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
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 1.0
36 */
37 public 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 }