java.io

Class ByteArrayInputStream

java.lang.Object

java.io.InputStream

java.io.ByteArrayInputStream

public class ByteArrayInputStream
extends InputStream

This class permits an array of bytes to be read as an input stream.

Author:

Warren Levy , Aaron M. Renn (arenn@urbanophile.com)

Field Summary

Fields

Modifier and Type	Field and Description
protected byte[]	buf The array that contains the data supplied during read operations
protected int	count This indicates the maximum number of bytes that can be read from this stream.
protected int	mark The currently marked position in the stream.
protected int	pos The array index of the next byte to be read from the buffer buf

Constructor Summary

Constructors

Constructor and Description
ByteArrayInputStream(byte[] buffer) Create a new ByteArrayInputStream that will read bytes from the passed in byte array.
ByteArrayInputStream(byte[] buffer, int offset, int length) Create a new ByteArrayInputStream that will read bytes from the passed in byte array.

Method Summary

Modifier and Type	Method and Description
int	available() This method returns the number of bytes available to be read from this stream.
void	mark(int readAheadLimit) This method sets the mark position in this stream to the current position.
boolean	markSupported() This method overrides the markSupported method in InputStream in order to return true - indicating that this stream class supports mark/reset functionality.
int	read() This method reads one byte from the stream.
int	read(byte[] b, int off, int len) This method reads bytes from the stream and stores them into a caller supplied buffer.
void	reset() This method sets the read position in the stream to the mark point by setting the pos variable equal to the mark variable.
long	skip(long n) This method attempts to skip the requested number of bytes in the input stream.

Methods inherited from class java.io.InputStream

close, finalize, hashCode, read

Methods inherited from class java.lang.Object

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

Field Detail

buf

protected byte[] buf

The array that contains the data supplied during read operations

pos

protected int pos

The array index of the next byte to be read from the buffer buf

mark

protected int mark

The currently marked position in the stream. This defaults to 0, so a reset operation on the stream resets it to read from array index 0 in the buffer - even if the stream was initially created with an offset greater than 0

count

protected int count

This indicates the maximum number of bytes that can be read from this stream. It is the array index of the position after the last valid byte in the buffer buf

Constructor Detail

ByteArrayInputStream

public ByteArrayInputStream(byte[] buffer)

Create a new ByteArrayInputStream that will read bytes from the passed in byte array. This stream will read from the beginning to the end of the array. It is identical to calling an overloaded constructor as ByteArrayInputStream(buf, 0, buf.length).

Note that this array is not copied. If its contents are changed while this stream is being read, those changes will be reflected in the bytes supplied to the reader. Please use caution in changing the contents of the buffer while this stream is open.

Parameters:

buf - The byte array buffer this stream will read from.

ByteArrayInputStream

public ByteArrayInputStream(byte[] buffer,
                            int offset,
                            int length)

Create a new ByteArrayInputStream that will read bytes from the passed in byte array. This stream will read from position offset in the array for a length of length bytes past offset. If the stream is reset to a position before offset then more than length bytes can be read from the stream. The length value should be viewed as the array index one greater than the last position in the buffer to read.

Note that this array is not copied. If its contents are changed while this stream is being read, those changes will be reflected in the bytes supplied to the reader. Please use caution in changing the contents of the buffer while this stream is open.

Parameters:

buf - The byte array buffer this stream will read from.

offset - The index into the buffer to start reading bytes from

length - The number of bytes to read from the buffer

Method Detail

available

public int available()

This method returns the number of bytes available to be read from this stream. The value returned will be equal to count - pos.

Overrides:

available in class InputStream

Returns:

The number of bytes that can be read from this stream before blocking, which is all of them

mark

public void mark(int readAheadLimit)

This method sets the mark position in this stream to the current position. Note that the readlimit parameter in this method does nothing as this stream is always capable of remembering all the bytes int it.

Note that in this class the mark position is set by default to position 0 in the stream. This is in constrast to some other stream types where there is no default mark position.

Overrides:

mark in class InputStream

Parameters:

readlimit - The number of bytes this stream must remember. This parameter is ignored.

markSupported

public boolean markSupported()

This method overrides the markSupported method in InputStream in order to return true - indicating that this stream class supports mark/reset functionality.

Overrides:

markSupported in class InputStream

Returns:

true to indicate that this class supports mark/reset.

read

public int read()

This method reads one byte from the stream. The pos counter is advanced to the next byte to be read. The byte read is returned as an int in the range of 0-255. If the stream position is already at the end of the buffer, no byte is read and a -1 is returned in order to indicate the end of the stream.

Overrides:

read in class InputStream

Returns:

The byte read, or -1 if end of stream

read

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

This method reads bytes from the stream and stores them into a caller supplied buffer. It starts storing the data at index offset into the buffer and attempts to read len bytes. This method can return before reading the number of bytes requested if the end of the stream is encountered first. The actual number of bytes read is returned. If no bytes can be read because the stream is already at the end of stream position, a -1 is returned.

This method does not block.

Overrides:

read in class InputStream

Parameters:

buf - The array into which the bytes read should be stored.

offset - The offset into the array to start storing bytes

len - The requested number of bytes to read

Returns:

The actual number of bytes read, or -1 if end of stream.

reset

public void reset()

This method sets the read position in the stream to the mark point by setting the pos variable equal to the mark variable. Since a mark can be set anywhere in the array, the mark/reset methods int this class can be used to provide random search capabilities for this type of stream.

Overrides:

reset in class InputStream

skip

public long skip(long n)

This method attempts to skip the requested number of bytes in the input stream. It does this by advancing the pos value by the specified number of bytes. It this would exceed the length of the buffer, then only enough bytes are skipped to position the stream at the end of the buffer. The actual number of bytes skipped is returned.

Overrides:

skip in class InputStream

Parameters:

num_bytes - The requested number of bytes to skip

Returns:

The actual number of bytes skipped.