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/*
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* Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.io;
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/**
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* Writes text to a character-output stream, buffering characters so as to
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* provide for the efficient writing of single characters, arrays, and strings.
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*
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* <p> The buffer size may be specified, or the default size may be accepted.
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* The default is large enough for most purposes.
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*
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* <p> A newLine() method is provided, which uses the platform's own notion of
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* line separator as defined by the system property <tt>line.separator</tt>.
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* Not all platforms use the newline character ('\n') to terminate lines.
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* Calling this method to terminate each output line is therefore preferred to
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* writing a newline character directly.
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*
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* <p> In general, a Writer sends its output immediately to the underlying
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* character or byte stream. Unless prompt output is required, it is advisable
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* to wrap a BufferedWriter around any Writer whose write() operations may be
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* costly, such as FileWriters and OutputStreamWriters. For example,
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*
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* <pre>
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* PrintWriter out
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* = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));
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* </pre>
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*
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* will buffer the PrintWriter's output to the file. Without buffering, each
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* invocation of a print() method would cause characters to be converted into
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* bytes that would then be written immediately to the file, which can be very
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* inefficient.
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*
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* @see PrintWriter
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* @see FileWriter
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* @see OutputStreamWriter
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* @see java.nio.file.Files#newBufferedWriter
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*
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* @author Mark Reinhold
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* @since JDK1.1
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*/
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public class BufferedWriter extends Writer {
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private Writer out;
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private char cb[];
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private int nChars, nextChar;
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private static int defaultCharBufferSize = 8192;
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/**
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* Line separator string. This is the value of the line.separator
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* property at the moment that the stream was created.
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*/
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private String lineSeparator;
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/**
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* Creates a buffered character-output stream that uses a default-sized
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* output buffer.
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*
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* @param out A Writer
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*/
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public BufferedWriter(Writer out) {
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this(out, defaultCharBufferSize);
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}
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/**
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* Creates a new buffered character-output stream that uses an output
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* buffer of the given size.
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*
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* @param out A Writer
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* @param sz Output-buffer size, a positive integer
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*
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* @exception IllegalArgumentException If sz is <= 0
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*/
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public BufferedWriter(Writer out, int sz) {
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super(out);
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if (sz <= 0)
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throw new IllegalArgumentException("Buffer size <= 0");
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this.out = out;
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cb = new char[sz];
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nChars = sz;
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nextChar = 0;
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lineSeparator = java.security.AccessController.doPrivileged(
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new sun.security.action.GetPropertyAction("line.separator"));
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}
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/** Checks to make sure that the stream has not been closed */
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private void ensureOpen() throws IOException {
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if (out == null)
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throw new IOException("Stream closed");
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}
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/**
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* Flushes the output buffer to the underlying character stream, without
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* flushing the stream itself. This method is non-private only so that it
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* may be invoked by PrintStream.
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*/
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void flushBuffer() throws IOException {
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synchronized (lock) {
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ensureOpen();
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if (nextChar == 0)
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return;
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out.write(cb, 0, nextChar);
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nextChar = 0;
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}
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}
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/**
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* Writes a single character.
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*
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* @exception IOException If an I/O error occurs
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*/
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public void write(int c) throws IOException {
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synchronized (lock) {
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ensureOpen();
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if (nextChar >= nChars)
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flushBuffer();
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cb[nextChar++] = (char) c;
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}
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}
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/**
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* Our own little min method, to avoid loading java.lang.Math if we've run
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* out of file descriptors and we're trying to print a stack trace.
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*/
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private int min(int a, int b) {
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if (a < b) return a;
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return b;
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}
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/**
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* Writes a portion of an array of characters.
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*
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* <p> Ordinarily this method stores characters from the given array into
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* this stream's buffer, flushing the buffer to the underlying stream as
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* needed. If the requested length is at least as large as the buffer,
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* however, then this method will flush the buffer and write the characters
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* directly to the underlying stream. Thus redundant
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* <code>BufferedWriter</code>s will not copy data unnecessarily.
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*
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* @param cbuf A character array
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* @param off Offset from which to start reading characters
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* @param len Number of characters to write
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*
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* @exception IOException If an I/O error occurs
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*/
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public void write(char cbuf[], int off, int len) throws IOException {
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synchronized (lock) {
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ensureOpen();
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if ((off < 0) || (off > cbuf.length) || (len < 0) ||
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((off + len) > cbuf.length) || ((off + len) < 0)) {
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throw new IndexOutOfBoundsException();
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} else if (len == 0) {
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return;
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}
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if (len >= nChars) {
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/* If the request length exceeds the size of the output buffer,
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flush the buffer and then write the data directly. In this
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way buffered streams will cascade harmlessly. */
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flushBuffer();
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out.write(cbuf, off, len);
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return;
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}
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int b = off, t = off + len;
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while (b < t) {
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int d = min(nChars - nextChar, t - b);
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System.arraycopy(cbuf, b, cb, nextChar, d);
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b += d;
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nextChar += d;
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if (nextChar >= nChars)
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flushBuffer();
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}
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}
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}
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/**
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* Writes a portion of a String.
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*
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* <p> If the value of the <tt>len</tt> parameter is negative then no
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* characters are written. This is contrary to the specification of this
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* method in the {@linkplain java.io.Writer#write(java.lang.String,int,int)
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* superclass}, which requires that an {@link IndexOutOfBoundsException} be
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* thrown.
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*
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* @param s String to be written
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* @param off Offset from which to start reading characters
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* @param len Number of characters to be written
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*
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* @exception IOException If an I/O error occurs
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*/
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public void write(String s, int off, int len) throws IOException {
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synchronized (lock) {
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ensureOpen();
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int b = off, t = off + len;
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while (b < t) {
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int d = min(nChars - nextChar, t - b);
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s.getChars(b, b + d, cb, nextChar);
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b += d;
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nextChar += d;
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if (nextChar >= nChars)
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flushBuffer();
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}
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}
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}
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/**
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* Writes a line separator. The line separator string is defined by the
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* system property <tt>line.separator</tt>, and is not necessarily a single
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* newline ('\n') character.
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*
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* @exception IOException If an I/O error occurs
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*/
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public void newLine() throws IOException {
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write(lineSeparator);
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}
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/**
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* Flushes the stream.
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*
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* @exception IOException If an I/O error occurs
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*/
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public void flush() throws IOException {
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synchronized (lock) {
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flushBuffer();
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out.flush();
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}
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}
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public void close() throws IOException {
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synchronized (lock) {
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if (out == null) {
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return;
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}
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try {
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flushBuffer();
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} finally {
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out.close();
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out = null;
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cb = null;
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}
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}
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}
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}
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