atomic_ref::compare_exchange_strong

Summary: [Folly] `atomic_ref::compare_exchange_strong` and `atomic_ref::compare_exchange_weak`.

Differential Revision: D21923944

fbshipit-source-id: 55620473ea253782cc1dbb95baef38c96a9fbc70

folly/synchronization/AtomicRef.h

@@ -43,6 +43,37 @@ struct atomic_ref_base {
     return atomic().load(order);
   }
 
+  bool compare_exchange_weak(
+      T& expected,
+      T desired,
+      std::memory_order success,
+      std::memory_order failure) const noexcept {
+    return atomic().compare_exchange_weak(expected, desired, success, failure);
+  }
+
+  bool compare_exchange_weak(
+      T& expected,
+      T desired,
+      std::memory_order order = std::memory_order_seq_cst) const noexcept {
+    return atomic().compare_exchange_weak(expected, desired, order);
+  }
+
+  bool compare_exchange_strong(
+      T& expected,
+      T desired,
+      std::memory_order success,
+      std::memory_order failure) const noexcept {
+    return atomic().compare_exchange_strong(
+        expected, desired, success, failure);
+  }
+
+  bool compare_exchange_strong(
+      T& expected,
+      T desired,
+      std::memory_order order = std::memory_order_seq_cst) const noexcept {
+    return atomic().compare_exchange_strong(expected, desired, order);
+  }
+
   std::atomic<T>& atomic() const noexcept {
     return reinterpret_cast<std::atomic<T>&>(ref_); // ub dragons be here
   }

folly/synchronization/test/AtomicRefTest.cpp

@@ -45,3 +45,89 @@ TEST_F(AtomicRefTest, integer) {
     EXPECT_EQ(13, value);
   }
 }
+
+TEST_F(AtomicRefTest, integer_compare_exchange_weak) {
+  auto const relaxed = std::memory_order_relaxed;
+  {
+    long value = 17;
+    auto ref = folly::make_atomic_ref(value);
+    auto expected = value;
+    auto done = ref.compare_exchange_weak(expected, 19);
+    EXPECT_TRUE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(17, expected);
+    done = ref.compare_exchange_weak(expected, 21);
+    EXPECT_FALSE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(19, expected);
+  }
+  {
+    long value = 17;
+    auto ref = folly::make_atomic_ref(value);
+    auto expected = value;
+    auto done = ref.compare_exchange_weak(expected, 19, relaxed);
+    EXPECT_TRUE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(17, expected);
+    done = ref.compare_exchange_weak(expected, 21, relaxed);
+    EXPECT_FALSE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(19, expected);
+  }
+  {
+    long value = 17;
+    auto ref = folly::make_atomic_ref(value);
+    auto expected = value;
+    auto done = ref.compare_exchange_weak(expected, 19, relaxed, relaxed);
+    EXPECT_TRUE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(17, expected);
+    done = ref.compare_exchange_weak(expected, 21, relaxed, relaxed);
+    EXPECT_FALSE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(19, expected);
+  }
+}
+
+TEST_F(AtomicRefTest, integer_compare_exchange_strong) {
+  auto const relaxed = std::memory_order_relaxed;
+  {
+    long value = 17;
+    auto ref = folly::make_atomic_ref(value);
+    auto expected = value;
+    auto done = ref.compare_exchange_strong(expected, 19);
+    EXPECT_TRUE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(17, expected);
+    done = ref.compare_exchange_strong(expected, 21);
+    EXPECT_FALSE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(19, expected);
+  }
+  {
+    long value = 17;
+    auto ref = folly::make_atomic_ref(value);
+    auto expected = value;
+    auto done = ref.compare_exchange_strong(expected, 19, relaxed);
+    EXPECT_TRUE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(17, expected);
+    done = ref.compare_exchange_strong(expected, 21, relaxed);
+    EXPECT_FALSE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(19, expected);
+  }
+  {
+    long value = 17;
+    auto ref = folly::make_atomic_ref(value);
+    auto expected = value;
+    auto done = ref.compare_exchange_strong(expected, 19, relaxed, relaxed);
+    EXPECT_TRUE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(17, expected);
+    done = ref.compare_exchange_strong(expected, 21, relaxed, relaxed);
+    EXPECT_FALSE(done);
+    EXPECT_EQ(19, value);
+    EXPECT_EQ(19, expected);
+  }
+}