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 javax.servlet;
021    
022    import java.io.InputStream;
023    import java.io.IOException;
024    
025    /**
026     * 
027     * Provides an input stream for reading binary data from a client
028     * request, including an efficient <code>readLine</code> method
029     * for reading data one line at a time. With some protocols, such
030     * as HTTP POST and PUT, a <code>ServletInputStream</code>
031     * object can be used to read data sent from the client.
032     *
033     * <p>A <code>ServletInputStream</code> object is normally retrieved via
034     * the {@link ServletRequest#getInputStream} method.
035     *
036     *
037     * <p>This is an abstract class that a servlet container implements.
038     * Subclasses of this class
039     * must implement the <code>java.io.InputStream.read()</code> method.
040     *
041     *
042     * @author      Various
043     * @version     $Version$
044     *
045     * @see         ServletRequest 
046     *
047     */
048    
049    public abstract class ServletInputStream extends InputStream {
050    
051    
052    
053        /**
054         * Does nothing, because this is an abstract class.
055         *
056         */
057    
058        protected ServletInputStream() { }
059    
060      
061      
062        
063        /**
064         *
065         * Reads the input stream, one line at a time. Starting at an
066         * offset, reads bytes into an array, until it reads a certain number
067         * of bytes or reaches a newline character, which it reads into the
068         * array as well.
069         *
070         * <p>This method returns -1 if it reaches the end of the input
071         * stream before reading the maximum number of bytes.
072         *
073         *
074         *
075         * @param b                 an array of bytes into which data is read
076         *
077         * @param off               an integer specifying the character at which
078         *                          this method begins reading
079         *
080         * @param len               an integer specifying the maximum number of 
081         *                          bytes to read
082         *
083         * @return                  an integer specifying the actual number of bytes 
084         *                          read, or -1 if the end of the stream is reached
085         *
086         * @exception IOException   if an input or output exception has occurred
087         *
088         */
089         
090        public int readLine(byte[] b, int off, int len) throws IOException {
091    
092            if (len <= 0) {
093                return 0;
094            }
095            int count = 0, c;
096    
097            while ((c = read()) != -1) {
098                b[off++] = (byte)c;
099                count++;
100                if (c == '\n' || count == len) {
101                    break;
102                }
103            }
104            return count > 0 ? count : -1;
105        }
106    }
107    
108    
109