1/*
2 * Copyright (c) 1994, 2015, 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 * The class implements a buffered output stream. By setting up such
30 * an output stream, an application can write bytes to the underlying
31 * output stream without necessarily causing a call to the underlying
32 * system for each byte written.
33 *
34 * @author  Arthur van Hoff
35 * @since   1.0
36 */
37public class BufferedOutputStream extends FilterOutputStream {
38    /**
39     * The internal buffer where data is stored.
40     */
41    protected byte buf[];
42
43    /**
44     * The number of valid bytes in the buffer. This value is always
45     * in the range {@code 0} through {@code buf.length}; elements
46     * {@code buf[0]} through {@code buf[count-1]} contain valid
47     * byte data.
48     */
49    protected int count;
50
51    /**
52     * Creates a new buffered output stream to write data to the
53     * specified underlying output stream.
54     *
55     * @param   out   the underlying output stream.
56     */
57    public BufferedOutputStream(OutputStream out) {
58        this(out, 8192);
59    }
60
61    /**
62     * Creates a new buffered output stream to write data to the
63     * specified underlying output stream with the specified buffer
64     * size.
65     *
66     * @param   out    the underlying output stream.
67     * @param   size   the buffer size.
68     * @exception IllegalArgumentException if size <= 0.
69     */
70    public BufferedOutputStream(OutputStream out, int size) {
71        super(out);
72        if (size <= 0) {
73            throw new IllegalArgumentException("Buffer size <= 0");
74        }
75        buf = new byte[size];
76    }
77
78    /** Flush the internal buffer */
79    private void flushBuffer() throws IOException {
80        if (count > 0) {
81            out.write(buf, 0, count);
82            count = 0;
83        }
84    }
85
86    /**
87     * Writes the specified byte to this buffered output stream.
88     *
89     * @param      b   the byte to be written.
90     * @exception  IOException  if an I/O error occurs.
91     */
92    @Override
93    public synchronized void write(int b) throws IOException {
94        if (count >= buf.length) {
95            flushBuffer();
96        }
97        buf[count++] = (byte)b;
98    }
99
100    /**
101     * Writes <code>len</code> bytes from the specified byte array
102     * starting at offset <code>off</code> to this buffered output stream.
103     *
104     * <p> Ordinarily this method stores bytes from the given array into this
105     * stream's buffer, flushing the buffer to the underlying output stream as
106     * needed.  If the requested length is at least as large as this stream's
107     * buffer, however, then this method will flush the buffer and write the
108     * bytes directly to the underlying output stream.  Thus redundant
109     * <code>BufferedOutputStream</code>s will not copy data unnecessarily.
110     *
111     * @param      b     the data.
112     * @param      off   the start offset in the data.
113     * @param      len   the number of bytes to write.
114     * @exception  IOException  if an I/O error occurs.
115     */
116    @Override
117    public synchronized void write(byte b[], int off, int len) throws IOException {
118        if (len >= buf.length) {
119            /* If the request length exceeds the size of the output buffer,
120               flush the output buffer and then write the data directly.
121               In this way buffered streams will cascade harmlessly. */
122            flushBuffer();
123            out.write(b, off, len);
124            return;
125        }
126        if (len > buf.length - count) {
127            flushBuffer();
128        }
129        System.arraycopy(b, off, buf, count, len);
130        count += len;
131    }
132
133    /**
134     * Flushes this buffered output stream. This forces any buffered
135     * output bytes to be written out to the underlying output stream.
136     *
137     * @exception  IOException  if an I/O error occurs.
138     * @see        java.io.FilterOutputStream#out
139     */
140    @Override
141    public synchronized void flush() throws IOException {
142        flushBuffer();
143        out.flush();
144    }
145}
146