java.io

Class ByteArrayInputStream

public class ByteArrayInputStream extends InputStream

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

Field Summary
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
	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
int	available() This method returns the number of bytes available to be read from this stream.
void	mark(int readLimit) 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[] buffer, int offset, int length) 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 num) This method attempts to skip the requested number of bytes in the input stream.

Field Detail

buf

protected byte[] buf

The array that contains the data supplied during read operations

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

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

pos

protected int pos

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

Parameters: buffer 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.

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

mark

public void mark(int readLimit)

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.

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.

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.

Returns: The byte read, or -1 if end of stream

read

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

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.

Parameters: buffer The array into which the bytes read should be stored. offset The offset into the array to start storing bytes length 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.

skip

public long skip(long num)

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.

Parameters: num The requested number of bytes to skip

Returns: The actual number of bytes skipped.