Mega Code Archive
Fast BufferedWriter
<![CDATA[
/*
* @(#)$Id$
*
* Copyright 2006-2008 Makoto YUI
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Contributors:
* Makoto YUI - initial implementation
*/
//package xbird.util.io;
import java.io.IOException;
import java.io.Writer;
/**
*
* <DIV lang="en"></DIV>
* <DIV lang="ja"></DIV>
*
* @author Makoto YUI (yuin405+xbird@gmail.com)
*/
public final class FastBufferedWriter extends Writer {
private Writer out;
private char cb[];
private int nChars, nextChar;
private static int defaultCharBufferSize = 8192;
/**
* Creates a buffered character-output stream that uses a default-sized
* output buffer.
*
* @param out A Writer
*/
public FastBufferedWriter(Writer out) {
this(out, defaultCharBufferSize);
}
/**
* Creates a new buffered character-output stream that uses an output
* buffer of the given size.
*
* @param out A Writer
* @param sz Output-buffer size, a positive integer
*
* @exception IllegalArgumentException If sz is <= 0
*/
public FastBufferedWriter(Writer out, int sz) {
super(out);
if(sz <= 0)
throw new IllegalArgumentException("Buffer size <= 0");
this.out = out;
cb = new char[sz];
nChars = sz;
nextChar = 0;
}
/**
* Flushes the output buffer to the underlying character stream, without
* flushing the stream itself. This method is non-private only so that it
* may be invoked by PrintStream.
*/
private void flushBuffer() throws IOException {
if(nextChar == 0)
return;
out.write(cb, 0, nextChar);
nextChar = 0;
}
/**
* Writes a single character.
*
* @exception IOException If an I/O error occurs
*/
public void write(int c) throws IOException {
if(nextChar >= nChars)
flushBuffer();
cb[nextChar++] = (char) c;
}
/**
* Our own little min method, to avoid loading java.lang.Math if we've run
* out of file descriptors and we're trying to print a stack trace.
*/
private int min(int a, int b) {
if(a < b)
return a;
return b;
}
/**
* Writes a portion of an array of characters.
*
* <p> Ordinarily this method stores characters from the given array into
* this stream's buffer, flushing the buffer to the underlying stream as
* needed. If the requested length is at least as large as the buffer,
* however, then this method will flush the buffer and write the characters
* directly to the underlying stream. Thus redundant
* <code>BufferedWriter</code>s will not copy data unnecessarily.
*
* @param cbuf A character array
* @param off Offset from which to start reading characters
* @param len Number of characters to write
*
* @exception IOException If an I/O error occurs
*/
public void write(char cbuf[], int off, int len) throws IOException {
if((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length)
|| ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if(len == 0) {
return;
}
if(len >= nChars) {
/* If the request length exceeds the size of the output buffer,
flush the buffer and then write the data directly. In this
way buffered streams will cascade harmlessly. */
flushBuffer();
out.write(cbuf, off, len);
return;
}
int b = off, t = off + len;
while(b < t) {
int d = min(nChars - nextChar, t - b);
System.arraycopy(cbuf, b, cb, nextChar, d);
b += d;
nextChar += d;
if(nextChar >= nChars)
flushBuffer();
}
}
/**
* Writes a portion of a String.
*
* <p> If the value of the <tt>len</tt> parameter is negative then no
* characters are written. This is contrary to the specification of this
* method in the {@linkplain java.io.Writer#write(java.lang.String,int,int)
* superclass}, which requires that an {@link IndexOutOfBoundsException} be
* thrown.
*
* @param s String to be written
* @param off Offset from which to start reading characters
* @param len Number of characters to be written
*
* @exception IOException If an I/O error occurs
*/
public void write(String s, int off, int len) throws IOException {
int b = off, t = off + len;
while(b < t) {
int d = min(nChars - nextChar, t - b);
s.getChars(b, b + d, cb, nextChar);
b += d;
nextChar += d;
if(nextChar >= nChars)
flushBuffer();
}
}
/**
* Flushes the stream.
*
* @exception IOException If an I/O error occurs
*/
public void flush() throws IOException {
flushBuffer();
out.flush();
}
public void close() throws IOException {
if(out == null) {
return;
}
try {
flushBuffer();
} finally {
out.close();
out = null;
cb = null;
}
}
}
]]>