com.aquenos.epics.jackie.common.protocol

Class ChannelAccessReadServerMessage

java.lang.Object

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

com.aquenos.epics.jackie.common.protocol.ChannelAccessReadMessage

com.aquenos.epics.jackie.common.protocol.ChannelAccessReadServerMessage

public final class ChannelAccessReadServerMessage
extends ChannelAccessReadMessage

Representation of a CA_PROTO_READ message that is sent from a server to a client. This message is sent in response to a ChannelAccessReadClientMessage from a client.}.

Author:

Sebastian Marsching

See Also:

ChannelAccessCommand.CA_PROTO_READ, ChannelAccessReadMessage, ChannelAccessReadClientMessage

Field Summary

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

command, originalMessageHeader

Constructor Summary

Constructors

Constructor and Description
ChannelAccessReadServerMessage(ChannelAccessValueType dataType, int count, int cid, int operationId, ChannelAccessGettableValue<?> value) Creates a CA_PROTO_READ message.

Method Summary

Modifier and Type	Method and Description
protected static ChannelAccessReadServerMessage	deserialize(ChannelAccessMessageHeader messageHeader, ByteSource byteSource, java.nio.charset.Charset charset) 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	geOperationId() Returns the client-assigned operation ID.
int	getChannelCID() Returns the channel CID used by the client.
int	getCount() Returns the number of elements the value in this message's payload has.
ChannelAccessValueType	getDataType() Returns the data type of the value in this message's payload.
ChannelAccessGettableValue<?>	getValue() Returns the current value of the channel.
int	hashCode() Returns a hash code value for this message.
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.
protected void	verify(ChannelAccessVersion version, int maxPayloadSize, java.nio.charset.Charset charset) Verifies that this message can be serialized.

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

ChannelAccessReadServerMessage

public ChannelAccessReadServerMessage(ChannelAccessValueType dataType,
                                      int count,
                                      int cid,
                                      int operationId,
                                      ChannelAccessGettableValue<?> value)

Creates a CA_PROTO_READ message. This constructor should be used to create a message that is supposed to be sent from a server to a client.

Parameters:

dataType - data type of the value in the message's payload (never null). This should always be the type that the client requested. If the type requested by the client is not supported by the server, an error message should be sent instead of this message.

count - number of value elements in the message's payload. This should always be the number of elements that the client requested. If the number requested by the client is not supported by the server, an error message should be sent instead of this message. Must not be negative.

cid - client-assigned ID identifying the channel.

operationId - client-assigned ID identifying the read request. This must be the ID sent with the read request so that the client can identify the request to which the reply belongs.

value - current value of the channel (never null).

Throws:

java.lang.IllegalArgumentException - if the dataType does not match the value's data type or count is negative or greater than the value's number of elements.

Method Detail

getDataType

public ChannelAccessValueType getDataType()

Returns the data type of the value in this message's payload. This should always match the data type that the client requested. Returns null if the specified data-type is unknown to this implementation.

Returns:

data-type of the value or null if the numeric identifier cannot be mapped to a data type known by this implementation.

getCount

public int getCount()

Returns the number of elements the value in this message's payload has. This should always match the element count that the client requested.

Returns:

number of value elements.

getChannelCID

public int getChannelCID()

Returns the channel CID used by the client. This is the identifier that the client uses to identify the channel. This number might be negative or zero.

Returns:

channel CID assigned to the respective channel by the client.

geOperationId

public int geOperationId()

Returns the client-assigned operation ID. The operation ID is used by the client in order to map replies sent in response to a read request to the respective request. This must always be the ID that was sent by the client. This number might be negative or zero.

Returns:

client-assigned operation identifier.

getValue

public ChannelAccessGettableValue<?> getValue()

Returns the current value of the channel. This method returns null if the data-type sent by the server is not supported by this implementation (getDataType() returns null).

Returns:

current value of the channel or null if the data type is not supported by this implementation. The value's data type is the same that is returned by getDataType() and the value's element count is equal to or greater than the number returned by getCount().

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).

verify

protected void verify(ChannelAccessVersion version,
                      int maxPayloadSize,
                      java.nio.charset.Charset charset)

Description copied from class: ChannelAccessMessage

Verifies that this message can be serialized. This method is only intended to be used by ChannelAccessMessageCodec.

Overrides:

verify in class ChannelAccessMessage

Parameters:

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 ChannelAccessMessage

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 ChannelAccessMessage

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 ChannelAccessReadServerMessage deserialize(ChannelAccessMessageHeader messageHeader,
                                                            ByteSource byteSource,
                                                            java.nio.charset.Charset charset)

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).

charset - encoding to use for deserializing the host name. Usually, host names should consist of ASCII characters only, however this is not strictly enforced by the protocol, so the encoding might matter.

Returns:

message constructed from the data in the header and the payload read from the byte source (if headerOnly is false).

Throws:

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

ShortPayloadException - if the message's payload size is less than the size needed for the data type and count.