Squeeze a bit more performance out of the ends_with bif

src/strings.bif

@@ -1366,9 +1366,15 @@ function ends_with%(str: string, sub: string%) : bool
 	if ( sub->Len() > str->Len() )
 		return zeek::val_mgr->Bool(false);
 
-	string s = str->ToStdString();
-	string sub_s = sub->ToStdString();
-	return zeek::val_mgr->Bool(s.rfind(sub_s) == (s.size() - sub_s.size()));
+	auto sub_s = sub->ToStdStringView();
+	auto s = str->ToStdStringView();
+
+	// Create a string_view that only looks at the end of the string being searched
+	// with the same number of characters as the search string. This avoids possible
+	// pathological searches of big strings if the search string doesn't exist.
+	auto end_s = std::string_view{s.data() + s.size() - sub_s.size(), sub_s.size()};
+
+	return zeek::val_mgr->Bool(end_s == sub_s);
 	%}
 
 ## Returns whether a string consists entirely of digits.

testing/btest/Baseline/bifs.string_utils/out

@@ -41,6 +41,7 @@ starts_with bro: 1
 starts_with ids: 0
 ends_with ids: 1
 ends_with bro: 0
+ends_with containing null: 1
 
 Transformations
 ---------------

testing/btest/bifs/string_utils.zeek

@@ -1,4 +1,4 @@
-# @TEST-EXEC: zeek -b %INPUT >out
+# @TEST-EXEC: zeek -b %INPUT >out 2>&1
 # @TEST-EXEC: btest-diff out
 
 event zeek_init()
@@ -51,6 +51,7 @@ event zeek_init()
 	print fmt("starts_with ids: %d", starts_with(s3, "ghi"));
 	print fmt("ends_with ids: %d", ends_with(s3, "ghi"));
 	print fmt("ends_with bro: %d", ends_with(s3, "abc"));
+	print fmt("ends_with containing null: %d", ends_with("a\x00\x00b", "\x00b"));
 	print "";
 
 	print "Transformations";