New enum ScalabilityMode.

Used instead of string representation in lower-levels of encoder configuration, to avoid string comparisons (with risk of misspelling) in lots of places.

Bug: webrtc:11607
Change-Id: I4d51c2265aac297c29976d2aa601d8ffb33b7326
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/259870
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36706}

modules/video_coding/svc/scalability_mode_util_unittest.cc

@@ -0,0 +1,47 @@
+/*
+ *  Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "modules/video_coding/svc/scalability_mode_util.h"
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/video_codecs/scalability_mode.h"
+#include "test/gtest.h"
+
+namespace webrtc {
+namespace {
+
+TEST(ScalabilityModeUtil, ConvertsL1T2) {
+  EXPECT_EQ(ScalabilityModeFromString("L1T2"), ScalabilityMode::kL1T2);
+  EXPECT_EQ(ScalabilityModeToString(ScalabilityMode::kL1T2), "L1T2");
+}
+
+TEST(ScalabilityModeUtil, RejectsUnknownString) {
+  EXPECT_EQ(ScalabilityModeFromString(""), absl::nullopt);
+  EXPECT_EQ(ScalabilityModeFromString("not-a-mode"), absl::nullopt);
+}
+
+// Check roundtrip conversion of all enum values.
+TEST(ScalabilityModeUtil, ConvertsAllToAndFromString) {
+  const ScalabilityMode kLastEnum = ScalabilityMode::kS3T3;
+  for (int numerical_enum = 0; numerical_enum <= static_cast<int>(kLastEnum);
+       numerical_enum++) {
+    ScalabilityMode scalability_mode =
+        static_cast<ScalabilityMode>(numerical_enum);
+    absl::string_view scalability_mode_string =
+        ScalabilityModeToString(scalability_mode);
+    EXPECT_FALSE(scalability_mode_string.empty());
+    EXPECT_EQ(ScalabilityModeFromString(scalability_mode_string),
+              scalability_mode);
+  }
+}
+
+}  // namespace
+}  // namespace webrtc