On Wed, Dec 21, 2005 at 10:58:44PM +0000, Paul LeoNerd Evans wrote:
> Yes, I've had a look at that patch. It's not very efficient; it
> allocates a new string buffer big enough to hold the string, then fills
> it, then strdup()s it into the GString, then frees the first buffer.
> That's unnecessary.
>
> My method is:
>
> void g_string_append_vprintf(GString *str, const gchar *fmt, va_list args)
> {
> gsize len = g_printf_string_upper_bound(fmt, args) + 1;
> g_string_maybe_expand(str, len);
> g_vsnprintf(str->str + str->len, len, fmt, args);
> str->len += len;
> }
>
> This doesn't double-allocate the buffer and then incur an unnecessary
> strcpy().
Well, I've done some benchmarking in this, and acutally I'd like to
retract that statement.
My method is slightly faster in a few trivial cases, for example a
format with no conversions, or just "%s", by somewhere around 5%. But,
this comes at the cost of being quite a bit slower (sometimes 50%) if
the format is more complex (I tried "%s%d%s" for example). I suspect
this might be because of the extra processing at having to scan the
format string and arguments list twice, count up the lengths of string
arguments passed in, that sort of thing. This only happens once in the
function in its original form.
In short; I'll leave it as it is. :)
--
Paul "LeoNerd" Evans
leonerd leonerd org uk
ICQ# 4135350 | Registered Linux# 179460
http://www.leonerd.org.uk/
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