java.io.BufferedInputStream Maven / Gradle / Ivy
/*
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documentation, such as a unified set of documents of API signatures for
a platform that includes technologies expressed as Java APIs. The file
may also be used to produce "compilation stubs," which allow
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Any work generated from this file, such as unified javadocs or compiled
stub files, must be accompanied by this notice in its entirety.
This work corresponds to the API signatures of JSR 219: Foundation
Profile 1.1. In the event of a discrepency between this work and the
JSR 219 specification, which is available at
http://www.jcp.org/en/jsr/detail?id=219, the latter takes precedence.
*/
package java.io;
/**
* 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 1.44 11/09/00
* @since JDK1.0
*/
public class BufferedInputStream extends FilterInputStream
{
/**
* The internal buffer array where the data is stored. When necessary,
* it may be replaced by another array of
* a different size.
*/
protected byte[] buf;
/**
* 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.
*/
protected int count;
/**
* 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 java.io.BufferedInputStream#buf
*/
protected int pos;
/**
* 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 java.io.BufferedInputStream#mark(int)
* @see java.io.BufferedInputStream#pos
*/
protected int markpos;
/**
* 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 java.io.BufferedInputStream#mark(int)
* @see java.io.BufferedInputStream#reset()
*/
protected int marklimit;
/**
* Creates a BufferedInputStream
* and saves its argument, the input stream
* in, for later use. An internal
* buffer array is created and stored in buf.
*
* @param in the underlying input stream.
*/
public BufferedInputStream(InputStream in) {
super(in);
}
/**
* 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.
*
* @param in the underlying input stream.
* @param size the buffer size.
* @exception IllegalArgumentException if size <= 0.
*/
public BufferedInputStream(InputStream in, int size) {
super(in);
}
/**
* See
* the general contract of the read
* method of InputStream.
*
* @return the next byte of data, or -1 if the end of the
* stream is reached.
* @exception IOException if an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
public synchronized int read() throws IOException {
return 0;
}
/**
* 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
* {@link InputStream#read(byte[], int, int) read} method of
* the {@link 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.
*
* @param b destination buffer.
* @param off offset at which to start storing bytes.
* @param len maximum number of bytes to read.
* @return the number of bytes read, or -1 if the end of
* the stream has been reached.
* @exception IOException if an I/O error occurs.
*/
public synchronized int read(byte[] b, int off, int len) throws IOException
{
return 0;
}
/**
* See the general contract of the skip
* method of InputStream.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException if an I/O error occurs.
*/
public synchronized long skip(long n) throws IOException {
return -1;
}
/**
* 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.
*
* @return the number of bytes that can be read from this input
* stream without blocking.
* @exception IOException if an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
public synchronized int available() throws IOException {
return 0;
}
/**
* See the general contract of the mark
* method of InputStream.
*
* @param readlimit the maximum limit of bytes that can be read before
* the mark position becomes invalid.
* @see java.io.BufferedInputStream#reset()
*/
public synchronized void mark(int readlimit) { }
/**
* 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.
* @see java.io.BufferedInputStream#mark(int)
*/
public synchronized void reset() throws IOException { }
/**
* Tests if this input stream supports the mark
* and reset methods. The markSupported
* method of BufferedInputStream returns
* true.
*
* @return a boolean indicating if this stream type supports
* the mark and reset methods.
* @see java.io.InputStream#mark(int)
* @see java.io.InputStream#reset()
*/
public boolean markSupported() {
return false;
}
/**
* Closes this input stream and releases any system resources
* associated with the stream.
*
* @exception IOException if an I/O error occurs.
*/
public void close() throws IOException { }
}