optimized command messages a bit

ipc/CommandMessage.cpp

@@ -66,10 +66,6 @@ size_t CommandMessage::getMinimumMessageSize() const {
 	return MINIMUM_COMMAND_MESSAGE_SIZE;
 }
 
-size_t CommandMessage::getMaximumMessageSize() const {
-	return MessageQueueMessage::MAX_MESSAGE_SIZE;
-}
-
 bool CommandMessage::isClearedCommandMessage() {
 	return getCommand() == CMD_NONE;
 }

ipc/CommandMessage.h

@@ -24,11 +24,11 @@ class CommandMessage: public CommandMessageBase {
 public:
 	/**
 	 * This is the size of a message as it is seen by the MessageQueue.
+	 * It can hold the CommandMessage header plus 2 4-byte parameters.
 	 * 14 of the 24 available MessageQueueMessage bytes are used.
 	 */
 	static const size_t MINIMUM_COMMAND_MESSAGE_SIZE =
-			MessageQueueMessage::HEADER_SIZE + sizeof(Command_t) +
-			2 * sizeof(uint32_t);
+			CommandMessageIF::HEADER_SIZE + 2 * sizeof(uint32_t);
 
 	/**
 	 * Default Constructor, does not initialize anything.
@@ -55,8 +55,6 @@ public:
 
 	/** MessageQueueMessageIF functions used for minimum size check. */
 	size_t getMinimumMessageSize() const override;
-	/** MessageQueueMessageIF functions used for maximum size check. */
-	size_t getMaximumMessageSize() const override;
 
 	/**
 	 * Get the first parameter of the message

ipc/CommandMessageBase.cpp

@@ -55,10 +55,18 @@ size_t CommandMessageBase::getMessageSize() const {
 	return internalMessage->getMessageSize();
 }
 
+size_t CommandMessageBase::getMaximumMessageSize() const {
+	return internalMessage->getMaximumMessageSize();
+}
+
 MessageQueueMessageIF* CommandMessageBase::getInternalMessage() const {
 	return internalMessage;
 }
 
+size_t CommandMessageBase::getMinimumMessageSize() const {
+	return MINIMUM_COMMAND_MESSAGE_BASE_SIZE;
+}
+
 void CommandMessageBase::setReplyRejected(ReturnValue_t reason,
 		Command_t initialCommand) {
 	std::memcpy(getData(), &reason, sizeof(reason));

ipc/CommandMessageBase.h

@@ -15,13 +15,21 @@
  * size checks:
  *
  *  1. getMinimumMessageSize()
- *  2. getMaximumMessageSize()
  *
+ * The maximum message size generally depends on the buffer size of the passed
+ * internal message.
  * Don't forget to set the message size of the passed message in the concrete
  * commandmessage implementation!
  */
 class CommandMessageBase: public CommandMessageIF {
 public:
+	//! This minimum size is derived from the interface requirement to be able
+	//! to set a rejected reply, which contains a returnvalue and the initial
+	//! command.
+	static constexpr size_t MINIMUM_COMMAND_MESSAGE_BASE_SIZE =
+			CommandMessageIF::HEADER_SIZE + sizeof(ReturnValue_t) +
+			sizeof(Command_t);
+
 	CommandMessageBase(MessageQueueMessageIF* message);
 
 	/**
@@ -58,6 +66,12 @@ public:
 	virtual void setMessageSize(size_t messageSize) override;
 	virtual size_t getMessageSize() const override;
 
+	//! This depends on the maximum message size of the passed internal message.
+	virtual size_t getMaximumMessageSize() const override;
+
+	//! Return the constant minimum message size.
+	virtual size_t getMinimumMessageSize() const override;
+
 	/**
 	 * A command message can be rejected and needs to offer a function
 	 * to set a rejected reply