2001-08-06 00:41:30 +02:00
|
|
|
/* InputStream.java -- Base class for input
|
|
|
|
Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.
|
1999-04-07 16:42:40 +02:00
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
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., 59 Temple Place, Suite 330, Boston, MA
|
|
|
|
02111-1307 USA.
|
|
|
|
|
2002-01-22 23:40:42 +01:00
|
|
|
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. */
|
1999-04-07 16:42:40 +02:00
|
|
|
|
|
|
|
|
|
|
|
package java.io;
|
|
|
|
|
|
|
|
/**
|
2001-08-06 00:41:30 +02:00
|
|
|
* This abstract class forms the base of the hierarchy of classes that read
|
|
|
|
* input as a stream of bytes. It provides a common set of methods for
|
|
|
|
* reading bytes from streams. Subclasses implement and extend these
|
|
|
|
* methods to read bytes from a particular input source such as a file
|
|
|
|
* or network connection.
|
|
|
|
*
|
|
|
|
* @author Aaron M. Renn (arenn@urbanophile.com)
|
|
|
|
* @author Warren Levy <warrenl@cygnus.com>
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public abstract class InputStream
|
|
|
|
{
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* Default, no-arg, public constructor
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public InputStream()
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* 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>
|
|
|
|
* This method always returns 0 in this class
|
|
|
|
*
|
|
|
|
* @return The number of bytes that can be read before blocking could occur
|
|
|
|
*
|
|
|
|
* @exception IOException If an error occurs
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public int available() throws IOException
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* This method closes the stream. Any futher attempts to read from the
|
|
|
|
* stream may generate an <code>IOException</code>
|
|
|
|
* <p>
|
|
|
|
* This method does nothing in this class, but subclasses may override
|
|
|
|
* this method in order to provide additional functionality.
|
|
|
|
*
|
|
|
|
* @exception IOException If an error occurs, which can only happen
|
|
|
|
* in a subclass
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public void close() throws IOException
|
|
|
|
{
|
|
|
|
// Do nothing
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* 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} 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>
|
|
|
|
* This method does nothing in this class, but subclasses may override it
|
|
|
|
* to provide mark/reset functionality.
|
|
|
|
*
|
|
|
|
* @param readLimit The number of bytes that can be read before the
|
|
|
|
* mark becomes invalid
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public void mark(int readlimit)
|
|
|
|
{
|
|
|
|
// Do nothing
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* This method returns a boolean that indicates whether the mark/reset
|
|
|
|
* methods are supported in this class. Those methods can be used to
|
|
|
|
* remember a specific point in the stream and reset the stream to that
|
|
|
|
* point.
|
|
|
|
* <p>
|
|
|
|
* This method always returns <code>false</code> in this class, but
|
|
|
|
* subclasses can override this method to return </code>true</code>
|
|
|
|
* if they support mark/reset functionality.
|
|
|
|
*
|
|
|
|
* @return <code>true</code> if mark/reset functionality is
|
|
|
|
* supported, <code>false</code> otherwise
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public boolean markSupported()
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* 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
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public abstract int read() throws IOException;
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* This method reads bytes from a stream and stores them into a caller
|
|
|
|
* supplied buffer. This method attempts to completely fill the buffer,
|
|
|
|
* but can return before doing so. 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.
|
|
|
|
* <p>
|
|
|
|
* This method operates by calling an overloaded read method like so:
|
|
|
|
* <code>read(b, 0, b.length)</code>
|
|
|
|
*
|
|
|
|
* @param b The buffer into which the bytes read will be stored.
|
|
|
|
*
|
|
|
|
* @return The number of bytes read or -1 if end of stream.
|
|
|
|
*
|
|
|
|
* @exception IOException If an error occurs.
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public int read(byte[] b) throws IOException
|
|
|
|
{
|
|
|
|
return read(b, 0, b.length);
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* This method read 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. 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.
|
|
|
|
* <p>
|
|
|
|
* This method operates by calling the single byte <code>read()</code> method
|
|
|
|
* in a loop until the desired number of bytes are read. The read loop
|
|
|
|
* stops short if the end of the stream is encountered or if an IOException
|
|
|
|
* is encountered on any read operation except the first. If the first
|
|
|
|
* attempt to read a bytes fails, the IOException is allowed to propagate
|
|
|
|
* upward. And subsequent IOException is caught and treated identically
|
|
|
|
* to an end of stream condition. Subclasses can (and should if possible)
|
|
|
|
* override this method to provide a more efficient implementation.
|
|
|
|
*
|
|
|
|
* @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.
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public int read(byte[] b, int off, int len) throws IOException
|
|
|
|
{
|
|
|
|
if (off < 0 || len < 0 || off + len > b.length)
|
|
|
|
throw new IndexOutOfBoundsException();
|
|
|
|
if (b.length == 0)
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
int i, ch;
|
|
|
|
|
|
|
|
for (i = 0; i < len; ++i)
|
|
|
|
try
|
2001-08-06 00:41:30 +02:00
|
|
|
{
|
|
|
|
if ((ch = read()) < 0)
|
|
|
|
return i == 0 ? -1 : i; // EOF
|
|
|
|
b[off + i] = (byte) ch;
|
|
|
|
}
|
1999-04-07 16:42:40 +02:00
|
|
|
catch (IOException ex)
|
2001-08-06 00:41:30 +02:00
|
|
|
{
|
|
|
|
// Only reading the first byte should cause an IOException.
|
|
|
|
if (i == 0)
|
|
|
|
throw ex;
|
|
|
|
return i;
|
|
|
|
}
|
1999-04-07 16:42:40 +02:00
|
|
|
|
|
|
|
return i;
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* 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 always throws an IOException in this class, but subclasses
|
|
|
|
* can override this method if they provide mark/reset functionality.
|
|
|
|
*
|
|
|
|
* @exception IOException Always thrown for this class
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public void reset() throws IOException
|
|
|
|
{
|
|
|
|
throw new IOException("mark/reset not supported");
|
|
|
|
}
|
|
|
|
|
2001-08-06 00:41:30 +02:00
|
|
|
/**
|
|
|
|
* 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.
|
|
|
|
* <p>
|
|
|
|
* This method reads and discards bytes into a byte array until the
|
|
|
|
* specified number of bytes were skipped or until either the end of stream
|
|
|
|
* is reached or a read attempt returns a short count. Subclasses can
|
|
|
|
* override this metho to provide a more efficient implementation where
|
|
|
|
* one exists.
|
|
|
|
*
|
|
|
|
* @param n The requested number of bytes to skip
|
|
|
|
*
|
|
|
|
* @return The actual number of bytes skipped.
|
|
|
|
*
|
|
|
|
* @exception IOException If an error occurs
|
|
|
|
*/
|
1999-04-07 16:42:40 +02:00
|
|
|
public long skip(long n) throws IOException
|
|
|
|
{
|
|
|
|
// Throw away n bytes by reading them into a temp byte[].
|
|
|
|
// Limit the temp array to 2Kb so we don't grab too much memory.
|
|
|
|
final int buflen = n > 2048 ? 2048 : (int) n;
|
|
|
|
byte[] tmpbuf = new byte[buflen];
|
|
|
|
final long origN = n;
|
|
|
|
|
|
|
|
while (n > 0L)
|
|
|
|
{
|
|
|
|
int numread = read(tmpbuf, 0, n > buflen ? buflen : (int) n);
|
|
|
|
if (numread <= 0)
|
|
|
|
break;
|
|
|
|
n -= numread;
|
|
|
|
}
|
|
|
|
|
|
|
|
return origN - n;
|
|
|
|
}
|
|
|
|
}
|