UnsynchronizedBufferedWriter.java

package org.caudexorigo.io;

import java.io.IOException;
import java.io.Writer;

public class UnsynchronizedBufferedWriter extends Writer
{

	private Writer out;

	private char cb[];
	private int nChars, nextChar;

	private static int defaultCharBufferSize = 8192;

	/**
	 * Line separator string. This is the value of the line.separator property at the moment that the stream was created.
	 */
	private String lineSeparator;

	/**
	 * Create a buffered character-output stream that uses a default-sized output buffer.
	 * 
	 * @param out
	 *            A Writer
	 */
	public UnsynchronizedBufferedWriter(Writer out)
	{
		this(out, defaultCharBufferSize);
	}

	/**
	 * Create 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 UnsynchronizedBufferedWriter(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;

		lineSeparator = String.format("%n", (Object[]) null);
	}

	/** Check to make sure that the stream has not been closed */
	private void ensureOpen() throws IOException
	{
		if (out == null)
			throw new IOException("Stream closed");
	}

	/**
	 * Flush 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.
	 */
	void flushBuffer() throws IOException
	{
		ensureOpen();
		if (nextChar == 0)
			return;
		out.write(cb, 0, nextChar);
		nextChar = 0;

	}

	/**
	 * Write a single character.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public void write(int c) throws IOException
	{
		ensureOpen();
		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;
	}

	/**
	 * Write 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>UnsynchronizedBufferedWriter</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
	{

		ensureOpen();
		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();
		}

	}

	/**
	 * Write 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
	{

		ensureOpen();

		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();
		}

	}

	/**
	 * Write a line separator. The line separator string is defined by the system property <tt>line.separator</tt>, and is not necessarily a single newline ('\n') character.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public void newLine() throws IOException
	{
		write(lineSeparator);
	}

	/**
	 * Flush the stream.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public void flush() throws IOException
	{

		flushBuffer();
		out.flush();

	}

	/**
	 * Close the stream.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public void close() throws IOException
	{

		if (out == null)
			return;
		flushBuffer();
		out.close();
		out = null;
		cb = null;

	}

}