001 /* BufferedOutputStream.java -- Buffer output into large blocks before writing
002 Copyright (C) 1998, 2000, 2003 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.io;
040
041 /**
042 * This class accumulates bytes written in a buffer instead of immediately
043 * writing the data to the underlying output sink. The bytes are instead
044 * as one large block when the buffer is filled, or when the stream is
045 * closed or explicitly flushed. This mode operation can provide a more
046 * efficient mechanism for writing versus doing numerous small unbuffered
047 * writes.
048 *
049 * @author Aaron M. Renn (arenn@urbanophile.com)
050 */
051 public class BufferedOutputStream extends FilterOutputStream
052 {
053 /**
054 * This is the default buffer size
055 */
056 private static final int DEFAULT_BUFFER_SIZE = 512;
057
058 /**
059 * This is the internal byte array used for buffering output before
060 * writing it.
061 */
062 protected byte[] buf;
063
064 /**
065 * This is the number of bytes that are currently in the buffer and
066 * are waiting to be written to the underlying stream. It always points to
067 * the index into the buffer where the next byte of data will be stored
068 */
069 protected int count;
070
071 /**
072 * This method initializes a new <code>BufferedOutputStream</code> instance
073 * that will write to the specified subordinate <code>OutputStream</code>
074 * and which will use a default buffer size of 512 bytes.
075 *
076 * @param out The underlying <code>OutputStream</code> to write data to
077 */
078 public BufferedOutputStream(OutputStream out)
079 {
080 this(out, DEFAULT_BUFFER_SIZE);
081 }
082
083 /**
084 * This method initializes a new <code>BufferedOutputStream</code> instance
085 * that will write to the specified subordinate <code>OutputStream</code>
086 * and which will use the specified buffer size
087 *
088 * @param out The underlying <code>OutputStream</code> to write data to
089 * @param size The size of the internal buffer
090 */
091 public BufferedOutputStream(OutputStream out, int size)
092 {
093 super(out);
094
095 buf = new byte[size];
096 }
097
098 /**
099 * This method causes any currently buffered bytes to be immediately
100 * written to the underlying output stream.
101 *
102 * @exception IOException If an error occurs
103 */
104 public synchronized void flush() throws IOException
105 {
106 if (count == 0)
107 return;
108
109 out.write(buf, 0, count);
110 count = 0;
111 out.flush();
112 }
113
114 /**
115 * This method flushes any remaining buffered bytes then closes the
116 * underlying output stream. Any further attempts to write to this stream
117 * may throw an exception
118 *
119 public synchronized void close() throws IOException
120 {
121 flush();
122 out.close();
123 }
124 */
125
126 /**
127 * This method runs when the object is garbage collected. It is
128 * responsible for ensuring that all buffered bytes are written and
129 * for closing the underlying stream.
130 *
131 * @exception IOException If an error occurs (ignored by the Java runtime)
132 *
133 protected void finalize() throws IOException
134 {
135 close();
136 }
137 */
138
139 /**
140 * This method writes a single byte of data. This will be written to the
141 * buffer instead of the underlying data source. However, if the buffer
142 * is filled as a result of this write request, it will be flushed to the
143 * underlying output stream.
144 *
145 * @param b The byte of data to be written, passed as an int
146 *
147 * @exception IOException If an error occurs
148 */
149 public synchronized void write(int b) throws IOException
150 {
151 if (count == buf.length)
152 flush();
153
154 buf[count] = (byte)(b & 0xFF);
155 ++count;
156 }
157
158 /**
159 * This method writes <code>len</code> bytes from the byte array
160 * <code>buf</code> starting at position <code>offset</code> in the buffer.
161 * These bytes will be written to the internal buffer. However, if this
162 * write operation fills the buffer, the buffer will be flushed to the
163 * underlying output stream.
164 *
165 * @param buf The array of bytes to write.
166 * @param offset The index into the byte array to start writing from.
167 * @param len The number of bytes to write.
168 *
169 * @exception IOException If an error occurs
170 */
171 public synchronized void write(byte[] buf, int offset, int len)
172 throws IOException
173 {
174 // Buffer can hold everything. Note that the case where LEN < 0
175 // is automatically handled by the downstream write.
176 if (len < (this.buf.length - count))
177 {
178 System.arraycopy(buf, offset, this.buf, count, len);
179 count += len;
180 }
181 else
182 {
183 // The write was too big. So flush the buffer and write the new
184 // bytes directly to the underlying stream, per the JDK 1.2
185 // docs.
186 flush();
187 out.write (buf, offset, len);
188 }
189 }
190
191 } // class BufferedOutputStream