🚀 go-pugleaf

natewild@mbnet.mb.ca (Nathan T. Wild) writes:

>I am implimenting a system, but which executable code modules are loaded
>from disk files into allocated blocks.

>This is working very well.  I allocated a big enough block, load the
>"driver" in and aim a function pointer ar it.  

>What I would like to do is have the code that I load in contain near
>pointers to it's own groups of functions.  I have placed a header on the
>driver module I wish to load that contains the offset from the current
>segment for two functions contained within the driver block.

>This time I want to calculate the segment and read in the offset and set
>both function pointers accordingly.

>I am having difficulty dereferencing things???



>Say, for example that my code block is allocated at XXXX:0004.  The first 2
>bytes are the pointer (within the block) to the first function and the next
>2 bytes are the pointer to the second function.

>I want to set my function pointer to the segment XXXX and the offset stored
>at XXXX:0004 & 0005.  No matter how I reference this, I get my function
>pointing to XXXX:0004!


>I have tried (where driverPtr == XXXX:0004 and is a void far *):
>	func1ptr = (void far **)driverPtr
>	func2ptr = (void far **)(driverPtr+2)
>	
>But I get XXXX:0004 every time?  I can set the function pointers to what I
>want if I use MK_FP(), FP_SEG() and peek(), but there has got to be a
>better way than this?

I would use MK_FP (it uses compiler primitives that manage segments and offsets)
, but you might get away with:

func1ptr = (void far *)(*(short *)driverPtr);
func2ptr = (void far *)(*(short *)(driverPtr+2));

Of course that last +2 may not work because driverPtr is void far *,
so you may have to do something like:

func2ptr = (void far *)(*(((short *)driverPtr)+1));

And maybe unsigned shorts would be smarter, I don't know.
And this still doesn't handle segments appropriately.  Oh well...



>In short, how, given the address of a stored pointer, set a function to
>point to the address stored, no to the location it is stored in???

>This is driving me nuts as I am sure it is fairly simple...

>Please respond via Email, I cannot access this group "live"...

>Thanks in advance...

>|--------------------------------------------------------------------|
>| ooooO (``)   (``) Ooooo | Nathan T. Wild                           | 
>| (   ) )  (   )  ( (   ) | natewild@mbnet.mb.ca                     |
>| )  (  (   ) (   ) )  (  | ftp://ftp.mbnet.mb.ca/pub/natewild       |
>| (__)  ooooO Ooooo (__)  | http://www.mbnet.mb.ca/~natewild         |
>|--------------------------------------------------------------------|