Fastest way to get array of NSRange objects for all uppercase letters in an NSString?

Question

I need NSRange objects for the position of each uppercase letter in a given NSString for input into a method for a custom attributed string class. 

There are of course q

Answer 1

It somewhat depends on the size of the string, but the absolute fastest way I can think of (note: internationalization safety not guaranteed, or even expected! Does the concept of uppercase even apply in say, Japanese?) is:

1) Get a pointer to a raw C string of the string, preferably in a stack buffer if it's small enough. CFString has functions for this. Read the comments in CFString.h.

2) malloc() a buffer big enough to hold one NSRange per character in the string.

3) Something like this (completely untested, written into this text field, pardon mistakes and typos)

NSRange *bufferCursor = rangeBuffer; 
NSRange range = {NSNotFound, 0}; 
for (int idx = 0; idx < numBytes; ++idx) { 
    if (isupper(buffer[idx])) { 
        if (range.length > 0) { //extend a range, we found more than one uppercase letter in a row
            range.length++;
        } else { //begin a range
            range.location = idx; 
            range.length = 1;
        }
    }
    else if (range.location != NSNotFound) { //end a range, we hit a lowercase letter
        *bufferCursor = range; 
        bufferCursor++;
        range.location = NSNotFound;
    }
}

4) realloc() the range buffer back down to the size you actually used (might need to keep a count of ranges begun to do that)