001    /*
002     *  Licensed to the Apache Software Foundation (ASF) under one
003     *  or more contributor license agreements.  See the NOTICE file
004     *  distributed with this work for additional information
005     *  regarding copyright ownership.  The ASF licenses this file
006     *  to you under the Apache License, Version 2.0 (the
007     *  "License"); you may not use this file except in compliance
008     *  with the License.  You may obtain a copy of the License at
009     *  
010     *    http://www.apache.org/licenses/LICENSE-2.0
011     *  
012     *  Unless required by applicable law or agreed to in writing,
013     *  software distributed under the License is distributed on an
014     *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015     *  KIND, either express or implied.  See the License for the
016     *  specific language governing permissions and limitations
017     *  under the License. 
018     *  
019     */
020    package org.apache.directory.shared.ldap.schema.syntaxCheckers;
021    
022    import org.apache.directory.shared.ldap.constants.SchemaConstants;
023    import org.apache.directory.shared.ldap.schema.SyntaxChecker;
024    import org.slf4j.Logger;
025    import org.slf4j.LoggerFactory;
026    
027    
028    /**
029     * A SyntaxChecker which verifies that a value is a Jpeg according to RFC 4517.
030     * 
031     * The JFIF (Jpeg File Interchange Format) specify that a jpeg image starts with
032     * the following bytes :
033     * 0xFF 0xD8 (SOI, Start Of Image)
034     * 0xFF 0xE0 (App0)
035     * 0xNN 0xNN (Header length)
036     * "JFIF\0" (JFIF string with an ending \0)
037     * some other bytes which are related to the image.
038     * 
039     * We will check for those 11 bytes, except the length.
040     * 
041     * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
042     * @version $Rev: 437007 $
043     */
044    public class JpegSyntaxChecker extends SyntaxChecker
045    {
046        /** A logger for this class */
047        private static final Logger LOG = LoggerFactory.getLogger( JpegSyntaxChecker.class );
048    
049        /** The serialVersionUID */
050        private static final long serialVersionUID = 1L;
051    
052        /**
053         * Creates a new instance of JpegSyntaxChecker.
054         */
055        public JpegSyntaxChecker()
056        {
057            super( SchemaConstants.JPEG_SYNTAX );
058        }
059        
060        
061        /**
062         * {@inheritDoc}
063         */
064        public boolean isValidSyntax( Object value )
065        {
066            if ( value == null )
067            {
068                LOG.debug( "Syntax invalid for '{}'", value );
069                return false;
070            }
071            
072            // The value must be a byte array
073            if ( ! ( value instanceof byte[] ) )
074            {
075                LOG.debug( "Syntax invalid for '{}'", value );
076                return false;
077            }
078            
079            byte[] bytes = (byte[])value;
080    
081            // The header must be at least 11 bytes long
082            if ( bytes.length < 11 )
083            {
084                LOG.debug( "Syntax invalid for '{}'", value );
085                return false;
086            }
087    
088            if ( ( bytes[0] == (byte)0x00FF ) && // SOI
089                 ( bytes[1] == (byte)0x00D8 ) &&
090                 ( bytes[2] == (byte)0x00FF ) && // APP0
091                 ( bytes[3] == (byte)0x00E0 ) &&
092                 ( bytes[6] == 'J' ) && // JFIF
093                 ( bytes[7] == 'F' ) && // JFIF
094                 ( bytes[8] == 'I' ) && // JFIF
095                 ( bytes[9] == 'F' ) &&
096                 ( bytes[10] == 0x00 ) ) // \0
097            {
098                // Note : this is not because the header is correct
099                // that the file is a jpeg file. There are much more
100                // elements to check, but we are not writing a jpeg
101                // file checker...
102                LOG.debug( "Syntax valid for '{}'", value );
103                return true;
104            }
105    
106            LOG.debug( "Syntax invalid for '{}'", value );
107            return false;
108        }
109    }