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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
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15  * accompanied this code).
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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      */
BufferedOutputStream(OutputStream out)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 &lt;= 0.
70      */
BufferedOutputStream(OutputStream out, int size)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 */
flushBuffer()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      */
write(int b)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      */
write(byte b[], int off, int len)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      */
flush()139     public synchronized void flush() throws IOException {
140         flushBuffer();
141         out.flush();
142     }
143 }
144