12.9 Planned features

AnyStrings

     GetCapacity (s):
       LongString            : s.Capacity
       UndiscriminatedString : MaxInt
       ShortString           : High (s)
       FixedString           : High (s) - Low (s) + 1
       CString (Array)       : High (s) - Low (s)
       CString (Zeiger)      : strlen (s)
       ObjectString          : s.GetCapacity
     
     GetLength (s):
       LongString            : s.Length
       UndiscriminatedString : s.Length
       ShortString           : Ord (s[0])
       FixedString           : c := High (s);
                               while (c >= Low (s)) and (s[c] = ' ') do
                                 Dec (c);
                               c - Low (s) + 1
       CString               : strlen (s)
       ObjectString          : s.GetLength
     
     SetLength (s,n):
       if n > GetCapacity (s) then
         if TruncateFlag then
           n := GetCapacity (s)
         else
           Error;
       LongString            : s.Length := n
       UndiscriminatedString : if n > s.Capacity then
                                 begin
                                   tmp := @s;
                                   { possibly round n up to m * 2^k
                                     to avoid frequent reallocations }
                                   New (@s, n);
                                   Move (tmp^[1], s[1], Length (tmp^);
                                   Dispose (tmp)
                                 end;
                               s.Length := n
       ShortString           : s[0] := Chr (n)
       FixedString           : FillChar (s[Low (s) + n],
                                 GetCapacity (s) - n, ' ')
       CString               : s[n] := #0
       ObjectString          : s.SetLength (n)
     
     GetFirstChar (s):
       LongString            : @s[1]
       UndiscriminatedString : @s[1]
       ShortString           : @s[1]
       FixedString           : @s[Low (s)]
       CString               : s
       ObjectString          : s.GetFirstChar

Anything else can be reduced to these, e.g. string assignment:

     SetLength (Dest, GetLength (Src));
     Move (GetFirstChar (Src) ^, GetFirstChar (Dest) ^, GetLength (Dest));
                                                                   ^^^^
                                                    (because of truncate!)

Note pointer CStrings because assignments to them (from long, undiscriminated (with appending #0) or CStrings, not from short, fixed or object strings) should set the pointer, not overwrite the memory pointed to.

Fully automatic C header translator

• C operators like += (increment a variable and return the new value), or / (integer or real division, depending on the arguments). They could be emulated by special built-in functions in GPC which do the same ...
• Types! C doesn't distinguish between pointers and arrays – and various other “jokes”. E.g., a CString and a pointer to an array of bytes can both be char * in C. Solutions could be to introduce “special types” in GPC which behave like the C types (not so nice ...)-:, or to let the translator choose one possible matching GPC type (by some heuristics perhaps), and leave it up to the user to type-cast when necessary (also not nice)-: ...
• Name clashes. How to map foo, FOO, struct foo, union foo etc. (which can potentially be totally different things in C) to Pascal identifiers in a reasonable way. Also, how to introduce identifiers for types when needed (e.g., typed used in parameter lists). Of course, that's solvable ...
• Macros. Since GPC has a preprocessor, we can translate most of them, but some particularly strange ones are virtually impossible to translate. But there's hope that such strange macros are not being used in the libraries' headers ...
• ...