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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/java/io/ByteArrayInputStream.java
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+/* ByteArrayInputStream.java -- Read an array as a stream
+ Copyright (C) 1998, 1999, 2001, 2005 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING. If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.io;
+
+/**
+ * This class permits an array of bytes to be read as an input stream.
+ *
+ * @author Warren Levy (warrenl@cygnus.com)
+ * @author Aaron M. Renn (arenn@urbanophile.com)
+ */
+public class ByteArrayInputStream extends InputStream
+{
+ /**
+ * The array that contains the data supplied during read operations
+ */
+ protected byte[] buf;
+
+ /**
+ * The array index of the next byte to be read from the buffer
+ * <code>buf</code>
+ */
+ protected int pos;
+
+ /**
+ * The currently marked position in the stream. This defaults to 0, so a
+ * reset operation on the stream resets it to read from array index 0 in
+ * the buffer - even if the stream was initially created with an offset
+ * greater than 0
+ */
+ protected int mark;
+
+ /**
+ * This indicates the maximum number of bytes that can be read from this
+ * stream. It is the array index of the position after the last valid
+ * byte in the buffer <code>buf</code>
+ */
+ protected int count;
+
+ /**
+ * Create a new ByteArrayInputStream that will read bytes from the passed
+ * in byte array. This stream will read from the beginning to the end
+ * of the array. It is identical to calling an overloaded constructor
+ * as <code>ByteArrayInputStream(buf, 0, buf.length)</code>.
+ * <p>
+ * Note that this array is not copied. If its contents are changed
+ * while this stream is being read, those changes will be reflected in the
+ * bytes supplied to the reader. Please use caution in changing the
+ * contents of the buffer while this stream is open.
+ *
+ * @param buffer The byte array buffer this stream will read from.
+ */
+ public ByteArrayInputStream(byte[] buffer)
+ {
+ this(buffer, 0, buffer.length);
+ }
+
+ /**
+ * Create a new ByteArrayInputStream that will read bytes from the
+ * passed in byte array. This stream will read from position
+ * <code>offset</code> in the array for a length of
+ * <code>length</code> bytes past <code>offset</code>. If the
+ * stream is reset to a position before <code>offset</code> then
+ * more than <code>length</code> bytes can be read from the stream.
+ * The <code>length</code> value should be viewed as the array index
+ * one greater than the last position in the buffer to read.
+ * <p>
+ * Note that this array is not copied. If its contents are changed
+ * while this stream is being read, those changes will be reflected in the
+ * bytes supplied to the reader. Please use caution in changing the
+ * contents of the buffer while this stream is open.
+ *
+ * @param buffer The byte array buffer this stream will read from.
+ * @param offset The index into the buffer to start reading bytes from
+ * @param length The number of bytes to read from the buffer
+ */
+ public ByteArrayInputStream(byte[] buffer, int offset, int length)
+ {
+ if (offset < 0 || length < 0 || offset > buffer.length)
+ throw new IllegalArgumentException();
+
+ buf = buffer;
+
+ count = offset + length;
+ if (count > buf.length)
+ count = buf.length;
+
+ pos = offset;
+ mark = pos;
+ }
+
+ /**
+ * This method returns the number of bytes available to be read from this
+ * stream. The value returned will be equal to <code>count - pos</code>.
+ *
+ * @return The number of bytes that can be read from this stream
+ * before blocking, which is all of them
+ */
+ public synchronized int available()
+ {
+ return count - pos;
+ }
+
+ /**
+ * This method sets the mark position in this stream to the current
+ * position. Note that the <code>readlimit</code> parameter in this
+ * method does nothing as this stream is always capable of
+ * remembering all the bytes int it.
+ * <p>
+ * Note that in this class the mark position is set by default to
+ * position 0 in the stream. This is in constrast to some other
+ * stream types where there is no default mark position.
+ *
+ * @param readLimit The number of bytes this stream must remember.
+ * This parameter is ignored.
+ */
+ public synchronized void mark(int readLimit)
+ {
+ // readLimit is ignored per Java Class Lib. book, p.220.
+ mark = pos;
+ }
+
+ /**
+ * This method overrides the <code>markSupported</code> method in
+ * <code>InputStream</code> in order to return <code>true</code> -
+ * indicating that this stream class supports mark/reset
+ * functionality.
+ *
+ * @return <code>true</code> to indicate that this class supports
+ * mark/reset.
+ */
+ public boolean markSupported()
+ {
+ return true;
+ }
+
+ /**
+ * This method reads one byte from the stream. The <code>pos</code>
+ * counter is advanced to the next byte to be read. The byte read is
+ * returned as an int in the range of 0-255. If the stream position
+ * is already at the end of the buffer, no byte is read and a -1 is
+ * returned in order to indicate the end of the stream.
+ *
+ * @return The byte read, or -1 if end of stream
+ */
+ public synchronized int read()
+ {
+ if (pos < count)
+ return ((int) buf[pos++]) & 0xFF;
+ return -1;
+ }
+
+ /**
+ * This method reads bytes from the stream and stores them into a
+ * caller supplied buffer. It starts storing the data at index
+ * <code>offset</code> into the buffer and attempts to read
+ * <code>len</code> bytes. This method can return before reading
+ * the number of bytes requested if the end of the stream is
+ * encountered first. The actual number of bytes read is returned.
+ * If no bytes can be read because the stream is already at the end
+ * of stream position, a -1 is returned.
+ * <p>
+ * This method does not block.
+ *
+ * @param buffer The array into which the bytes read should be stored.
+ * @param offset The offset into the array to start storing bytes
+ * @param length The requested number of bytes to read
+ *
+ * @return The actual number of bytes read, or -1 if end of stream.
+ */
+ public synchronized int read(byte[] buffer, int offset, int length)
+ {
+ if (pos >= count)
+ return -1;
+
+ int numBytes = Math.min(count - pos, length);
+ System.arraycopy(buf, pos, buffer, offset, numBytes);
+ pos += numBytes;
+ return numBytes;
+ }
+
+ /**
+ * This method sets the read position in the stream to the mark
+ * point by setting the <code>pos</code> variable equal to the
+ * <code>mark</code> variable. Since a mark can be set anywhere in
+ * the array, the mark/reset methods int this class can be used to
+ * provide random search capabilities for this type of stream.
+ */
+ public synchronized void reset()
+ {
+ pos = mark;
+ }
+
+ /**
+ * This method attempts to skip the requested number of bytes in the
+ * input stream. It does this by advancing the <code>pos</code>
+ * value by the specified number of bytes. It this would exceed the
+ * length of the buffer, then only enough bytes are skipped to
+ * position the stream at the end of the buffer. The actual number
+ * of bytes skipped is returned.
+ *
+ * @param num The requested number of bytes to skip
+ *
+ * @return The actual number of bytes skipped.
+ */
+ public synchronized long skip(long num)
+ {
+ // Even though the var numBytes is a long, in reality it can never
+ // be larger than an int since the result of subtracting 2 positive
+ // ints will always fit in an int. Since we have to return a long
+ // anyway, numBytes might as well just be a long.
+ long numBytes = Math.min((long) (count - pos), num < 0 ? 0L : num);
+ pos += numBytes;
+ return numBytes;
+ }
+}