Exif.php

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<?php
use Wikimedia\AtEase\AtEase;
 
class Exif {
    private const BYTE = 1;
 
    private const ASCII = 2;
 
    private const SHORT = 3;
 
    private const LONG = 4;
 
    private const RATIONAL = 5;
 
    private const SHORT_OR_LONG = 6;
 
    private const UNDEFINED = 7;
 
    private const SLONG = 9;
 
    private const SRATIONAL = 10;
 
    private const IGNORE = -1;
 
    private $mExifTags;
 
    private $mRawExifData;
 
    private $mFilteredExifData;
 
    private $file;
 
    private $basename;
 
    private $log = false;
 
    private $byteOrder;
 
    public function __construct( $file, $byteOrder = '' ) {
        $this->mExifTags = [
            # TIFF Rev. 6.0 Attribute Information (p22)
            'IFD0' => [
                # Tags relating to image structure
                # Image width
                'ImageWidth' => self::SHORT_OR_LONG,
                # Image height
                'ImageLength' => self::SHORT_OR_LONG,
                # Number of bits per component
                'BitsPerSample' => [ self::SHORT, 3 ],
 
                # "When a primary image is JPEG compressed, this designation is not"
                # "necessary and is omitted." (p23)
                # Compression scheme #p23
                'Compression' => self::SHORT,
                # Pixel composition #p23
                'PhotometricInterpretation' => self::SHORT,
                # Orientation of image #p24
                'Orientation' => self::SHORT,
                # Number of components
                'SamplesPerPixel' => self::SHORT,
                # Image data arrangement #p24
                'PlanarConfiguration' => self::SHORT,
                # Subsampling ratio of Y to C #p24
                'YCbCrSubSampling' => [ self::SHORT, 2 ],
                # Y and C positioning #p24-25
                'YCbCrPositioning' => self::SHORT,
                # Image resolution in width direction
                'XResolution' => self::RATIONAL,
                # Image resolution in height direction
                'YResolution' => self::RATIONAL,
                # Unit of X and Y resolution #(p26)
                'ResolutionUnit' => self::SHORT,
 
                # Tags relating to recording offset
                # Image data location
                'StripOffsets' => self::SHORT_OR_LONG,
                # Number of rows per strip
                'RowsPerStrip' => self::SHORT_OR_LONG,
                # Bytes per compressed strip
                'StripByteCounts' => self::SHORT_OR_LONG,
                # Offset to JPEG SOI
                'JPEGInterchangeFormat' => self::SHORT_OR_LONG,
                # Bytes of JPEG data
                'JPEGInterchangeFormatLength' => self::SHORT_OR_LONG,
 
                # Tags relating to image data characteristics
                # Transfer function
                'TransferFunction' => self::IGNORE,
                # White point chromaticity
                'WhitePoint' => [ self::RATIONAL, 2 ],
                # Chromaticities of primarities
                'PrimaryChromaticities' => [ self::RATIONAL, 6 ],
                # Color space transformation matrix coefficients #p27
                'YCbCrCoefficients' => [ self::RATIONAL, 3 ],
                # Pair of black and white reference values
                'ReferenceBlackWhite' => [ self::RATIONAL, 6 ],
 
                # Other tags
                # File change date and time
                'DateTime' => self::ASCII,
                # Image title
                'ImageDescription' => self::ASCII,
                # Image input equipment manufacturer
                'Make' => self::ASCII,
                # Image input equipment model
                'Model' => self::ASCII,
                # Software used
                'Software' => self::ASCII,
                # Person who created the image
                'Artist' => self::ASCII,
                # Copyright holder
                'Copyright' => self::ASCII,
            ],
 
            # Exif IFD Attribute Information (p30-31)
            'EXIF' => [
                # @todo NOTE: Nonexistence of this field is taken to mean non-conformance
                # to the Exif 2.1 AND 2.2 standards
                'ExifVersion' => self::UNDEFINED,
                # Supported Flashpix version #p32
                'FlashPixVersion' => self::UNDEFINED,
 
                # Tags relating to Image Data Characteristics
                # Color space information #p32
                'ColorSpace' => self::SHORT,
 
                # Tags relating to image configuration
                # Meaning of each component #p33
                'ComponentsConfiguration' => self::UNDEFINED,
                # Image compression mode
                'CompressedBitsPerPixel' => self::RATIONAL,
                # Valid image height
                'PixelYDimension' => self::SHORT_OR_LONG,
                # Valid image width
                'PixelXDimension' => self::SHORT_OR_LONG,
 
                # Tags relating to related user information
                # Manufacturer notes
                'MakerNote' => self::IGNORE,
                # User comments #p34
                'UserComment' => self::UNDEFINED,
 
                # Tags relating to related file information
                # Related audio file
                'RelatedSoundFile' => self::ASCII,
 
                # Tags relating to date and time
                # Date and time of original data generation #p36
                'DateTimeOriginal' => self::ASCII,
                # Date and time of original data generation
                'DateTimeDigitized' => self::ASCII,
                # DateTime subseconds
                'SubSecTime' => self::ASCII,
                # DateTimeOriginal subseconds
                'SubSecTimeOriginal' => self::ASCII,
                # DateTimeDigitized subseconds
                'SubSecTimeDigitized' => self::ASCII,
 
                # Tags relating to picture-taking conditions (p31)
                # Exposure time
                'ExposureTime' => self::RATIONAL,
                # F Number
                'FNumber' => self::RATIONAL,
                # Exposure Program #p38
                'ExposureProgram' => self::SHORT,
                # Spectral sensitivity
                'SpectralSensitivity' => self::ASCII,
                # ISO speed rating
                'ISOSpeedRatings' => self::SHORT,
 
                # Optoelectronic conversion factor. Note: We don't have support for this atm.
                'OECF' => self::IGNORE,
 
                # Shutter speed
                'ShutterSpeedValue' => self::SRATIONAL,
                # Aperture
                'ApertureValue' => self::RATIONAL,
                # Brightness
                'BrightnessValue' => self::SRATIONAL,
                # Exposure bias
                'ExposureBiasValue' => self::SRATIONAL,
                # Maximum land aperture
                'MaxApertureValue' => self::RATIONAL,
                # Subject distance
                'SubjectDistance' => self::RATIONAL,
                # Metering mode #p40
                'MeteringMode' => self::SHORT,
                # Light source #p40-41
                'LightSource' => self::SHORT,
                # Flash #p41-42
                'Flash' => self::SHORT,
                # Lens focal length
                'FocalLength' => self::RATIONAL,
                # Subject area
                'SubjectArea' => [ self::SHORT, 4 ],
                # Flash energy
                'FlashEnergy' => self::RATIONAL,
                # Spatial frequency response. Not supported atm.
                'SpatialFrequencyResponse' => self::IGNORE,
                # Focal plane X resolution
                'FocalPlaneXResolution' => self::RATIONAL,
                # Focal plane Y resolution
                'FocalPlaneYResolution' => self::RATIONAL,
                # Focal plane resolution unit #p46
                'FocalPlaneResolutionUnit' => self::SHORT,
                # Subject location
                'SubjectLocation' => [ self::SHORT, 2 ],
                # Exposure index
                'ExposureIndex' => self::RATIONAL,
                # Sensing method #p46
                'SensingMethod' => self::SHORT,
                # File source #p47
                'FileSource' => self::UNDEFINED,
                # Scene type #p47
                'SceneType' => self::UNDEFINED,
                # CFA pattern. not supported atm.
                'CFAPattern' => self::IGNORE,
                # Custom image processing #p48
                'CustomRendered' => self::SHORT,
                # Exposure mode #p48
                'ExposureMode' => self::SHORT,
                # White Balance #p49
                'WhiteBalance' => self::SHORT,
                # Digital zoom ratio
                'DigitalZoomRatio' => self::RATIONAL,
                # Focal length in 35 mm film
                'FocalLengthIn35mmFilm' => self::SHORT,
                # Scene capture type #p49
                'SceneCaptureType' => self::SHORT,
                # Scene control #p49-50
                'GainControl' => self::SHORT,
                # Contrast #p50
                'Contrast' => self::SHORT,
                # Saturation #p50
                'Saturation' => self::SHORT,
                # Sharpness #p50
                'Sharpness' => self::SHORT,
 
                # Device settings description. This could maybe be supported. Need to find an
                # example file that uses this to see if it has stuff of interest in it.
                'DeviceSettingDescription' => self::IGNORE,
 
                # Subject distance range #p51
                'SubjectDistanceRange' => self::SHORT,
 
                # Unique image ID
                'ImageUniqueID' => self::ASCII,
            ],
 
            # GPS Attribute Information (p52)
            'GPS' => [
                'GPSVersion' => self::UNDEFINED,
                # Should be an array of 4 Exif::BYTE's. However, php treats it as an undefined
                # Note exif standard calls this GPSVersionID, but php doesn't like the id suffix
                # North or South Latitude #p52-53
                'GPSLatitudeRef' => self::ASCII,
                # Latitude
                'GPSLatitude' => [ self::RATIONAL, 3 ],
                # East or West Longitude #p53
                'GPSLongitudeRef' => self::ASCII,
                # Longitude
                'GPSLongitude' => [ self::RATIONAL, 3 ],
                'GPSAltitudeRef' => self::UNDEFINED,
 
                # Altitude reference. Note, the exif standard says this should be an EXIF::Byte,
                # but php seems to disagree.
                # Altitude
                'GPSAltitude' => self::RATIONAL,
                # GPS time (atomic clock)
                'GPSTimeStamp' => [ self::RATIONAL, 3 ],
                # Satellites used for measurement
                'GPSSatellites' => self::ASCII,
                # Receiver status #p54
                'GPSStatus' => self::ASCII,
                # Measurement mode #p54-55
                'GPSMeasureMode' => self::ASCII,
                # Measurement precision
                'GPSDOP' => self::RATIONAL,
                # Speed unit #p55
                'GPSSpeedRef' => self::ASCII,
                # Speed of GPS receiver
                'GPSSpeed' => self::RATIONAL,
                # Reference for direction of movement #p55
                'GPSTrackRef' => self::ASCII,
                # Direction of movement
                'GPSTrack' => self::RATIONAL,
                # Reference for direction of image #p56
                'GPSImgDirectionRef' => self::ASCII,
                # Direction of image
                'GPSImgDirection' => self::RATIONAL,
                # Geodetic survey data used
                'GPSMapDatum' => self::ASCII,
                # Reference for latitude of destination #p56
                'GPSDestLatitudeRef' => self::ASCII,
                # Latitude destination
                'GPSDestLatitude' => [ self::RATIONAL, 3 ],
                # Reference for longitude of destination #p57
                'GPSDestLongitudeRef' => self::ASCII,
                # Longitude of destination
                'GPSDestLongitude' => [ self::RATIONAL, 3 ],
                # Reference for bearing of destination #p57
                'GPSDestBearingRef' => self::ASCII,
                # Bearing of destination
                'GPSDestBearing' => self::RATIONAL,
                # Reference for distance to destination #p57-58
                'GPSDestDistanceRef' => self::ASCII,
                # Distance to destination
                'GPSDestDistance' => self::RATIONAL,
                # Name of GPS processing method
                'GPSProcessingMethod' => self::UNDEFINED,
                # Name of GPS area
                'GPSAreaInformation' => self::UNDEFINED,
                # GPS date
                'GPSDateStamp' => self::ASCII,
                # GPS differential correction
                'GPSDifferential' => self::SHORT,
            ],
        ];
 
        $this->file = $file;
        $this->basename = wfBaseName( $this->file );
        if ( $byteOrder === 'BE' || $byteOrder === 'LE' ) {
            $this->byteOrder = $byteOrder;
        } else {
            // Only give a warning for b/c, since originally we didn't
            // require this. The number of things affected by this is
            // rather small.
            wfWarn( 'Exif class did not have byte order specified. ' .
                'Some properties may be decoded incorrectly.' );
            // BE seems about twice as popular as LE in jpg's.
            $this->byteOrder = 'BE';
        }
 
        $this->debugFile( __FUNCTION__, true );
        if ( function_exists( 'exif_read_data' ) ) {
            AtEase::suppressWarnings();
            $data = exif_read_data( $this->file, '', true );
            AtEase::restoreWarnings();
        } else {
            throw new MWException( "Internal error: exif_read_data not present. " .
                "\$wgShowEXIF may be incorrectly set or not checked by an extension." );
        }
        $this->mRawExifData = $data ?: [];
        $this->makeFilteredData();
        $this->collapseData();
        $this->debugFile( __FUNCTION__, false );
    }
 
    private function makeFilteredData() {
        $this->mFilteredExifData = [];
 
        foreach ( $this->mRawExifData as $section => $data ) {
            if ( !array_key_exists( $section, $this->mExifTags ) ) {
                $this->debug( $section, __FUNCTION__, "'$section' is not a valid Exif section" );
                continue;
            }
 
            foreach ( $data as $tag => $value ) {
                if ( !array_key_exists( $tag, $this->mExifTags[$section] ) ) {
                    $this->debug( $tag, __FUNCTION__, "'$tag' is not a valid tag in '$section'" );
                    continue;
                }
 
                if ( $this->validate( $section, $tag, $value ) ) {
                    // This is ok, as the tags in the different sections do not conflict.
                    // except in computed and thumbnail section, which we don't use.
                    $this->mFilteredExifData[$tag] = $value;
                } else {
                    $this->debug( $value, __FUNCTION__, "'$tag' contained invalid data" );
                }
            }
        }
    }
 
    private function collapseData() {
        $this->exifGPStoNumber( 'GPSLatitude' );
        $this->exifGPStoNumber( 'GPSDestLatitude' );
        $this->exifGPStoNumber( 'GPSLongitude' );
        $this->exifGPStoNumber( 'GPSDestLongitude' );
 
        if ( isset( $this->mFilteredExifData['GPSAltitude'] ) ) {
            // We know altitude data is a <num>/<denom> from the validation
            // functions ran earlier. But multiplying such a string by -1
            // doesn't work well, so convert.
            [ $num, $denom ] = explode( '/', $this->mFilteredExifData['GPSAltitude'], 2 );
            $this->mFilteredExifData['GPSAltitude'] = (int)$num / (int)$denom;
 
            if ( isset( $this->mFilteredExifData['GPSAltitudeRef'] ) ) {
                switch ( $this->mFilteredExifData['GPSAltitudeRef'] ) {
                case "\0":
                    // Above sea level
                    break;
                case "\1":
                    // Below sea level
                    $this->mFilteredExifData['GPSAltitude'] *= -1;
                    break;
                default:
                    // Invalid
                    unset( $this->mFilteredExifData['GPSAltitude'] );
                    break;
                }
            }
        }
        unset( $this->mFilteredExifData['GPSAltitudeRef'] );
 
        $this->exifPropToOrd( 'FileSource' );
        $this->exifPropToOrd( 'SceneType' );
 
        $this->charCodeString( 'UserComment' );
        $this->charCodeString( 'GPSProcessingMethod' );
        $this->charCodeString( 'GPSAreaInformation' );
 
        // ComponentsConfiguration should really be an array instead of a string...
        // This turns a string of binary numbers into an array of numbers.
 
        if ( isset( $this->mFilteredExifData['ComponentsConfiguration'] ) ) {
            $val = $this->mFilteredExifData['ComponentsConfiguration'];
            $ccVals = [];
 
            $strLen = strlen( $val );
            for ( $i = 0; $i < $strLen; $i++ ) {
                $ccVals[$i] = ord( substr( $val, $i, 1 ) );
            }
            // this is for formatting later.
            $ccVals['_type'] = 'ol';
            $this->mFilteredExifData['ComponentsConfiguration'] = $ccVals;
        }
 
        // GPSVersion(ID) is treated as the wrong type by php exif support.
        // Go through each byte turning it into a version string.
        // For example: "\x02\x02\x00\x00" -> "2.2.0.0"
 
        // Also change exif tag name from GPSVersion (what php exif thinks it is)
        // to GPSVersionID (what the exif standard thinks it is).
 
        if ( isset( $this->mFilteredExifData['GPSVersion'] ) ) {
            $val = $this->mFilteredExifData['GPSVersion'];
            $newVal = '';
 
            $strLen = strlen( $val );
            for ( $i = 0; $i < $strLen; $i++ ) {
                if ( $i !== 0 ) {
                    $newVal .= '.';
                }
                $newVal .= ord( substr( $val, $i, 1 ) );
            }
 
            if ( $this->byteOrder === 'LE' ) {
                // Need to reverse the string
                $newVal2 = '';
                for ( $i = strlen( $newVal ) - 1; $i >= 0; $i-- ) {
                    $newVal2 .= substr( $newVal, $i, 1 );
                }
                $this->mFilteredExifData['GPSVersionID'] = $newVal2;
            } else {
                $this->mFilteredExifData['GPSVersionID'] = $newVal;
            }
            unset( $this->mFilteredExifData['GPSVersion'] );
        }
    }
 
    private function charCodeString( $prop ) {
        if ( isset( $this->mFilteredExifData[$prop] ) ) {
            if ( strlen( $this->mFilteredExifData[$prop] ) <= 8 ) {
                // invalid. Must be at least 9 bytes long.
 
                $this->debug( $this->mFilteredExifData[$prop], __FUNCTION__, false );
                unset( $this->mFilteredExifData[$prop] );
 
                return;
            }
            $charCode = substr( $this->mFilteredExifData[$prop], 0, 8 );
            $val = substr( $this->mFilteredExifData[$prop], 8 );
 
            switch ( $charCode ) {
                case "JIS\x00\x00\x00\x00\x00":
                    $charset = "Shift-JIS";
                    break;
                case "UNICODE\x00":
                    $charset = "UTF-16" . $this->byteOrder;
                    break;
                default:
                    // ascii or undefined.
                    $charset = "";
                    break;
            }
            if ( $charset ) {
                AtEase::suppressWarnings();
                $val = iconv( $charset, 'UTF-8//IGNORE', $val );
                AtEase::restoreWarnings();
            } else {
                // if valid utf-8, assume that, otherwise assume windows-1252
                $valCopy = $val;
                UtfNormal\Validator::quickIsNFCVerify( $valCopy );
                if ( $valCopy !== $val ) {
                    AtEase::suppressWarnings();
                    $val = iconv( 'Windows-1252', 'UTF-8//IGNORE', $val );
                    AtEase::restoreWarnings();
                }
            }
 
            // trim and check to make sure not only whitespace.
            $val = trim( $val );
            if ( strlen( $val ) === 0 ) {
                // only whitespace.
                $this->debug( $this->mFilteredExifData[$prop], __FUNCTION__, "$prop: Is only whitespace" );
                unset( $this->mFilteredExifData[$prop] );
 
                return;
            }
 
            // all's good.
            $this->mFilteredExifData[$prop] = $val;
        }
    }
 
    private function exifPropToOrd( $prop ) {
        if ( isset( $this->mFilteredExifData[$prop] ) ) {
            $this->mFilteredExifData[$prop] = ord( $this->mFilteredExifData[$prop] );
        }
    }
 
    private function exifGPStoNumber( $prop ) {
        $loc =& $this->mFilteredExifData[$prop];
        $dir =& $this->mFilteredExifData[$prop . 'Ref'];
        $res = false;
 
        if ( isset( $loc ) && isset( $dir )
            && ( $dir === 'N' || $dir === 'S' || $dir === 'E' || $dir === 'W' )
        ) {
            [ $num, $denom ] = explode( '/', $loc[0], 2 );
            $res = (int)$num / (int)$denom;
            [ $num, $denom ] = explode( '/', $loc[1], 2 );
            $res += ( (int)$num / (int)$denom ) * ( 1 / 60 );
            [ $num, $denom ] = explode( '/', $loc[2], 2 );
            $res += ( (int)$num / (int)$denom ) * ( 1 / 3600 );
 
            if ( $dir === 'S' || $dir === 'W' ) {
                // make negative
                $res *= -1;
            }
        }
 
        // update the exif records.
 
        // using !== as $res could potentially be 0
        if ( $res !== false ) {
            $this->mFilteredExifData[$prop] = $res;
        } else {
            // if invalid
            unset( $this->mFilteredExifData[$prop] );
        }
        unset( $this->mFilteredExifData[$prop . 'Ref'] );
    }
 
    public function getData() {
        return $this->mRawExifData;
    }
 
    public function getFilteredData() {
        return $this->mFilteredExifData;
    }
 
    public static function version() {
        return 2;
    }
 
    private function isByte( $in ) {
        if ( !is_array( $in ) && sprintf( '%d', $in ) == $in && $in >= 0 && $in <= 255 ) {
            $this->debug( $in, __FUNCTION__, true );
 
            return true;
        }
 
        $this->debug( $in, __FUNCTION__, false );
 
        return false;
    }
 
    private function isASCII( $in ) {
        if ( is_array( $in ) ) {
            return false;
        }
 
        if ( preg_match( "/[^\x0a\x20-\x7e]/", $in ) ) {
            $this->debug( $in, __FUNCTION__, 'found a character that is not allowed' );
 
            return false;
        }
 
        if ( preg_match( '/^\s*$/', $in ) ) {
            $this->debug( $in, __FUNCTION__, 'input consisted solely of whitespace' );
 
            return false;
        }
 
        return true;
    }
 
    private function isShort( $in ) {
        if ( !is_array( $in ) && sprintf( '%d', $in ) == $in && $in >= 0 && $in <= 65536 ) {
            $this->debug( $in, __FUNCTION__, true );
 
            return true;
        }
 
        $this->debug( $in, __FUNCTION__, false );
 
        return false;
    }
 
    private function isLong( $in ) {
        if ( !is_array( $in ) && sprintf( '%d', $in ) == $in && $in >= 0 && $in <= 4294967296 ) {
            $this->debug( $in, __FUNCTION__, true );
 
            return true;
        }
 
        $this->debug( $in, __FUNCTION__, false );
 
        return false;
    }
 
    private function isRational( $in ) {
        $m = [];
 
        # Avoid division by zero
        if ( !is_array( $in )
            && preg_match( '/^(\d+)\/(\d+[1-9]|[1-9]\d*)$/', $in, $m )
        ) {
            return $this->isLong( $m[1] ) && $this->isLong( $m[2] );
        }
 
        $this->debug( $in, __FUNCTION__, 'fed a non-fraction value' );
 
        return false;
    }
 
    private function isUndefined( $in ) {
        $this->debug( $in, __FUNCTION__, true );
 
        return true;
    }
 
    private function isSlong( $in ) {
        if ( $this->isLong( abs( (float)$in ) ) ) {
            $this->debug( $in, __FUNCTION__, true );
 
            return true;
        }
 
        $this->debug( $in, __FUNCTION__, false );
 
        return false;
    }
 
    private function isSrational( $in ) {
        $m = [];
 
        # Avoid division by zero
        if ( !is_array( $in ) &&
            preg_match( '/^(-?\d+)\/(\d+[1-9]|[1-9]\d*)$/', $in, $m )
        ) {
            return $this->isSlong( $m[0] ) && $this->isSlong( $m[1] );
        }
 
        $this->debug( $in, __FUNCTION__, 'fed a non-fraction value' );
 
        return false;
    }
 
    private function validate( $section, $tag, $val, $recursive = false ): bool {
        $debug = "tag is '$tag'";
        $etype = $this->mExifTags[$section][$tag];
        $ecount = 1;
        if ( is_array( $etype ) ) {
            [ $etype, $ecount ] = $etype;
            if ( $recursive ) {
                // checking individual elements
                $ecount = 1;
            }
        }
 
        $count = 1;
        if ( is_array( $val ) ) {
            $count = count( $val );
            if ( $ecount !== $count ) {
                $this->debug( $val, __FUNCTION__, "Expected $ecount elements for $tag but got $count" );
                return false;
            }
        }
        // If there are multiple values, recursively validate each of them.
        if ( $count > 1 ) {
            foreach ( $val as $v ) {
                if ( !$this->validate( $section, $tag, $v, true ) ) {
                    return false;
                }
            }
 
            return true;
        }
 
        // NULL values are considered valid. T315202.
        if ( $val === null ) {
            return true;
        }
 
        // Does not work if not typecast
        switch ( (string)$etype ) {
            case (string)self::BYTE:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isByte( $val );
            case (string)self::ASCII:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isASCII( $val );
            case (string)self::SHORT:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isShort( $val );
            case (string)self::LONG:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isLong( $val );
            case (string)self::RATIONAL:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isRational( $val );
            case (string)self::SHORT_OR_LONG:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isShort( $val ) || $this->isLong( $val );
            case (string)self::UNDEFINED:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isUndefined( $val );
            case (string)self::SLONG:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isSlong( $val );
            case (string)self::SRATIONAL:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return $this->isSrational( $val );
            case (string)self::IGNORE:
                $this->debug( $val, __FUNCTION__, $debug );
 
                return false;
            default:
                $this->debug( $val, __FUNCTION__, "The tag '$tag' is unknown" );
 
                return false;
        }
    }
 
    private function debug( $in, $fname, $action = null ) {
        if ( !$this->log ) {
            return;
        }
        $type = gettype( $in );
        $class = ucfirst( __CLASS__ );
        if ( is_array( $in ) ) {
            $in = print_r( $in, true );
        }
 
        if ( $action === true ) {
            wfDebugLog( $this->log, "$class::$fname: accepted: '$in' (type: $type)" );
        } elseif ( $action === false ) {
            wfDebugLog( $this->log, "$class::$fname: rejected: '$in' (type: $type)" );
        } elseif ( $action === null ) {
            wfDebugLog( $this->log, "$class::$fname: input was: '$in' (type: $type)" );
        } else {
            wfDebugLog( $this->log, "$class::$fname: $action (type: $type; content: '$in')" );
        }
    }
 
    private function debugFile( $fname, $io ) {
        if ( !$this->log ) {
            return;
        }
        $class = ucfirst( __CLASS__ );
        if ( $io ) {
            wfDebugLog( $this->log, "$class::$fname: begin processing: '{$this->basename}'" );
        } else {
            wfDebugLog( $this->log, "$class::$fname: end processing: '{$this->basename}'" );
        }
    }
}