252 lines
9.0 KiB
Java
252 lines
9.0 KiB
Java
/* ByteArrayInputStream.java -- Read an array as a stream
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Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.io;
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/**
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* This class permits an array of bytes to be read as an input stream.
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*
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* @author Warren Levy <warrenl@cygnus.com>
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* @author Aaron M. Renn (arenn@urbanophile.com)
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*/
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public class ByteArrayInputStream extends InputStream
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{
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/**
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* The array that contains the data supplied during read operations
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*/
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protected byte[] buf;
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/**
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* The array index of the next byte to be read from the buffer
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* <code>buf</code>
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*/
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protected int pos;
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/**
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* The currently marked position in the stream. This defaults to 0, so a
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* reset operation on the stream resets it to read from array index 0 in
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* the buffer - even if the stream was initially created with an offset
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* greater than 0
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*/
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protected int mark;
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/**
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* This indicates the maximum number of bytes that can be read from this
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* stream. It is the array index of the position after the last valid
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* byte in the buffer <code>buf</code>
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*/
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protected int count;
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/**
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* Create a new ByteArrayInputStream that will read bytes from the passed
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* in byte array. This stream will read from the beginning to the end
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* of the array. It is identical to calling an overloaded constructor
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* as <code>ByteArrayInputStream(buf, 0, buf.length)</code>.
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* <p>
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* Note that this array is not copied. If its contents are changed
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* while this stream is being read, those changes will be reflected in the
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* bytes supplied to the reader. Please use caution in changing the
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* contents of the buffer while this stream is open.
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*
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* @param buf The byte array buffer this stream will read from.
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*/
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public ByteArrayInputStream(byte[] buffer)
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{
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this(buffer, 0, buffer.length);
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}
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/**
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* Create a new ByteArrayInputStream that will read bytes from the
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* passed in byte array. This stream will read from position
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* <code>offset</code> in the array for a length of
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* <code>length</code> bytes past <code>offset</code>. If the
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* stream is reset to a position before <code>offset</code> then
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* more than <code>length</code> bytes can be read from the stream.
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* The <code>length</code> value should be viewed as the array index
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* one greater than the last position in the buffer to read.
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* <p>
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* Note that this array is not copied. If its contents are changed
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* while this stream is being read, those changes will be reflected in the
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* bytes supplied to the reader. Please use caution in changing the
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* contents of the buffer while this stream is open.
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*
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* @param buf The byte array buffer this stream will read from.
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* @param offset The index into the buffer to start reading bytes from
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* @param length The number of bytes to read from the buffer
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*/
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public ByteArrayInputStream(byte[] buffer, int offset, int length)
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{
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if (offset < 0 || length < 0 || offset > buffer.length)
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throw new IllegalArgumentException();
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buf = buffer;
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count = offset + length;
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if (count > buf.length)
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count = buf.length;
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pos = offset;
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mark = pos;
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}
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/**
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* This method returns the number of bytes available to be read from this
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* stream. The value returned will be equal to <code>count - pos</code>.
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*
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* @return The number of bytes that can be read from this stream
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* before blocking, which is all of them
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*/
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public synchronized int available()
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{
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return count - pos;
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}
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/**
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* This method sets the mark position in this stream to the current
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* position. Note that the <code>readlimit</code> parameter in this
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* method does nothing as this stream is always capable of
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* remembering all the bytes int it.
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* <p>
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* Note that in this class the mark position is set by default to
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* position 0 in the stream. This is in constrast to some other
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* stream types where there is no default mark position.
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*
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* @param readlimit The number of bytes this stream must remember.
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* This parameter is ignored.
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*/
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public synchronized void mark(int readAheadLimit)
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{
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// readAheadLimit is ignored per Java Class Lib. book, p.220.
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mark = pos;
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}
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/**
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* This method overrides the <code>markSupported</code> method in
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* <code>InputStream</code> in order to return <code>true</code> -
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* indicating that this stream class supports mark/reset
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* functionality.
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*
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* @return <code>true</code> to indicate that this class supports
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* mark/reset.
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*/
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public boolean markSupported()
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{
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return true;
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}
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/**
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* This method reads one byte from the stream. The <code>pos</code>
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* counter is advanced to the next byte to be read. The byte read is
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* returned as an int in the range of 0-255. If the stream position
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* is already at the end of the buffer, no byte is read and a -1 is
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* returned in order to indicate the end of the stream.
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*
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* @return The byte read, or -1 if end of stream
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*/
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public synchronized int read()
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{
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if (pos < count)
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return ((int) buf[pos++]) & 0xFF;
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return -1;
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}
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/**
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* This method reads bytes from the stream and stores them into a
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* caller supplied buffer. It starts storing the data at index
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* <code>offset</code> into the buffer and attempts to read
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* <code>len</code> bytes. This method can return before reading
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* the number of bytes requested if the end of the stream is
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* encountered first. The actual number of bytes read is returned.
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* If no bytes can be read because the stream is already at the end
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* of stream position, a -1 is returned.
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* <p>
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* This method does not block.
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*
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* @param buf The array into which the bytes read should be stored.
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* @param offset The offset into the array to start storing bytes
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* @param len The requested number of bytes to read
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*
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* @return The actual number of bytes read, or -1 if end of stream.
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*/
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public synchronized int read(byte[] b, int off, int len)
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{
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if (pos >= count)
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return -1;
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int numBytes = Math.min(count - pos, len);
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System.arraycopy(buf, pos, b, off, numBytes);
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pos += numBytes;
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return numBytes;
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}
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/**
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* This method sets the read position in the stream to the mark
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* point by setting the <code>pos</code> variable equal to the
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* <code>mark</code> variable. Since a mark can be set anywhere in
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* the array, the mark/reset methods int this class can be used to
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* provide random search capabilities for this type of stream.
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*/
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public synchronized void reset()
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{
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pos = mark;
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}
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/**
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* This method attempts to skip the requested number of bytes in the
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* input stream. It does this by advancing the <code>pos</code>
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* value by the specified number of bytes. It this would exceed the
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* length of the buffer, then only enough bytes are skipped to
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* position the stream at the end of the buffer. The actual number
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* of bytes skipped is returned.
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*
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* @param num_bytes The requested number of bytes to skip
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*
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* @return The actual number of bytes skipped.
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*/
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public synchronized long skip(long n)
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{
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// Even though the var numBytes is a long, in reality it can never
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// be larger than an int since the result of subtracting 2 positive
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// ints will always fit in an int. Since we have to return a long
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// anyway, numBytes might as well just be a long.
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long numBytes = Math.min((long) (count - pos), n < 0 ? 0L : n);
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pos += numBytes;
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return numBytes;
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}
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}
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