1 /*
   2  * Copyright (c) 1994, 2017, 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 import java.util.Arrays;
  29 import java.util.Objects;
  30 
  31 /**
  32  * A {@code ByteArrayInputStream} contains
  33  * an internal buffer that contains bytes that
  34  * may be read from the stream. An internal
  35  * counter keeps track of the next byte to
  36  * be supplied by the {@code read} method.
  37  * <p>
  38  * Closing a {@code ByteArrayInputStream} has no effect. The methods in
  39  * this class can be called after the stream has been closed without
  40  * generating an {@code IOException}.
  41  *
  42  * @author  Arthur van Hoff
  43  * @see     java.io.StringBufferInputStream
  44  * @since   1.0
  45  */
  46 public class ByteArrayInputStream extends InputStream {
  47 
  48     /**
  49      * An array of bytes that was provided
  50      * by the creator of the stream. Elements {@code buf[0]}
  51      * through {@code buf[count-1]} are the
  52      * only bytes that can ever be read from the
  53      * stream;  element {@code buf[pos]} is
  54      * the next byte to be read.
  55      */
  56     protected byte buf[];
  57 
  58     /**
  59      * The index of the next character to read from the input stream buffer.
  60      * This value should always be nonnegative
  61      * and not larger than the value of {@code count}.
  62      * The next byte to be read from the input stream buffer
  63      * will be {@code buf[pos]}.
  64      */
  65     protected int pos;
  66 
  67     /**
  68      * The currently marked position in the stream.
  69      * ByteArrayInputStream objects are marked at position zero by
  70      * default when constructed.  They may be marked at another
  71      * position within the buffer by the {@code mark()} method.
  72      * The current buffer position is set to this point by the
  73      * {@code reset()} method.
  74      * <p>
  75      * If no mark has been set, then the value of mark is the offset
  76      * passed to the constructor (or 0 if the offset was not supplied).
  77      *
  78      * @since   1.1
  79      */
  80     protected int mark = 0;
  81 
  82     /**
  83      * The index one greater than the last valid character in the input
  84      * stream buffer.
  85      * This value should always be nonnegative
  86      * and not larger than the length of {@code buf}.
  87      * It  is one greater than the position of
  88      * the last byte within {@code buf} that
  89      * can ever be read  from the input stream buffer.
  90      */
  91     protected int count;
  92 
  93     /**
  94      * Creates a {@code ByteArrayInputStream}
  95      * so that it  uses {@code buf} as its
  96      * buffer array.
  97      * The buffer array is not copied.
  98      * The initial value of {@code pos}
  99      * is {@code 0} and the initial value
 100      * of  {@code count} is the length of
 101      * {@code buf}.
 102      *
 103      * @param   buf   the input buffer.
 104      */
 105     public ByteArrayInputStream(byte buf[]) {
 106         this.buf = buf;
 107         this.pos = 0;
 108         this.count = buf.length;
 109     }
 110 
 111     /**
 112      * Creates {@code ByteArrayInputStream}
 113      * that uses {@code buf} as its
 114      * buffer array. The initial value of {@code pos}
 115      * is {@code offset} and the initial value
 116      * of {@code count} is the minimum of {@code offset+length}
 117      * and {@code buf.length}.
 118      * The buffer array is not copied. The buffer's mark is
 119      * set to the specified offset.
 120      *
 121      * @param   buf      the input buffer.
 122      * @param   offset   the offset in the buffer of the first byte to read.
 123      * @param   length   the maximum number of bytes to read from the buffer.
 124      */
 125     public ByteArrayInputStream(byte buf[], int offset, int length) {
 126         this.buf = buf;
 127         this.pos = offset;
 128         this.count = Math.min(offset + length, buf.length);
 129         this.mark = offset;
 130     }
 131 
 132     /**
 133      * Reads the next byte of data from this input stream. The value
 134      * byte is returned as an {@code int} in the range
 135      * {@code 0} to {@code 255}. If no byte is available
 136      * because the end of the stream has been reached, the value
 137      * {@code -1} is returned.
 138      * <p>
 139      * This {@code read} method
 140      * cannot block.
 141      *
 142      * @return  the next byte of data, or {@code -1} if the end of the
 143      *          stream has been reached.
 144      */
 145     public synchronized int read() {
 146         return (pos < count) ? (buf[pos++] & 0xff) : -1;
 147     }
 148 
 149     /**
 150      * Reads up to {@code len} bytes of data into an array of bytes
 151      * from this input stream.
 152      * If {@code pos} equals {@code count},
 153      * then {@code -1} is returned to indicate
 154      * end of file. Otherwise, the  number {@code k}
 155      * of bytes read is equal to the smaller of
 156      * {@code len} and {@code count-pos}.
 157      * If {@code k} is positive, then bytes
 158      * {@code buf[pos]} through {@code buf[pos+k-1]}
 159      * are copied into {@code b[off]}  through
 160      * {@code b[off+k-1]} in the manner performed
 161      * by {@code System.arraycopy}. The
 162      * value {@code k} is added into {@code pos}
 163      * and {@code k} is returned.
 164      * <p>
 165      * This {@code read} method cannot block.
 166      *
 167      * @param   b     the buffer into which the data is read.
 168      * @param   off   the start offset in the destination array {@code b}
 169      * @param   len   the maximum number of bytes read.
 170      * @return  the total number of bytes read into the buffer, or
 171      *          {@code -1} if there is no more data because the end of
 172      *          the stream has been reached.
 173      * @throws  NullPointerException If {@code b} is {@code null}.
 174      * @throws  IndexOutOfBoundsException If {@code off} is negative,
 175      * {@code len} is negative, or {@code len} is greater than
 176      * {@code b.length - off}
 177      */
 178     public synchronized int read(byte b[], int off, int len) {
 179         Objects.checkFromIndexSize(off, len, b.length);
 180 
 181         if (pos >= count) {
 182             return -1;
 183         }
 184 
 185         int avail = count - pos;
 186         if (len > avail) {
 187             len = avail;
 188         }
 189         if (len <= 0) {
 190             return 0;
 191         }
 192         System.arraycopy(buf, pos, b, off, len);
 193         pos += len;
 194         return len;
 195     }
 196 
 197     public synchronized byte[] readAllBytes() {
 198         byte[] result = Arrays.copyOfRange(buf, pos, count);
 199         pos = count;
 200         return result;
 201     }
 202 
 203     public synchronized int readNBytes(byte[] b, int off, int len) {
 204         int n = read(b, off, len);
 205         return n == -1 ? 0 : n;
 206     }
 207 
 208     public synchronized long transferTo(OutputStream out) throws IOException {
 209         int pos0 = pos;
 210         out.write(buf, pos, count - pos);
 211         pos = count;
 212         return count - pos0;
 213     }
 214 
 215     /**
 216      * Skips {@code n} bytes of input from this input stream. Fewer
 217      * bytes might be skipped if the end of the input stream is reached.
 218      * The actual number {@code k}
 219      * of bytes to be skipped is equal to the smaller
 220      * of {@code n} and  {@code count-pos}.
 221      * The value {@code k} is added into {@code pos}
 222      * and {@code k} is returned.
 223      *
 224      * @param   n   the number of bytes to be skipped.
 225      * @return  the actual number of bytes skipped.
 226      */
 227     public synchronized long skip(long n) {
 228         long k = count - pos;
 229         if (n < k) {
 230             k = n < 0 ? 0 : n;
 231         }
 232 
 233         pos += k;
 234         return k;
 235     }
 236 
 237     /**
 238      * Returns the number of remaining bytes that can be read (or skipped over)
 239      * from this input stream.
 240      * <p>
 241      * The value returned is {@code count - pos},
 242      * which is the number of bytes remaining to be read from the input buffer.
 243      *
 244      * @return  the number of remaining bytes that can be read (or skipped
 245      *          over) from this input stream without blocking.
 246      */
 247     public synchronized int available() {
 248         return count - pos;
 249     }
 250 
 251     /**
 252      * Tests if this {@code InputStream} supports mark/reset. The
 253      * {@code markSupported} method of {@code ByteArrayInputStream}
 254      * always returns {@code true}.
 255      *
 256      * @since   1.1
 257      */
 258     public boolean markSupported() {
 259         return true;
 260     }
 261 
 262     /**
 263      * Set the current marked position in the stream.
 264      * ByteArrayInputStream objects are marked at position zero by
 265      * default when constructed.  They may be marked at another
 266      * position within the buffer by this method.
 267      * <p>
 268      * If no mark has been set, then the value of the mark is the
 269      * offset passed to the constructor (or 0 if the offset was not
 270      * supplied).
 271      *
 272      * <p> Note: The {@code readAheadLimit} for this class
 273      *  has no meaning.
 274      *
 275      * @since   1.1
 276      */
 277     public void mark(int readAheadLimit) {
 278         mark = pos;
 279     }
 280 
 281     /**
 282      * Resets the buffer to the marked position.  The marked position
 283      * is 0 unless another position was marked or an offset was specified
 284      * in the constructor.
 285      */
 286     public synchronized void reset() {
 287         pos = mark;
 288     }
 289 
 290     /**
 291      * Closing a {@code ByteArrayInputStream} has no effect. The methods in
 292      * this class can be called after the stream has been closed without
 293      * generating an {@code IOException}.
 294      */
 295     public void close() throws IOException {
 296     }
 297 
 298 }