While SysUtils.StrScan() takes PWideChar const as the parameter, is there a StrScan() like built-in function for string/Unicodestring type?
Thanks in advance.
+2
A:
Plain old Pos will work well enough for most cases. The second parameter will simply be a one-character string instead of a Char.
If the string you're searching through will not have embedded null characters, then you can also use StrScan directly; just type-cast the string parameter to PChar. StrScan will stop searching when it reaches the null character.
Rob Kennedy
2010-09-08 15:40:52
Yes, but since the plain Pos() was designed to search a substring, its internal code should be not optimal for searching a single character. OK, I think I will still use StrScan() like this: pTempPtr := Pointer(SomeString); Position := StrScan(pTempPtr, AChar) - pTempPtr);
Phantom
2010-09-08 15:51:47
What do you think?
Phantom
2010-09-08 15:52:15
I mean PChar typecasting versus the bare Pointer typecasting?
Phantom
2010-09-08 15:53:59
Is there a downside by using Pointer typecasting instead of PChar typecasting? I see the compiler will generate less code with Pointer typecasting.
Phantom
2010-09-08 15:56:50
Always cast to the most specific type available. The function asks for a character pointer, so give it one. Also, type-casting to Pointer will yield a *null* pointer if the string is empty, which is not what the function wants. Finally, it might be worth looking at the `Pos` implementation to see whether it has any optimizations for searching for short strings. (There'd still be a hit for *allocating* the string, though.)
Rob Kennedy
2010-09-08 15:58:54
I assume POS is overloaded for single characters.
Marco van de Voort
2010-09-08 16:51:16
@Macro: Pos() is not overloaded for single chars but its algorithm searches for the first char in the substring first. So if you have a 1-char substring, it isn't that slow.
Andreas Hausladen
2010-09-08 17:23:19
Pos() is overloaded in FPC, but not in Delphi. IMO, Delphi should follow FPC in this case to generate more optimized code.
Phantom
2010-09-08 19:00:58