Class java.io.BufferedInputStream





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Class java.io.BufferedInputStream


java.lang.Object
|
+----java.io.InputStream
|
+----java.io.FilterInputStream
|
+----java.io.BufferedInputStream



public class BufferedInputStream
extends FilterInputStream

The class implements a buffered input stream. By setting up such
an input stream, an application can read bytes from a stream
without necessarily causing a call to the underlying system for
each byte read. The data is read by blocks into a buffer;
subsequent reads can access the data directly from the buffer.








buf
The buffer where data is stored.

count
The index one greater than the index of the last valid byte in
the buffer.

marklimit
The maximum read ahead allowed after a call to the
mark method before subsequent calls to the
reset method fail.

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

pos
The current position in the buffer.






BufferedInputStream(InputStream)
Creates a new buffered input stream to read data from the
specified input stream with a default 512-byte buffer size.

BufferedInputStream(InputStream, int)
Creates a new buffered input stream to read data from the
specified input stream with the specified buffer size.






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

mark(int)
Marks the current position in this input stream.

markSupported()
Tests if this input stream supports the mark
and reset methods.

read()
Reads the next byte of data from this buffered input stream.

read(byte[], int, int)
Reads bytes into a portion of an array.

reset()
Repositions this stream to the position at the time the
mark method was last called on this input stream.

skip(long)
Skips over and discards n bytes of data from the
input stream.






buf

protected byte buf[]


The buffer where data is stored.


count

protected int count


The index one greater than the index of the last valid byte in
the buffer.


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.

See Also:
buf



markpos

protected int markpos


The value of the pos field at the time the last
mark method was called. The value of this field is
-1 if there is no current mark.

See Also:
mark, 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.

See Also:
mark, reset








BufferedInputStream

public BufferedInputStream(InputStream in)


Creates a new buffered input stream to read data from the
specified input stream with a default 512-byte buffer size.


Parameters:
in - the underlying input stream.



BufferedInputStream

public BufferedInputStream(InputStream in,
int size)


Creates a new buffered input stream to read data from the
specified input stream with the specified buffer size.


Parameters:
in - the underlying input stream.
size - the buffer size.







read

public synchronized int read() throws IOException


Reads the next byte of data from this buffered input stream. The
value byte is returned as an int in the range
0 to 255. If no byte is available
because the end of the stream has been reached, the value
-1 is returned. This method blocks until input data
is available, the end of the stream is detected, or an exception
is thrown.

The read method of BufferedInputStream
returns the next byte of data from its buffer if the buffer is not
empty. Otherwise, it refills the buffer from the underlying input
stream and returns the next character, if the underlying stream
has not returned an end-of-stream indicator.


Returns:
the next byte of data, or -1 if the end of the
stream is reached.
Throws: IOException
if an I/O error occurs.
Overrides:
read in class FilterInputStream
See Also:
in



read

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


Reads bytes into a portion of an array. This method will block until
some input is available, an I/O error occurs, or the end of the stream
is reached.
If this stream's buffer is not empty, bytes are copied from it into
the array argument. Otherwise, the buffer is refilled from the
underlying input stream and, unless the stream returns an end-of-stream
indication, the array argument is filled with characters from the
newly-filled buffer.
As an optimization, if the buffer is empty, the mark is not valid,
and len is at least as large as the buffer, then this
method will read directly from the underlying stream into the given
array. Thus redundant BufferedInputStreams will not copy
data unnecessarily.


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.
Overrides:
read in class FilterInputStream



skip

public synchronized long skip(long n) throws IOException


Skips over and discards n bytes of data from the
input stream. The skip method may, for a variety of
reasons, end up skipping over some smaller number of bytes,
possibly zero. The actual number of bytes skipped is returned.

The skip method of BufferedInputStream
compares the number of bytes it has available in its buffer,
k, where k = count - pos,
with n. If n ≤ k,
then the pos field is incremented by n.
Otherwise, the pos field is incremented to have the
value count, and the remaining bytes are skipped by
calling the skip method on the underlying input
stream, supplying the argument n - k.


Parameters:
n - the number of bytes to be skipped.
Returns:
the actual number of bytes skipped.
Throws: IOException
if an I/O error occurs.
Overrides:
skip in class FilterInputStream



available

public synchronized 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.


Returns:
the number of bytes that can be read from this input
stream without blocking.
Throws: IOException
if an I/O error occurs.
Overrides:
available in class FilterInputStream
See Also:
in



mark

public synchronized void mark(int readlimit)


Marks the current position in this input stream. A subsequent
call to the reset method repositions the stream at
the last marked position so that subsequent reads re-read the same
bytes.

The readlimit argument tells the input stream to
allow that many bytes to be read before the mark position gets
invalidated.


Parameters:
readlimit - the maximum limit of bytes that can be read before
the mark position becomes invalid.
Overrides:
mark in class FilterInputStream
See Also:
reset



reset

public synchronized void reset() throws IOException


Repositions this stream to the position at the time the
mark method was last called on this input stream.

If the stream has not been marked, or if the mark has been invalidated,
an IOException is thrown. Stream marks are intended to be used in
situations where you need to read ahead a little to see what's in
the stream. Often this is most easily done by invoking some
general parser. If the stream is of the type handled by the
parser, it just chugs along happily. If the stream is not of
that type, the parser should toss an exception when it fails. If an
exception gets tossed within readlimit bytes, the parser will allow the
outer code to reset the stream and to try another parser.


Throws: IOException
if this stream has not been marked or
if the mark has been invalidated.
Overrides:
reset in class FilterInputStream
See Also:
mark



markSupported

public boolean markSupported()


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


Returns:
a boolean indicating if this stream type supports
the mark and reset methods.
Overrides:
markSupported in class FilterInputStream
See Also:
mark, reset




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