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;
    }
}