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-rw-r--r--include/ftl/InitializerList.h41
-rw-r--r--include/ftl/SmallMap.h205
-rw-r--r--libs/ftl/Android.bp1
-rw-r--r--libs/ftl/SmallMap_test.cpp131
4 files changed, 378 insertions, 0 deletions
diff --git a/include/ftl/InitializerList.h b/include/ftl/InitializerList.h
index 204f79bb92..bb99280745 100644
--- a/include/ftl/InitializerList.h
+++ b/include/ftl/InitializerList.h
@@ -34,6 +34,14 @@ namespace android::ftl {
//
// ... = ftl::init::list<std::string>("abc")()(3u, '?');
//
+// The following syntax is a shorthand for key-value pairs, where the first argument is the
+// key, and the rest construct the value. The types of the key and value are deduced if the
+// first pair contains exactly two arguments:
+//
+// ... = ftl::init::map<int, std::string>(-1, "abc")(-2)(-3, 3u, '?');
+//
+// ... = ftl::init::map(0, 'a')(1, 'b')(2, 'c');
+//
// WARNING: The InitializerList returned by an ftl::init::list expression must be consumed
// immediately, since temporary arguments are destroyed after the full expression. Storing
// an InitializerList results in dangling references.
@@ -58,6 +66,29 @@ struct InitializerList<T, std::index_sequence<Sizes...>, Types...> {
std::tuple<Types...> tuple;
};
+template <typename K, typename V>
+struct KeyValue {};
+
+// Shorthand for key-value pairs that assigns the first argument to the key, and the rest to the
+// value. The specialization is on KeyValue rather than std::pair, so that ftl::init::list works
+// with the latter.
+template <typename K, typename V, size_t... Sizes, typename... Types>
+struct InitializerList<KeyValue<K, V>, std::index_sequence<Sizes...>, Types...> {
+ // Accumulate the three arguments to std::pair's piecewise constructor.
+ template <typename... Args>
+ [[nodiscard]] constexpr auto operator()(K&& k, Args&&... args) && -> InitializerList<
+ KeyValue<K, V>, std::index_sequence<Sizes..., 3>, Types..., std::piecewise_construct_t,
+ std::tuple<K&&>, std::tuple<Args&&...>> {
+ return {std::tuple_cat(std::move(tuple),
+ std::forward_as_tuple(std::piecewise_construct,
+ std::forward_as_tuple(std::forward<K>(k)),
+ std::forward_as_tuple(
+ std::forward<Args>(args)...)))};
+ }
+
+ std::tuple<Types...> tuple;
+};
+
namespace init {
template <typename T, typename... Args>
@@ -65,5 +96,15 @@ template <typename T, typename... Args>
return InitializerList<T>{}(std::forward<Args>(args)...);
}
+template <typename K, typename V, typename... Args>
+[[nodiscard]] constexpr auto map(Args&&... args) {
+ return list<KeyValue<K, V>>(std::forward<Args>(args)...);
+}
+
+template <typename K, typename V>
+[[nodiscard]] constexpr auto map(K&& k, V&& v) {
+ return list<KeyValue<K, V>>(std::forward<K>(k), std::forward<V>(v));
+}
+
} // namespace init
} // namespace android::ftl
diff --git a/include/ftl/SmallMap.h b/include/ftl/SmallMap.h
new file mode 100644
index 0000000000..87ae99cace
--- /dev/null
+++ b/include/ftl/SmallMap.h
@@ -0,0 +1,205 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <ftl/InitializerList.h>
+#include <ftl/SmallVector.h>
+
+#include <functional>
+#include <optional>
+#include <type_traits>
+#include <utility>
+
+namespace android::ftl {
+
+// Associative container with unique, unordered keys. Unlike std::unordered_map, key-value pairs are
+// stored in contiguous storage for cache efficiency. The map is allocated statically until its size
+// exceeds N, at which point mappings are relocated to dynamic memory.
+//
+// SmallMap<K, V, 0> unconditionally allocates on the heap.
+//
+// Example usage:
+//
+// ftl::SmallMap<int, std::string, 3> map;
+// assert(map.empty());
+// assert(!map.dynamic());
+//
+// map = ftl::init::map<int, std::string>(123, "abc")(-1)(42, 3u, '?');
+// assert(map.size() == 3u);
+// assert(!map.dynamic());
+//
+// assert(map.contains(123));
+// assert(map.find(42, [](const std::string& s) { return s.size(); }) == 3u);
+//
+// const auto opt = map.find(-1);
+// assert(opt);
+//
+// std::string& ref = *opt;
+// assert(ref.empty());
+// ref = "xyz";
+//
+// assert(map == SmallMap(ftl::init::map(-1, "xyz")(42, "???")(123, "abc")));
+//
+template <typename K, typename V, size_t N>
+class SmallMap final {
+ using Map = SmallVector<std::pair<const K, V>, N>;
+
+public:
+ using key_type = K;
+ using mapped_type = V;
+
+ using value_type = typename Map::value_type;
+ using size_type = typename Map::size_type;
+ using difference_type = typename Map::difference_type;
+
+ using reference = typename Map::reference;
+ using iterator = typename Map::iterator;
+
+ using const_reference = typename Map::const_reference;
+ using const_iterator = typename Map::const_iterator;
+
+ // Creates an empty map.
+ SmallMap() = default;
+
+ // Constructs at most N key-value pairs in place by forwarding per-pair constructor arguments.
+ // The template arguments K, V, and N are inferred using the deduction guide defined below.
+ // The syntax for listing pairs is as follows:
+ //
+ // ftl::SmallMap map = ftl::init::map<int, std::string>(123, "abc")(-1)(42, 3u, '?');
+ //
+ // static_assert(std::is_same_v<decltype(map), ftl::SmallMap<int, std::string, 3>>);
+ // assert(map.size() == 3u);
+ // assert(map.contains(-1) && map.find(-1)->get().empty());
+ // assert(map.contains(42) && map.find(42)->get() == "???");
+ // assert(map.contains(123) && map.find(123)->get() == "abc");
+ //
+ // The types of the key and value are deduced if the first pair contains exactly two arguments:
+ //
+ // ftl::SmallMap map = ftl::init::map(0, 'a')(1, 'b')(2, 'c');
+ // static_assert(std::is_same_v<decltype(map), ftl::SmallMap<int, char, 3>>);
+ //
+ template <typename U, size_t... Sizes, typename... Types>
+ SmallMap(InitializerList<U, std::index_sequence<Sizes...>, Types...>&& init)
+ : mMap(std::move(init)) {
+ // TODO: Enforce unique keys.
+ }
+
+ size_type max_size() const { return mMap.max_size(); }
+ size_type size() const { return mMap.size(); }
+ bool empty() const { return mMap.empty(); }
+
+ // Returns whether the map is backed by static or dynamic storage.
+ bool dynamic() const { return mMap.dynamic(); }
+
+ iterator begin() { return mMap.begin(); }
+ const_iterator begin() const { return cbegin(); }
+ const_iterator cbegin() const { return mMap.cbegin(); }
+
+ iterator end() { return mMap.end(); }
+ const_iterator end() const { return cend(); }
+ const_iterator cend() const { return mMap.cend(); }
+
+ // Returns whether a mapping exists for the given key.
+ bool contains(const key_type& key) const {
+ return find(key, [](const mapped_type&) {});
+ }
+
+ // Returns a reference to the value for the given key, or std::nullopt if the key was not found.
+ //
+ // ftl::SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
+ //
+ // const auto opt = map.find('c');
+ // assert(opt == 'C');
+ //
+ // char d = 'd';
+ // const auto ref = map.find('d').value_or(std::ref(d));
+ // ref.get() = 'D';
+ // assert(d == 'D');
+ //
+ auto find(const key_type& key) const
+ -> std::optional<std::reference_wrapper<const mapped_type>> {
+ return find(key, [](const mapped_type& v) { return std::cref(v); });
+ }
+
+ auto find(const key_type& key) -> std::optional<std::reference_wrapper<mapped_type>> {
+ return find(key, [](mapped_type& v) { return std::ref(v); });
+ }
+
+ // Returns the result R of a unary operation F on (a constant or mutable reference to) the value
+ // for the given key, or std::nullopt if the key was not found. If F has a return type of void,
+ // then the Boolean result indicates whether the key was found.
+ //
+ // ftl::SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
+ //
+ // assert(map.find('c', [](char c) { return std::toupper(c); }) == 'Z');
+ // assert(map.find('c', [](char& c) { c = std::toupper(c); }));
+ //
+ template <typename F, typename R = std::invoke_result_t<F, const mapped_type&>>
+ auto find(const key_type& key, F f) const
+ -> std::conditional_t<std::is_void_v<R>, bool, std::optional<R>> {
+ for (auto& [k, v] : *this) {
+ if (k == key) {
+ if constexpr (std::is_void_v<R>) {
+ f(v);
+ return true;
+ } else {
+ return f(v);
+ }
+ }
+ }
+
+ return {};
+ }
+
+ template <typename F>
+ auto find(const key_type& key, F f) {
+ return std::as_const(*this).find(key, [&f](const mapped_type& v) {
+ return f(const_cast<mapped_type&>(v));
+ });
+ }
+
+private:
+ Map mMap;
+};
+
+// Deduction guide for in-place constructor.
+template <typename K, typename V, size_t... Sizes, typename... Types>
+SmallMap(InitializerList<KeyValue<K, V>, std::index_sequence<Sizes...>, Types...>&&)
+ -> SmallMap<K, V, sizeof...(Sizes)>;
+
+// Returns whether the key-value pairs of two maps are equal.
+template <typename K, typename V, size_t N, typename Q, typename W, size_t M>
+bool operator==(const SmallMap<K, V, N>& lhs, const SmallMap<Q, W, M>& rhs) {
+ if (lhs.size() != rhs.size()) return false;
+
+ for (const auto& [k, v] : lhs) {
+ const auto& lv = v;
+ if (!rhs.find(k, [&lv](const auto& rv) { return lv == rv; }).value_or(false)) {
+ return false;
+ }
+ }
+
+ return true;
+}
+
+// TODO: Remove in C++20.
+template <typename K, typename V, size_t N, typename Q, typename W, size_t M>
+inline bool operator!=(const SmallMap<K, V, N>& lhs, const SmallMap<Q, W, M>& rhs) {
+ return !(lhs == rhs);
+}
+
+} // namespace android::ftl
diff --git a/libs/ftl/Android.bp b/libs/ftl/Android.bp
index fb3238215c..eb8e57a911 100644
--- a/libs/ftl/Android.bp
+++ b/libs/ftl/Android.bp
@@ -5,6 +5,7 @@ cc_test {
address: true,
},
srcs: [
+ "SmallMap_test.cpp",
"SmallVector_test.cpp",
"StaticVector_test.cpp",
],
diff --git a/libs/ftl/SmallMap_test.cpp b/libs/ftl/SmallMap_test.cpp
new file mode 100644
index 0000000000..fa00c06a70
--- /dev/null
+++ b/libs/ftl/SmallMap_test.cpp
@@ -0,0 +1,131 @@
+/*
+ * 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 <ftl/SmallMap.h>
+#include <gtest/gtest.h>
+
+#include <cctype>
+
+namespace android::test {
+
+using ftl::SmallMap;
+
+// Keep in sync with example usage in header file.
+TEST(SmallMap, Example) {
+ ftl::SmallMap<int, std::string, 3> map;
+ EXPECT_TRUE(map.empty());
+ EXPECT_FALSE(map.dynamic());
+
+ map = ftl::init::map<int, std::string>(123, "abc")(-1)(42, 3u, '?');
+ EXPECT_EQ(map.size(), 3u);
+ EXPECT_FALSE(map.dynamic());
+
+ EXPECT_TRUE(map.contains(123));
+
+ EXPECT_EQ(map.find(42, [](const std::string& s) { return s.size(); }), 3u);
+
+ const auto opt = map.find(-1);
+ ASSERT_TRUE(opt);
+
+ std::string& ref = *opt;
+ EXPECT_TRUE(ref.empty());
+ ref = "xyz";
+
+ EXPECT_EQ(map, SmallMap(ftl::init::map(-1, "xyz")(42, "???")(123, "abc")));
+}
+
+TEST(SmallMap, Construct) {
+ {
+ // Default constructor.
+ SmallMap<int, std::string, 2> map;
+
+ EXPECT_TRUE(map.empty());
+ EXPECT_FALSE(map.dynamic());
+ }
+ {
+ // In-place constructor with same types.
+ SmallMap<int, std::string, 5> map =
+ ftl::init::map<int, std::string>(123, "abc")(456, "def")(789, "ghi");
+
+ EXPECT_EQ(map.size(), 3u);
+ EXPECT_EQ(map.max_size(), 5u);
+ EXPECT_FALSE(map.dynamic());
+
+ EXPECT_EQ(map, SmallMap(ftl::init::map(123, "abc")(456, "def")(789, "ghi")));
+ }
+ {
+ // In-place constructor with different types.
+ SmallMap<int, std::string, 5> map =
+ ftl::init::map<int, std::string>(123, "abc")(-1)(42, 3u, '?');
+
+ EXPECT_EQ(map.size(), 3u);
+ EXPECT_EQ(map.max_size(), 5u);
+ EXPECT_FALSE(map.dynamic());
+
+ EXPECT_EQ(map, SmallMap(ftl::init::map(42, "???")(123, "abc")(-1, "\0\0\0")));
+ }
+ {
+ // In-place constructor with implicit size.
+ SmallMap map = ftl::init::map<int, std::string>(123, "abc")(-1)(42, 3u, '?');
+
+ static_assert(std::is_same_v<decltype(map), SmallMap<int, std::string, 3>>);
+ EXPECT_EQ(map.size(), 3u);
+ EXPECT_EQ(map.max_size(), 3u);
+ EXPECT_FALSE(map.dynamic());
+
+ EXPECT_EQ(map, SmallMap(ftl::init::map(-1, "\0\0\0")(42, "???")(123, "abc")));
+ }
+}
+
+TEST(SmallMap, Find) {
+ {
+ // Constant reference.
+ const ftl::SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
+
+ const auto opt = map.find('b');
+ EXPECT_EQ(opt, 'B');
+
+ const char d = 'D';
+ const auto ref = map.find('d').value_or(std::cref(d));
+ EXPECT_EQ(ref.get(), 'D');
+ }
+ {
+ // Mutable reference.
+ ftl::SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
+
+ const auto opt = map.find('c');
+ EXPECT_EQ(opt, 'C');
+
+ char d = 'd';
+ const auto ref = map.find('d').value_or(std::ref(d));
+ ref.get() = 'D';
+ EXPECT_EQ(d, 'D');
+ }
+ {
+ // Constant unary operation.
+ const ftl::SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
+ EXPECT_EQ(map.find('c', [](char c) { return std::toupper(c); }), 'Z');
+ }
+ {
+ // Mutable unary operation.
+ ftl::SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
+ EXPECT_TRUE(map.find('c', [](char& c) { c = std::toupper(c); }));
+
+ EXPECT_EQ(map, SmallMap(ftl::init::map('c', 'Z')('b', 'y')('a', 'x')));
+ }
+}
+
+} // namespace android::test
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