[Gambas-devel] Comparing Gambas strings

[Tobias Boege]

Hi Benoit,

I'm a little uncertain about the following code:

---
BEGIN_METHOD(Class_Method, GB_STRING a; GB_STRING b)

	char *b = GB.NewString(STRING(b), LENGTH(b));

	int res = strncmp(STRING(a), b, LENGTH(a) + 1);

END_METHOD
---

I just want to compare (case-unsensitively) the given Gambas strings 'a' and
'b'. As I saw in the sources of STRING_new(), the resulting string 'b' is
always NUL terminated. (I need it GB.NewString'd anyway.)

So this seems correct to me: strncmp() compares the maybe-not-NUL-terminated
string 'a' and 'b' until either string reaches a NUL or the given number of
bytes was searched.

That there is a NUL in 'b' is sure. And for 'a', the NUL is either at
LENGTH(a) + 1 or the string is part of a larger one, right? As if we called

Class.Method(Mid$("String containing 'a'", 3, 3), "string b")

In any case it will *not* produce a segfault if I instruct strncmp() to
examine LENGTH(a) + 1 bytes. Is this correct?

Additionally, it will lead me a correct comparison of the two strings, or
not? I fear that something like this could produce false positives:

Class.Method(Mid$("sample", 1, 2), "sample")

Should I also compare the strings' lengths? Sounds kind of inconvenient
because all I want is to compare ASCII strings case-unsensitively. Maybe I
have overlooked an API or I don't get the right idea just now.

Regards,
Tobi