001 /* BufferedWriter.java -- Buffer output into large blocks before writing 002 Copyright (C) 1998, 1999, 2000, 2001 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 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 042 * "The Java Language Specification", ISBN 0-201-63451-1 043 * Status: Complete to version 1.1. 044 */ 045 046 /** 047 * This class accumulates chars written in a buffer instead of immediately 048 * writing the data to the underlying output sink. The chars are instead 049 * as one large block when the buffer is filled, or when the stream is 050 * closed or explicitly flushed. This mode operation can provide a more 051 * efficient mechanism for writing versus doing numerous small unbuffered 052 * writes. 053 * 054 * @author Aaron M. Renn (arenn@urbanophile.com) 055 * @author Tom Tromey (tromey@cygnus.com) 056 * @date September 25, 1998 057 */ 058 public class BufferedWriter extends Writer 059 { 060 /** 061 * This is the default buffer size 062 */ 063 private static final int DEFAULT_BUFFER_SIZE = 8192; 064 065 /** 066 * This is the underlying <code>Writer</code> to which this object 067 * sends its output. 068 */ 069 private Writer out; 070 071 /** 072 * This is the internal char array used for buffering output before 073 * writing it. 074 */ 075 char[] buffer; 076 077 /** 078 * This is the number of chars that are currently in the buffer and 079 * are waiting to be written to the underlying stream. It always points to 080 * the index into the buffer where the next char of data will be stored 081 */ 082 int count; 083 084 /** 085 * This method initializes a new <code>BufferedWriter</code> instance 086 * that will write to the specified subordinate <code>Writer</code> 087 * and which will use a default buffer size of 8192 chars. 088 * 089 * @param out The underlying <code>Writer</code> to write data to 090 */ 091 public BufferedWriter (Writer out) 092 { 093 this (out, DEFAULT_BUFFER_SIZE); 094 } 095 096 /** 097 * This method initializes a new <code>BufferedWriter</code> instance 098 * that will write to the specified subordinate <code>Writer</code> 099 * and which will use the specified buffer size 100 * 101 * @param out The underlying <code>Writer</code> to write data to 102 * @param size The size of the internal buffer 103 */ 104 public BufferedWriter (Writer out, int size) 105 { 106 super(out.lock); 107 this.out = out; 108 this.buffer = new char[size]; 109 this.count = 0; 110 } 111 112 /** 113 * This method flushes any remaining buffered chars then closes the 114 * underlying output stream. Any further attempts to write to this stream 115 * may throw an exception 116 * 117 * @exception IOException If an error occurs. 118 */ 119 public void close () throws IOException 120 { 121 synchronized (lock) 122 { 123 // It is safe to call localFlush even if the stream is already 124 // closed. 125 localFlush (); 126 out.close(); 127 buffer = null; 128 } 129 } 130 131 /** 132 * This method causes any currently buffered chars to be immediately 133 * written to the underlying output stream. 134 * 135 * @exception IOException If an error occurs 136 */ 137 public void flush () throws IOException 138 { 139 synchronized (lock) 140 { 141 if (buffer == null) 142 throw new IOException ("Stream closed"); 143 localFlush (); 144 out.flush(); 145 } 146 } 147 148 /** 149 * This method writes out a system depedent line separator sequence. The 150 * actual value written is detemined from the <xmp>line.separator</xmp> 151 * system property. 152 * 153 * @exception IOException If an error occurs 154 */ 155 public void newLine () throws IOException 156 { 157 write (System.getProperty("line.separator")); 158 } 159 160 /** 161 * This method writes a single char of data. This will be written to the 162 * buffer instead of the underlying data source. However, if the buffer 163 * is filled as a result of this write request, it will be flushed to the 164 * underlying output stream. 165 * 166 * @param oneChar The char of data to be written, passed as an int 167 * 168 * @exception IOException If an error occurs 169 */ 170 public void write (int oneChar) throws IOException 171 { 172 synchronized (lock) 173 { 174 if (buffer == null) 175 throw new IOException ("Stream closed"); 176 buffer[count++] = (char) oneChar; 177 if (count == buffer.length) 178 localFlush (); 179 } 180 } 181 182 /** 183 * This method writes <code>len</code> chars from the char array 184 * <code>buf</code> starting at position <code>offset</code> in the buffer. 185 * These chars will be written to the internal buffer. However, if this 186 * write operation fills the buffer, the buffer will be flushed to the 187 * underlying output stream. 188 * 189 * @param buf The array of chars to write. 190 * @param offset The index into the char array to start writing from. 191 * @param len The number of chars to write. 192 * 193 * @exception IOException If an error occurs 194 */ 195 public void write (char[] buf, int offset, int len) throws IOException 196 { 197 synchronized (lock) 198 { 199 if (buffer == null) 200 throw new IOException ("Stream closed"); 201 202 // Bypass buffering if there is too much incoming data. 203 if (count + len > buffer.length) 204 { 205 localFlush (); 206 out.write(buf, offset, len); 207 } 208 else 209 { 210 System.arraycopy(buf, offset, buffer, count, len); 211 count += len; 212 if (count == buffer.length) 213 localFlush (); 214 } 215 } 216 } 217 218 /** 219 * This method writes <code>len</code> chars from the <code>String</code> 220 * <code>str</code> starting at position <code>offset</code> in the string. 221 * These chars will be written to the internal buffer. However, if this 222 * write operation fills the buffer, the buffer will be flushed to the 223 * underlying output stream. 224 * 225 * @param str The <code>String</code> to write. 226 * @param offset The index into the string to start writing from. 227 * @param len The number of chars to write. 228 * 229 * @exception IOException If an error occurs 230 */ 231 public void write (String str, int offset, int len) throws IOException 232 { 233 synchronized (lock) 234 { 235 if (buffer == null) 236 throw new IOException ("Stream closed"); 237 238 if (count + len > buffer.length) 239 { 240 localFlush (); 241 out.write(str, offset, len); 242 } 243 else 244 { 245 str.getChars(offset, offset + len, buffer, count); 246 count += len; 247 if (count == buffer.length) 248 localFlush (); 249 } 250 } 251 } 252 253 // This should only be called with the lock held. 254 private void localFlush () throws IOException 255 { 256 if (count > 0) 257 { 258 out.write(buffer, 0, count); 259 count = 0; 260 } 261 } 262 }