com.sun.spot.util
Class CrcOutputStream

java.lang.Object
  java.io.OutputStream
      com.sun.spot.util.CrcOutputStream

All Implemented Interfaces:

Closeable, Flushable

public class CrcOutputStream
extends OutputStream

CrcOutputStream provides CRC checking and flow control for two Java programs communicating with two input and output stream pairs. To use this class, open a CrcOutputStream around the InputStream and OutputStream at each end. Then use the accessor getInputStream() to obtain an InputStream and do further io using the CrcOutputStream and the InputStream obtained from getInputStream(). Data is sent over the output stream in blocks whose size can be specified in CrcOutputStream constructor. A smaller block is sent whenever a flush is done on the CrcOutputStream. If data corruption occurs, IOExceptions will be thrown on both the sending and receiving threads. Subsequent read and writes will still be valid. The streams are not thread-safe in the presence of multiple simultaneous accessors; each stream should be accessed from one thread.

Constructor Summary

CrcOutputStream(OutputStream outputStream, InputStream inputStream)
Open an output stream that will add CRC checking and flow control to the outgoing data stream.

CrcOutputStream(OutputStream outputStream, InputStream inputStream, int blockSize)
Open an output stream that will add CRC checking and flow control to the outgoing data stream.

Method Summary

void	close()
void	flush()
InputStream	getInputStream()
boolean	probe() Returns true if there's a CrcOutputStream at the far end, and someone there is waiting on a read.
void	write(byte[] b, int off, int len)
void	write(int b)

Methods inherited from class java.io.OutputStream

write

Methods inherited from class java.lang.Object

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

Constructor Detail

CrcOutputStream

public CrcOutputStream(OutputStream outputStream,
                       InputStream inputStream)

Open an output stream that will add CRC checking and flow control to the outgoing data stream.

Parameters:

outputStream - the underlying output stream on which to write data.

inputStream - to receive data from the remote CRCOutputStream, and acknowledgements and CRC hashes from the remote CRC InputStream.

CrcOutputStream

public CrcOutputStream(OutputStream outputStream,
                       InputStream inputStream,
                       int blockSize)

Open an output stream that will add CRC checking and flow control to the outgoing data stream.

Parameters:

outputStream - the underlying output stream on which to write data.

inputStream - to receive data from the remote CRCOutputStream, and acknowledgements and CRC hashes from the remote CRC InputStream.

blockSize - the maximum number of bytes of data to be written before waiting for a CRC confirmation from the remote device. Also, the remote device will never buffer more than (2 * blockSize) bytes of data awaiting reading from the containing CRC InputStream.

Method Detail

getInputStream

public InputStream getInputStream()

Returns:

a CRC InputStream. This supplies data received from the remote device's CrcOutputStream whose integrity has been checked using a CRC hash. No more than (2 * blockSize) bytes of data will be buffered locally.

write

public void write(int b)
           throws IOException

Specified by:

write in class OutputStream

Throws:

IOException

See Also:

OutputStream.write(int)

write

public void write(byte[] b,
                  int off,
                  int len)
           throws IOException

Overrides:

write in class OutputStream

Throws:

IOException

See Also:

OutputStream.write(byte[], int, int)

flush

public void flush()
           throws IOException

Specified by:

flush in interface Flushable

Overrides:

flush in class OutputStream

Throws:

IOException

See Also:

OutputStream.flush()

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Overrides:

close in class OutputStream

Throws:

IOException

See Also:

OutputStream.close()

probe

public boolean probe()
              throws IOException

Returns true if there's a CrcOutputStream at the far end, and someone there is waiting on a read. This method can only be called when no-one is waiting on a local read, and will hang if this condition is not met.

Returns:

true if there's a reader at the far end

Throws:

IOException