com.aquenos.epics.jackie.common.protocol

Class ChannelAccessVersionUDPMessage

java.lang.Object

com.aquenos.epics.jackie.common.protocol.ChannelAccessMessage

com.aquenos.epics.jackie.common.protocol.ChannelAccessVersionMessage

com.aquenos.epics.jackie.common.protocol.ChannelAccessVersionUDPMessage

public final class ChannelAccessVersionUDPMessage
extends ChannelAccessVersionMessage

Representation of a CA_PROTO_VERSION message that is sent from a client to a server or the other way round via UDP. This message is usually send at the start of each UDP packet in order to communicate the protocol version supported by the client (or server) and in order to communicate the sequence number associated with the search requests in the same packet.

Author:

Sebastian Marsching

See Also:

ChannelAccessCommand.CA_PROTO_VERSION, ChannelAccessVersionTCPClientMessage, ChannelAccessVersionTCPServerMessage

Field Summary

Fields inherited from class com.aquenos.epics.jackie.common.protocol.ChannelAccessVersionMessage

version

Fields inherited from class com.aquenos.epics.jackie.common.protocol.ChannelAccessMessage

command, originalMessageHeader

Constructor Summary

Constructors

Constructor and Description
ChannelAccessVersionUDPMessage(ChannelAccessVersion version, boolean sequenceNumberIsValid, int sequenceNumber) Creates a CA_PROTO_VERSION message.

Method Summary

Modifier and Type	Method and Description
protected static ChannelAccessVersionUDPMessage	deserialize(ChannelAccessMessageHeader messageHeader, ByteSource byteSource, boolean headerOnly) Constructs a message from a header and a byte source.
boolean	equals(java.lang.Object obj) Tells whether the specified object represents the same message.
int	getSequenceNumber() Returns the sequence number of this message.
int	hashCode() Returns a hash code value for this message.
boolean	isSequenceNumberValid() Returns the sequence-number-is-valid flag.
protected void	serialize(ByteSink byteSink, ChannelAccessVersion version, int maxPayloadSize, java.nio.charset.Charset charset) Serializes this message to a byte sink.
java.lang.String	toString() Returns a string representation of this message.

Methods inherited from class com.aquenos.epics.jackie.common.protocol.ChannelAccessVersionMessage

getVersion

Methods inherited from class com.aquenos.epics.jackie.common.protocol.ChannelAccessMessage

addByteArrayToStringBuilder, calculatePaddingSize, getCommand, getOriginalMessageHeader, hasOriginalMessageHeader, serializeHeader, verify, verifyHeader

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ChannelAccessVersionUDPMessage

public ChannelAccessVersionUDPMessage(ChannelAccessVersion version,
                                      boolean sequenceNumberIsValid,
                                      int sequenceNumber)

Creates a CA_PROTO_VERSION message. This constructor should be used to create a message that is supposed to be sent in any direction using the UDP protocol. It should be the first message in each UDP packet.

Parameters:

version - Channel Access version supported by the sender.

sequenceNumberIsValid - indicator whether the sequence number should be considered to be valid. If this flag is set, the sequence number might be used to calculate an estimation of the round-trip time.

sequenceNumber - sequence number. This number is supposed to be incremented with each packet sent. It might be used to calculate an estimation of the round-trip time.

Method Detail

isSequenceNumberValid

public boolean isSequenceNumberValid()

Returns the sequence-number-is-valid flag. This flag may be set by a client when sending a message over UDP and should be returned by the server together with the respective sequence number.

Returns:

sequence-number-is-valid flag, indicating whether the number returned by getSequenceNumber() should be used to update the round-trip time estimate.

getSequenceNumber

public int getSequenceNumber()

Returns the sequence number of this message. This number may be used to update the round-trip time estimate, but only if isSequenceNumberValid() returns true.

Returns:

sequence number. The sequence number should be increased with each packet sent but may be negative if it wraps.

serialize

protected void serialize(ByteSink byteSink,
                         ChannelAccessVersion version,
                         int maxPayloadSize,
                         java.nio.charset.Charset charset)

Description copied from class: ChannelAccessMessage

Serializes this message to a byte sink. This method is only intended to be used by ChannelAccessMessageCodec.

Specified by:

serialize in class ChannelAccessMessage

Parameters:

byteSink - byte sink that is used for writing the serialized data.

version - protocol version to stay compatible with. This is the protocol version of the peer the message is sent to.

maxPayloadSize - maximum size of the payload.

charset - encoding to use for serializing the string data (e.g. channel names, error strings, string data-values).

equals

public boolean equals(java.lang.Object obj)

Description copied from class: ChannelAccessMessage

Tells whether the specified object represents the same message.

Two messages are considered equal if they are of the same type and have the same headers and payload. For comparing the types, the actual Java type and not just the Channel Access command is compared.

Overrides:

equals in class ChannelAccessVersionMessage

Parameters:

obj - reference object with which this object is compared.

Returns:

true if obj is a message that is of the same type and has the same headers and payload as this message. false if obj is null or of a different type than this message or differs in the headers or payload.

hashCode

public int hashCode()

Description copied from class: ChannelAccessMessage

Returns a hash code value for this message. This method is supported for the benefit of hash tables. The hash code is calculated as a combination of the hash codes of this messages headers (including the Channel Access command) and its payload (if present).

If two messages are equal (as indicated by the return value of ChannelAccessMessage.equals(Object)), they also have the same hash code. However, the fact that two messages have the same hash code does not imply that they are equal.

Overrides:

hashCode in class ChannelAccessVersionMessage

Returns:

hash code suitable for use by a hash table.

toString

public java.lang.String toString()

Description copied from class: ChannelAccessMessage

Returns a string representation of this message. The string representation contains the messages command, its header fields (if relevant for the command type) and its payload if present.

Overrides:

toString in class ChannelAccessMessage

Returns:

string representation of this message.

deserialize

protected static ChannelAccessVersionUDPMessage deserialize(ChannelAccessMessageHeader messageHeader,
                                                            ByteSource byteSource,
                                                            boolean headerOnly)

Constructs a message from a header and a byte source. This method is only intended for use by ChannelAccessMessageCodec.

Parameters:

messageHeader - CA message header.

byteSource - byte source for reading the message's payload (if any).

headerOnly - if true this method will not try to read the payload but just read the header. This is useful for reading a message that is sent in the payload of a ChannelAccessErrorMessage. Such a message will have all headers but no payload (even so the payload size might be non-zero).

Returns:

message constructed from the data in the header and the payload read from the byte source.

Throws:

java.nio.BufferUnderflowException - if there is not enough data in the byte source to read the complete payload.