Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!psuvax1!psuvm!cxt105
From: CXT105@PSUVM.BITNET (Christopher Tate)
Newsgroups: comp.sys.mac.programmer
Subject: Re: ARRGH (Strings and things)
Message-ID: <89300.054241CXT105@PSUVM.BITNET>
Date: 27 Oct 89 09:42:41 GMT
References: <16004@netnews.upenn.edu>
Distribution: usa
Organization: Penn State University
Lines: 52

In article <16004@netnews.upenn.edu>, parnes@eniac.seas.upenn.edu (Gary Parnes)
says:

>So what's wrong with this?
>
>Str255 myString;
>StringHandle mystringhandle;
>
>myString=**mystringhandle;

What you're trying to do here, in actuality, is copy every element of the
Str255 you find with **mystringhandle into the Str255 variable called
myString.  You can't do this, for the same reason that you can't simply
assign two arrays to be equal:  C doesn't let you do it.  That's why the
compiler gives you an "illegal operation on array" message.

Since you're dealing with Pascal strings, the copying gets a little
messy.  What I do is copy the length byte, then use it as a counter as I copy
the string from **mystringhandle into myString, thus:

          StringHandle  mystringhandle;
          Str255        myString;
          char          *toPtr, *fromPtr;
          int           i;

          fromPtr = (char *)(*mystringhandle);  /* point to the first char */
          toPtr = (char *) &myString;           /*   of both strings       */
          *toPtr = *fromPtr;          /* copy the length byte */
          i = *fromPtr;               /* set up the counter */
          toPtr++;  fromPtr++;        /* point to the actual string data */
          for (;i>0;i--)    /* do this for each character in the string.... */
          {
              *toPtr = *fromPtr;      /* copy a byte of the string */
              toPtr++;  fromPtr++;    /* move along one byte */
          }

This fragment copies the contents of the string accessed through mystringhandle
into the Str255 variable myString.  (At least, that's what I *think* it does;
I wrote it off the cuff and it may be wrong :-).  I wrote out all the
pointer incrementing explicitly to help you see what's going on.  If you're
a new programmer, you probably have the same problem with C that I had:
reading it ("C" stands for "Cryptic").

Anyway, you'll probably hear different ways of doing it, but that's what
springs to my mind.  Hope it helps.

-------
Christopher Tate                        |   "Oh wow:  not only is 57
                                        |    prime, but it's also
Bitnet: cxt105@psuvm                    |    divisible by three!"
Uucp: ...!psuvax1!psuvm.bitnet!cxt105   |
Internet: cxt105@psuvm.psu.edu          |    - a very sincere math major