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java.io

Class BufferedInputStream

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


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.

Authors:

Field Summary

byte[]buf

The buffer used for storing data from the underlying stream.
intcount

The number of valid bytes currently in the buffer.
intmarklimit

This is the maximum number of bytes than can be read after a call to mark() before the mark can be discarded.
intmarkpos

The value of pos when the mark() method was called.
intpos

The index of the next character that will by read from the buffer.

Constructor Summary

BufferedInputStream(java.io.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(java.io.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

synchronized intavailable()

This method returns the number of bytes that can be read from this stream before a read can block.
voidclose()

This method closes the underlying input stream and frees any resources associated with it.
synchronized voidmark(int readlimit)

This method marks a position in the input to which the stream can be "reset" by calling the reset() method.
booleanmarkSupported()

This method returns true to indicate that this class supports mark/reset functionality.
synchronized intread()

This method reads an unsigned byte from the input stream and returns it as an int in the range of 0-255.
synchronized intread(byte[] b, int off, int len)

This method reads bytes from a stream and stores them into a caller supplied buffer.
synchronized voidreset()

This method resets a stream to the point where the mark() method was called.
synchronized longskip(long n)

This method skips the specified number of bytes in the stream.

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(java.io.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:


BufferedInputStream

public BufferedInputStream(java.io.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:

Throws:


Method Details

available

public synchronized int available()

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.

Returns:

Throws:


close

public void close()

This method closes the underlying input stream and frees any resources associated with it. Sets buf to null.

Throws:


mark

public synchronized 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.

Parameters:


markSupported

public boolean markSupported()

This method returns true to indicate that this class supports mark/reset functionality.

Returns:


read

public synchronized int read()

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.

Returns:

Throws:


read

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

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. 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.

Parameters:

Returns:

Throws:


reset

public synchronized void reset()

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.

Throws:


skip

public synchronized long skip(long n)

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.

Parameters:

Returns:

Throws: