FTL: Extend enum utilities imported from IF

Generalize compile-time and run-time lookup of enumerator names by
recognizing ftl_first and ftl_last to customize the range.

Add enum_range<E>() for iteration using range-based `for` loop.

Bug: 185536303
Test: Check assembly for small LUT in .rodata, and unrolled loops.
Test: ftl_test, libinput_tests, inputflinger_tests
Test: m libinputflinger
Change-Id: I0581611f4cfcf5837b0293867cb323742afb2c87
diff --git a/libs/ftl/Android.bp b/libs/ftl/Android.bp
index 3026921..5a80ad0 100644
--- a/libs/ftl/Android.bp
+++ b/libs/ftl/Android.bp
@@ -14,10 +14,10 @@
         address: true,
     },
     srcs: [
-        "cast_test.cpp",
         "Flags_test.cpp",
+        "cast_test.cpp",
+        "enum_test.cpp",
         "future_test.cpp",
-        "NamedEnum_test.cpp",
         "small_map_test.cpp",
         "small_vector_test.cpp",
         "static_vector_test.cpp",
diff --git a/libs/ftl/Flags_test.cpp b/libs/ftl/Flags_test.cpp
index 8c00b52..d241fa2 100644
--- a/libs/ftl/Flags_test.cpp
+++ b/libs/ftl/Flags_test.cpp
@@ -23,7 +23,7 @@
 
 using namespace android::flag_operators;
 
-enum class TestFlags { ONE = 0x1, TWO = 0x2, THREE = 0x4 };
+enum class TestFlags : uint8_t { ONE = 0x1, TWO = 0x2, THREE = 0x4 };
 
 TEST(Flags, Test) {
     Flags<TestFlags> flags = TestFlags::ONE;
@@ -165,7 +165,7 @@
 
 TEST(Flags, String_UnknownValues) {
     auto flags = Flags<TestFlags>(0b1011);
-    ASSERT_EQ(flags.string(), "ONE | TWO | 0x00000008");
+    ASSERT_EQ(flags.string(), "ONE | TWO | 0b1000");
 }
 
 TEST(FlagsIterator, IteratesOverAllFlags) {
@@ -210,18 +210,4 @@
     ASSERT_EQ(++iter, flags.end());
 }
 
-TEST(FlagNames, RuntimeFlagName) {
-    TestFlags f = TestFlags::ONE;
-    ASSERT_EQ(flag_name(f), "ONE");
-}
-
-TEST(FlagNames, RuntimeUnknownFlagName) {
-    TestFlags f = static_cast<TestFlags>(0x8);
-    ASSERT_EQ(flag_name(f), std::nullopt);
-}
-
-TEST(FlagNames, CompileTimeFlagName) {
-    static_assert(flag_name<TestFlags::TWO>() == "TWO");
-}
-
-} // namespace android::test
\ No newline at end of file
+} // namespace android::test
diff --git a/libs/ftl/NamedEnum_test.cpp b/libs/ftl/NamedEnum_test.cpp
deleted file mode 100644
index dff2b8a..0000000
--- a/libs/ftl/NamedEnum_test.cpp
+++ /dev/null
@@ -1,101 +0,0 @@
-/*
- * Copyright 2020 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <gtest/gtest.h>
-#include <ftl/NamedEnum.h>
-
-namespace android {
-
-// Test enum class maximum enum value smaller than default maximum of 8.
-enum class TestEnums { ZERO = 0x0, ONE = 0x1, TWO = 0x2, THREE = 0x3, SEVEN = 0x7 };
-// Big enum contains enum values greater than default maximum of 8.
-enum class TestBigEnums { ZERO = 0x0, FIFTEEN = 0xF };
-
-// Declared to specialize the maximum enum since the enum size exceeds 8 by default.
-template <>
-constexpr size_t NamedEnum::max<TestBigEnums> = 16;
-
-namespace test {
-using android::TestBigEnums;
-using android::TestEnums;
-
-TEST(NamedEnum, RuntimeNamedEnum) {
-    TestEnums e = TestEnums::ZERO;
-    ASSERT_EQ(NamedEnum::enum_name(e), "ZERO");
-
-    e = TestEnums::ONE;
-    ASSERT_EQ(NamedEnum::enum_name(e), "ONE");
-
-    e = TestEnums::THREE;
-    ASSERT_EQ(NamedEnum::enum_name(e), "THREE");
-
-    e = TestEnums::SEVEN;
-    ASSERT_EQ(NamedEnum::enum_name(e), "SEVEN");
-}
-
-// Test big enum
-TEST(NamedEnum, RuntimeBigNamedEnum) {
-    TestBigEnums e = TestBigEnums::ZERO;
-    ASSERT_EQ(NamedEnum::enum_name(e), "ZERO");
-
-    e = TestBigEnums::FIFTEEN;
-    ASSERT_EQ(NamedEnum::enum_name(e), "FIFTEEN");
-}
-
-TEST(NamedEnum, RuntimeNamedEnumAsString) {
-    TestEnums e = TestEnums::ZERO;
-    ASSERT_EQ(NamedEnum::string(e), "ZERO");
-
-    e = TestEnums::ONE;
-    ASSERT_EQ(NamedEnum::string(e), "ONE");
-
-    e = TestEnums::THREE;
-    ASSERT_EQ(NamedEnum::string(e), "THREE");
-
-    e = TestEnums::SEVEN;
-    ASSERT_EQ(NamedEnum::string(e), "SEVEN");
-}
-
-TEST(NamedEnum, RuntimeBigNamedEnumAsString) {
-    TestBigEnums e = TestBigEnums::ZERO;
-    ASSERT_EQ(NamedEnum::string(e), "ZERO");
-
-    e = TestBigEnums::FIFTEEN;
-    ASSERT_EQ(NamedEnum::string(e), "FIFTEEN");
-}
-
-TEST(NamedEnum, RuntimeUnknownNamedEnum) {
-    TestEnums e = static_cast<TestEnums>(0x5);
-    ASSERT_EQ(NamedEnum::enum_name(e), std::nullopt);
-    e = static_cast<TestEnums>(0x9);
-    ASSERT_EQ(NamedEnum::enum_name(e), std::nullopt);
-}
-
-TEST(NamedEnum, RuntimeUnknownNamedEnumAsString) {
-    TestEnums e = static_cast<TestEnums>(0x5);
-    ASSERT_EQ(NamedEnum::string(e), "05");
-    e = static_cast<TestEnums>(0x9);
-    ASSERT_EQ(NamedEnum::string(e, "0x%08x"), "0x00000009");
-}
-
-TEST(NamedEnum, CompileTimeFlagName) {
-    static_assert(NamedEnum::enum_name<TestEnums::TWO>() == "TWO");
-    static_assert(NamedEnum::enum_name<TestEnums::THREE>() == "THREE");
-}
-
-} // namespace test
-
-} // namespace android
diff --git a/libs/ftl/enum_test.cpp b/libs/ftl/enum_test.cpp
new file mode 100644
index 0000000..1fd43ab
--- /dev/null
+++ b/libs/ftl/enum_test.cpp
@@ -0,0 +1,164 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <ftl/enum.h>
+#include <gtest/gtest.h>
+
+namespace android::test {
+
+// Keep in sync with example usage in header file.
+namespace {
+
+enum class E { A, B, C, F = 5, ftl_last = F };
+
+static_assert(ftl::enum_begin_v<E> == E::A);
+static_assert(ftl::enum_last_v<E> == E::F);
+static_assert(ftl::enum_size_v<E> == 6);
+
+static_assert(ftl::enum_name<E::B>() == "B");
+static_assert(ftl::enum_name<E::ftl_last>() == "F");
+static_assert(ftl::enum_name(E::C).value_or("?") == "C");
+static_assert(ftl::enum_name(E{3}).value_or("?") == "?");
+
+enum class F : std::uint16_t { X = 0b1, Y = 0b10, Z = 0b100 };
+
+static_assert(ftl::enum_begin_v<F> == F{0});
+static_assert(ftl::enum_last_v<F> == F{15});
+static_assert(ftl::enum_size_v<F> == 16);
+
+static_assert(ftl::flag_name(F::Z).value_or("?") == "Z");
+static_assert(ftl::flag_name(F{0b111}).value_or("?") == "?");
+
+// If a scoped enum is unsigned, its implicit range corresponds to its bit indices.
+enum class Flags : std::uint8_t {
+  kNone = 0,
+  kFlag1 = 0b0000'0010,
+  kFlag4 = 0b0001'0000,
+  kFlag7 = 0b1000'0000,
+  kMask = kFlag1 | kFlag4 | kFlag7,
+  kAll = 0b1111'1111
+};
+
+static_assert(ftl::enum_begin_v<Flags> == Flags{0});
+static_assert(ftl::enum_last_v<Flags> == Flags{7});
+static_assert(ftl::enum_size_v<Flags> == 8);
+
+static_assert(ftl::enum_name<Flags::kNone>() == "kNone");
+static_assert(ftl::enum_name<Flags::kFlag4>() == "kFlag4");
+static_assert(ftl::enum_name<Flags::kFlag7>() == "kFlag7");
+
+// Though not flags, the enumerators are within the implicit range of bit indices.
+enum class Planet : std::uint8_t {
+  kMercury,
+  kVenus,
+  kEarth,
+  kMars,
+  kJupiter,
+  kSaturn,
+  kUranus,
+  kNeptune
+};
+
+constexpr Planet kPluto{ftl::enum_cast(Planet::kNeptune) + 1};  // Honorable mention.
+
+static_assert(ftl::enum_begin_v<Planet> == Planet::kMercury);
+static_assert(ftl::enum_last_v<Planet> == Planet::kNeptune);
+static_assert(ftl::enum_size_v<Planet> == 8);
+
+static_assert(ftl::enum_name<Planet::kMercury>() == "kMercury");
+static_assert(ftl::enum_name<Planet::kSaturn>() == "kSaturn");
+
+// Unscoped enum must define explicit range, even if the underlying type is fixed.
+enum Temperature : int {
+  kRoom = 20,
+  kFridge = 4,
+  kFreezer = -18,
+
+  ftl_first = kFreezer,
+  ftl_last = kRoom
+};
+
+static_assert(ftl::enum_begin_v<Temperature> == kFreezer);
+static_assert(ftl::enum_last_v<Temperature> == kRoom);
+static_assert(ftl::enum_size_v<Temperature> == 39);
+
+static_assert(ftl::enum_name<kFreezer>() == "kFreezer");
+static_assert(ftl::enum_name<kFridge>() == "kFridge");
+static_assert(ftl::enum_name<kRoom>() == "kRoom");
+
+}  // namespace
+
+TEST(Enum, Range) {
+  std::string string;
+  for (E v : ftl::enum_range<E>()) {
+    string += ftl::enum_name(v).value_or("?");
+  }
+  EXPECT_EQ(string, "ABC??F");
+}
+
+TEST(Enum, Name) {
+  {
+    EXPECT_EQ(ftl::flag_name(Flags::kFlag1), "kFlag1");
+    EXPECT_EQ(ftl::flag_name(Flags::kFlag7), "kFlag7");
+
+    EXPECT_EQ(ftl::flag_name(Flags::kNone), std::nullopt);
+    EXPECT_EQ(ftl::flag_name(Flags::kMask), std::nullopt);
+    EXPECT_EQ(ftl::flag_name(Flags::kAll), std::nullopt);
+  }
+  {
+    EXPECT_EQ(ftl::enum_name(Planet::kEarth), "kEarth");
+    EXPECT_EQ(ftl::enum_name(Planet::kNeptune), "kNeptune");
+
+    EXPECT_EQ(ftl::enum_name(kPluto), std::nullopt);
+  }
+  {
+    EXPECT_EQ(ftl::enum_name(kRoom), "kRoom");
+    EXPECT_EQ(ftl::enum_name(kFridge), "kFridge");
+    EXPECT_EQ(ftl::enum_name(kFreezer), "kFreezer");
+
+    EXPECT_EQ(ftl::enum_name(static_cast<Temperature>(-30)), std::nullopt);
+    EXPECT_EQ(ftl::enum_name(static_cast<Temperature>(0)), std::nullopt);
+    EXPECT_EQ(ftl::enum_name(static_cast<Temperature>(100)), std::nullopt);
+  }
+}
+
+TEST(Enum, String) {
+  {
+    EXPECT_EQ(ftl::flag_string(Flags::kFlag1), "kFlag1");
+    EXPECT_EQ(ftl::flag_string(Flags::kFlag7), "kFlag7");
+
+    EXPECT_EQ(ftl::flag_string(Flags::kNone), "0b0");
+    EXPECT_EQ(ftl::flag_string(Flags::kMask), "0b10010010");
+    EXPECT_EQ(ftl::flag_string(Flags::kAll), "0b11111111");
+  }
+  {
+    EXPECT_EQ(ftl::enum_string(Planet::kEarth), "kEarth");
+    EXPECT_EQ(ftl::enum_string(Planet::kNeptune), "kNeptune");
+
+    EXPECT_EQ(ftl::enum_string(kPluto), "8");
+  }
+  {
+    EXPECT_EQ(ftl::enum_string(kRoom), "kRoom");
+    EXPECT_EQ(ftl::enum_string(kFridge), "kFridge");
+    EXPECT_EQ(ftl::enum_string(kFreezer), "kFreezer");
+
+    EXPECT_EQ(ftl::enum_string(static_cast<Temperature>(-30)), "-30");
+    EXPECT_EQ(ftl::enum_string(static_cast<Temperature>(0)), "0");
+    EXPECT_EQ(ftl::enum_string(static_cast<Temperature>(100)), "100");
+  }
+}
+
+}  // namespace android::test