1 /*
   2  * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.io;
  27 
  28 /**
  29  * This class is the superclass of all classes that filter output
  30  * streams. These streams sit on top of an already existing output
  31  * stream (the <i>underlying</i> output stream) which it uses as its
  32  * basic sink of data, but possibly transforming the data along the
  33  * way or providing additional functionality.
  34  * <p>
  35  * The class <code>FilterOutputStream</code> itself simply overrides
  36  * all methods of <code>OutputStream</code> with versions that pass
  37  * all requests to the underlying output stream. Subclasses of
  38  * <code>FilterOutputStream</code> may further override some of these
  39  * methods as well as provide additional methods and fields.
  40  *
  41  * @author  Jonathan Payne
  42  * @since   JDK1.0
  43  */
  44 public
  45 class FilterOutputStream extends OutputStream {
  46     /**
  47      * The underlying output stream to be filtered.
  48      */
  49     protected OutputStream out;
  50 
  51     /**
  52      * Creates an output stream filter built on top of the specified
  53      * underlying output stream.
  54      *
  55      * @param   out   the underlying output stream to be assigned to
  56      *                the field <tt>this.out</tt> for later use, or
  57      *                <code>null</code> if this instance is to be
  58      *                created without an underlying stream.
  59      */
  60     public FilterOutputStream(OutputStream out) {
  61         this.out = out;
  62     }
  63 
  64     /**
  65      * Writes the specified <code>byte</code> to this output stream.
  66      * <p>
  67      * The <code>write</code> method of <code>FilterOutputStream</code>
  68      * calls the <code>write</code> method of its underlying output stream,
  69      * that is, it performs <tt>out.write(b)</tt>.
  70      * <p>
  71      * Implements the abstract <tt>write</tt> method of <tt>OutputStream</tt>.
  72      *
  73      * @param      b   the <code>byte</code>.
  74      * @exception  IOException  if an I/O error occurs.
  75      */
  76     public void write(int b) throws IOException {
  77         out.write(b);
  78     }
  79 
  80     /**
  81      * Writes <code>b.length</code> bytes to this output stream.
  82      * <p>
  83      * The <code>write</code> method of <code>FilterOutputStream</code>
  84      * calls its <code>write</code> method of three arguments with the
  85      * arguments <code>b</code>, <code>0</code>, and
  86      * <code>b.length</code>.
  87      * <p>
  88      * Note that this method does not call the one-argument
  89      * <code>write</code> method of its underlying stream with the single
  90      * argument <code>b</code>.
  91      *
  92      * @param      b   the data to be written.
  93      * @exception  IOException  if an I/O error occurs.
  94      * @see        java.io.FilterOutputStream#write(byte[], int, int)
  95      */
  96     public void write(byte b[]) throws IOException {
  97         write(b, 0, b.length);
  98     }
  99 
 100     /**
 101      * Writes <code>len</code> bytes from the specified
 102      * <code>byte</code> array starting at offset <code>off</code> to
 103      * this output stream.
 104      * <p>
 105      * The <code>write</code> method of <code>FilterOutputStream</code>
 106      * calls the <code>write</code> method of one argument on each
 107      * <code>byte</code> to output.
 108      * <p>
 109      * Note that this method does not call the <code>write</code> method
 110      * of its underlying input stream with the same arguments. Subclasses
 111      * of <code>FilterOutputStream</code> should provide a more efficient
 112      * implementation of this method.
 113      *
 114      * @param      b     the data.
 115      * @param      off   the start offset in the data.
 116      * @param      len   the number of bytes to write.
 117      * @exception  IOException  if an I/O error occurs.
 118      * @see        java.io.FilterOutputStream#write(int)
 119      */
 120     public void write(byte b[], int off, int len) throws IOException {
 121         if ((off | len | (b.length - (len + off)) | (off + len)) < 0)
 122             throw new IndexOutOfBoundsException();
 123 
 124         for (int i = 0 ; i < len ; i++) {
 125             write(b[off + i]);
 126         }
 127     }
 128 
 129     /**
 130      * Flushes this output stream and forces any buffered output bytes
 131      * to be written out to the stream.
 132      * <p>
 133      * The <code>flush</code> method of <code>FilterOutputStream</code>
 134      * calls the <code>flush</code> method of its underlying output stream.
 135      *
 136      * @exception  IOException  if an I/O error occurs.
 137      * @see        java.io.FilterOutputStream#out
 138      */
 139     public void flush() throws IOException {
 140         out.flush();
 141     }
 142 
 143     /**
 144      * Closes this output stream and releases any system resources
 145      * associated with the stream.
 146      * <p>
 147      * The <code>close</code> method of <code>FilterOutputStream</code>
 148      * calls its <code>flush</code> method, and then calls the
 149      * <code>close</code> method of its underlying output stream.
 150      *
 151      * @exception  IOException  if an I/O error occurs.
 152      * @see        java.io.FilterOutputStream#flush()
 153      * @see        java.io.FilterOutputStream#out
 154      */
 155     @SuppressWarnings("try")
 156     public void close() throws IOException {
 157         try (OutputStream ostream = out) {
 158             flush();
 159         }
 160     }
 161 }