[Openmcl-devel] Re: Hemlock performance investigation
Andrew P. Lentvorski, Jr.
bsder at mail.allcaps.org
Sat Aug 28 02:04:15 EDT 2004
On Aug 27, 2004, at 4:47 PM, Andrew P. Lentvorski, Jr. wrote:
> Would the buffer happen to be one monolithic Unicode NSString (or is
> something expecting to be accessing an NSString)? If so, O(n)
> accesses occur for every call to character-at-index since this is
> Unicode. It has to walk the entire string from the beginning since
> the size in bytes of a character is not fixed. If you scan every
> character in the file, then that is also O(n).
This certainly might be the culprit. Quoting the NSString
- (void)getCharacters:(unichar *)buffer range:(NSRange)aRange
Copies characters from aRange in the receiver into buffer, which must
be large enough to contain them. Does not add a zero character. Raises
an NSRangeException if any part of aRange lies beyond the end of the
The abstract implementation of this method uses characterAtIndex:
repeatedly, correctly extracting the characters, though very
inefficiently. Subclasses should override it to provide a fast
You will probably need to implement some of abstract methods on the
NSString to see if this is actually the problem, though.
> 1) The better option is probably to use an NSTextView. People seem to
> be doing very nice editors with them. (cf. subethaedit and smultron).
I had meant to imply subclassing NSTextView. However, both of my
references suggest that NSTextView should be used by providing a
delegate rather than subclassing. Mea culpa.
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