DjVuImage.php

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<?php
class DjVuImage {
        function __construct( $filename ) {
                $this->mFilename = $filename;
        }

        const DJVUTXT_MEMORY_LIMIT = 300000;

        public function isValid() {
                $info = $this->getInfo();
                return $info !== false;
        }

        public function getImageSize() {
                $data = $this->getInfo();

                if( $data !== false ) {
                        $width = $data['width'];
                        $height = $data['height'];

                        return array( $width, $height, 'DjVu',
                                "width=\"$width\" height=\"$height\"" );
                }
                return false;
        }

        // ---------

        function dump() {
                $file = fopen( $this->mFilename, 'rb' );
                $header = fread( $file, 12 );
                // @todo FIXME: Would be good to replace this extract() call with something that explicitly initializes local variables.
                extract( unpack( 'a4magic/a4chunk/NchunkLength', $header ) );
                echo "$chunk $chunkLength\n";
                $this->dumpForm( $file, $chunkLength, 1 );
                fclose( $file );
        }

        private function dumpForm( $file, $length, $indent ) {
                $start = ftell( $file );
                $secondary = fread( $file, 4 );
                echo str_repeat( ' ', $indent * 4 ) . "($secondary)\n";
                while( ftell( $file ) - $start < $length ) {
                        $chunkHeader = fread( $file, 8 );
                        if( $chunkHeader == '' ) {
                                break;
                        }
                        // @todo FIXME: Would be good to replace this extract() call with something that explicitly initializes local variables.
                        extract( unpack( 'a4chunk/NchunkLength', $chunkHeader ) );
                        echo str_repeat( ' ', $indent * 4 ) . "$chunk $chunkLength\n";

                        if( $chunk == 'FORM' ) {
                                $this->dumpForm( $file, $chunkLength, $indent + 1 );
                        } else {
                                fseek( $file, $chunkLength, SEEK_CUR );
                                if( $chunkLength & 1 == 1 ) {
                                        // Padding byte between chunks
                                        fseek( $file, 1, SEEK_CUR );
                                }
                        }
                }
        }

        function getInfo() {
                wfSuppressWarnings();
                $file = fopen( $this->mFilename, 'rb' );
                wfRestoreWarnings();
                if( $file === false ) {
                        wfDebug( __METHOD__ . ": missing or failed file read\n" );
                        return false;
                }

                $header = fread( $file, 16 );
                $info = false;

                if( strlen( $header ) < 16 ) {
                        wfDebug( __METHOD__ . ": too short file header\n" );
                } else {
                        // @todo FIXME: Would be good to replace this extract() call with something that explicitly initializes local variables.
                        extract( unpack( 'a4magic/a4form/NformLength/a4subtype', $header ) );

                        if( $magic != 'AT&T' ) {
                                wfDebug( __METHOD__ . ": not a DjVu file\n" );
                        } elseif( $subtype == 'DJVU' ) {
                                // Single-page document
                                $info = $this->getPageInfo( $file, $formLength );
                        } elseif( $subtype == 'DJVM' ) {
                                // Multi-page document
                                $info = $this->getMultiPageInfo( $file, $formLength );
                        } else  {
                                wfDebug( __METHOD__ . ": unrecognized DJVU file type '$formType'\n" );
                        }
                }
                fclose( $file );
                return $info;
        }

        private function readChunk( $file ) {
                $header = fread( $file, 8 );
                if( strlen( $header ) < 8 ) {
                        return array( false, 0 );
                } else {
                        // @todo FIXME: Would be good to replace this extract() call with something that explicitly initializes local variables.
                        extract( unpack( 'a4chunk/Nlength', $header ) );
                        return array( $chunk, $length );
                }
        }

        private function skipChunk( $file, $chunkLength ) {
                fseek( $file, $chunkLength, SEEK_CUR );

                if( $chunkLength & 0x01 == 1 && !feof( $file ) ) {
                        // padding byte
                        fseek( $file, 1, SEEK_CUR );
                }
        }

        private function getMultiPageInfo( $file, $formLength ) {
                // For now, we'll just look for the first page in the file
                // and report its information, hoping others are the same size.
                $start = ftell( $file );
                do {
                        list( $chunk, $length ) = $this->readChunk( $file );
                        if( !$chunk ) {
                                break;
                        }

                        if( $chunk == 'FORM' ) {
                                $subtype = fread( $file, 4 );
                                if( $subtype == 'DJVU' ) {
                                        wfDebug( __METHOD__ . ": found first subpage\n" );
                                        return $this->getPageInfo( $file, $length );
                                }
                                $this->skipChunk( $file, $length - 4 );
                        } else {
                                wfDebug( __METHOD__ . ": skipping '$chunk' chunk\n" );
                                $this->skipChunk( $file, $length );
                        }
                } while( $length != 0 && !feof( $file ) && ftell( $file ) - $start < $formLength );

                wfDebug( __METHOD__ . ": multi-page DJVU file contained no pages\n" );
                return false;
        }

        private function getPageInfo( $file, $formLength ) {
                list( $chunk, $length ) = $this->readChunk( $file );
                if( $chunk != 'INFO' ) {
                        wfDebug( __METHOD__ . ": expected INFO chunk, got '$chunk'\n" );
                        return false;
                }

                if( $length < 9 ) {
                        wfDebug( __METHOD__ . ": INFO should be 9 or 10 bytes, found $length\n" );
                        return false;
                }
                $data = fread( $file, $length );
                if( strlen( $data ) < $length ) {
                        wfDebug( __METHOD__ . ": INFO chunk cut off\n" );
                        return false;
                }

                // @todo FIXME: Would be good to replace this extract() call with something that explicitly initializes local variables.
                extract( unpack(
                        'nwidth/' .
                        'nheight/' .
                        'Cminor/' .
                        'Cmajor/' .
                        'vresolution/' .
                        'Cgamma', $data ) );
                # Newer files have rotation info in byte 10, but we don't use it yet.

                return array(
                        'width' => $width,
                        'height' => $height,
                        'version' => "$major.$minor",
                        'resolution' => $resolution,
                        'gamma' => $gamma / 10.0 );
        }

        function retrieveMetaData() {
                global $wgDjvuToXML, $wgDjvuDump, $wgDjvuTxt;
                wfProfileIn( __METHOD__ );

                if ( isset( $wgDjvuDump ) ) {
                        # djvudump is faster as of version 3.5
                        # http://sourceforge.net/tracker/index.php?func=detail&aid=1704049&group_id=32953&atid=406583
                        wfProfileIn( 'djvudump' );
                        $cmd = wfEscapeShellArg( $wgDjvuDump ) . ' ' . wfEscapeShellArg( $this->mFilename );
                        $dump = wfShellExec( $cmd );
                        $xml = $this->convertDumpToXML( $dump );
                        wfProfileOut( 'djvudump' );
                } elseif ( isset( $wgDjvuToXML ) ) {
                        wfProfileIn( 'djvutoxml' );
                        $cmd = wfEscapeShellArg( $wgDjvuToXML ) . ' --without-anno --without-text ' .
                                wfEscapeShellArg( $this->mFilename );
                        $xml = wfShellExec( $cmd );
                        wfProfileOut( 'djvutoxml' );
                } else {
                        $xml = null;
                }
                # Text layer
                if ( isset( $wgDjvuTxt ) ) {
                        wfProfileIn( 'djvutxt' );
                        $cmd = wfEscapeShellArg( $wgDjvuTxt ) . ' --detail=page ' . wfEscapeShellArg( $this->mFilename );
                        wfDebug( __METHOD__ . ": $cmd\n" );
                        $retval = '';
                        $txt = wfShellExec( $cmd, $retval, array(), array( 'memory' => self::DJVUTXT_MEMORY_LIMIT ) );
                        wfProfileOut( 'djvutxt' );
                        if( $retval == 0) {
                                # Strip some control characters
                                $txt = preg_replace( "/[\013\035\037]/", "", $txt );
                                $reg = <<<EOR
                                        /\(page\s[\d-]*\s[\d-]*\s[\d-]*\s[\d-]*\s*"
                                        ((?>    # Text to match is composed of atoms of either:
                                          \\\\. # - any escaped character
                                          |     # - any character different from " and \
                                          [^"\\\\]+
                                        )*?)
                                        "\s*\)
                                        | # Or page can be empty ; in this case, djvutxt dumps ()
                                        \(\s*()\)/sx
EOR;
                                $txt = preg_replace_callback( $reg, array( $this, 'pageTextCallback' ), $txt );
                                $txt = "<DjVuTxt>\n<HEAD></HEAD>\n<BODY>\n" . $txt . "</BODY>\n</DjVuTxt>\n";
                                $xml = preg_replace( "/<DjVuXML>/", "<mw-djvu><DjVuXML>", $xml, 1 );
                                $xml = $xml . $txt. '</mw-djvu>';
                        }
                }
                wfProfileOut( __METHOD__ );
                return $xml;
        }

        function pageTextCallback( $matches ) {
                # Get rid of invalid UTF-8, strip control characters
                return '<PAGE value="' . htmlspecialchars( UtfNormal::cleanUp( $matches[1] ) ) . '" />';
        }

        function convertDumpToXML( $dump ) {
                if ( strval( $dump ) == '' ) {
                        return false;
                }

                $xml = <<<EOT
<?xml version="1.0" ?>
<!DOCTYPE DjVuXML PUBLIC "-//W3C//DTD DjVuXML 1.1//EN" "pubtext/DjVuXML-s.dtd">
<DjVuXML>
<HEAD></HEAD>
<BODY>
EOT;

                $dump = str_replace( "\r", '', $dump );
                $line = strtok( $dump, "\n" );
                $m = false;
                $good = false;
                if ( preg_match( '/^( *)FORM:DJVU/', $line, $m ) ) {
                        # Single-page
                        if ( $this->parseFormDjvu( $line, $xml ) ) {
                                $good = true;
                        } else {
                                return false;
                        }
                } elseif ( preg_match( '/^( *)FORM:DJVM/', $line, $m ) ) {
                        # Multi-page
                        $parentLevel = strlen( $m[1] );
                        # Find DIRM
                        $line = strtok( "\n" );
                        while ( $line !== false ) {
                                $childLevel = strspn( $line, ' ' );
                                if ( $childLevel <= $parentLevel ) {
                                        # End of chunk
                                        break;
                                }

                                if ( preg_match( '/^ *DIRM.*indirect/', $line ) ) {
                                        wfDebug( "Indirect multi-page DjVu document, bad for server!\n" );
                                        return false;
                                }
                                if ( preg_match( '/^ *FORM:DJVU/', $line ) ) {
                                        # Found page
                                        if ( $this->parseFormDjvu( $line, $xml ) ) {
                                                $good = true;
                                        } else {
                                                return false;
                                        }
                                }
                                $line = strtok( "\n" );
                        }
                }
                if ( !$good ) {
                        return false;
                }

                $xml .= "</BODY>\n</DjVuXML>\n";
                return $xml;
        }

        function parseFormDjvu( $line, &$xml ) {
                $parentLevel = strspn( $line, ' ' );
                $line = strtok( "\n" );

                # Find INFO
                while ( $line !== false ) {
                        $childLevel = strspn( $line, ' ' );
                        if ( $childLevel <= $parentLevel ) {
                                # End of chunk
                                break;
                        }

                        if ( preg_match( '/^ *INFO *\[\d*\] *DjVu *(\d+)x(\d+), *\w*, *(\d+) *dpi, *gamma=([0-9.-]+)/', $line, $m ) ) {
                                $xml .= Xml::tags( 'OBJECT',
                                        array(
                                                #'data' => '',
                                                #'type' => 'image/x.djvu',
                                                'height' => $m[2],
                                                'width' => $m[1],
                                                #'usemap' => '',
                                        ),
                                        "\n" .
                                        Xml::element( 'PARAM', array( 'name' => 'DPI', 'value' => $m[3] ) ) . "\n" .
                                        Xml::element( 'PARAM', array( 'name' => 'GAMMA', 'value' => $m[4] ) ) . "\n"
                                ) . "\n";
                                return true;
                        }
                        $line = strtok( "\n" );
                }
                # Not found
                return false;
        }
}