1 /*
2 * Copyright 1994-2003 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package 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 JDK1.0
36 */
37 public
38 class BufferedOutputStream extends FilterOutputStream {
39 /**
40 * The internal buffer where data is stored.
41 */
42 protected byte buf[];
43
44 /**
45 * The number of valid bytes in the buffer. This value is always
46 * in the range <tt>0</tt> through <tt>buf.length</tt>; elements
47 * <tt>buf[0]</tt> through <tt>buf[count-1]</tt> contain valid
48 * byte data.
49 */
50 protected int count;
51
52 /**
53 * Creates a new buffered output stream to write data to the
54 * specified underlying output stream.
55 *
56 * @param out the underlying output stream.
57 */
58 public BufferedOutputStream(OutputStream out) {
59 this(out, 8192);
60 }
61
62 /**
63 * Creates a new buffered output stream to write data to the
64 * specified underlying output stream with the specified buffer
65 * size.
66 *
67 * @param out the underlying output stream.
68 * @param size the buffer size.
69 * @exception IllegalArgumentException if size <= 0.
70 */
71 public BufferedOutputStream(OutputStream out, int size) {
72 super(out);
73 if (size <= 0) {
74 throw new IllegalArgumentException("Buffer size <= 0");
75 }
76 buf = new byte[size];
77 }
78
79 /** Flush the internal buffer */
80 private void flushBuffer() throws IOException {
81 if (count > 0) {
82 out.write(buf, 0, count);
83 count = 0;
84 }
85 }
86
87 /**
88 * Writes the specified byte to this buffered output stream.
89 *
90 * @param b the byte to be written.
91 * @exception IOException if an I/O error occurs.
92 */
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 public synchronized void write(byte b[], int off, int len) throws IOException {
117 if (len >= buf.length) {
118 /* If the request length exceeds the size of the output buffer,
119 flush the output buffer and then write the data directly.
120 In this way buffered streams will cascade harmlessly. */
121 flushBuffer();
122 out.write(b, off, len);
123 return;
124 }
125 if (len > buf.length - count) {
126 flushBuffer();
127 }
128 System.arraycopy(b, off, buf, count, len);
129 count += len;
130 }
131
132 /**
133 * Flushes this buffered output stream. This forces any buffered
134 * output bytes to be written out to the underlying output stream.
135 *
136 * @exception IOException if an I/O error occurs.
137 * @see java.io.FilterOutputStream#out
138 */
139 public synchronized void flush() throws IOException {
140 flushBuffer();
141 out.flush();
142 }
143 }
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