Backport C++17 container access functions: size, empty, data

Summary: [Folly] Backport C++17 container access functions: `size`, `empty`, `data`.

Reviewed By: Orvid

Differential Revision: D6301986

fbshipit-source-id: 65c31df68b7743d5ed4a2cf2419586b862683c48

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 518e3df6200dc5e9279b1cd468252b4f3d7b8e4b..699489bf19438376d2803706ce0e315ac719554e 100755 (executable)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -331,6 +331,7 @@ if (BUILD_TESTS)
       TEST compression_test SOURCES CompressionTest.cpp
 
     DIRECTORY container/test/
+      TEST access_test SOURCES AccessTest.cpp
       TEST array_test SOURCES ArrayTest.cpp
       TEST enumerate_test SOURCES EnumerateTest.cpp
       TEST evicting_cache_map_test SOURCES EvictingCacheMapTest.cpp

diff --git a/folly/Makefile.am b/folly/Makefile.am
index 83f79c20e3f736d3689bc9caa4dd674b59a1675d..0639ff90b7f388f03701ba2660a5db61e3dd2fd9 100644 (file)
--- a/folly/Makefile.am
+++ b/folly/Makefile.am
@@ -56,6 +56,7 @@ nobase_follyinclude_HEADERS = \
        concurrency/ConcurrentHashMap.h \
        concurrency/CoreCachedSharedPtr.h \
        concurrency/detail/ConcurrentHashMap-detail.h \
+       container/Access.h \
        container/Array.h \
        container/Iterator.h \
        container/Enumerate.h \

diff --git a/folly/container/Access.h b/folly/container/Access.h
new file mode 100644 (file)
index 0000000..8116c19
--- /dev/null
+++ b/folly/container/Access.h
@@ -0,0 +1,89 @@
+/*
+ * Copyright 2017 Facebook, Inc.
+ *
+ * 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 <initializer_list>
+#include <iterator>
+
+/**
+ *  include or backport:
+ *  * std::size
+ *  * std::empty
+ *  * std::data
+ */
+
+#if __cpp_lib_nonmember_container_access >= 201411 || _MSC_VER
+
+namespace folly {
+
+/* using override */ using std::size;
+/* using override */ using std::empty;
+/* using override */ using std::data;
+
+}
+
+#else
+
+namespace folly {
+
+//  mimic: std::size, C++17
+template <typename C>
+constexpr auto size(C const& c) -> decltype(c.size()) {
+  return c.size();
+}
+template <typename T, std::size_t N>
+constexpr std::size_t size(T const (&)[N]) noexcept {
+  return N;
+}
+
+//  mimic: std::empty, C++17
+template <typename C>
+constexpr auto empty(C const& c) -> decltype(c.empty()) {
+  return c.empty();
+}
+template <typename T, std::size_t N>
+constexpr bool empty(T const (&)[N]) noexcept {
+  //  while zero-length arrays are not allowed in the language, some compilers
+  //  may permit them in some cases
+  return N == 0;
+}
+template <typename E>
+constexpr bool empty(std::initializer_list<E> il) noexcept {
+  return il.size() == 0;
+}
+
+//  mimic: std::data, C++17
+template <typename C>
+constexpr auto data(C& c) -> decltype(c.data()) {
+  return c.data();
+}
+template <typename C>
+constexpr auto data(C const& c) -> decltype(c.data()) {
+  return c.data();
+}
+template <typename T, std::size_t N>
+constexpr T* data(T (&a)[N]) noexcept {
+  return a;
+}
+template <typename E>
+constexpr E const* data(std::initializer_list<E> il) noexcept {
+  return il.begin();
+}
+
+}
+
+#endif

diff --git a/folly/container/test/AccessTest.cpp b/folly/container/test/AccessTest.cpp
new file mode 100644 (file)
index 0000000..56ae745
--- /dev/null
+++ b/folly/container/test/AccessTest.cpp
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2017 Facebook, Inc.
+ *
+ * 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 <folly/container/Access.h>
+
+#include <array>
+#include <initializer_list>
+#include <vector>
+
+#include <folly/portability/GTest.h>
+
+class AccessTest : public testing::Test {};
+
+TEST_F(AccessTest, size_vector) {
+  EXPECT_EQ(3, folly::size(std::vector<int>{1, 2, 3}));
+}
+
+TEST_F(AccessTest, size_array) {
+  constexpr auto const a = std::array<int, 3>{{1, 2, 3}};
+  constexpr auto const size = folly::size(a);
+  EXPECT_EQ(3, size);
+}
+
+TEST_F(AccessTest, size_carray) {
+  constexpr int const a[3] = {1, 2, 3};
+  constexpr auto const size = folly::size(a);
+  EXPECT_EQ(3, size);
+}
+
+TEST_F(AccessTest, size_initializer_list) {
+  EXPECT_EQ(3, folly::size({1, 2, 3}));
+  EXPECT_EQ(3, folly::size(std::initializer_list<int>{1, 2, 3}));
+}
+
+TEST_F(AccessTest, empty_vector) {
+  EXPECT_FALSE(folly::empty(std::vector<int>{1, 2, 3}));
+  EXPECT_TRUE(folly::empty(std::vector<int>{}));
+}
+
+TEST_F(AccessTest, empty_array) {
+  {
+    constexpr auto const a = std::array<int, 3>{{1, 2, 3}};
+    constexpr auto const empty = folly::empty(a);
+    EXPECT_FALSE(empty);
+  }
+  {
+    constexpr auto const a = std::array<int, 0>{{}};
+    constexpr auto const empty = folly::empty(a);
+    EXPECT_TRUE(empty);
+  }
+}
+
+TEST_F(AccessTest, empty_carray) {
+  constexpr int const a[3] = {1, 2, 3};
+  constexpr auto const empty = folly::empty(a);
+  EXPECT_FALSE(empty);
+  //  zero-length arrays are not allowed in the language
+}
+
+TEST_F(AccessTest, empty_initializer_list) {
+  EXPECT_FALSE(folly::empty({1, 2, 3}));
+  EXPECT_FALSE(folly::empty(std::initializer_list<int>{1, 2, 3}));
+  EXPECT_TRUE(folly::empty(std::initializer_list<int>{}));
+}
+
+TEST_F(AccessTest, data_vector) {
+  EXPECT_EQ(1, *folly::data(std::vector<int>{1, 2, 3}));
+  auto v = std::vector<int>{1, 2, 3};
+  *folly::data(v) = 4;
+  EXPECT_EQ(4, v[0]);
+}
+
+TEST_F(AccessTest, data_array) {
+  constexpr auto const a = std::array<int, 3>{{1, 2, 3}};
+  auto const data = folly::data(a); // not constexpr until C++17
+  EXPECT_EQ(1, *data);
+}
+
+TEST_F(AccessTest, data_carray) {
+  constexpr int const a[3] = {1, 2, 3};
+  auto const data = folly::data(a); // not constexpr until C++17
+  EXPECT_EQ(1, *data);
+}
+
+TEST_F(AccessTest, data_initializer_list) {
+  EXPECT_EQ(1, *folly::data({1, 2, 3}));
+  EXPECT_EQ(1, *folly::data(std::initializer_list<int>{1, 2, 3}));
+}

diff --git a/folly/test/Makefile.am b/folly/test/Makefile.am
index 697fd7420c68c2c209443d8661be7b7c922cb0a3..a19368d81de90a1ab7fa55de96d9993044d51667 100644 (file)
--- a/folly/test/Makefile.am
+++ b/folly/test/Makefile.am
@@ -81,6 +81,9 @@ endif
 sorted_vector_types_test_SOURCES = sorted_vector_test.cpp
 sorted_vector_types_test_LDADD = libfollytestmain.la
 
+container_access_test_SOURCES = ../container/test/AccessTets.cpp
+container_access_test_LDADD = libfollytestmain.la
+TESTS += container_access_test
 
 foreach_test_SOURCES = ../container/test/ForeachTest.cpp
 foreach_test_LDADD = libfollytestmain.la