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113 lines
1.9 KiB
Markdown
113 lines
1.9 KiB
Markdown
---
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title: "message"
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weight: 1
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---
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{{< callout type="info">}}
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Header: `message.h`
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{{< /callout >}}
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Message types used for many of the framework classes.
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---
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```cpp
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etl::message_id_t
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```
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The type used for message ids.
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By default can hold a value between 0 and 255.
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If `ETL_MESSAGE_ID_TYPE` is defined then this type will be used instead.
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---
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```cpp
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etl::message_router_id_t
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```
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The type used for message router ids.
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Can hold a value between 0 and 255.
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---
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The message classes are the common communication method across all of the message capable frameworks.
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They are identified by a unique id number that specialises the base class.
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## imessage
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The base class for messages.
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It is this class that is passed around, usually by const reference.
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The class is abstract.
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---
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```cpp
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etl::message_id_t get_message_id() const ETL_NOEXCEPT = 0;
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```
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Returns the id of the message.
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---
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## message
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```cpp
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message<size_t ID, typename TParent = etl::imessage>
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```
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Requires an integral id as the template parameter.
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Inherits from `TParent`, which defaults to `etl::imessage`.
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`TParent` allows additional base interfaces or functionality to be included.
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static asserts if `TParent` is not a base of `etl::imessage`.
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---
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```cpp
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ID
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```
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The id of the message as an enum.
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Can be accessed by `etl::message` instances.
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---
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```cpp
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TParent
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```
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The class that it inherits from. It must ultimately derive from `etl::imessage`.
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The default is `etl::imessage`.
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---
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## Example
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```cpp
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enum
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{
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START,
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STOP,
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SET_SPEED
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};
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struct MyInterface : public etl::imessage
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{
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virtual void DoStuff() = 0;
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};
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// Start implements MyIterface
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struct Start : public etl::message<START, MyInterface>
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{
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void DoStuff() override
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{
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// Do stuff here.
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}
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};
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struct Stop : public etl::message<STOP>
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{
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bool isEmergencyStop;
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};
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struct SetSpeed : public etl::message<SET_SPEED>
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{
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uint32_t speed;
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};
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void Receive(const etl::imessage& msg);
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```
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