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utf8.c: speculatively assume utf-8 in strbuf_add_wrapped_text()

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is_utf8() works by calling utf8_width() for each character at the
supplied location.  In strbuf_add_wrapped_text(), we do that anyway
while wrapping the lines.  So instead of checking the encoding
beforehand, optimistically assume that it's utf-8 and wrap along
until an invalid character is hit, and when that happens start over.

This pays off if the text consists only of valid utf-8 characters.
The following command was run against the Linux kernel repo with
git 1.7.0:

	$ time git log --format='%b' v2.6.32 >/dev/null

	real	0m2.679s
	user	0m2.580s
	sys	0m0.100s

	$ time git log --format='%w(60,4,8)%b' >/dev/null

	real	0m4.342s
	user	0m4.230s
	sys	0m0.110s

And with this patch series:

	$ time git log --format='%w(60,4,8)%b' >/dev/null

	real	0m3.741s
	user	0m3.630s
	sys	0m0.110s

So the cost of wrapping is reduced to 70% in this case.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe 2010-02-19 23:20:44 +01:00 committed by Junio C Hamano
parent 68ad5e1e9c
commit 462749b728
1 changed files with 17 additions and 6 deletions
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23
utf8.c
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@ -324,16 +324,21 @@ static size_t display_mode_esc_sequence_len(const char *s)
* consumed (and no extra indent is necessary for the first line).
*/
int strbuf_add_wrapped_text(struct strbuf *buf,
const char *text, int indent, int indent2, int width)
const char *text, int indent1, int indent2, int width)
{
int w = indent, assume_utf8 = is_utf8(text);
const char *bol = text, *space = NULL;
int indent, w, assume_utf8 = 1;
const char *bol, *space, *start = text;
size_t orig_len = buf->len;
if (width <= 0) {
strbuf_add_indented_text(buf, text, indent, indent2);
strbuf_add_indented_text(buf, text, indent1, indent2);
return 1;
}
retry:
bol = text;
w = indent = indent1;
space = NULL;
if (indent < 0) {
w = -indent;
space = text;
@ -385,9 +390,15 @@ new_line:
}
continue;
}
if (assume_utf8)
if (assume_utf8) {
w += utf8_width(&text, NULL);
else {
if (!text) {
assume_utf8 = 0;
text = start;
strbuf_setlen(buf, orig_len);
goto retry;
}
} else {
w++;
text++;
}