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digitalmars.D.learn - C callbacks?

reply Chris Andrews <CodexArcanum gmail.com> writes:
I've hit another snag on my C library interfacing.  The .h defines a function:

//typedef bool (*TCOD_bsp_callback_t)(TCOD_bsp_t *node, void *userData);
bool* bsp_callback_t(bsp_t* node, void* userData); //bsp_t is a struct defining
the bsp tree

Sidenote: Did I translate that right?

Anyway, this function is later passed into various functions, like:

bool bsp_traverse_pre_order(bsp_t *node, bsp_callback_t listener, void
*userData);


I've tried doing some reading on this board regarding c callbacks and
delegates, but it feels a bit over my head.  Can anyone assist me in figuring
out how to D-ify this bit of code so I can interact with the C dll?
Mar 18 2009
parent reply BCS <ao pathlink.com> writes:
Reply to Chris,


 I've hit another snag on my C library interfacing.  The .h defines a
 function:
 
 //typedef bool (*TCOD_bsp_callback_t)(TCOD_bsp_t *node, void *userData);


In C read this as: pointer to function taking ... (stuff) and returning bool

in D the more normal way to write that would be:

typedef bool function(bsp_t* node, void* userData) TCOD_bsp_callback_t;

if you are passing this to C code you will need an exter(C) in there somewhere.


 bool* bsp_callback_t(bsp_t* node, void* userData); //bsp_t is a struct 


defining the bsp tree

 
 Sidenote: Did I translate that right?
 


Try it, test it, beat the snot out of it. If it works it's likely correct.


 Anyway, this function is later passed into various functions, like:
 
 bool bsp_traverse_pre_order(bsp_t *node, bsp_callback_t listener, void
 *userData);
 
 I've tried doing some reading on this board regarding c callbacks and
 delegates, but it feels a bit over my head.  Can anyone assist me in
 figuring out how to D-ify this bit of code so I can interact with the
 C dll?
 


C code and delegates are incomparable but C and function pointers are not.
Mar 18 2009
next sibling parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
BCS wrote:
<snip>

 in D the more normal way to write that would be:
 
 typedef bool function(bsp_t* node, void* userData) TCOD_bsp_callback_t;


<snip>

But do check whether you really want an alias (the D equivalent of 
typedef in C) or a typedef (an actual new type in D).

Stewart.
Mar 19 2009
parent Chris Andrews <CodexArcanum gmail.com> writes:
Stewart Gordon Wrote:


 But do check whether you really want an alias (the D equivalent of 
 typedef in C) or a typedef (an actual new type in D).


I believe it was a typedef in this case.  There were other points where I used
alias to get it all fixed up.  Thankfully, my conversion seems to compile just
fine, so now I'm writing the wrappers on that to make sure it all works
correctly!

Thank you for the heads up.
Mar 19 2009
prev sibling parent reply Chris Andrews <CodexArcanum gmail.com> writes:
BCS Wrote:

 in D the more normal way to write that would be:
 
 typedef bool function(bsp_t* node, void* userData) TCOD_bsp_callback_t;


Ahh! Thanks a ton, that seems to work like I needed.  


 C code and delegates are incomparable but C and function pointers are not.


I must have been misreading that bit then, thanks for clarifying. 
Listeners/Delegates have always confused me, I really need to do some tutorials
and try to understand them better.
Mar 19 2009
parent BCS <ao pathlink.com> writes:
Reply to Chris,


 BCS Wrote:
 

 in D the more normal way to write that would be:
 
 typedef bool function(bsp_t* node, void* userData)
 TCOD_bsp_callback_t;
 


 Ahh! Thanks a ton, that seems to work like I needed.
 

 C code and delegates are incomparable but C and function pointers are
 not.
 


 I must have been misreading that bit then, thanks for clarifying.
 Listeners/Delegates have always confused me, I really need to do some
 tutorials and try to understand them better.
 


The under-the-hood for delegate is that they are a
function-pointer/context-pointer 
pair where the context pointer is passed like in the this point in methods. 
In fact, for delegates based on objects, the context is the this pointer. 
For local functions and delegate literals, it is a pointer into the stack 
or some such.
Mar 19 2009