1 files changed, 13 insertions, 0 deletions
diff --git a/shell/hush.c b/shell/hush.c
index 6b91056..179155f 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -6466,6 +6466,19 @@ static arith_t expand_and_evaluate_arith(const char *arg, const char **errmsg_p)
 /* ${var/[/]pattern[/repl]} helpers */
 static char *strstr_pattern(char *val, const char *pattern, int *size)
 {
+	if (!strpbrk(pattern, "*?[\\")) {
+		/* Optimization for trivial patterns.
+		 * Testcase for very slow replace (performs about 22k replaces):
+		 * x=::::::::::::::::::::::
+		 * x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;echo ${#x}
+		 * echo "${x//:/|}"
+		 */
+		char *found = strstr(val, pattern);
+		if (found)
+			*size = strlen(pattern);
+		return found;
+	}
+
 	while (1) {
 		char *end = scan_and_match(val, pattern, SCAN_MOVE_FROM_RIGHT + SCAN_MATCH_LEFT_HALF);
 		debug_printf_varexp("val:'%s' pattern:'%s' end:'%s'\n", val, pattern, end);