1 /*
   2  * Copyright (c) 1994, 2013, 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  * A <code>ByteArrayInputStream</code> contains
  30  * an internal buffer that contains bytes that
  31  * may be read from the stream. An internal
  32  * counter keeps track of the next byte to
  33  * be supplied by the <code>read</code> method.
  34  * <p>
  35  * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
  36  * this class can be called after the stream has been closed without
  37  * generating an <tt>IOException</tt>.
  38  *
  39  * @author  Arthur van Hoff
  40  * @see     java.io.StringBufferInputStream
  41  * @since   JDK1.0
  42  */
  43 public
  44 class ByteArrayInputStream extends InputStream {
  45 
  46     /**
  47      * An array of bytes that was provided
  48      * by the creator of the stream. Elements <code>buf[0]</code>
  49      * through <code>buf[count-1]</code> are the
  50      * only bytes that can ever be read from the
  51      * stream;  element <code>buf[pos]</code> is
  52      * the next byte to be read.
  53      */
  54     protected byte buf[];
  55 
  56     /**
  57      * The index of the next character to read from the input stream buffer.
  58      * This value should always be nonnegative
  59      * and not larger than the value of <code>count</code>.
  60      * The next byte to be read from the input stream buffer
  61      * will be <code>buf[pos]</code>.
  62      */
  63     protected int pos;
  64 
  65     /**
  66      * The currently marked position in the stream.
  67      * ByteArrayInputStream objects are marked at position zero by
  68      * default when constructed.  They may be marked at another
  69      * position within the buffer by the <code>mark()</code> method.
  70      * The current buffer position is set to this point by the
  71      * <code>reset()</code> method.
  72      * <p>
  73      * If no mark has been set, then the value of mark is the offset
  74      * passed to the constructor (or 0 if the offset was not supplied).
  75      *
  76      * @since   JDK1.1
  77      */
  78     protected int mark = 0;
  79 
  80     /**
  81      * The index one greater than the last valid character in the input
  82      * stream buffer.
  83      * This value should always be nonnegative
  84      * and not larger than the length of <code>buf</code>.
  85      * It  is one greater than the position of
  86      * the last byte within <code>buf</code> that
  87      * can ever be read  from the input stream buffer.
  88      */
  89     protected int count;
  90 
  91     /**
  92      * Creates a <code>ByteArrayInputStream</code>
  93      * so that it  uses <code>buf</code> as its
  94      * buffer array.
  95      * The buffer array is not copied.
  96      * The initial value of <code>pos</code>
  97      * is <code>0</code> and the initial value
  98      * of  <code>count</code> is the length of
  99      * <code>buf</code>.
 100      *
 101      * @param   buf   the input buffer.
 102      */
 103     public ByteArrayInputStream(byte buf[]) {
 104         this.buf = buf;
 105         this.pos = 0;
 106         this.count = buf.length;
 107     }
 108 
 109     /**
 110      * Creates <code>ByteArrayInputStream</code>
 111      * that uses <code>buf</code> as its
 112      * buffer array. The initial value of <code>pos</code>
 113      * is <code>offset</code> and the initial value
 114      * of <code>count</code> is the minimum of <code>offset+length</code>
 115      * and <code>buf.length</code>.
 116      * The buffer array is not copied. The buffer's mark is
 117      * set to the specified offset.
 118      *
 119      * @param   buf      the input buffer.
 120      * @param   offset   the offset in the buffer of the first byte to read.
 121      * @param   length   the maximum number of bytes to read from the buffer.
 122      */
 123     public ByteArrayInputStream(byte buf[], int offset, int length) {
 124         this.buf = buf;
 125         this.pos = offset;
 126         this.count = Math.min(offset + length, buf.length);
 127         this.mark = offset;
 128     }
 129 
 130     /**
 131      * Reads the next byte of data from this input stream. The value
 132      * byte is returned as an <code>int</code> in the range
 133      * <code>0</code> to <code>255</code>. If no byte is available
 134      * because the end of the stream has been reached, the value
 135      * <code>-1</code> is returned.
 136      * <p>
 137      * This <code>read</code> method
 138      * cannot block.
 139      *
 140      * @return  the next byte of data, or <code>-1</code> if the end of the
 141      *          stream has been reached.
 142      */
 143     public synchronized int read() {
 144         return (pos < count) ? (buf[pos++] & 0xff) : -1;
 145     }
 146 
 147     /**
 148      * Reads up to <code>len</code> bytes of data into an array of bytes
 149      * from this input stream.
 150      * If <code>pos</code> equals <code>count</code>,
 151      * then <code>-1</code> is returned to indicate
 152      * end of file. Otherwise, the  number <code>k</code>
 153      * of bytes read is equal to the smaller of
 154      * <code>len</code> and <code>count-pos</code>.
 155      * If <code>k</code> is positive, then bytes
 156      * <code>buf[pos]</code> through <code>buf[pos+k-1]</code>
 157      * are copied into <code>b[off]</code>  through
 158      * <code>b[off+k-1]</code> in the manner performed
 159      * by <code>System.arraycopy</code>. The
 160      * value <code>k</code> is added into <code>pos</code>
 161      * and <code>k</code> is returned.
 162      * <p>
 163      * This <code>read</code> method cannot block.
 164      *
 165      * @param   b     the buffer into which the data is read.
 166      * @param   off   the start offset in the destination array <code>b</code>
 167      * @param   len   the maximum number of bytes read.
 168      * @return  the total number of bytes read into the buffer, or
 169      *          <code>-1</code> if there is no more data because the end of
 170      *          the stream has been reached.
 171      * @exception  NullPointerException If <code>b</code> is <code>null</code>.
 172      * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
 173      * <code>len</code> is negative, or <code>len</code> is greater than
 174      * <code>b.length - off</code>
 175      */
 176     public synchronized int read(byte b[], int off, int len) {
 177         if (b == null) {
 178             throw new NullPointerException();
 179         } else if (off < 0 || len < 0 || len > b.length - off) {
 180             throw new IndexOutOfBoundsException();
 181         }
 182 
 183         if (pos >= count) {
 184             return -1;
 185         }
 186 
 187         int avail = count - pos;
 188         if (len > avail) {
 189             len = avail;
 190         }
 191         if (len <= 0) {
 192             return 0;
 193         }
 194         System.arraycopy(buf, pos, b, off, len);
 195         pos += len;
 196         return len;
 197     }
 198 
 199     /**
 200      * Skips <code>n</code> bytes of input from this input stream. Fewer
 201      * bytes might be skipped if the end of the input stream is reached.
 202      * The actual number <code>k</code>
 203      * of bytes to be skipped is equal to the smaller
 204      * of <code>n</code> and  <code>count-pos</code>.
 205      * The value <code>k</code> is added into <code>pos</code>
 206      * and <code>k</code> is returned.
 207      *
 208      * @param   n   the number of bytes to be skipped.
 209      * @return  the actual number of bytes skipped.
 210      */
 211     public synchronized long skip(long n) {
 212         long k = count - pos;
 213         if (n < k) {
 214             k = n < 0 ? 0 : n;
 215         }
 216 
 217         pos += k;
 218         return k;
 219     }
 220 
 221     /**
 222      * Returns the number of remaining bytes that can be read (or skipped over)
 223      * from this input stream.
 224      * <p>
 225      * The value returned is <code>count&nbsp;- pos</code>,
 226      * which is the number of bytes remaining to be read from the input buffer.
 227      *
 228      * @return  the number of remaining bytes that can be read (or skipped
 229      *          over) from this input stream without blocking.
 230      */
 231     public synchronized int available() {
 232         return count - pos;
 233     }
 234 
 235     /**
 236      * Tests if this <code>InputStream</code> supports mark/reset. The
 237      * <code>markSupported</code> method of <code>ByteArrayInputStream</code>
 238      * always returns <code>true</code>.
 239      *
 240      * @since   JDK1.1
 241      */
 242     public boolean markSupported() {
 243         return true;
 244     }
 245 
 246     /**
 247      * Set the current marked position in the stream.
 248      * ByteArrayInputStream objects are marked at position zero by
 249      * default when constructed.  They may be marked at another
 250      * position within the buffer by this method.
 251      * <p>
 252      * If no mark has been set, then the value of the mark is the
 253      * offset passed to the constructor (or 0 if the offset was not
 254      * supplied).
 255      *
 256      * <p> Note: The <code>readAheadLimit</code> for this class
 257      *  has no meaning.
 258      *
 259      * @since   JDK1.1
 260      */
 261     public void mark(int readAheadLimit) {
 262         mark = pos;
 263     }
 264 
 265     /**
 266      * Resets the buffer to the marked position.  The marked position
 267      * is 0 unless another position was marked or an offset was specified
 268      * in the constructor.
 269      */
 270     public synchronized void reset() {
 271         pos = mark;
 272     }
 273 
 274     /**
 275      * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
 276      * this class can be called after the stream has been closed without
 277      * generating an <tt>IOException</tt>.
 278      */
 279     public void close() throws IOException {
 280     }
 281 
 282 }