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.
author: Arthur van Hoff version: 1.63, 05/05/07 since: JDK1.0
Field Summary
protected volatile 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.
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.
This value is always
in the range -1 through pos.
If there is no marked position in the input
stream, this field is -1.
BufferedInputStream(InputStream in) Creates a BufferedInputStream
and saves its argument, the input stream
in, for later use.
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.
Method Summary
public synchronized int
available() Returns an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking by the next
invocation of a method for this input stream.
public void
close() Closes this input stream and releases any system resources
associated with the stream.
public synchronized void
mark(int readlimit) See the general contract of the mark
method of InputStream.
public boolean
markSupported() Tests if this input stream supports the mark
and reset methods.
public synchronized int
read() See
the general contract of the read
method of InputStream.
the next byte of data, or -1 if the end of thestream is reached. exception: IOException - if this input stream has been closed byinvoking its BufferedInputStream.close() method,or an I/O error occurs.
public synchronized 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.
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.
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:java.io.BufferedInputStream.mark(int) See Also:java.io.BufferedInputStream.reset
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:java.io.BufferedInputStream.mark(int) See Also:java.io.BufferedInputStream.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:java.io.BufferedInputStream.buf
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.
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. Parameters: size - the buffer size. exception: IllegalArgumentException - if size <= 0.
Returns an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking by the next
invocation of a method for this input stream. The next invocation might be
the same thread or another thread. A single read or skip of this
many bytes will not block, but may read or skip fewer bytes.
This method returns the sum of the number of bytes remaining to be read in
the buffer (count - pos) and the result of calling the
java.io.FilterInputStream.in in .available().
an estimate of the number of bytes that can be read (or skippedover) from this input stream without blocking. exception: IOException - if this input stream has been closed byinvoking its BufferedInputStream.close() method,or an I/O error occurs.
Closes this input stream and releases any system resources
associated with the stream.
Once the stream has been closed, further read(), available(), reset(),
or skip() invocations will throw an IOException.
Closing a previously closed stream has no effect.
exception: IOException - if an I/O error occurs.
mark
public synchronized void mark(int readlimit)(Code)
See the general contract of the mark
method of InputStream.
Parameters: readlimit - the maximum limit of bytes that can be read beforethe mark position becomes invalid. See Also:java.io.BufferedInputStream.reset
Tests if this input stream supports the mark
and reset methods. The markSupported
method of BufferedInputStream returns
true.
a boolean indicating if this stream type supportsthe mark and reset methods. See Also:java.io.InputStream.mark(int) See Also:java.io.InputStream.reset
See
the general contract of the read
method of InputStream.
the next byte of data, or -1 if the end of thestream is reached. exception: IOException - if this input stream has been closed byinvoking its BufferedInputStream.close() method,or an I/O error occurs. See Also:java.io.FilterInputStream.in
read
public synchronized int read(byte b, int off, int len) throws IOException(Code)
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
InputStream.read(byte[]intint) 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.
Parameters: b - destination buffer. Parameters: off - offset at which to start storing bytes. Parameters: len - maximum number of bytes to read. the number of bytes read, or -1 if the end ofthe stream has been reached. exception: IOException - if this input stream has been closed byinvoking its BufferedInputStream.close() method,or an I/O error occurs.
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.
exception: IOException - if this stream has not been marked or,if the mark has been invalidated, or the stream has been closed by invoking its BufferedInputStream.close()method, or an I/O error occurs. See Also:java.io.BufferedInputStream.mark(int)
See the general contract of the skip
method of InputStream.
exception: IOException - if the stream does not support seek,or if this input stream has been closed byinvoking its BufferedInputStream.close() method, or anI/O error occurs.
