MediaWiki REL1_33
GIFMetadataExtractor.php
Go to the documentation of this file.
1<?php
36 private static $gifFrameSep;
37
39 private static $gifExtensionSep;
40
42 private static $gifTerm;
43
44 const VERSION = 1;
45
46 // Each sub-block is less than or equal to 255 bytes.
47 // Most of the time its 255 bytes, except for in XMP
48 // blocks, where it's usually between 32-127 bytes each.
49 const MAX_SUBBLOCKS = 262144; // 5mb divided by 20.
50
56 static function getMetadata( $filename ) {
57 self::$gifFrameSep = pack( "C", ord( "," ) ); // 2C
58 self::$gifExtensionSep = pack( "C", ord( "!" ) ); // 21
59 self::$gifTerm = pack( "C", ord( ";" ) ); // 3B
60
61 $frameCount = 0;
62 $duration = 0.0;
63 $isLooped = false;
64 $xmp = "";
65 $comment = [];
66
67 if ( !$filename ) {
68 throw new Exception( "No file name specified" );
69 } elseif ( !file_exists( $filename ) || is_dir( $filename ) ) {
70 throw new Exception( "File $filename does not exist" );
71 }
72
73 $fh = fopen( $filename, 'rb' );
74
75 if ( !$fh ) {
76 throw new Exception( "Unable to open file $filename" );
77 }
78
79 // Check for the GIF header
80 $buf = fread( $fh, 6 );
81 if ( !( $buf == 'GIF87a' || $buf == 'GIF89a' ) ) {
82 throw new Exception( "Not a valid GIF file; header: $buf" );
83 }
84
85 // Read width and height.
86 $buf = fread( $fh, 2 );
87 $width = unpack( 'v', $buf )[1];
88 $buf = fread( $fh, 2 );
89 $height = unpack( 'v', $buf )[1];
90
91 // Read BPP
92 $buf = fread( $fh, 1 );
93 $bpp = self::decodeBPP( $buf );
94
95 // Skip over background and aspect ratio
96 fread( $fh, 2 );
97
98 // Skip over the GCT
99 self::readGCT( $fh, $bpp );
100
101 while ( !feof( $fh ) ) {
102 $buf = fread( $fh, 1 );
103
104 if ( $buf == self::$gifFrameSep ) {
105 // Found a frame
106 $frameCount++;
107
108 # # Skip bounding box
109 fread( $fh, 8 );
110
111 # # Read BPP
112 $buf = fread( $fh, 1 );
113 $bpp = self::decodeBPP( $buf );
114
115 # # Read GCT
116 self::readGCT( $fh, $bpp );
117 fread( $fh, 1 );
118 self::skipBlock( $fh );
119 } elseif ( $buf == self::$gifExtensionSep ) {
120 $buf = fread( $fh, 1 );
121 if ( strlen( $buf ) < 1 ) {
122 throw new Exception( "Ran out of input" );
123 }
124 $extension_code = unpack( 'C', $buf )[1];
125
126 if ( $extension_code == 0xF9 ) {
127 // Graphics Control Extension.
128 fread( $fh, 1 ); // Block size
129
130 fread( $fh, 1 ); // Transparency, disposal method, user input
131
132 $buf = fread( $fh, 2 ); // Delay, in hundredths of seconds.
133 if ( strlen( $buf ) < 2 ) {
134 throw new Exception( "Ran out of input" );
135 }
136 $delay = unpack( 'v', $buf )[1];
137 $duration += $delay * 0.01;
138
139 fread( $fh, 1 ); // Transparent colour index
140
141 $term = fread( $fh, 1 ); // Should be a terminator
142 if ( strlen( $term ) < 1 ) {
143 throw new Exception( "Ran out of input" );
144 }
145 $term = unpack( 'C', $term )[1];
146 if ( $term != 0 ) {
147 throw new Exception( "Malformed Graphics Control Extension block" );
148 }
149 } elseif ( $extension_code == 0xFE ) {
150 // Comment block(s).
151 $data = self::readBlock( $fh );
152 if ( $data === "" ) {
153 throw new Exception( 'Read error, zero-length comment block' );
154 }
155
156 // The standard says this should be ASCII, however its unclear if
157 // thats true in practise. Check to see if its valid utf-8, if so
158 // assume its that, otherwise assume its windows-1252 (iso-8859-1)
159 $dataCopy = $data;
160 // quickIsNFCVerify has the side effect of replacing any invalid characters
161 UtfNormal\Validator::quickIsNFCVerify( $dataCopy );
162
163 if ( $dataCopy !== $data ) {
164 Wikimedia\suppressWarnings();
165 $data = iconv( 'windows-1252', 'UTF-8', $data );
166 Wikimedia\restoreWarnings();
167 }
168
169 $commentCount = count( $comment );
170 if ( $commentCount === 0
171 || $comment[$commentCount - 1] !== $data
172 ) {
173 // Some applications repeat the same comment on each
174 // frame of an animated GIF image, so if this comment
175 // is identical to the last, only extract once.
176 $comment[] = $data;
177 }
178 } elseif ( $extension_code == 0xFF ) {
179 // Application extension (Netscape info about the animated gif)
180 // or XMP (or theoretically any other type of extension block)
181 $blockLength = fread( $fh, 1 );
182 if ( strlen( $blockLength ) < 1 ) {
183 throw new Exception( "Ran out of input" );
184 }
185 $blockLength = unpack( 'C', $blockLength )[1];
186 $data = fread( $fh, $blockLength );
187
188 if ( $blockLength != 11 ) {
189 wfDebug( __METHOD__ . " GIF application block with wrong length\n" );
190 fseek( $fh, -( $blockLength + 1 ), SEEK_CUR );
191 self::skipBlock( $fh );
192 continue;
193 }
194
195 // NETSCAPE2.0 (application name for animated gif)
196 if ( $data == 'NETSCAPE2.0' ) {
197 $data = fread( $fh, 2 ); // Block length and introduction, should be 03 01
198
199 if ( $data != "\x03\x01" ) {
200 throw new Exception( "Expected \x03\x01, got $data" );
201 }
202
203 // Unsigned little-endian integer, loop count or zero for "forever"
204 $loopData = fread( $fh, 2 );
205 if ( strlen( $loopData ) < 2 ) {
206 throw new Exception( "Ran out of input" );
207 }
208 $loopCount = unpack( 'v', $loopData )[1];
209
210 if ( $loopCount != 1 ) {
211 $isLooped = true;
212 }
213
214 // Read out terminator byte
215 fread( $fh, 1 );
216 } elseif ( $data == 'XMP DataXMP' ) {
217 // application name for XMP data.
218 // see pg 18 of XMP spec part 3.
219
220 $xmp = self::readBlock( $fh, true );
221
222 if ( substr( $xmp, -257, 3 ) !== "\x01\xFF\xFE"
223 || substr( $xmp, -4 ) !== "\x03\x02\x01\x00"
224 ) {
225 // this is just a sanity check.
226 throw new Exception( "XMP does not have magic trailer!" );
227 }
228
229 // strip out trailer.
230 $xmp = substr( $xmp, 0, -257 );
231 } else {
232 // unrecognized extension block
233 fseek( $fh, -( $blockLength + 1 ), SEEK_CUR );
234 self::skipBlock( $fh );
235 continue;
236 }
237 } else {
238 self::skipBlock( $fh );
239 }
240 } elseif ( $buf == self::$gifTerm ) {
241 break;
242 } else {
243 if ( strlen( $buf ) < 1 ) {
244 throw new Exception( "Ran out of input" );
245 }
246 $byte = unpack( 'C', $buf )[1];
247 throw new Exception( "At position: " . ftell( $fh ) . ", Unknown byte " . $byte );
248 }
249 }
250
251 return [
252 'frameCount' => $frameCount,
253 'looped' => $isLooped,
254 'duration' => $duration,
255 'xmp' => $xmp,
256 'comment' => $comment,
257 ];
258 }
259
265 static function readGCT( $fh, $bpp ) {
266 if ( $bpp > 0 ) {
267 $max = 2 ** $bpp;
268 for ( $i = 1; $i <= $max; ++$i ) {
269 fread( $fh, 3 );
270 }
271 }
272 }
273
279 static function decodeBPP( $data ) {
280 if ( strlen( $data ) < 1 ) {
281 throw new Exception( "Ran out of input" );
282 }
283 $buf = unpack( 'C', $data )[1];
284 $bpp = ( $buf & 7 ) + 1;
285 $buf >>= 7;
286
287 $have_map = $buf & 1;
288
289 return $have_map ? $bpp : 0;
290 }
291
296 static function skipBlock( $fh ) {
297 while ( !feof( $fh ) ) {
298 $buf = fread( $fh, 1 );
299 if ( strlen( $buf ) < 1 ) {
300 throw new Exception( "Ran out of input" );
301 }
302 $block_len = unpack( 'C', $buf )[1];
303 if ( $block_len == 0 ) {
304 return;
305 }
306 fread( $fh, $block_len );
307 }
308 }
309
324 static function readBlock( $fh, $includeLengths = false ) {
325 $data = '';
326 $subLength = fread( $fh, 1 );
327 $blocks = 0;
328
329 while ( $subLength !== "\0" ) {
330 $blocks++;
331 if ( $blocks > self::MAX_SUBBLOCKS ) {
332 throw new Exception( "MAX_SUBBLOCKS exceeded (over $blocks sub-blocks)" );
333 }
334 if ( feof( $fh ) ) {
335 throw new Exception( "Read error: Unexpected EOF." );
336 }
337 if ( $includeLengths ) {
338 $data .= $subLength;
339 }
340
341 $data .= fread( $fh, ord( $subLength ) );
342 $subLength = fread( $fh, 1 );
343 }
344
345 return $data;
346 }
347}
wfDebug( $text, $dest='all', array $context=[])
Sends a line to the debug log if enabled or, optionally, to a comment in output.
static getMetadata( $filename)
static readBlock( $fh, $includeLengths=false)
Read a block.
$data
Utility to generate mapping file used in mw.Title (phpCharToUpper.json)
whereas SearchGetNearMatch runs after $term
Definition hooks.txt:2889
injection txt This is an overview of how MediaWiki makes use of dependency injection The design described here grew from the discussion of RFC T384 The term dependency this means that anything an object needs to operate should be injected from the the object itself should only know narrow no concrete implementation of the logic it relies on The requirement to inject everything typically results in an architecture that based on two main types of and essentially stateless service objects that use other service objects to operate on the value objects As of the beginning MediaWiki is only starting to use the DI approach Much of the code still relies on global state or direct resulting in a highly cyclical dependency which acts as the top level factory for services in MediaWiki which can be used to gain access to default instances of various services MediaWikiServices however also allows new services to be defined and default services to be redefined Services are defined or redefined by providing a callback the instantiator that will return a new instance of the service When it will create an instance of MediaWikiServices and populate it with the services defined in the files listed by thereby bootstrapping the DI framework Per $wgServiceWiringFiles lists includes ServiceWiring php
Definition injection.txt:37