Re: [PATCH] split_ident: parse timestamp from end of line

Jeff King [off-list ref] writes:

quoted

Yeah, unrolling the loop is probably better.  You may even be able
to do so in a single pass with an extra "last > seen" pointer
variable without too much additional code complexity, I would think.

I'm not sure what you mean here.

If you mean doing a single pass to find the final ">", that is easy,
because we know the length of the line already and can jump past and
start from the back.

I meant a single forward pass, like this.

 ident.c | 29 +++++++++++------------------
 1 file changed, 11 insertions(+), 18 deletions(-)

diff --git a/ident.c b/ident.c
index 7d1c79c..ff29779 100644
--- a/ident.c
+++ b/ident.c

@@ -200,7 +200,7 @@ static void strbuf_addstr_without_crud(struct strbuf *sb, const char *src)
  */
 int split_ident_line(struct ident_split *split, const char *line, int len)
 {
-	const char *cp;
+	const char *cp, *last_ket;
 	size_t span;
 	int status = -1;
 

@@ -225,29 +225,22 @@ int split_ident_line(struct ident_split *split, const char *line, int len)
 		split->name_end = split->name_begin;
 	}
 
-	for (cp = split->mail_begin; cp < line + len; cp++)
-		if (*cp == '>') {
+	for (cp = split->mail_begin, last_ket = NULL; cp < line + len; cp++) {
+		if (*cp != '>')
+			continue;
+		if (!last_ket)
 			split->mail_end = cp;
-			break;
-		}
+		last_ket = cp;
+	}
 	if (!split->mail_end)
 		return status;
 
 	/*
-	 * Look from the end-of-line to find the trailing ">" of the mail
-	 * address, even though we should already know it as split->mail_end.
-	 * This can help in cases of broken idents with an extra ">" somewhere
-	 * in the email address.  Note that we are assuming the timestamp will
-	 * never have a ">" in it.
-	 *
-	 * Note that we will always find some ">" before going off the front of
-	 * the string, because will always hit the split->mail_end closing
-	 * bracket.
+	 * Typically, last_ket is the same as split_mail_end, but with
+	 * a broken identity line, there may be multiple closing ket '>';
+	 * read the timestamp after the last one.
 	 */
-	for (cp = line + len - 1; *cp != '>'; cp--)
-		;
-
-	for (cp = cp + 1; cp < line + len && isspace(*cp); cp++)
+	for (cp = last_ket + 1; cp < line + len && isspace(*cp); cp++)
 		;
 	if (line + len <= cp)
 		goto person_only;

On Tue, Oct 15, 2013 at 10:52:55AM -0700, Junio C Hamano wrote:

Jeff King [off-list ref] writes:

quoted

quoted

Yeah, unrolling the loop is probably better.  You may even be able
to do so in a single pass with an extra "last > seen" pointer
variable without too much additional code complexity, I would think.

I'm not sure what you mean here.

quoted

If you mean doing a single pass to find the final ">", that is easy,
because we know the length of the line already and can jump past and
start from the back.

I meant a single forward pass, like this.

Ah, I see. You are combining with the pass before, not the pass after.

I do not think this is any more (nor less) efficient than what I posted.
We still pass over the space after split->mail_end one additional time
searching for the closing bracket. Mine is _slightly_ more efficient in
that by going backwards we can stop when we see the first '>', avoiding
looking at the space between "mail_end" and "last_ket". But that space
is 0 in the normal case, and even if it is not, we are talking about
tens of bytes at most. So I doubt it would ever matter.

My version seems a little clearer to me, but that is probably because I
wrote it. If you strongly prefer the other, feel free to mark up my
patch.

-Peff

PS I learned a new term, "ket". I always called it "closing angle
   bracket".