1/*
2 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package java.io;
27
28
29/**
30 * Writes text to a character-output stream, buffering characters so as to
31 * provide for the efficient writing of single characters, arrays, and strings.
32 *
33 * <p> The buffer size may be specified, or the default size may be accepted.
34 * The default is large enough for most purposes.
35 *
36 * <p> A newLine() method is provided, which uses the platform's own notion of
37 * line separator as defined by the system property <tt>line.separator</tt>.
38 * Not all platforms use the newline character ('\n') to terminate lines.
39 * Calling this method to terminate each output line is therefore preferred to
40 * writing a newline character directly.
41 *
42 * <p> In general, a Writer sends its output immediately to the underlying
43 * character or byte stream.  Unless prompt output is required, it is advisable
44 * to wrap a BufferedWriter around any Writer whose write() operations may be
45 * costly, such as FileWriters and OutputStreamWriters.  For example,
46 *
47 * <pre>
48 * PrintWriter out
49 *   = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));
50 * </pre>
51 *
52 * will buffer the PrintWriter's output to the file.  Without buffering, each
53 * invocation of a print() method would cause characters to be converted into
54 * bytes that would then be written immediately to the file, which can be very
55 * inefficient.
56 *
57 * @see PrintWriter
58 * @see FileWriter
59 * @see OutputStreamWriter
60 * @see java.nio.file.Files#newBufferedWriter
61 *
62 * @author      Mark Reinhold
63 * @since       JDK1.1
64 */
65
66public class BufferedWriter extends Writer {
67
68    private Writer out;
69
70    private char cb[];
71    private int nChars, nextChar;
72
73    private static int defaultCharBufferSize = 8192;
74
75    /**
76     * Line separator string.  This is the value of the line.separator
77     * property at the moment that the stream was created.
78     */
79    private String lineSeparator;
80
81    /**
82     * Creates a buffered character-output stream that uses a default-sized
83     * output buffer.
84     *
85     * @param  out  A Writer
86     */
87    public BufferedWriter(Writer out) {
88        this(out, defaultCharBufferSize);
89    }
90
91    /**
92     * Creates a new buffered character-output stream that uses an output
93     * buffer of the given size.
94     *
95     * @param  out  A Writer
96     * @param  sz   Output-buffer size, a positive integer
97     *
98     * @exception  IllegalArgumentException  If {@code sz <= 0}
99     */
100    public BufferedWriter(Writer out, int sz) {
101        super(out);
102        if (sz <= 0)
103            throw new IllegalArgumentException("Buffer size <= 0");
104        this.out = out;
105        cb = new char[sz];
106        nChars = sz;
107        nextChar = 0;
108
109        lineSeparator = java.security.AccessController.doPrivileged(
110            new sun.security.action.GetPropertyAction("line.separator"));
111    }
112
113    /** Checks to make sure that the stream has not been closed */
114    private void ensureOpen() throws IOException {
115        if (out == null)
116            throw new IOException("Stream closed");
117    }
118
119    /**
120     * Flushes the output buffer to the underlying character stream, without
121     * flushing the stream itself.  This method is non-private only so that it
122     * may be invoked by PrintStream.
123     */
124    void flushBuffer() throws IOException {
125        synchronized (lock) {
126            ensureOpen();
127            if (nextChar == 0)
128                return;
129            out.write(cb, 0, nextChar);
130            nextChar = 0;
131        }
132    }
133
134    /**
135     * Writes a single character.
136     *
137     * @exception  IOException  If an I/O error occurs
138     */
139    public void write(int c) throws IOException {
140        synchronized (lock) {
141            ensureOpen();
142            if (nextChar >= nChars)
143                flushBuffer();
144            cb[nextChar++] = (char) c;
145        }
146    }
147
148    /**
149     * Our own little min method, to avoid loading java.lang.Math if we've run
150     * out of file descriptors and we're trying to print a stack trace.
151     */
152    private int min(int a, int b) {
153        if (a < b) return a;
154        return b;
155    }
156
157    /**
158     * Writes a portion of an array of characters.
159     *
160     * <p> Ordinarily this method stores characters from the given array into
161     * this stream's buffer, flushing the buffer to the underlying stream as
162     * needed.  If the requested length is at least as large as the buffer,
163     * however, then this method will flush the buffer and write the characters
164     * directly to the underlying stream.  Thus redundant
165     * <code>BufferedWriter</code>s will not copy data unnecessarily.
166     *
167     * @param  cbuf  A character array
168     * @param  off   Offset from which to start reading characters
169     * @param  len   Number of characters to write
170     *
171     * @exception  IOException  If an I/O error occurs
172     */
173    public void write(char cbuf[], int off, int len) throws IOException {
174        synchronized (lock) {
175            ensureOpen();
176            if ((off < 0) || (off > cbuf.length) || (len < 0) ||
177                ((off + len) > cbuf.length) || ((off + len) < 0)) {
178                throw new IndexOutOfBoundsException();
179            } else if (len == 0) {
180                return;
181            }
182
183            if (len >= nChars) {
184                /* If the request length exceeds the size of the output buffer,
185                   flush the buffer and then write the data directly.  In this
186                   way buffered streams will cascade harmlessly. */
187                flushBuffer();
188                out.write(cbuf, off, len);
189                return;
190            }
191
192            int b = off, t = off + len;
193            while (b < t) {
194                int d = min(nChars - nextChar, t - b);
195                System.arraycopy(cbuf, b, cb, nextChar, d);
196                b += d;
197                nextChar += d;
198                if (nextChar >= nChars)
199                    flushBuffer();
200            }
201        }
202    }
203
204    /**
205     * Writes a portion of a String.
206     *
207     * <p> If the value of the <tt>len</tt> parameter is negative then no
208     * characters are written.  This is contrary to the specification of this
209     * method in the {@linkplain java.io.Writer#write(java.lang.String,int,int)
210     * superclass}, which requires that an {@link IndexOutOfBoundsException} be
211     * thrown.
212     *
213     * @param  s     String to be written
214     * @param  off   Offset from which to start reading characters
215     * @param  len   Number of characters to be written
216     *
217     * @exception  IOException  If an I/O error occurs
218     */
219    public void write(String s, int off, int len) throws IOException {
220        synchronized (lock) {
221            ensureOpen();
222
223            int b = off, t = off + len;
224            while (b < t) {
225                int d = min(nChars - nextChar, t - b);
226                s.getChars(b, b + d, cb, nextChar);
227                b += d;
228                nextChar += d;
229                if (nextChar >= nChars)
230                    flushBuffer();
231            }
232        }
233    }
234
235    /**
236     * Writes a line separator.  The line separator string is defined by the
237     * system property <tt>line.separator</tt>, and is not necessarily a single
238     * newline ('\n') character.
239     *
240     * @exception  IOException  If an I/O error occurs
241     */
242    public void newLine() throws IOException {
243        write(lineSeparator);
244    }
245
246    /**
247     * Flushes the stream.
248     *
249     * @exception  IOException  If an I/O error occurs
250     */
251    public void flush() throws IOException {
252        synchronized (lock) {
253            flushBuffer();
254            out.flush();
255        }
256    }
257
258    @SuppressWarnings("try")
259    public void close() throws IOException {
260        synchronized (lock) {
261            if (out == null) {
262                return;
263            }
264            try (Writer w = out) {
265                flushBuffer();
266            } finally {
267                out = null;
268                cb = null;
269            }
270        }
271    }
272}
273