Fast BufferedWriter : Buffered Reader Writer « File Input Output « Java

1. Java
2. File Input Output
3. Buffered Reader Writer

Fast BufferedWriter

 
/*
 * @(#)$Id$
 *
 * 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;
        }
    }

}

   
  

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