1 /*
  2  * Copyright (c) 1994, 2019, 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      * @throws  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      * @throws     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} bytes from the specified byte array
102      * starting at offset {@code off} 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}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      * @throws     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      * @throws     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 }