[Coco] basename() source
robert.gault at worldnet.att.net
Sat Dec 31 14:20:07 EST 2005
After about 15 years of not using C and trying to relearn it in about
one week, I am remembering why I detest the language. :)
Bob, your program works and seems simple but after digging into this
further I've come up with some interesting finds and thoughts.
Clearly there is a problem with the Microware compiler but I have found
what triggers the lead mmnn,pcr syntax.
strrchr(file,"/" || "\\")
gives the lead opcode but
strrchr(file,'/' || '\\')
does not. Both of them give the ldd #1, which does not make any sense
but that's another story. The trigger was the double vs single quote.
A short test program (below)displays some information on how strrchr
works in the OS-9 software. It also suggests how your program (below)
could be trimmed of excess code. Here is the program and the relevant
part of the resulting assembly code.
/* test for strrchr() */
char *file = "/dd/src/test";
name = strrchr(file,'/');
name = strrchr(file,'\\');
The above as it stands does not give the desired result but does show
that strrchr does not change the string file. Here is the relevant
ldd #'\ this was #92
std 0,s save the result of strrchr
ldd #'/ this was #47
std 0,s if this line and the next are replaced with addd 0,s
ldd 0,s then the second result won't trash the first
Note above where the result of one strrchr is trashed by the second.
Since strrchr returns either $0000 or the address of the right-most
character, all we need is to add the result of the second strrchr to the
first to duplicate your code in a smaller package.
I can't remember or find any C syntax that will result in the above
code. Hand trimming of the assembly code is not the most desirable thing
in the world even if it produces better code than the optimizer can.
Anyone see a way to get this result from the C code alone?
Bob Devries wrote:
> Here's my source for basename() :
> char *basename(pathname)
> char *pathname;
> char *name;
> char *strrchr();
> if ((name = strrchr(pathname, '/')) == NULL)
> if ((name = strrchr(pathname, '\\')) == NULL)
> return(name + 1);
> It works on both windows(DOS Box) and OS9 (MESS).
> Regards, Bob Devries, Dalby, Queensland, Australia
> Isaiah 50:4 The sovereign Lord has given me
> the capacity to be his spokesman,
> so that I know how to help the weary.
> website: http://www.home.gil.com.au/~bdevasl
> my blog: http://bdevries.invigorated.org/
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