java.io

Class BufferedInputStream

Implemented Interfaces:
AutoCloseable, Closeable

public class BufferedInputStream
extends FilterInputStream

This subclass of FilterInputStream 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.

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 Integer.MAX_VALUE

Please note that this class does not properly handle character encodings. Consider using the BufferedReader class which does.

Field Summary

protected byte[]
buf
The buffer used for storing data from the underlying stream.
protected int
count
The number of valid bytes currently in the buffer.
protected int
marklimit
This is the maximum number of bytes than can be read after a call to mark() before the mark can be discarded.
protected int
markpos
The value of pos when the mark() method was called.
protected int
pos
The index of the next character that will by read from the buffer.

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

BufferedInputStream(InputStream in)
This method initializes a new BufferedInputStream that will read from the specified subordinate stream with a default buffer size of 2048 bytes
BufferedInputStream(InputStream in, int size)
This method initializes a new BufferedInputStream that will read from the specified subordinate stream with a buffer size that is specified by the caller.

Method Summary

int
available()
This method returns the number of bytes that can be read from this stream before a read can block.
void
close()
This method closes the underlying input stream and frees any resources associated with it.
void
mark(int readlimit)
This method marks a position in the input to which the stream can be "reset" by calling the reset() method.
boolean
markSupported()
This method returns true to indicate that this class supports mark/reset functionality.
int
read()
This method reads an unsigned byte from the input stream and returns it as an int in the range of 0-255.
int
read(byte[] b, int off, int len)
This method reads bytes from a stream and stores them into a caller supplied buffer.
void
reset()
This method resets a stream to the point where the mark() method was called.
long
skip(long n)
This method skips the specified number of bytes in the stream.

Methods inherited from class java.io.FilterInputStream

available, close, mark, markSupported, read, read, read, reset, skip

Methods inherited from class java.io.InputStream

available, close, mark, markSupported, read, read, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

buf

protected byte[] buf
The buffer used for storing data from the underlying stream.

count

protected int count
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.

marklimit

protected int marklimit
This is the maximum number of bytes than can be read after a call to mark() before the mark can be discarded. After this may bytes are read, the reset() method may not be called successfully.

markpos

protected int markpos
The value of pos when the mark() method was called. This is set to -1 if there is no mark set.

pos

protected int pos
The index of the next character that will by read from the buffer. When pos == count, the buffer is empty.

Constructor Details

BufferedInputStream

public BufferedInputStream(InputStream in)
This method initializes a new BufferedInputStream that will read from the specified subordinate stream with a default buffer size of 2048 bytes
Parameters:
in - The subordinate stream to read from

BufferedInputStream

public BufferedInputStream(InputStream in,
                           int size)
This method initializes a new BufferedInputStream that will read from the specified subordinate stream with a buffer size that is specified by the caller.
Parameters:
in - The subordinate stream to read from
size - The buffer size to use
Throws:
IllegalArgumentException - when size is smaller then 1

Method Details

available

public int available()
            throws IOException
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.

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.

Overrides:
available in interface FilterInputStream
Returns:
The number of bytes that can be read before blocking could occur
Throws:
IOException - If an error occurs

close

public void close()
            throws IOException
This method closes the underlying input stream and frees any resources associated with it. Sets buf to null.
Specified by:
close in interface Closeable
close in interface AutoCloseable
Overrides:
close in interface FilterInputStream
Throws:
IOException - If an error occurs.

mark

public void mark(int readlimit)
This method marks a position in the input to which the stream can be "reset" by calling the reset() method. The parameter 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 mark() is called with a read limit of 10, then when 11 bytes of data are read from the stream before the reset() method is called, then the mark is invalid and the stream object instance is not required to remember the mark.

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.

Overrides:
mark in interface FilterInputStream
Parameters:
readlimit - The number of bytes that can be read before the mark becomes invalid

markSupported

public boolean markSupported()
This method returns true to indicate that this class supports mark/reset functionality.
Overrides:
markSupported in interface FilterInputStream
Returns:
true to indicate that mark/reset functionality is supported

read

public int read()
            throws IOException
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.

This method will block until the byte can be read.

Overrides:
read in interface FilterInputStream
Returns:
The byte read or -1 if end of stream
Throws:
IOException - If an error occurs

read

public int read(byte[] b,
                int off,
                int len)
            throws IOException
This method reads bytes from a stream and stores them into a caller supplied buffer. It starts storing the data at index off into the buffer and attempts to read len 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.

This method will block until some data can be read.

Overrides:
read in interface FilterInputStream
Parameters:
b - The array into which the bytes read should be stored
off - The offset into the array to start storing bytes
len - The requested number of bytes to read
Returns:
The actual number of bytes read, or -1 if end of stream.
Throws:
IOException - If an error occurs.
IndexOutOfBoundsException - when off or len are negative, or when off + len is larger then the size of b,

reset

public void reset()
            throws IOException
This method resets a stream to the point where the mark() method was called. Any bytes that were read after the mark point was set will be re-read during subsequent reads.

This method will throw an IOException if the number of bytes read from the stream since the call to mark() exceeds the mark limit passed when establishing the mark.

Overrides:
reset in interface FilterInputStream
Throws:
IOException - If mark() was never called or more then marklimit bytes were read since the last call to mark()

skip

public long skip(long n)
            throws IOException
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.
Overrides:
skip in interface FilterInputStream
Parameters:
n - The requested number of bytes to skip
Returns:
The actual number of bytes skipped.
Throws:
IOException - If an error occurs

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.