380 lines
12 KiB
Java
380 lines
12 KiB
Java
/* BufferedInputStream.java -- An input stream that implements buffering
|
|
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;
|
|
|
|
/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
|
|
* "The Java Language Specification", ISBN 0-201-63451-1
|
|
* plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
|
|
* Status: Believed complete and correct.
|
|
*/
|
|
|
|
/**
|
|
* This subclass of <code>FilterInputStream</code> buffers input from an
|
|
* underlying implementation to provide a possibly more efficient read
|
|
* mechanism. It maintains the buffer and buffer state in instance
|
|
* variables that are available to subclasses. The default buffer size
|
|
* of 2048 bytes can be overridden by the creator of the stream.
|
|
* <p>
|
|
* This class also implements mark/reset functionality. It is capable
|
|
* of remembering any number of input bytes, to the limits of
|
|
* system memory or the size of <code>Integer.MAX_VALUE</code>
|
|
* <p>
|
|
* Please note that this class does not properly handle character
|
|
* encodings. Consider using the <code>BufferedReader</code> class which
|
|
* does.
|
|
*
|
|
* @author Aaron M. Renn (arenn@urbanophile.com)
|
|
* @author Warren Levy (warrenl@cygnus.com)
|
|
* @author Jeroen Frijters (jeroen@frijters.net)
|
|
*/
|
|
public class BufferedInputStream extends FilterInputStream
|
|
{
|
|
|
|
/**
|
|
* This is the default buffer size
|
|
*/
|
|
private static final int DEFAULT_BUFFER_SIZE = 2048;
|
|
|
|
/**
|
|
* The buffer used for storing data from the underlying stream.
|
|
*/
|
|
protected byte[] buf;
|
|
|
|
/**
|
|
* The number of valid bytes currently in the buffer. It is also the index
|
|
* of the buffer position one byte past the end of the valid data.
|
|
*/
|
|
protected int count;
|
|
|
|
/**
|
|
* The index of the next character that will by read from the buffer.
|
|
* When <code>pos == count</code>, the buffer is empty.
|
|
*/
|
|
protected int pos;
|
|
|
|
/**
|
|
* The value of <code>pos</code> when the <code>mark()</code> method was
|
|
* called.
|
|
* This is set to -1 if there is no mark set.
|
|
*/
|
|
protected int markpos = -1;
|
|
|
|
/**
|
|
* This is the maximum number of bytes than can be read after a
|
|
* call to <code>mark()</code> before the mark can be discarded.
|
|
* After this may bytes are read, the <code>reset()</code> method
|
|
* may not be called successfully.
|
|
*/
|
|
protected int marklimit;
|
|
|
|
/**
|
|
* This is the initial buffer size. When the buffer is grown because
|
|
* of marking requirements, it will be grown by bufferSize increments.
|
|
* The underlying stream will be read in chunks of bufferSize.
|
|
*/
|
|
private final int bufferSize;
|
|
|
|
/**
|
|
* This method initializes a new <code>BufferedInputStream</code> that will
|
|
* read from the specified subordinate stream with a default buffer size
|
|
* of 2048 bytes
|
|
*
|
|
* @param in The subordinate stream to read from
|
|
*/
|
|
public BufferedInputStream(InputStream in)
|
|
{
|
|
this(in, DEFAULT_BUFFER_SIZE);
|
|
}
|
|
|
|
/**
|
|
* This method initializes a new <code>BufferedInputStream</code> that will
|
|
* read from the specified subordinate stream with a buffer size that
|
|
* is specified by the caller.
|
|
*
|
|
* @param in The subordinate stream to read from
|
|
* @param size The buffer size to use
|
|
*
|
|
* @exception IllegalArgumentException when size is smaller then 1
|
|
*/
|
|
public BufferedInputStream(InputStream in, int size)
|
|
{
|
|
super(in);
|
|
if (size <= 0)
|
|
throw new IllegalArgumentException();
|
|
buf = new byte[size];
|
|
// initialize pos & count to bufferSize, to prevent refill from
|
|
// allocating a new buffer (if the caller starts out by calling mark()).
|
|
pos = count = bufferSize = size;
|
|
}
|
|
|
|
/**
|
|
* This method returns the number of bytes that can be read from this
|
|
* stream before a read can block. A return of 0 indicates that blocking
|
|
* might (or might not) occur on the very next read attempt.
|
|
* <p>
|
|
* The number of available bytes will be the number of read ahead bytes
|
|
* stored in the internal buffer plus the number of available bytes in
|
|
* the underlying stream.
|
|
*
|
|
* @return The number of bytes that can be read before blocking could occur
|
|
*
|
|
* @exception IOException If an error occurs
|
|
*/
|
|
public synchronized int available() throws IOException
|
|
{
|
|
return count - pos + super.available();
|
|
}
|
|
|
|
/**
|
|
* This method closes the underlying input stream and frees any
|
|
* resources associated with it. Sets <code>buf</code> to <code>null</code>.
|
|
*
|
|
* @exception IOException If an error occurs.
|
|
*/
|
|
public void close() throws IOException
|
|
{
|
|
// Free up the array memory.
|
|
buf = null;
|
|
pos = count = 0;
|
|
markpos = -1;
|
|
super.close();
|
|
}
|
|
|
|
/**
|
|
* This method marks a position in the input to which the stream can be
|
|
* "reset" by calling the <code>reset()</code> method. The parameter
|
|
* <code>readlimit</code> is the number of bytes that can be read from the
|
|
* stream after setting the mark before the mark becomes invalid. For
|
|
* example, if <code>mark()</code> is called with a read limit of 10, then
|
|
* when 11 bytes of data are read from the stream before the
|
|
* <code>reset()</code> method is called, then the mark is invalid and the
|
|
* stream object instance is not required to remember the mark.
|
|
* <p>
|
|
* Note that the number of bytes that can be remembered by this method
|
|
* can be greater than the size of the internal read buffer. It is also
|
|
* not dependent on the subordinate stream supporting mark/reset
|
|
* functionality.
|
|
*
|
|
* @param readlimit The number of bytes that can be read before the mark
|
|
* becomes invalid
|
|
*/
|
|
public synchronized void mark(int readlimit)
|
|
{
|
|
marklimit = readlimit;
|
|
markpos = pos;
|
|
}
|
|
|
|
/**
|
|
* This method returns <code>true</code> to indicate that this class
|
|
* supports mark/reset functionality.
|
|
*
|
|
* @return <code>true</code> to indicate that mark/reset functionality is
|
|
* supported
|
|
*
|
|
*/
|
|
public boolean markSupported()
|
|
{
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* This method reads an unsigned byte from the input stream and returns it
|
|
* as an int in the range of 0-255. This method also will return -1 if
|
|
* the end of the stream has been reached.
|
|
* <p>
|
|
* This method will block until the byte can be read.
|
|
*
|
|
* @return The byte read or -1 if end of stream
|
|
*
|
|
* @exception IOException If an error occurs
|
|
*/
|
|
public synchronized int read() throws IOException
|
|
{
|
|
if (pos >= count && !refill())
|
|
return -1; // EOF
|
|
|
|
return buf[pos++] & 0xFF;
|
|
}
|
|
|
|
/**
|
|
* This method reads bytes from a stream and stores them into a caller
|
|
* supplied buffer. It starts storing the data at index <code>off</code>
|
|
* into the buffer and attempts to read <code>len</code> bytes. This method
|
|
* can return before reading the number of bytes requested, but it will try
|
|
* to read the requested number of bytes by repeatedly calling the underlying
|
|
* stream as long as available() for this stream continues to return a
|
|
* non-zero value (or until the requested number of bytes have been read).
|
|
* The actual number of bytes read is returned as an int. A -1 is returned
|
|
* to indicate the end of the stream.
|
|
* <p>
|
|
* This method will block until some data can be read.
|
|
*
|
|
* @param b The array into which the bytes read should be stored
|
|
* @param off The offset into the array to start storing bytes
|
|
* @param len The requested number of bytes to read
|
|
*
|
|
* @return The actual number of bytes read, or -1 if end of stream.
|
|
*
|
|
* @exception IOException If an error occurs.
|
|
* @exception IndexOutOfBoundsException when <code>off</code> or
|
|
* <code>len</code> are negative, or when <code>off + len</code>
|
|
* is larger then the size of <code>b</code>,
|
|
*/
|
|
public synchronized int read(byte[] b, int off, int len) throws IOException
|
|
{
|
|
if (off < 0 || len < 0 || b.length - off < len)
|
|
throw new IndexOutOfBoundsException();
|
|
|
|
if (len == 0)
|
|
return 0;
|
|
|
|
if (pos >= count && !refill())
|
|
return -1; // No bytes were read before EOF.
|
|
|
|
int totalBytesRead = Math.min(count - pos, len);
|
|
System.arraycopy(buf, pos, b, off, totalBytesRead);
|
|
pos += totalBytesRead;
|
|
off += totalBytesRead;
|
|
len -= totalBytesRead;
|
|
|
|
while (len > 0 && super.available() > 0 && refill())
|
|
{
|
|
int remain = Math.min(count - pos, len);
|
|
System.arraycopy(buf, pos, b, off, remain);
|
|
pos += remain;
|
|
off += remain;
|
|
len -= remain;
|
|
totalBytesRead += remain;
|
|
}
|
|
|
|
return totalBytesRead;
|
|
}
|
|
|
|
/**
|
|
* This method resets a stream to the point where the <code>mark()</code>
|
|
* method was called. Any bytes that were read after the mark point was
|
|
* set will be re-read during subsequent reads.
|
|
* <p>
|
|
* This method will throw an IOException if the number of bytes read from
|
|
* the stream since the call to <code>mark()</code> exceeds the mark limit
|
|
* passed when establishing the mark.
|
|
*
|
|
* @exception IOException If <code>mark()</code> was never called or more
|
|
* then <code>marklimit</code> bytes were read since the last
|
|
* call to <code>mark()</code>
|
|
*/
|
|
public synchronized void reset() throws IOException
|
|
{
|
|
if (markpos == -1)
|
|
throw new IOException(buf == null ? "Stream closed." : "Invalid mark.");
|
|
|
|
pos = markpos;
|
|
}
|
|
|
|
/**
|
|
* This method skips the specified number of bytes in the stream. It
|
|
* returns the actual number of bytes skipped, which may be less than the
|
|
* requested amount.
|
|
*
|
|
* @param n The requested number of bytes to skip
|
|
*
|
|
* @return The actual number of bytes skipped.
|
|
*
|
|
* @exception IOException If an error occurs
|
|
*/
|
|
public synchronized long skip(long n) throws IOException
|
|
{
|
|
if (buf == null)
|
|
throw new IOException("Stream closed.");
|
|
|
|
final long origN = n;
|
|
|
|
while (n > 0L)
|
|
{
|
|
if (pos >= count && !refill())
|
|
break;
|
|
|
|
int numread = (int) Math.min((long) (count - pos), n);
|
|
pos += numread;
|
|
n -= numread;
|
|
}
|
|
|
|
return origN - n;
|
|
}
|
|
|
|
/**
|
|
* Called to refill the buffer (when count is equal to pos).
|
|
*
|
|
* @return <code>true</code> when at least one additional byte was read
|
|
* into <code>buf</code>, <code>false</code> otherwise (at EOF).
|
|
*/
|
|
private boolean refill() throws IOException
|
|
{
|
|
if (buf == null)
|
|
throw new IOException("Stream closed.");
|
|
|
|
if (markpos == -1 || count - markpos >= marklimit)
|
|
{
|
|
markpos = -1;
|
|
pos = count = 0;
|
|
}
|
|
else
|
|
{
|
|
byte[] newbuf = buf;
|
|
if (markpos < bufferSize)
|
|
{
|
|
newbuf = new byte[count - markpos + bufferSize];
|
|
}
|
|
System.arraycopy(buf, markpos, newbuf, 0, count - markpos);
|
|
buf = newbuf;
|
|
count -= markpos;
|
|
pos -= markpos;
|
|
markpos = 0;
|
|
}
|
|
|
|
int numread = super.read(buf, count, bufferSize);
|
|
|
|
if (numread <= 0) // EOF
|
|
return false;
|
|
|
|
count += numread;
|
|
return true;
|
|
}
|
|
}
|