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 192