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From: jsorenso@thesis1.med.uth.tmc.edu (JEFFREY MARIUS SORENSON)
Newsgroups: comp.sys.mac.programmer
Subject: newD() function for ThinkC
Message-ID: <5149@lib.tmc.edu>
Date: 25 Jun 91 06:22:57 GMT
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I'm working on a project which involves lots of small
"direct" (implemented as pointers) objects in ThinkC.
As it stands, each time I create one of these objects
I have to go through the sequence:

size=sizeof(ClassName);
newObject=(ClassName*)NewPtr(size);
blessD(newObject, ClassName);

To create (allocate) an indirect object, there is 
a function Symantec provided.
void	*new(void*);

Now since I might have hundreds of different classes,
I would like to write a functions, analogous to Symantec's
new(), called newD() that allocates and blesses a direct object.

This would seem feasible, so I created one with the same
arguments as Symantec's new(). So Ideally I could write:
newObject=newD(ClassName);

However, since ClassName is passed as a pointer to void, I
can't seem to get the size of the class from within my newD()
function.			void	*newD(void	*dummyClassName);

since dummyClassName is just a pointer, sizeof(dummyClassName)
is simply 4.  You can't call sizeof(*dummyClassName), because
that is an illegal use of the void type.  Now I'm sure that this pointer
to className must contain some sort of information about the size of
the class.  But how do I get to it?  How does Symantec do it? (with their
new() function, one passes the class name as a pointer to void).
Has anyone been able to write a newD() function?  If so, I would appreciate
any tips.  If it is for some reason impossible, I would like to know that too
so I can give it up.  I'm curious about why Symantec didn't provide a newD()
function.  I'm guessing that either they thought it would be easy enought for
me to implement myself, or that there is something about using a pointer instead
of a handle that makes it too difficult/impossible. Any clues?
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