org.jnetstream.capture
Class PacketInputStream

java.lang.Object
  java.io.InputStream
      org.jnetstream.capture.PacketInputStream

All Implemented Interfaces:

java.io.Closeable, CapturePacketInput<CapturePacket>

public class PacketInputStream
extends java.io.InputStream
implements CapturePacketInput<CapturePacket>, java.io.Closeable

A PacketInputStream deserializes Packet objects into DeserializedPacket objects previously written using a PacketOutputStream. DeserializedPacket interface is a subclass of CapturePacket which adds several new methods that contain information about the serialization process.

Here is an example:

 
 FileOutputStream fos = new FileOutputStream("test.stream");
 PacketOutputStream cos = new PacketOutputStream(fos);
 CapturePacket packet = //gotten from live network or file 
     cos.writePacket(packet);
 cos.close();
 
 FileInputStream fis = new FileInputStream("test.stream");
 PacketInputStream cis = new PacketInputStream(fis);
 packet = cis.readPacket();
 cis.close();
 
 

Author:

Mark Bednarczyk, Sly Technologies, Inc.

Field Summary

protected java.io.ObjectInputStream

in

Constructor Summary

protected	PacketInputStream() Provide a way for subclasses that are completely reimplementing CapturePacketInputStream to not have to allocate private data just used by this implementation of CapturePacketInputStream.
	PacketInputStream(java.io.InputStream in) Creates an ObjectInputStream that reads from the specified InputStream.

Method Summary

int	available() Gets the number of bytes available for read without blocking the operation.
void	close() Closes this and the underlying input stream.
void	mark(int readlimit) Marks the current position in this input stream.
boolean	markSupported() Tests if this input stream supports the mark and reset methods.
int	read()
int	read(byte[] b) Reads some number of bytes from the input stream and stores them into the buffer array b.
int	read(byte[] b, int off, int len) Reads up to len bytes of data from the input stream into an array of bytes.
DeserializedPacket	readPacket() Deserializes a packet from the underlying input stream that was previously serialized by a corresponding PacketOutputStream object.
void	reset() Repositions this stream to the position at the time the mark method was last called on this input stream.
long	skip(long n) Skips over and discards n bytes of data from this input stream.

Methods inherited from class java.lang.Object

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

Field Detail

in

protected java.io.ObjectInputStream in

Constructor Detail

PacketInputStream

protected PacketInputStream()

Provide a way for subclasses that are completely reimplementing CapturePacketInputStream to not have to allocate private data just used by this implementation of CapturePacketInputStream.

PacketInputStream

public PacketInputStream(java.io.InputStream in)
                  throws java.io.IOException

Creates an ObjectInputStream that reads from the specified InputStream. A serialization stream header is read from the stream and verified. This constructor will block until the corresponding CapturePacketOutputStream has written and flushed the header.

Parameters:

in - input stream to read from

Throws:

java.io.IOException - any usual I/O errors

Method Detail

available

public int available()
              throws java.io.IOException

Gets the number of bytes available for read without blocking the operation.

Overrides:

available in class java.io.InputStream

Returns:

number of byte available for immediate read

Throws:

java.io.IOException - any IO errors

See Also:

InputStream.available()

close

public void close()
           throws java.io.IOException

Closes this and the underlying input stream.

Specified by:

close in interface java.io.Closeable

Overrides:

close in class java.io.InputStream

Throws:

java.io.IOException - any IO errors

See Also:

InputStream.close()

mark

public void mark(int readlimit)

Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes. The readlimit arguments tells this input stream to allow that many bytes to be read before the mark position gets invalidated. The general contract of mark is that, if the method markSupported returns true, the stream somehow remembers all the bytes read after the call to mark and stands ready to supply those same bytes again if and whenever the method reset is called. However, the stream is not required to remember any data at all if more than readlimit bytes are read from the stream before reset is called. The mark method of InputStream does nothing.

Overrides:

mark in class java.io.InputStream

Parameters:

readlimit - the maximum limit of bytes that can be read before the mark position becomes invalid.

See Also:

InputStream.mark(int)

markSupported

public boolean markSupported()

Tests if this input stream supports the mark and reset methods. Whether or not mark and reset are supported is an invariant property of a particular input stream instance. The markSupported method of InputStream returns false.

Overrides:

markSupported in class java.io.InputStream

Returns:

true if this stream instance supports the mark and reset methods; false otherwise.

See Also:

InputStream.markSupported()

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException

Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

The read(b, off, len) method for class InputStream simply calls the method read() repeatedly. If the first such call results in an IOException, that exception is returned from the call to the read(b, off, len) method. If any subsequent call to read() results in a IOException, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b and the number of bytes read before the exception occurred is returned. Subclasses are encouraged to provide a more efficient implementation of this method.

Overrides:

read in class java.io.InputStream

Parameters:

b - the buffer into which the data is read

off - the start offset in array b at which the data is written

len - the maximum number of bytes to read

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached

Throws:

java.io.IOException - any IO errors

java.lang.NullPointerException - if b is null

See Also:

InputStream.read(byte[], int, int)

read

public int read(byte[] b)
         throws java.io.IOException

Reads some number of bytes from the input stream and stores them into the buffer array b. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown.

If b is null, a NullPointerException is thrown. If the length of b is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[0], the next one into b[1], and so on. The number of bytes read is, at most, equal to the length of b. Let k be the number of bytes actually read; these bytes will be stored in elements b[0] through b[k-1], leaving elements b[k] through b[b.length-1] unaffected.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

The read(b) method for class InputStream has the same effect as: read(b, 0, b.length)

Overrides:

read in class java.io.InputStream

Throws:

java.io.IOException

reset

public void reset()
           throws java.io.IOException

Repositions this stream to the position at the time the mark method was last called on this input stream. The general contract of reset is:

• If the method markSupported returns true, then:
  • If the method mark has not been called since the stream was created, or the number of bytes read from the stream since mark was last called is larger than the argument to mark at that last call, then an IOException might be thrown.
  • If such an IOException is not thrown, then the stream is reset to a state such that all the bytes read since the most recent call to mark (or since the start of the file, if mark has not been called) will be resupplied to subsequent callers of the read method, followed by any bytes that otherwise would have been the next input data as of the time of the call to reset.
• If the method markSupported returns false, then:
  • The call to reset may throw an IOException.
  • If an IOException is not thrown, then the stream is reset to a fixed state that depends on the particular type of the input stream and how it was created. The bytes that will be supplied to subsequent callers of the read method depend on the particular type of the input stream.

The method reset for class InputStream does nothing except throw an IOException.

Overrides:

reset in class java.io.InputStream

Throws:

java.io.IOException

See Also:

InputStream.mark(int)

skip

public long skip(long n)
          throws java.io.IOException

Skips over and discards n bytes of data from this input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped. The skip method of InputStream creates a byte array and then repeatedly reads into it until n bytes have been read or the end of the stream has been reached. Subclasses are encouraged to provide a more efficient implementation of this method.

Overrides:

skip in class java.io.InputStream

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

java.io.IOException

See Also:

InputStream.skip(long)

read

public int read()
         throws java.io.IOException

Specified by:

read in class java.io.InputStream

Throws:

java.io.IOException

readPacket

public DeserializedPacket readPacket()
                              throws java.io.IOException

Deserializes a packet from the underlying input stream that was previously serialized by a corresponding PacketOutputStream object.

Specified by:

readPacket in interface CapturePacketInput<CapturePacket>

Returns:

a deserialized a packet

Throws:

java.io.IOException - if any of the usual InputOutput related exceptions occur

See Also:

com.slytechs.capture.stream.CapturePacketInput#readCapturePacket()