pointer2function method in pthread_create

[fantasticamir]

Guys,

I want to call a pointer2functio n method in pthread_create. .. I do not know how to do that.

here is the code...

 .....
void * EventInterface::receiveEvent(int x, void (*ptToFunc)(char *, int))
.....

EventInterface::EventInterface(void (*ptToFunc)(char *, int)){

    int x;
    pthread_create( &receiveThread, NULL, EventInterface::receiveEvent, ???????)
    ....
}

Would you please help me? I have no idea about the syntax I should follow in where I've shown with ????? !

[svlsr2000]

You cannot pass pass any function which would take arguements other then void * as input to ptheread_create call.

Probably you could create a void * function T1() which waits for some event to happen in message queue.
When you want to execute any function in thread context you can pass on those values in message queue.
Then T1 can get these messages and process them.

[AdrianH]

You cannot pass pass any function which would take arguements other then void * as input to ptheread_create call.

Probably you could create a void * function T1() which waits for some event to happen in message queue.
When you want to execute any function in thread context you can pass on those values in message queue.
Then T1 can get these messages and process them.

That is actually library dependent. I've seen an OS that will allow you to pass up to 10 parameters (VxWorks).

However, if you wish to make this portable, you should only have one parameter passed. That parameter is a pointer to something which can be a struct containing as much information you are wanting to pass. You just need to document what that object is so that anyone maintaining the code will be able to see that.

You will of course, have to cast that received value to the passed pointer type.


Adrian

[fantasticamir]

You cannot pass pass any function which would take arguements other then void * as input to ptheread_create call.

Probably you could create a void * function T1() which waits for some event to happen in message queue.
When you want to execute any function in thread context you can pass on those values in message queue.
Then T1 can get these messages and process them.

Ok if we ignore "int x" part (first argument), the second one (the *pt2Func) is a void *, isn't it?

I mean, may I define this like:

.....
void * EventInterface::receiveEvent(void (*ptToFunc)(char *, int));
.....
EventInterface::EventInterface(void (*ptToFunc)(char *, int)){

     pthread_create( &receiveThread, NULL, EventInterface::receiveEvent, (void *)(*ptToFunc)(char *, int));

}

[AdrianH]

Ok if we ignore "int x" part (first argument), the second one (the *pt2Func) is a void *, isn't it?

I mean, may I define this like:

.....
void * EventInterface::receiveEvent(void (*ptToFunc)(char *, int));
.....
EventInterface::EventInterface(void (*ptToFunc)(char *, int)){

     pthread_create( &receiveThread, NULL, EventInterface::receiveEvent, (void *)(*ptToFunc)(char *, int));

}

Don't bother casting the ptrToFunc, pthread_create takes a void*, so it will just autocast it back (if it can, I think that is valid in C/C++).

I may consider typedefing your function pointer parameter, but that is debatable.


Adrian

[fantasticamir]

Don't bother casting the ptrToFunc, pthread_create takes a void*, so it will just autocast it back (if it can, I think that is valid in C/C++).

I may consider typedefing your function pointer parameter, but that is debatable.


Adrian

how about the function declaration:
should be like this?

void * EventInterface::receiveEvent(void (*ptToFunc)(char *, int));

or 

void * EventInterface::receiveEvent(void * (*ptToFunc)(char *, int));

By the way, I guess I should play with that to see which one would be accepted by g++.

[AdrianH]

how about the function declaration:
should be like this?

void * EventInterface::receiveEvent(void (*ptToFunc)(char *, int));

or 

void * EventInterface::receiveEvent(void * (*ptToFunc)(char *, int));

By the way, I guess I should play with that to see which one would be accepted by g++.

They both should be accepted. All you did was change the signature of the function pointer from returning nothing to returning a void pointer.


Adrian

[fantasticamir]

They both should be accepted. All you did was change the signature of the function pointer from returning nothing to returning a void pointer.


Adrian

Thanks for your help,

I do appreciate it.

[AdrianH]

Thanks for your help,

I do appreciate it.

No problem. Glad to help.


Adrian