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+<?php
+/**
+ * GIF frame counter.
+ *
+ * Originally written in Perl by Steve Sanbeg.
+ * Ported to PHP by Andrew Garrett
+ * Deliberately not using MWExceptions to avoid external dependencies, encouraging
+ * redistribution.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Media
+ */
+
+/**
+ * GIF frame counter.
+ *
+ * @ingroup Media
+ */
+class GIFMetadataExtractor {
+ /** @var string */
+ private static $gifFrameSep;
+
+ /** @var string */
+ private static $gifExtensionSep;
+
+ /** @var string */
+ private static $gifTerm;
+
+ const VERSION = 1;
+
+ // Each sub-block is less than or equal to 255 bytes.
+ // Most of the time its 255 bytes, except for in XMP
+ // blocks, where it's usually between 32-127 bytes each.
+ const MAX_SUBBLOCKS = 262144; // 5mb divided by 20.
+
+ /**
+ * @throws Exception
+ * @param string $filename
+ * @return array
+ */
+ static function getMetadata( $filename ) {
+ self::$gifFrameSep = pack( "C", ord( "," ) ); // 2C
+ self::$gifExtensionSep = pack( "C", ord( "!" ) ); // 21
+ self::$gifTerm = pack( "C", ord( ";" ) ); // 3B
+
+ $frameCount = 0;
+ $duration = 0.0;
+ $isLooped = false;
+ $xmp = "";
+ $comment = [];
+
+ if ( !$filename ) {
+ throw new Exception( "No file name specified" );
+ } elseif ( !file_exists( $filename ) || is_dir( $filename ) ) {
+ throw new Exception( "File $filename does not exist" );
+ }
+
+ $fh = fopen( $filename, 'rb' );
+
+ if ( !$fh ) {
+ throw new Exception( "Unable to open file $filename" );
+ }
+
+ // Check for the GIF header
+ $buf = fread( $fh, 6 );
+ if ( !( $buf == 'GIF87a' || $buf == 'GIF89a' ) ) {
+ throw new Exception( "Not a valid GIF file; header: $buf" );
+ }
+
+ // Read width and height.
+ $buf = fread( $fh, 2 );
+ $width = unpack( 'v', $buf )[1];
+ $buf = fread( $fh, 2 );
+ $height = unpack( 'v', $buf )[1];
+
+ // Read BPP
+ $buf = fread( $fh, 1 );
+ $bpp = self::decodeBPP( $buf );
+
+ // Skip over background and aspect ratio
+ fread( $fh, 2 );
+
+ // Skip over the GCT
+ self::readGCT( $fh, $bpp );
+
+ while ( !feof( $fh ) ) {
+ $buf = fread( $fh, 1 );
+
+ if ( $buf == self::$gifFrameSep ) {
+ // Found a frame
+ $frameCount++;
+
+ # # Skip bounding box
+ fread( $fh, 8 );
+
+ # # Read BPP
+ $buf = fread( $fh, 1 );
+ $bpp = self::decodeBPP( $buf );
+
+ # # Read GCT
+ self::readGCT( $fh, $bpp );
+ fread( $fh, 1 );
+ self::skipBlock( $fh );
+ } elseif ( $buf == self::$gifExtensionSep ) {
+ $buf = fread( $fh, 1 );
+ if ( strlen( $buf ) < 1 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $extension_code = unpack( 'C', $buf )[1];
+
+ if ( $extension_code == 0xF9 ) {
+ // Graphics Control Extension.
+ fread( $fh, 1 ); // Block size
+
+ fread( $fh, 1 ); // Transparency, disposal method, user input
+
+ $buf = fread( $fh, 2 ); // Delay, in hundredths of seconds.
+ if ( strlen( $buf ) < 2 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $delay = unpack( 'v', $buf )[1];
+ $duration += $delay * 0.01;
+
+ fread( $fh, 1 ); // Transparent colour index
+
+ $term = fread( $fh, 1 ); // Should be a terminator
+ if ( strlen( $term ) < 1 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $term = unpack( 'C', $term )[1];
+ if ( $term != 0 ) {
+ throw new Exception( "Malformed Graphics Control Extension block" );
+ }
+ } elseif ( $extension_code == 0xFE ) {
+ // Comment block(s).
+ $data = self::readBlock( $fh );
+ if ( $data === "" ) {
+ throw new Exception( 'Read error, zero-length comment block' );
+ }
+
+ // The standard says this should be ASCII, however its unclear if
+ // thats true in practise. Check to see if its valid utf-8, if so
+ // assume its that, otherwise assume its windows-1252 (iso-8859-1)
+ $dataCopy = $data;
+ // quickIsNFCVerify has the side effect of replacing any invalid characters
+ UtfNormal\Validator::quickIsNFCVerify( $dataCopy );
+
+ if ( $dataCopy !== $data ) {
+ Wikimedia\suppressWarnings();
+ $data = iconv( 'windows-1252', 'UTF-8', $data );
+ Wikimedia\restoreWarnings();
+ }
+
+ $commentCount = count( $comment );
+ if ( $commentCount === 0
+ || $comment[$commentCount - 1] !== $data
+ ) {
+ // Some applications repeat the same comment on each
+ // frame of an animated GIF image, so if this comment
+ // is identical to the last, only extract once.
+ $comment[] = $data;
+ }
+ } elseif ( $extension_code == 0xFF ) {
+ // Application extension (Netscape info about the animated gif)
+ // or XMP (or theoretically any other type of extension block)
+ $blockLength = fread( $fh, 1 );
+ if ( strlen( $blockLength ) < 1 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $blockLength = unpack( 'C', $blockLength )[1];
+ $data = fread( $fh, $blockLength );
+
+ if ( $blockLength != 11 ) {
+ wfDebug( __METHOD__ . " GIF application block with wrong length\n" );
+ fseek( $fh, -( $blockLength + 1 ), SEEK_CUR );
+ self::skipBlock( $fh );
+ continue;
+ }
+
+ // NETSCAPE2.0 (application name for animated gif)
+ if ( $data == 'NETSCAPE2.0' ) {
+ $data = fread( $fh, 2 ); // Block length and introduction, should be 03 01
+
+ if ( $data != "\x03\x01" ) {
+ throw new Exception( "Expected \x03\x01, got $data" );
+ }
+
+ // Unsigned little-endian integer, loop count or zero for "forever"
+ $loopData = fread( $fh, 2 );
+ if ( strlen( $loopData ) < 2 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $loopCount = unpack( 'v', $loopData )[1];
+
+ if ( $loopCount != 1 ) {
+ $isLooped = true;
+ }
+
+ // Read out terminator byte
+ fread( $fh, 1 );
+ } elseif ( $data == 'XMP DataXMP' ) {
+ // application name for XMP data.
+ // see pg 18 of XMP spec part 3.
+
+ $xmp = self::readBlock( $fh, true );
+
+ if ( substr( $xmp, -257, 3 ) !== "\x01\xFF\xFE"
+ || substr( $xmp, -4 ) !== "\x03\x02\x01\x00"
+ ) {
+ // this is just a sanity check.
+ throw new Exception( "XMP does not have magic trailer!" );
+ }
+
+ // strip out trailer.
+ $xmp = substr( $xmp, 0, -257 );
+ } else {
+ // unrecognized extension block
+ fseek( $fh, -( $blockLength + 1 ), SEEK_CUR );
+ self::skipBlock( $fh );
+ continue;
+ }
+ } else {
+ self::skipBlock( $fh );
+ }
+ } elseif ( $buf == self::$gifTerm ) {
+ break;
+ } else {
+ if ( strlen( $buf ) < 1 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $byte = unpack( 'C', $buf )[1];
+ throw new Exception( "At position: " . ftell( $fh ) . ", Unknown byte " . $byte );
+ }
+ }
+
+ return [
+ 'frameCount' => $frameCount,
+ 'looped' => $isLooped,
+ 'duration' => $duration,
+ 'xmp' => $xmp,
+ 'comment' => $comment,
+ ];
+ }
+
+ /**
+ * @param resource $fh
+ * @param int $bpp
+ * @return void
+ */
+ static function readGCT( $fh, $bpp ) {
+ if ( $bpp > 0 ) {
+ $max = pow( 2, $bpp );
+ for ( $i = 1; $i <= $max; ++$i ) {
+ fread( $fh, 3 );
+ }
+ }
+ }
+
+ /**
+ * @param string $data
+ * @throws Exception
+ * @return int
+ */
+ static function decodeBPP( $data ) {
+ if ( strlen( $data ) < 1 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $buf = unpack( 'C', $data )[1];
+ $bpp = ( $buf & 7 ) + 1;
+ $buf >>= 7;
+
+ $have_map = $buf & 1;
+
+ return $have_map ? $bpp : 0;
+ }
+
+ /**
+ * @param resource $fh
+ * @throws Exception
+ */
+ static function skipBlock( $fh ) {
+ while ( !feof( $fh ) ) {
+ $buf = fread( $fh, 1 );
+ if ( strlen( $buf ) < 1 ) {
+ throw new Exception( "Ran out of input" );
+ }
+ $block_len = unpack( 'C', $buf )[1];
+ if ( $block_len == 0 ) {
+ return;
+ }
+ fread( $fh, $block_len );
+ }
+ }
+
+ /**
+ * Read a block. In the GIF format, a block is made up of
+ * several sub-blocks. Each sub block starts with one byte
+ * saying how long the sub-block is, followed by the sub-block.
+ * The entire block is terminated by a sub-block of length
+ * 0.
+ * @param resource $fh File handle
+ * @param bool $includeLengths Include the length bytes of the
+ * sub-blocks in the returned value. Normally this is false,
+ * except XMP is weird and does a hack where you need to keep
+ * these length bytes.
+ * @throws Exception
+ * @return string The data.
+ */
+ static function readBlock( $fh, $includeLengths = false ) {
+ $data = '';
+ $subLength = fread( $fh, 1 );
+ $blocks = 0;
+
+ while ( $subLength !== "\0" ) {
+ $blocks++;
+ if ( $blocks > self::MAX_SUBBLOCKS ) {
+ throw new Exception( "MAX_SUBBLOCKS exceeded (over $blocks sub-blocks)" );
+ }
+ if ( feof( $fh ) ) {
+ throw new Exception( "Read error: Unexpected EOF." );
+ }
+ if ( $includeLengths ) {
+ $data .= $subLength;
+ }
+
+ $data .= fread( $fh, ord( $subLength ) );
+ $subLength = fread( $fh, 1 );
+ }
+
+ return $data;
+ }
+}
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