Low-hanging optimization

If the user didn't add more characters to the query all choices have to
be reconsidered as potential matches. In the opposite scenario, there's
no point in reconsidered all choices again since the ones that didn't
match the previous query will clearly not match the current one due to
the fact that previous query is a left-most substring of the current
one.

pick.c

@@ -70,7 +70,7 @@ struct choice {
 static int			 choicecmp(const void *, const void *);
 static void			 delete_between(char *, size_t, size_t, size_t);
 static char			*eager_strpbrk(const char *, const char *);
-static void			 filter_choices(void);
+static void			 filter_choices(size_t);
 static char			*get_choices(void);
 static enum key			 get_key(const char **);
 static void			 handle_sigwinch(int);
@@ -302,14 +302,28 @@ selected_choice(void)
 	size_t		 selection = 0;
 	size_t		 yscroll = 0;
 	int		 dofilter = 1;
+	int		 query_grew = 0;
 
 	cursor_position = query_length;
 
 	for (;;) {
+		/*
+		 * If the user didn't add more characters to the query all
+		 * choices have to be reconsidered as potential matches.
+		 * In the opposite scenario, there's no point in reconsidered
+		 * all choices again since the ones that didn't match the
+		 * previous query will clearly not match the current one due to
+		 * the fact that previous query is a left-most substring of the
+		 * current one.
+		 */
+		if (!query_grew)
+			choices_count = choices.length;
+		query_grew = 0;
 		if (dofilter) {
 			filter_choices(choices_count);
 			dofilter = selection = yscroll = 0;
 		}
+
 		tty_putp(cursor_invisible, 0);
 		tty_putp(carriage_return, 1);	/* move cursor to first column */
 		if (cursor_position >= tty_columns)
@@ -517,7 +531,7 @@ selected_choice(void)
 			cursor_position += length;
 			query_length += length;
 			query[query_length] = '\0';
-			dofilter = 1;
+			dofilter = query_grew = 1;
 			break;
 		case UNKNOWN:
 			break;
@@ -528,16 +542,17 @@ selected_choice(void)
 /*
  * Filter choices using the current query while there is no new user input
  * available.
+ * The first nchoices number of choices will be filtered.
  */
 void
-filter_choices(void)
+filter_choices(size_t nchoices)
 {
 	struct choice	*c;
 	struct pollfd	 pfd;
 	size_t		 i, match_length;
 	int		 nready;
 
-	for (i = 0; i < choices.length; i++) {
+	for (i = 0; i < nchoices; i++) {
 		c = &choices.v[i];
 		if (min_match(c->string, 0,
 			    &c->match_start, &c->match_end) == INT_MAX) {
@@ -566,7 +581,7 @@ filter_choices(void)
 		}
 	}
 
-	qsort(choices.v, choices.length, sizeof(struct choice), choicecmp);
+	qsort(choices.v, nchoices, sizeof(struct choice), choicecmp);
 }
 
 int