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.nio.charset.Charset;
  29 import java.util.Arrays;
  30 
  31 /**
  32  * This class implements an output stream in which the data is
  33  * written into a byte array. The buffer automatically grows as data
  34  * is written to it.
  35  * The data can be retrieved using {@code toByteArray()} and
  36  * {@code toString()}.
  37  * <p>
  38  * Closing a {@code ByteArrayOutputStream} 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  * @since   1.0
  44  */
  45 
  46 public class ByteArrayOutputStream extends OutputStream {
  47 
  48     /**
  49      * The buffer where data is stored.
  50      */
  51     protected byte buf[];
  52 
  53     /**
  54      * The number of valid bytes in the buffer.
  55      */
  56     protected int count;
  57 
  58     /**
  59      * Creates a new byte array output stream. The buffer capacity is
  60      * initially 32 bytes, though its size increases if necessary.
  61      */
  62     public ByteArrayOutputStream() {
  63         this(32);
  64     }
  65 
  66     /**
  67      * Creates a new byte array output stream, with a buffer capacity of
  68      * the specified size, in bytes.
  69      *
  70      * @param   size   the initial size.
  71      * @exception  IllegalArgumentException if size is negative.
  72      */
  73     public ByteArrayOutputStream(int size) {
  74         if (size < 0) {
  75             throw new IllegalArgumentException("Negative initial size: "
  76                                                + size);
  77         }
  78         buf = new byte[size];
  79     }
  80 
  81     /**
  82      * Increases the capacity if necessary to ensure that it can hold
  83      * at least the number of elements specified by the minimum
  84      * capacity argument.
  85      *
  86      * @param minCapacity the desired minimum capacity
  87      * @throws OutOfMemoryError if {@code minCapacity < 0}.  This is
  88      * interpreted as a request for the unsatisfiably large capacity
  89      * {@code (long) Integer.MAX_VALUE + (minCapacity - Integer.MAX_VALUE)}.
  90      */
  91     private void ensureCapacity(int minCapacity) {
  92         // overflow-conscious code
  93         if (minCapacity - buf.length > 0)
  94             grow(minCapacity);
  95     }
  96 
  97     /**
  98      * The maximum size of array to allocate.
  99      * Some VMs reserve some header words in an array.
 100      * Attempts to allocate larger arrays may result in
 101      * OutOfMemoryError: Requested array size exceeds VM limit
 102      */
 103     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
 104 
 105     /**
 106      * Increases the capacity to ensure that it can hold at least the
 107      * number of elements specified by the minimum capacity argument.
 108      *
 109      * @param minCapacity the desired minimum capacity
 110      */
 111     private void grow(int minCapacity) {
 112         // overflow-conscious code
 113         int oldCapacity = buf.length;
 114         int newCapacity = oldCapacity << 1;
 115         if (newCapacity - minCapacity < 0)
 116             newCapacity = minCapacity;
 117         if (newCapacity - MAX_ARRAY_SIZE > 0)
 118             newCapacity = hugeCapacity(minCapacity);
 119         buf = Arrays.copyOf(buf, newCapacity);
 120     }
 121 
 122     private static int hugeCapacity(int minCapacity) {
 123         if (minCapacity < 0) // overflow
 124             throw new OutOfMemoryError();
 125         return (minCapacity > MAX_ARRAY_SIZE) ?
 126             Integer.MAX_VALUE :
 127             MAX_ARRAY_SIZE;
 128     }
 129 
 130     /**
 131      * Writes the specified byte to this byte array output stream.
 132      *
 133      * @param   b   the byte to be written.
 134      */
 135     public synchronized void write(int b) {
 136         ensureCapacity(count + 1);
 137         buf[count] = (byte) b;
 138         count += 1;
 139     }
 140 
 141     /**
 142      * Writes {@code len} bytes from the specified byte array
 143      * starting at offset {@code off} to this byte array output stream.
 144      *
 145      * @param   b     the data.
 146      * @param   off   the start offset in the data.
 147      * @param   len   the number of bytes to write.
 148      */
 149     public synchronized void write(byte b[], int off, int len) {
 150         if ((off < 0) || (off > b.length) || (len < 0) ||
 151             ((off + len) - b.length > 0)) {
 152             throw new IndexOutOfBoundsException();
 153         }
 154         ensureCapacity(count + len);
 155         System.arraycopy(b, off, buf, count, len);
 156         count += len;
 157     }
 158 
 159     /**
 160      * Writes the complete contents of this byte array output stream to
 161      * the specified output stream argument, as if by calling the output
 162      * stream's write method using {@code out.write(buf, 0, count)}.
 163      *
 164      * @param      out   the output stream to which to write the data.
 165      * @exception  IOException  if an I/O error occurs.
 166      */
 167     public synchronized void writeTo(OutputStream out) throws IOException {
 168         out.write(buf, 0, count);
 169     }
 170 
 171     /**
 172      * Resets the {@code count} field of this byte array output
 173      * stream to zero, so that all currently accumulated output in the
 174      * output stream is discarded. The output stream can be used again,
 175      * reusing the already allocated buffer space.
 176      *
 177      * @see     java.io.ByteArrayInputStream#count
 178      */
 179     public synchronized void reset() {
 180         count = 0;
 181     }
 182 
 183     /**
 184      * Creates a newly allocated byte array. Its size is the current
 185      * size of this output stream and the valid contents of the buffer
 186      * have been copied into it.
 187      *
 188      * @return  the current contents of this output stream, as a byte array.
 189      * @see     java.io.ByteArrayOutputStream#size()
 190      */
 191     public synchronized byte[] toByteArray() {
 192         return Arrays.copyOf(buf, count);
 193     }
 194 
 195     /**
 196      * Returns the current size of the buffer.
 197      *
 198      * @return  the value of the {@code count} field, which is the number
 199      *          of valid bytes in this output stream.
 200      * @see     java.io.ByteArrayOutputStream#count
 201      */
 202     public synchronized int size() {
 203         return count;
 204     }
 205 
 206     /**
 207      * Converts the buffer's contents into a string decoding bytes using the
 208      * platform's default character set. The length of the new {@code String}
 209      * is a function of the character set, and hence may not be equal to the
 210      * size of the buffer.
 211      *
 212      * <p> This method always replaces malformed-input and unmappable-character
 213      * sequences with the default replacement string for the platform's
 214      * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
 215      * class should be used when more control over the decoding process is
 216      * required.
 217      *
 218      * @return String decoded from the buffer's contents.
 219      * @since  1.1
 220      */
 221     public synchronized String toString() {
 222         return new String(buf, 0, count);
 223     }
 224 
 225     /**
 226      * Converts the buffer's contents into a string by decoding the bytes using
 227      * the named {@link java.nio.charset.Charset charset}.
 228      *
 229      * <p> This method is equivalent to {@code #toString(charset)} that takes a
 230      * {@link java.nio.charset.Charset charset}.
 231      *
 232      * <p> An invocation of this method of the form
 233      *
 234      * <pre> {@code
 235      *      ByteArrayOutputStream b = ...
 236      *      b.toString("UTF-8")
 237      *      }
 238      * </pre>
 239      *
 240      * behaves in exactly the same way as the expression
 241      *
 242      * <pre> {@code
 243      *      ByteArrayOutputStream b = ...
 244      *      b.toString(StandardCharsets.UTF_8)
 245      *      }
 246      * </pre>
 247      *
 248      *
 249      * @param      charsetName  the name of a supported
 250      *             {@link java.nio.charset.Charset charset}
 251      * @return     String decoded from the buffer's contents.
 252      * @exception  UnsupportedEncodingException
 253      *             If the named charset is not supported
 254      * @since      1.1
 255      */
 256     public synchronized String toString(String charsetName)
 257         throws UnsupportedEncodingException
 258     {
 259         return new String(buf, 0, count, charsetName);
 260     }
 261 
 262     /**
 263      * Converts the buffer's contents into a string by decoding the bytes using
 264      * the specified {@link java.nio.charset.Charset charset}. The length of the new
 265      * {@code String} is a function of the charset, and hence may not be equal
 266      * to the length of the byte array.
 267      *
 268      * <p> This method always replaces malformed-input and unmappable-character
 269      * sequences with the charset's default replacement string. The {@link
 270      * java.nio.charset.CharsetDecoder} class should be used when more control
 271      * over the decoding process is required.
 272      *
 273      * @param      charset  the {@linkplain java.nio.charset.Charset charset}
 274      *             to be used to decode the {@code bytes}
 275      * @return     String decoded from the buffer's contents.
 276      * @since      10
 277      */
 278     public synchronized String toString(Charset charset) {
 279         return new String(buf, 0, count, charset);
 280     }
 281 
 282     /**
 283      * Creates a newly allocated string. Its size is the current size of
 284      * the output stream and the valid contents of the buffer have been
 285      * copied into it. Each character <i>c</i> in the resulting string is
 286      * constructed from the corresponding element <i>b</i> in the byte
 287      * array such that:
 288      * <blockquote><pre>{@code
 289      *     c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
 290      * }</pre></blockquote>
 291      *
 292      * @deprecated This method does not properly convert bytes into characters.
 293      * As of JDK&nbsp;1.1, the preferred way to do this is via the
 294      * {@link #toString(String charsetName)} or {@link #toString(Charset charset)}
 295      * method, which takes an encoding-name or charset argument,
 296      * or the {@code toString()} method, which uses the platform's default
 297      * character encoding.
 298      *
 299      * @param      hibyte    the high byte of each resulting Unicode character.
 300      * @return     the current contents of the output stream, as a string.
 301      * @see        java.io.ByteArrayOutputStream#size()
 302      * @see        java.io.ByteArrayOutputStream#toString(String)
 303      * @see        java.io.ByteArrayOutputStream#toString()
 304      */
 305     @Deprecated
 306     public synchronized String toString(int hibyte) {
 307         return new String(buf, hibyte, 0, count);
 308     }
 309 
 310     /**
 311      * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
 312      * this class can be called after the stream has been closed without
 313      * generating an {@code IOException}.
 314      */
 315     public void close() throws IOException {
 316     }
 317 
 318 }