Timer and Network interfaces

[Greblys]

I think this is a better approach to share same Timer and Network interfaces between different platforms. The actual structure definitions for Timer and Network objects is hidden from MQTTClient and it contains only void * pointers to these Timer and Network objects. The functions declarations which needs to be implemented by specific platform are in Timer.h and Network.h header files. Each platform implements them and MQTTClient uses it like this:

void *networkObjectPointer;
networkObjectPointer = createNetwork(); //platform creates a network object for you
connect(networkObjectPointer); //platform will connect you to the network, but you need to pass the network object to it. 
read(networkObjectPointer, buffer, timeout); 
destroyNetwork(networkObjectPointer); //destroy network object and free its memory 

Currently I applied these interfaces only to linux implementation. This approach simplifies compilation and no sed magic is needed in the build script. Have a look into build script for stdoutsub.c.

[RostakaGmfun]

Great work!
I've added some comments suggesting improvements. I would be grateful if you prepare the PR for merging it because your changes are really useful to me.

Thanks in advance

[RostakaGmfun]

I suggest to place forward declarations to Network structure here, to avoid using pointers to void everywhere.
Something like this:
typedef struct Network Network;

The same applies to Timer interface.

[RostakaGmfun]

How about checking for NULL pointers everywhere?

[RostakaGmfun]

As an alternative approach, you can keep the function pointers in the Network interface and implement them for each platform. Then, each platform provides the NetworkInit() function, which initializes these pointers to platform-specific functions. This way, you define the Network structure once in the common header and don't need any forward declarations.

[rafaeldelucena]

Hi @Greblys this is a pretty cool PR!

Do you intend to end this PR? I can help if you're out of time.

Best regards

[icraggs]

The IP check for this PR failed. I assume that a signature of "noreply@github.com" is an error? The IP check must pass for the PR to be merged.

[BruegelN]

Hi there,

@icraggs thank for providing this embedded C implementation and thanks @Greblys for your improvements.
Is there any progress on this specific topic?
I do like the idea of using a timer and a network interface, including some suggestions made by @RostakaGmfun
Is there a way I can help regarding the current situation?

Best regards,
Nico