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Re: Some 'missing' string functions [message #16339 is a reply to message #16334]

Mon, 09 June 2008 10:51

hans
Messages: 44
Registered: March 2006
Location: Germany

Member

The function has a bug, because in

	const tchar *se = s + (len * sizeof(tchar)); :

the multiply with sizeof(tchar) is nonsense, pointer arithmetic
is defined to work with object size already;

And the function makes too many assumptions too, namely it accesses memory after len, which may work for String objects,
but not in general case:

A valid call may be

char* s= new char('A');
string.FindFirstOf(1, s, 0);

So I would suggest to change this function to

int AString<B>::FindFirstOf(int len, const tchar *s, int from) const
{
	ASSERT(from >= 0 && from <= GetLength());
	const tchar *ptr = B::Begin();
	const tchar *e = End();
	const tchar *se = s + len;
	if(len == 1) {
		tchar c1 = s[0];
		for(const tchar *bs = ptr + from; bs < e; bs++) {
			if(*bs == c1)
				return (int)(bs - ptr);
		}
		return -1;
	}
	if(len == 2) {
			tchar c1 = s[0];
			tchar c2 = s[1];
			for(const tchar *bs = ptr + from; bs < e; bs++) {
				tchar ch = *bs;
				if(ch == c1 || ch == c2)
					return (int)(bs - ptr);
			}
			return -1;
		}
	if(len == 3) {
			tchar c1 = s[0];
			tchar c2 = s[1];
			tchar c3 = s[2];
			for(const tchar *bs = ptr + from; bs < e; bs++) {
				tchar ch = *bs;
				if(ch == c1 || ch == c2 || ch == c3)
					return (int)(bs - ptr);
			}
			return -1;
		}
	if(len == 4) {
			tchar c1 = s[0];
			tchar c2 = s[1];
			tchar c3 = s[2];
			tchar c4 = s[3];
			for(const tchar *bs = ptr + from; bs < e; bs++) {
				tchar ch = *bs;
				if(ch == c1 || ch == c2 || ch == c3 || ch == c4)
					return (int)(bs - ptr);
			}
			return -1;
	}
	for(const tchar *bs = ptr + from; bs < e; bs++)
		for(const tchar *ss = s; ss < se; ss++)
			if(*bs == *ss)
				return (int)(bs - ptr);
	return -1;
}

Regards,
Hans

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