or no more space in the output buffer |
|
535 (see below about the flush parameter). |
|
536 </ul> <p> |
|
537 |
|
538 Before the call of <a href="#inflate">inflate</a>(), the application should ensure that at least |
|
539 one of the actions is possible, by providing more input and/or consuming |
|
540 more output, and updating the next_* and avail_* values accordingly. |
|
541 The application can consume the uncompressed output when it wants, for |
|
542 example when the output buffer is full (<a href="#avail_out">avail_out</a> == 0), or after each |
|
543 call of <a href="#inflate">inflate</a>(). If <a href="#inflate">inflate</a> returns <a href="#Z_OK">Z_OK</a> and with zero <a href="#avail_out">avail_out</a>, it |
|
544 must be called again after making room in the output buffer because there |
|
545 might be more output pending. |
|
546 <p> |
|
547 |
|
548 If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, <a href="#inflate">inflate</a> flushes as much |
|
549 output as possible to the output buffer. The flushing behavior of <a href="#inflate">inflate</a> is |
|
550 not specified for values of the flush parameter other than <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> |
|
551 and <a href="#Z_FINISH">Z_FINISH</a>, but the current implementation actually flushes as much output |
|
552 as possible anyway. |
|
553 <p> |
|
554 |
|
555 <a href="#inflate">inflate</a>() should normally be called until it returns <a href="#Z_STREAM_END">Z_STREAM_END</a> or an |
|
556 error. However if all decompression is to be performed in a single step |
|
557 (a single call of <a href="#inflate">inflate</a>), the parameter flush should be set to |
|
558 <a href="#Z_FINISH">Z_FINISH</a>. In this case all pending input is processed and all pending |
|
559 output is flushed ; <a href="#avail_out">avail_out</a> must be large enough to hold all the |
|
560 uncompressed data. (The size of the uncompressed data may have been saved |
|
561 by the compressor for this purpose.) The next operation on this stream must |
|
562 be <a href="#inflateEnd">inflateEnd</a> to deallocate the decompression <a href="#state">state</a>. The use of <a href="#Z_FINISH">Z_FINISH</a> |
|
563 is never required, but can be used to inform <a href="#inflate">inflate</a> that a faster routine |
|
564 may be used for the single <a href="#inflate">inflate</a>() call. |
|
565 <p> |
|
566 |
|
567 If a preset dictionary is needed at this point (see <a href="#inflateSetDictionary">inflateSetDictionary</a> |
|
568 below), <a href="#inflate">inflate</a> sets strm-<a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of the |
|
569 dictionary chosen by the compressor and returns <a href="#Z_NEED_DICT">Z_NEED_DICT</a> ; otherwise |
|
570 it sets strm-> <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all output produced |
|
571 so far (that is, <a href="#total_out">total_out</a> bytes) and returns <a href="#Z_OK">Z_OK</a>, <a href="#Z_STREAM_END">Z_STREAM_END</a> or |
|
572 an error code as described below. At the end of the stream, <a href="#inflate">inflate</a>() |
|
573 checks that its computed <a href="#adler32">adler32</a> checksum is equal to that saved by the |
|
574 compressor and returns <a href="#Z_STREAM_END">Z_STREAM_END</a> only if the checksum is correct. |
|
575 <p> |
|
576 |
|
577 <a href="#inflate">inflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input processed |
|
578 or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if the end of the compressed data has |
|
579 been reached and all uncompressed output has been produced, <a href="#Z_NEED_DICT">Z_NEED_DICT</a> if a |
|
580 preset dictionary is needed at this point, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was |
|
581 corrupted (input stream not conforming to the zlib format or incorrect |
|
582 <a href="#adler32">adler32</a> checksum), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent |
|
583 (for example if <a href="#next_in">next_in</a> or <a href="#next_out">next_out</a> was NULL), <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not |
|
584 enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible or if there was not |
|
585 enough room in the output buffer when <a href="#Z_FINISH">Z_FINISH</a> is used. In the <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> |
|
586 case, the application may then call <a href="#inflateSync">inflateSync</a> to look for a good |
|
587 compression block. |
|
588 <p> |
|
589 |
|
590 <font color="Blue"><dt> int <a name="inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
|
591 <dd> |
|
592 All dynamically allocated data structures for this stream are freed. |
|
593 This function discards any unprocessed input and does not flush any |
|
594 pending output. |
|
595 <p> |
|
596 |
|
597 <a href="#inflateEnd">inflateEnd</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream <a href="#state">state</a> |
|
598 was inconsistent. In the error case, <a href="#msg">msg</a> may be set but then points to a |
|
599 static string (which must not be deallocated). |
|
600 </dl> |
|
601 <hr> |
|
602 <a name="Advanced functions"><h2> Advanced functions </h2> |
|
603 The following functions are needed only in some special applications. |
|
604 <h3> Function list </h3> |
|
605 <ul> |
|
606 <li> int <a href="#deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, |
|
607 <li> int <a href="#deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength); |
|
608 <li> int <a href="#deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source); |
|
609 <li> int <a href="#deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm); |
|
610 <li> int <a href="#deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy); |
|
611 <li> int <a href="#inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int windowBits); |
|
612 <li> int <a href="#inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength); |
|
613 <li> int <a href="#inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm); |
|
614 <li> int <a href="#inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm); |
|
615 |
|
616 </ul> |
|
617 <h3> Function description </h3> |
|
618 <dl> |
|
619 <font color="Blue"><dt> int <a name="deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int method, int windowBits, int memLevel, int strategy);</font> |
|
620 |
|
621 <dd> This is another version of <a href="#deflateInit">deflateInit</a> with more compression options. The |
|
622 fields <a href="#next_in">next_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by |
|
623 the caller.<p> |
|
624 |
|
625 The method parameter is the compression method. It must be <a href="#Z_DEFLATED">Z_DEFLATED</a> in |
|
626 this version of the library.<p> |
|
627 |
|
628 The windowBits parameter is the base two logarithm of the window size |
|
629 (the size of the history buffer). It should be in the range 8..15 for this |
|
630 version of the library. Larger values of this parameter result in better |
|
631 compression at the expense of memory usage. The default value is 15 if |
|
632 <a href="#deflateInit">deflateInit</a> is used instead.<p> |
|
633 |
|
634 The memLevel parameter specifies how much memory should be allocated |
|
635 for the internal compression <a href="#state">state</a>. memLevel=1 uses minimum memory but |
|
636 is slow and reduces compression ratio ; memLevel=9 uses maximum memory |
|
637 for optimal speed. The default value is 8. See zconf.h for total memory |
|
638 usage as a function of windowBits and memLevel.<p> |
|
639 |
|
640 The strategy parameter is used to tune the compression algorithm. Use the |
|
641 value <a href="#Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a> for normal data, <a href="#Z_FILTERED">Z_FILTERED</a> for data produced by a |
|
642 filter (or predictor), or <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> to force Huffman encoding only (no |
|
643 string match). Filtered data consists mostly of small values with a |
|
644 somewhat random distribution. In this case, the compression algorithm is |
|
645 tuned to <a href="#compress">compress</a> them better. The effect of <a href="#Z_FILTERED">Z_FILTERED</a> is to force more |
|
646 Huffman coding and less string matching ; it is somewhat intermediate |
|
647 between Z_DEFAULT and <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a>. The strategy parameter only affects |
|
648 the compression ratio but not the correctness of the compressed output even |
|
649 if it is not set appropriately.<p> |
|
650 |
|
651 <a href="#deflateInit2">deflateInit2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough |
|
652 memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as an invalid |
|
653 method). <a href="#msg">msg</a> is set to null if there is no error message. <a href="#deflateInit2">deflateInit2</a> does |
|
654 not perform any compression: this will be done by <a href="#deflate">deflate</a>().<p> |
|
655 |
|
656 <font color="Blue"><dt> int <a name="deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);</font> |
|
657 <dd> |
|
658 Initializes the compression dictionary from the given byte sequence |
|
659 without producing any compressed output. This function must be called |
|
660 immediately after <a href="#deflateInit">deflateInit</a>, <a href="#deflateInit2">deflateInit2</a> or <a href="#deflateReset">deflateReset</a>, before any |
|
661 call of <a href="#deflate">deflate</a>. The compressor and decompressor must use exactly the same |
|
662 dictionary (see <a href="#inflateSetDictionary">inflateSetDictionary</a>).<p> |
|
663 |
|
664 The dictionary should consist of strings (byte sequences) that are likely |
|
665 to be encountered later in the data to be compressed, with the most commonly |
|
666 used strings preferably put towards the end of the dictionary. Using a |
|
667 dictionary is most useful when the data to be compressed is short and can be |
|
668 predicted with good accuracy ; the data can then be compressed better than |
|
669 with the default empty dictionary.<p> |
|
670 |
|
671 Depending on the size of the compression data structures selected by |
|
672 <a href="#deflateInit">deflateInit</a> or <a href="#deflateInit2">deflateInit2</a>, a part of the dictionary may in effect be |
|
673 discarded, for example if the dictionary is larger than the window size in |
|
674 <a href="#deflate">deflate</a> or deflate2. Thus the strings most likely to be useful should be |
|
675 put at the end of the dictionary, not at the front.<p> |
|
676 |
|
677 Upon return of this function, strm-> <a href="#adler">adler</a> is set to the Adler32 value |
|
678 of the dictionary ; the decompressor may later use this value to determine |
|
679 which dictionary has been used by the compressor. (The Adler32 value |
|
680 applies to the whole dictionary even if only a subset of the dictionary is |
|
681 actually used by the compressor.)<p> |
|
682 |
|
683 <a href="#deflateSetDictionary">deflateSetDictionary</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a |
|
684 parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is |
|
685 inconsistent (for example if <a href="#deflate">deflate</a> has already been called for this stream |
|
686 or if the compression method is bsort). <a href="#deflateSetDictionary">deflateSetDictionary</a> does not |
|
687 perform any compression: this will be done by <a href="#deflate">deflate</a>().<p> |
|
688 |
|
689 <font color="Blue"><dt> int <a name="deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source);</font> |
|
690 <dd> |
|
691 Sets the destination stream as a complete copy of the source stream.<p> |
|
692 |
|
693 This function can be useful when several compression strategies will be |
|
694 tried, for example when there are several ways of pre-processing the input |
|
695 data with a filter. The streams that will be discarded should then be freed |
|
696 by calling <a href="#deflateEnd">deflateEnd</a>. Note that <a href="#deflateCopy">deflateCopy</a> duplicates the internal |
|
697 compression <a href="#state">state</a> which can be quite large, so this strategy is slow and |
|
698 can consume lots of memory.<p> |
|
699 |
|
700 <a href="#deflateCopy">deflateCopy</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not |
|
701 enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source stream <a href="#state">state</a> was inconsistent |
|
702 (such as <a href="#zalloc">zalloc</a> being NULL). <a href="#msg">msg</a> is left unchanged in both source and |
|
703 destination.<p> |
|
704 |
|
705 <font color="Blue"><dt> int <a name="deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
|
706 <dd> This function is equivalent to <a href="#deflateEnd">deflateEnd</a> followed by <a href="#deflateInit">deflateInit</a>, |
|
707 but does not free and reallocate all the internal compression <a href="#state">state</a>. |
|
708 The stream will keep the same compression level and any other attributes |
|
709 that may have been set by <a href="#deflateInit2">deflateInit2</a>.<p> |
|
710 |
|
711 <a href="#deflateReset">deflateReset</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source |
|
712 stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).<p> |
|
713 |
|
714 <font color="Blue"><dt> int <a name="deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);</font> |
|
715 <dd> |
|
716 Dynamically update the compression level and compression strategy. The |
|
717 interpretation of level and strategy is as in <a href="#deflateInit2">deflateInit2</a>. This can be |
|
718 used to switch between compression and straight copy of the input data, or |
|
719 to switch to a different kind of input data requiring a different |
|
720 strategy. If the compression level is changed, the input available so far |
|
721 is compressed with the old level (and may be flushed); the new level will |
|
722 take effect only at the next call of <a href="#deflate">deflate</a>().<p> |
|
723 |
|
724 Before the call of <a href="#deflateParams">deflateParams</a>, the stream <a href="#state">state</a> must be set as for |
|
725 a call of <a href="#deflate">deflate</a>(), since the currently available input may have to |
|
726 be compressed and flushed. In particular, strm-> <a href="#avail_out">avail_out</a> must be |
|
727 non-zero.<p> |
|
728 |
|
729 <a href="#deflateParams">deflateParams</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source |
|
730 stream <a href="#state">state</a> was inconsistent or if a parameter was invalid, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> |
|
731 if strm->avail_out was zero.<p> |
|
732 |
|
733 <font color="Blue"><dt> int <a name="inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int windowBits);</font> |
|
734 |
|
735 <dd> This is another version of <a href="#inflateInit">inflateInit</a> with an extra parameter. The |
|
736 fields <a href="#next_in">next_in</a>, <a href="#avail_in">avail_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized |
|
737 before by the caller.<p> |
|
738 |
|
739 The windowBits parameter is the base two logarithm of the maximum window |
|
740 size (the size of the history buffer). It should be in the range 8..15 for |
|
741 this version of the library. The default value is 15 if <a href="#inflateInit">inflateInit</a> is used |
|
742 instead. If a compressed stream with a larger window size is given as |
|
743 input, <a href="#inflate">inflate</a>() will return with the error code <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> instead of |
|
744 trying to allocate a larger window.<p> |
|
745 |
|
746 <a href="#inflateInit2">inflateInit2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough |
|
747 memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as a negative |
|
748 memLevel). <a href="#msg">msg</a> is set to null if there is no error message. <a href="#inflateInit2">inflateInit2</a> |
|
749 does not perform any decompression apart from reading the zlib header if |
|
750 present: this will be done by <a href="#inflate">inflate</a>(). (So <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> may be |
|
751 modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.)<p> |
|
752 |
|
753 <font color="Blue"><dt> int <a name="inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);</font> |
|
754 <dd> |
|
755 Initializes the decompression dictionary from the given uncompressed byte |
|
756 sequence. This function must be called immediately after a call of <a href="#inflate">inflate</a> |
|
757 if this call returned <a href="#Z_NEED_DICT">Z_NEED_DICT</a>. The dictionary chosen by the compressor |
|
758 can be determined from the Adler32 value returned by this call of |
|
759 <a href="#inflate">inflate</a>. The compressor and decompressor must use exactly the same |
|
760 dictionary (see <a href="#deflateSetDictionary">deflateSetDictionary</a>).<p> |
|
761 |
|
762 <a href="#inflateSetDictionary">inflateSetDictionary</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a |
|
763 parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is |
|
764 inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the given dictionary doesn't match the |
|
765 expected one (incorrect Adler32 value). <a href="#inflateSetDictionary">inflateSetDictionary</a> does not |
|
766 perform any decompression: this will be done by subsequent calls of |
|
767 <a href="#inflate">inflate</a>().<p> |
|
768 |
|
769 <font color="Blue"><dt> int <a name="inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
|
770 |
|
771 <dd> Skips invalid compressed data until a full flush point (see above the |
|
772 description of <a href="#deflate">deflate</a> with <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>) can be found, or until all |
|
773 available input is skipped. No output is provided.<p> |
|
774 |
|
775 <a href="#inflateSync">inflateSync</a> returns <a href="#Z_OK">Z_OK</a> if a full flush point has been found, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> |
|
776 if no more input was provided, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if no flush point has been found, |
|
777 or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent. In the success |
|
778 case, the application may save the current current value of <a href="#total_in">total_in</a> which |
|
779 indicates where valid compressed data was found. In the error case, the |
|
780 application may repeatedly call <a href="#inflateSync">inflateSync</a>, providing more input each time, |
|
781 until success or end of the input data.<p> |
|
782 |
|
783 <font color="Blue"><dt> int <a name="inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
|
784 <dd> |
|
785 This function is equivalent to <a href="#inflateEnd">inflateEnd</a> followed by <a href="#inflateInit">inflateInit</a>, |
|
786 but does not free and reallocate all the internal decompression <a href="#state">state</a>. |
|
787 The stream will keep attributes that may have been set by <a href="#inflateInit2">inflateInit2</a>. |
|
788 <p> |
|
789 |
|
790 <a href="#inflateReset">inflateReset</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source |
|
791 stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL). |
|
792 <p> |
|
793 </dl> |
|
794 |
|
795 <hr> |
|
796 <a name="Checksum functions"><h2> Checksum functions </h2> |
|
797 These functions are not related to compression but are exported |
|
798 anyway because they might be useful in applications using the |
|
799 compression library. |
|
800 <h3> Function list </h3> |
|
801 <ul> |
|
802 <li> uLong <a href="#adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len); |
|
803 <li> uLong <a href="#crc32">crc32</a> (uLong crc, const Bytef *buf, uInt len); |
|
804 </ul> |
|
805 <h3> Function description </h3> |
|
806 <dl> |
|
807 <font color="Blue"><dt> uLong <a name="adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);</font> |
|
808 <dd> |
|
809 Update a running Adler-32 checksum with the bytes buf[0..len-1] and |
|
810 return the updated checksum. If buf is NULL, this function returns |
|
811 the required initial value for the checksum. |
|
812 <p> |
|
813 An Adler-32 checksum is almost as reliable as a CRC32 but can be computed |
|
814 much faster. Usage example: |
|
815 <pre> |
|
816 |
|
817 uLong <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0); |
|
818 |
|
819 while (read_buffer(buffer, length) != EOF) { |
|
820 <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(<a href="#adler">adler</a>, buffer, length); |
|
821 } |
|
822 if (<a href="#adler">adler</a> != original_adler) error(); |
|
823 </pre> |
|
824 |
|
825 <font color="Blue"><dt> uLong <a name="crc32">crc32</a> (uLong crc, const Bytef *buf, uInt len);</font> |
|
826 <dd> |
|
827 Update a running crc with the bytes buf[0..len-1] and return the updated |
|
828 crc. If buf is NULL, this function returns the required initial value |
|
829 for the crc. Pre- and post-conditioning (one's complement) is performed |
|
830 within this function so it shouldn't be done by the application. |
|
831 Usage example: |
|
832 <pre> |
|
833 |
|
834 uLong crc = <a href="#crc32">crc32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0); |
|
835 |
|
836 while (read_buffer(buffer, length) != EOF) { |
|
837 crc = <a href="#crc32">crc32</a>(crc, buffer, length); |
|
838 } |
|
839 if (crc != original_crc) error(); |
|
840 </pre> |
|
841 </dl> |
|
842 <hr> |
|
843 <a name="struct z_stream_s"><h2> struct z_stream_s </h2> |
|
844 <font color="Blue"> |
|
845 <a name="z_stream_s"> |
|
846 <pre> |
|
847 typedef struct z_stream_s { |
|
848 Bytef *<a name="next_in">next_in</a>; /* next input byte */ |
|
849 uInt <a name="avail_in">avail_in</a>; /* number of bytes available at <a href="#next_in">next_in</a> */ |
|
850 uLong <a name="total_in">total_in</a>; /* total nb of input bytes read so far */ |
|
851 |
|
852 Bytef *<a name="next_out">next_out</a>; /* next output byte should be put there */ |
|
853 uInt <a name="avail_out">avail_out</a>; /* remaining free space at <a href="#next_out">next_out</a> */ |
|
854 uLong <a name="total_out">total_out</a>; /* total nb of bytes output so far */ |
|
855 |
|
856 char *<a name="msg">msg</a>; /* last error message, NULL if no error */ |
|
857 struct internal_state FAR *<a name="state">state</a>; /* not visible by applications */ |
|
858 |
|
859 alloc_func <a name="zalloc">zalloc</a>; /* used to allocate the internal <a href="#state">state</a> */ |
|
860 free_func <a name="zfree">zfree</a>; /* used to free the internal <a href="#state">state</a> */ |
|
861 voidpf <a name="opaque">opaque</a>; /* private data object passed to <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> */ |
|
862 |
|
863 int <a name="data_type">data_type</a>; /* best guess about the data type: ascii or binary */ |
|
864 uLong <a name="adler">adler</a>; /* <a href="#adler32">adler32</a> value of the uncompressed data */ |
|
865 uLong <a name="reserved">reserved</a>; /* <a href="#reserved">reserved</a> for future use */ |
|
866 } <a href="#z_stream_s">z_stream</a> ; |
|
867 |
|
868 typedef <a href="#z_stream_s">z_stream</a> FAR * <a name="z_streamp">z_streamp</a>; ÿ |
|
869 </pre> |
|
870 </font> |
|
871 The application must update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> when <a href="#avail_in">avail_in</a> has |
|
872 dropped to zero. It must update <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> when <a href="#avail_out">avail_out</a> |
|
873 has dropped to zero. The application must initialize <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and |
|
874 <a href="#opaque">opaque</a> before calling the init function. All other fields are set by the |
|
875 compression library and must not be updated by the application. <p> |
|
876 |
|
877 The <a href="#opaque">opaque</a> value provided by the application will be passed as the first |
|
878 parameter for calls of <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a>. This can be useful for custom |
|
879 memory management. The compression library attaches no meaning to the |
|
880 <a href="#opaque">opaque</a> value. <p> |
|
881 |
|
882 <a href="#zalloc">zalloc</a> must return <a href="#Z_NULL">Z_NULL</a> if there is not enough memory for the object. |
|
883 If zlib is used in a multi-threaded application, <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be |
|
884 thread safe. <p> |
|
885 |
|
886 On 16-bit systems, the functions <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be able to allocate |
|
887 exactly 65536 bytes, but will not be required to allocate more than this |
|
888 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS, |
|
889 pointers returned by <a href="#zalloc">zalloc</a> for objects of exactly 65536 bytes *must* |
|
890 have their offset normalized to zero. The default allocation function |
|
891 provided by this library ensures this (see zutil.c). To reduce memory |
|
892 requirements and avoid any allocation of 64K objects, at the expense of |
|
893 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h). |
|
894 <p> |
|
895 |
|
896 The fields <a href="#total_in">total_in</a> and <a href="#total_out">total_out</a> can be used for statistics or |
|
897 progress reports. After compression, <a href="#total_in">total_in</a> holds the total size of |
|
898 the uncompressed data and may be saved for use in the decompressor |
|
899 (particularly if the decompressor wants to decompress everything in |
|
900 a single step). <p> |
|
901 |
|
902 <hr> |
|
903 <a name="Constants"><h2> Constants </h2> |
|
904 <font color="Blue"> |
|
905 <pre> |
|
906 #define <a name="Z_NO_FLUSH">Z_NO_FLUSH</a> 0 |
|
907 #define <a name="Z_PARTIAL_FLUSH">Z_PARTIAL_FLUSH</a> 1 |
|
908 /* will be removed, use <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> instead */ |
|
909 #define <a name="Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> 2 |
|
910 #define <a name="Z_FULL_FLUSH">Z_FULL_FLUSH</a> 3 |
|
911 #define <a name="Z_FINISH">Z_FINISH</a> 4 |
|
912 /* Allowed flush values ; see <a href="#deflate">deflate</a>() below for details */ |
|
913 |
|
914 #define <a name="Z_OK">Z_OK</a> 0 |
|
915 #define <a name="Z_STREAM_END">Z_STREAM_END</a> 1 |
|
916 #define <a name="Z_NEED_DICT">Z_NEED_DICT</a> 2 |
|
917 #define <a name="Z_ERRNO">Z_ERRNO</a> (-1) |
|
918 #define <a name="Z_STREAM_ERROR">Z_STREAM_ERROR</a> (-2) |
|
919 #define <a name="Z_DATA_ERROR">Z_DATA_ERROR</a> (-3) |
|
920 #define <a name="Z_MEM_ERROR">Z_MEM_ERROR</a> (-4) |
|
921 #define <a name="Z_BUF_ERROR">Z_BUF_ERROR</a> (-5) |
|
922 #define <a name="Z_VERSION_ERROR">Z_VERSION_ERROR</a> (-6) |
|
923 /* Return codes for the compression/decompression functions. Negative |
|
924 * values are errors, positive values are used for special but normal events. |
|
925 */ |
|
926 |
|
927 #define <a name="Z_NO_COMPRESSION">Z_NO_COMPRESSION</a> 0 |
|
928 #define <a name="Z_BEST_SPEED">Z_BEST_SPEED</a> 1 |
|
929 #define <a name="Z_BEST_COMPRESSION">Z_BEST_COMPRESSION</a> 9 |
|
930 #define <a name="Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> (-1) |
|
931 /* compression levels */ |
|
932 |
|
933 #define <a name="Z_FILTERED">Z_FILTERED</a> 1 |
|
934 #define <a name="Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> 2 |
|
935 #define <a name="Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a> 0 |
|
936 /* compression strategy ; see <a href="#deflateInit2">deflateInit2</a>() below for details */ |
|
937 |
|
938 #define <a name="Z_BINARY">Z_BINARY</a> 0 |
|
939 #define <a name="Z_ASCII">Z_ASCII</a> 1 |
|
940 #define <a name="Z_UNKNOWN">Z_UNKNOWN</a> 2 |
|
941 /* Possible values of the <a href="#data_type">data_type</a> field */ |
|
942 |
|
943 #define <a name="Z_DEFLATED">Z_DEFLATED</a> 8 |
|
944 /* The <a href="#deflate">deflate</a> compression method (the only one supported in this version) */ |
|
945 |
|
946 #define <a name="Z_NULL">Z_NULL</a> 0 /* for initializing <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a>, <a href="#opaque">opaque</a> */ |
|
947 |
|
948 #define <a name="zlib_version">zlib_version</a> <a href="#zlibVersion">zlibVersion</a>() |
|
949 /* for compatibility with versions less than 1.0.2 */ |
|
950 </pre> |
|
951 </font> |
|
952 |
|
953 <hr> |
|
954 <a name="Misc"><h2> Misc </h2> |
|
955 <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a> are macros to allow checking the zlib version |
|
956 and the compiler's view of <a href="#z_stream_s">z_stream</a>. |
|
957 <p> |
|
958 Other functions: |
|
959 <dl> |
|
960 <font color="Blue"><dt> const char * <a name="zError">zError</a> (int err);</font> |
|
961 <font color="Blue"><dt> int <a name="inflateSyncPoint">inflateSyncPoint</a> (<a href="#z_streamp">z_streamp</a> z);</font> |
|
962 <font color="Blue"><dt> const uLongf * <a name="get_crc_table">get_crc_table</a> (void);</font> |
|
963 </dl> |
|
964 <hr> |
|
965 <font size="-1"> |
|
966 Last update: Wed Oct 13 20:42:34 1999<br> |
|
967 piapi@csie.ntu.edu.tw |
|
968 </font> |
|
969 |
|
970 </body> |
|
971 </html> |