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253 lines
7.2 KiB
Java
253 lines
7.2 KiB
Java
/* BufferedWriter.java -- Buffer output into large blocks before writing
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Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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As a special exception, if you link this library with other files to
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produce an executable, this library does not by itself cause the
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resulting executable to be covered by the GNU General Public License.
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This exception does not however invalidate any other reasons why the
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executable file might be covered by the GNU General Public License. */
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package java.io;
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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* "The Java Language Specification", ISBN 0-201-63451-1
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* Status: Complete to version 1.1.
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*/
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/**
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* This class accumulates chars written in a buffer instead of immediately
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* writing the data to the underlying output sink. The chars are instead
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* as one large block when the buffer is filled, or when the stream is
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* closed or explicitly flushed. This mode operation can provide a more
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* efficient mechanism for writing versus doing numerous small unbuffered
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* writes.
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*
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* @version 0.0
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*
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @author Tom Tromey <tromey@cygnus.com>
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* @date September 25, 1998
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*/
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public class BufferedWriter extends Writer
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{
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/**
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* This method initializes a new <code>BufferedWriter</code> instance
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* that will write to the specified subordinate <code>Writer</code>
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* and which will use a default buffer size of 512 chars.
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*
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* @param out The underlying <code>Writer</code> to write data to
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*/
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public BufferedWriter (Writer out)
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{
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this (out, DEFAULT_BUFFER_SIZE);
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}
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/**
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* This method initializes a new <code>BufferedWriter</code> instance
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* that will write to the specified subordinate <code>Writer</code>
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* and which will use the specified buffer size
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*
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* @param out The underlying <code>Writer</code> to write data to
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* @param size The size of the internal buffer
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*/
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public BufferedWriter (Writer ox, int size)
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{
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super (ox);
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out = ox;
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buffer = new char[size];
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count = 0;
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}
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/**
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* This method flushes any remaining buffered chars then closes the
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* underlying output stream. Any further attempts to write to this stream
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* may throw an exception
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*/
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public void close () throws IOException
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{
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synchronized (lock)
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{
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// It is safe to call localFlush even if the stream is already
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// closed.
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localFlush ();
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out.close();
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buffer = null;
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}
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}
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/**
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* This method causes any currently buffered chars to be immediately
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* written to the underlying output stream.
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*
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* @exception IOException If an error occurs
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*/
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public void flush () throws IOException
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{
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synchronized (lock)
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{
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if (buffer == null)
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throw new IOException ("Stream closed");
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localFlush ();
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out.flush();
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}
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}
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/**
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* This method writes out a system depedent line separator sequence. The
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* actual value written is detemined from the <xmp>line.separator</xmp>
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* system property.
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*
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* @exception IOException If an error occurs
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*/
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public void newLine () throws IOException
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{
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write (System.getProperty("line.separator"));
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}
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/**
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* This method writes a single char of data. This will be written to the
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* buffer instead of the underlying data source. However, if the buffer
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* is filled as a result of this write request, it will be flushed to the
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* underlying output stream.
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*
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* @param b The char of data to be written, passed as an int
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*
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* @exception IOException If an error occurs
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*/
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public void write (int oneChar) throws IOException
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{
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synchronized (lock)
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{
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if (buffer == null)
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throw new IOException ("Stream closed");
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buffer[count++] = (char) oneChar;
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if (count == buffer.length)
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localFlush ();
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}
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}
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/**
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* This method writes <code>len</code> chars from the char array
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* <code>buf</code> starting at position <code>offset</code> in the buffer.
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* These chars will be written to the internal buffer. However, if this
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* write operation fills the buffer, the buffer will be flushed to the
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* underlying output stream.
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*
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* @param buf The array of chars to write.
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* @param offset The index into the char array to start writing from.
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* @param len The number of chars to write.
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*
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* @exception IOException If an error occurs
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*/
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public void write (char[] buf, int offset, int len) throws IOException
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{
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synchronized (lock)
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{
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if (buffer == null)
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throw new IOException ("Stream closed");
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// Bypass buffering if there is too much incoming data.
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if (count + len > buffer.length)
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{
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localFlush ();
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out.write(buf, offset, len);
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}
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else
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{
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System.arraycopy(buf, offset, buffer, count, len);
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count += len;
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if (count == buffer.length)
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localFlush ();
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}
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}
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}
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/**
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* This method writes <code>len</code> chars from the <code>String</code>
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* <code>str</code> starting at position <code>offset</code> in the string.
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* These chars will be written to the internal buffer. However, if this
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* write operation fills the buffer, the buffer will be flushed to the
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* underlying output stream.
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*
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* @param str The <code>String</code> to write.
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* @param offset The index into the string to start writing from.
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* @param len The number of chars to write.
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*
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* @exception IOException If an error occurs
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*/
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public void write (String str, int offset, int len) throws IOException
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{
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synchronized (lock)
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{
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if (buffer == null)
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throw new IOException ("Stream closed");
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if (count + len > buffer.length)
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{
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localFlush ();
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out.write(str, offset, len);
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}
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else
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{
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str.getChars(offset, offset + len, buffer, count);
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count += len;
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if (count == buffer.length)
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localFlush ();
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}
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}
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}
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// This should only be called with the lock held.
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private final void localFlush () throws IOException
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{
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if (count > 0)
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{
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out.write(buffer, 0, count);
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count = 0;
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}
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}
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/**
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* This is the underlying <code>Writer</code> to which this object
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* sends its output.
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*/
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private Writer out;
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/**
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* This is the internal char array used for buffering output before
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* writing it.
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*/
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char[] buffer;
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/**
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* This is the number of chars that are currently in the buffer and
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* are waiting to be written to the underlying stream. It always points to
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* the index into the buffer where the next char of data will be stored
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*/
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int count;
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/**
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* This is the default buffer size
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*/
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private static final int DEFAULT_BUFFER_SIZE = 8192;
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}
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