🚀 go-pugleaf

[depeche@quiche.cs.mcgill.ca (Sam Alan EZUST) writes...]
[.. responding to email I sent to him ..]

> :   Alternately, does Lazer C allow copying structures using a simple
> : assignment?  <struct2> = <struct1>;  If so, what I've ocassionaly used in
> : situations like yours is to define a struct containing the array and
> : moved copys of the array arround by just using assignments...
> 
> that's a good idea. I should try it. I didn't think it was possible though,
> as struct names are just pointers to memory locations of data, just
> like arrays,

  Nope.  A struct name is the name of a structure.  It is -not- a pointer
even though it has an address that you can obtain by using: &structname
(Note that the address you obtain (unless you cast it or store it into a
pointer of some other type) still "knows" that it's pointing to a struct
so if you use *(&structname) it references the original structure, not
just the 1st byte in the structure.

  *(unsigned char *)(&structname) would give you the structures 1st byte...

> and you can address the 5th byte of a structure with
> *(structname+5) just like arrays.

  Nope....  *(structname+5) is an illegal construct.  You can't increment
a structure itself and contrary to your assumption, a structname is -not-
the same as a pointer to a structure.

  On the other hand, ((&structname)+5) (which is different) would point
to a location 5 STRUCTURES higher in memory than &structname.  In C, any
addition to a pointer is taken as increasing the pointer by (the value
added multiplied by the size of the object being pointed at (in this case
a structure)).  This sometimes causes confuses because many people
normaly only deal with arrarys of characters (so the sizeof object == 1).

  Example:

	struct foo
		{
		int foo_1[32][100];
		};

	foocpy()
		{
		struct foo src, dst;

		/* if your compiler allows structure assignment, */
		/* the next line should copy an array 32 x 100   */
		/* integers long with a single assignment...     */

		dst = src;

		/* individual elements would be referenced as... */

		src.foo_1[23][7] = 2619;
		}
 
> you are exactly right. However, I got it working now via the brute-force
> loop-of-assign statements. If I can get dlibs installed properly on
> Laser C (and I am having trouble, as you will soon see in one of 
> my messages posted on c-s-a-st which I posted today), I will then
> translate them all into memcpy's.

  Good luck.  You may still want to consider using struct assignments
since I've been told Lazer-C does support them...

> :   .. although, it would be a real-good-idea if you posted a note on the
> : net mentioning that strncpy doesn't move <n> bytes so other beginning
> : programmers who see your message won't think that it's a correct
> : substitution....
> 
> ok.. I shall. Thanks for your help/reply!!

  You're welcome...

> -- 
> S. Alan Ezust                                   depeche@calvin.cs.mcgill.ca
> McGill University Department of Computer Science - Montreal, Quebec, Canada

---
John Stanley <dynasoft!john@stag.UUCP>
Software Consultant / Dynasoft Systems