java.io
Class BufferedInputStream

java.lang.Object
  java.io.InputStream
      java.io.FilterInputStream
          java.io.BufferedInputStream

public class BufferedInputStream

extends FilterInputStream

A BufferedInputStream adds functionality to another input stream-namely, the ability to buffer the input and to support the mark and reset methods. When the BufferedInputStream is created, an internal buffer array is created. As bytes from the stream are read or skipped, the internal buffer is refilled as necessary from the contained input stream, many bytes at a time. The mark operation remembers a point in the input stream and the reset operation causes all the bytes read since the most recent mark operation to be reread before new bytes are taken from the contained input stream.

Since:

JDK1.0

Author:

Arthur van Hoff

Field Summary

protected byte[]	buf The internal buffer array where the data is stored.
protected int	count The index one greater than the index of the last valid byte in the buffer.
private static int	defaultBufferSize
protected int	marklimit The maximum read ahead allowed after a call to the mark method before subsequent calls to the reset method fail.
protected int	markpos The value of the pos field at the time the last mark method was called.
protected int	pos The current position in the buffer.

Fields inherited from class java.io.FilterInputStream

in

Fields inherited from class java.io.InputStream

Constructor Summary

BufferedInputStream(InputStream in)
Creates a BufferedInputStream and saves its argument, the input stream in, for later use.

BufferedInputStream(InputStream in, int size)
Creates a BufferedInputStream with the specified buffer size, and saves its argument, the input stream in, for later use.

Method Summary

int	available() Returns the number of bytes that can be read from this input stream without blocking.
void	close() Closes this input stream and releases any system resources associated with the stream.
private void	ensureOpen() Check to make sure that this stream has not been closed
private void	fill() Fills the buffer with more data, taking into account shuffling and other tricks for dealing with marks.
void	mark(int readlimit) See the general contract of the mark method of InputStream.
boolean	markSupported() Tests if this input stream supports the mark and reset methods.
int	read() See the general contract of the read method of InputStream.
int	read(byte[] b, int off, int len) Reads bytes from this byte-input stream into the specified byte array, starting at the given offset.
private int	read1(byte[] b, int off, int len) Read characters into a portion of an array, reading from the underlying stream at most once if necessary.
void	reset() See the general contract of the reset method of InputStream.
long	skip(long n) See the general contract of the skip method of InputStream.

Methods inherited from class java.io.FilterInputStream

read

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

defaultBufferSize

private static int defaultBufferSize

buf

protected byte[] buf

The internal buffer array where the data is stored. When necessary, it may be replaced by another array of a different size.

count

protected int count

The index one greater than the index of the last valid byte in the buffer. This value is always in the range 0 through buf.length; elements buf[0] through buf[count-1] contain buffered input data obtained from the underlying input stream.

pos

protected int pos

The current position in the buffer. This is the index of the next character to be read from the buf array.

This value is always in the range 0 through count. If it is less than count, then buf[pos] is the next byte to be supplied as input; if it is equal to count, then the next read or skip operation will require more bytes to be read from the contained input stream.

See Also:

buf

markpos

protected int markpos

The value of the pos field at the time the last mark method was called.

This value is always in the range -1 through pos. If there is no marked position in the input stream, this field is -1. If there is a marked position in the input stream, then buf[markpos] is the first byte to be supplied as input after a reset operation. If markpos is not -1, then all bytes from positions buf[markpos] through buf[pos-1] must remain in the buffer array (though they may be moved to another place in the buffer array, with suitable adjustments to the values of count, pos, and markpos); they may not be discarded unless and until the difference between pos and markpos exceeds marklimit.

See Also:

mark(int), pos

marklimit

protected int marklimit

The maximum read ahead allowed after a call to the mark method before subsequent calls to the reset method fail. Whenever the difference between pos and markpos exceeds marklimit, then the mark may be dropped by setting markpos to -1.

See Also:

mark(int), reset()

Constructor Detail

BufferedInputStream

public BufferedInputStream(InputStream in)

Creates a BufferedInputStream and saves its argument, the input stream in, for later use. An internal buffer array is created and stored in buf.

Parameters:

in - the underlying input stream.

BufferedInputStream

public BufferedInputStream(InputStream in,
                           int size)

Creates a BufferedInputStream with the specified buffer size, and saves its argument, the input stream in, for later use. An internal buffer array of length size is created and stored in buf.

Parameters:

in - the underlying input stream.

size - the buffer size.

Throws:

IllegalArgumentException - if size <= 0.

Method Detail

ensureOpen

private void ensureOpen()
                 throws IOException

Check to make sure that this stream has not been closed

Throws:

IOException

fill

private void fill()
           throws IOException

Fills the buffer with more data, taking into account shuffling and other tricks for dealing with marks. Assumes that it is being called by a synchronized method. This method also assumes that all data has already been read in, hence pos > count.

Throws:

IOException

read

public int read()
         throws IOException

See the general contract of the read method of InputStream.

Overrides:

read in class FilterInputStream

Returns:

the next byte of data, or -1 if the end of the stream is reached.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterInputStream.in

read1

private int read1(byte[] b,
                  int off,
                  int len)
           throws IOException

Read characters into a portion of an array, reading from the underlying stream at most once if necessary.

Throws:

IOException

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Reads bytes from this byte-input stream into the specified byte array, starting at the given offset.

This method implements the general contract of the corresponding read method of the InputStream class. As an additional convenience, it attempts to read as many bytes as possible by repeatedly invoking the read method of the underlying stream. This iterated read continues until one of the following conditions becomes true:

• The specified number of bytes have been read,
• The read method of the underlying stream returns -1, indicating end-of-file, or
• The available method of the underlying stream returns zero, indicating that further input requests would block.

If the first read on the underlying stream returns -1 to indicate end-of-file then this method returns -1. Otherwise this method returns the number of bytes actually read.

Subclasses of this class are encouraged, but not required, to attempt to read as many bytes as possible in the same fashion.

Overrides:

read in class FilterInputStream

Parameters:

b - destination buffer.

off - offset at which to start storing bytes.

len - maximum number of bytes to read.

Returns:

the number of bytes read, or -1 if the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterInputStream.in

skip

public long skip(long n)
          throws IOException

See the general contract of the skip method of InputStream.

Overrides:

skip in class FilterInputStream

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if an I/O error occurs.

available

public int available()
              throws IOException

Returns the number of bytes that can be read from this input stream without blocking.

The available method of BufferedInputStream returns the sum of the the number of bytes remaining to be read in the buffer (count - pos) and the result of calling the available method of the underlying input stream.

Overrides:

available in class FilterInputStream

Returns:

the number of bytes that can be read from this input stream without blocking.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterInputStream.in

mark

public void mark(int readlimit)

See the general contract of the mark method of InputStream.

Overrides:

mark in class FilterInputStream

Parameters:

readlimit - the maximum limit of bytes that can be read before the mark position becomes invalid.

See Also:

reset()

reset

public void reset()
           throws IOException

See the general contract of the reset method of InputStream.

If markpos is -1 (no mark has been set or the mark has been invalidated), an IOException is thrown. Otherwise, pos is set equal to markpos.

Overrides:

reset in class FilterInputStream

Throws:

IOException - if this stream has not been marked or if the mark has been invalidated.

See Also:

mark(int)

markSupported

public boolean markSupported()

Tests if this input stream supports the mark and reset methods. The markSupported method of BufferedInputStream returns true.

Overrides:

markSupported in class FilterInputStream

Returns:

a boolean indicating if this stream type supports the mark and reset methods.

See Also:

InputStream.mark(int), InputStream.reset()

close

public void close()
           throws IOException

Closes this input stream and releases any system resources associated with the stream.

Overrides:

close in class FilterInputStream

Throws:

IOException - if an I/O error occurs.

See Also:

FilterInputStream.in