objc4-781.tar.gz

[apple/objc4.git] / runtime / PointerUnion.h

diff --git a/runtime/PointerUnion.h b/runtime/PointerUnion.h
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+/*
+ * Copyright (c) 2019 Apple Inc.  All Rights Reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#ifndef POINTERUNION_H
+#define POINTERUNION_H
+
+#include <cstdint>
+#include <atomic>
+
+namespace objc {
+
+template <typename T> struct PointerUnionTypeSelectorReturn {
+  using Return = T;
+};
+
+/// Get a type based on whether two types are the same or not.
+///
+/// For:
+///
+/// \code
+///   using Ret = typename PointerUnionTypeSelector<T1, T2, EQ, NE>::Return;
+/// \endcode
+///
+/// Ret will be EQ type if T1 is same as T2 or NE type otherwise.
+template <typename T1, typename T2, typename RET_EQ, typename RET_NE>
+struct PointerUnionTypeSelector {
+  using Return = typename PointerUnionTypeSelectorReturn<RET_NE>::Return;
+};
+
+template <typename T, typename RET_EQ, typename RET_NE>
+struct PointerUnionTypeSelector<T, T, RET_EQ, RET_NE> {
+  using Return = typename PointerUnionTypeSelectorReturn<RET_EQ>::Return;
+};
+
+template <typename T1, typename T2, typename RET_EQ, typename RET_NE>
+struct PointerUnionTypeSelectorReturn<
+    PointerUnionTypeSelector<T1, T2, RET_EQ, RET_NE>> {
+  using Return =
+      typename PointerUnionTypeSelector<T1, T2, RET_EQ, RET_NE>::Return;
+};
+
+template <class PT1, class PT2>
+class PointerUnion {
+    uintptr_t _value;
+
+    static_assert(alignof(PT1) >= 2, "alignment requirement");
+    static_assert(alignof(PT2) >= 2, "alignment requirement");
+
+    struct IsPT1 {
+      static const uintptr_t Num = 0;
+    };
+    struct IsPT2 {
+      static const uintptr_t Num = 1;
+    };
+    template <typename T> struct UNION_DOESNT_CONTAIN_TYPE {};
+
+    uintptr_t getPointer() const {
+        return _value & ~1;
+    }
+    uintptr_t getTag() const {
+        return _value & 1;
+    }
+
+public:
+    explicit PointerUnion(const std::atomic<uintptr_t> &raw)
+    : _value(raw.load(std::memory_order_relaxed))
+    { }
+    PointerUnion(PT1 t) : _value((uintptr_t)t) { }
+    PointerUnion(PT2 t) : _value((uintptr_t)t | 1) { }
+
+    void storeAt(std::atomic<uintptr_t> &raw, std::memory_order order) const {
+        raw.store(_value, order);
+    }
+
+    template <typename T>
+    bool is() const {
+        using Ty = typename PointerUnionTypeSelector<PT1, T, IsPT1,
+            PointerUnionTypeSelector<PT2, T, IsPT2,
+            UNION_DOESNT_CONTAIN_TYPE<T>>>::Return;
+        return getTag() == Ty::Num;
+    }
+
+    template <typename T> T get() const {
+      ASSERT(is<T>() && "Invalid accessor called");
+      return reinterpret_cast<T>(getPointer());
+    }
+
+    template <typename T> T dyn_cast() const {
+      if (is<T>())
+        return get<T>();
+      return T();
+    }
+};
+
+template <class PT1, class PT2, class PT3, class PT4 = void>
+class PointerUnion4 {
+    uintptr_t _value;
+
+    static_assert(alignof(PT1) >= 4, "alignment requirement");
+    static_assert(alignof(PT2) >= 4, "alignment requirement");
+    static_assert(alignof(PT3) >= 4, "alignment requirement");
+    static_assert(alignof(PT4) >= 4, "alignment requirement");
+
+    struct IsPT1 {
+      static const uintptr_t Num = 0;
+    };
+    struct IsPT2 {
+      static const uintptr_t Num = 1;
+    };
+    struct IsPT3 {
+      static const uintptr_t Num = 2;
+    };
+    struct IsPT4 {
+      static const uintptr_t Num = 3;
+    };
+    template <typename T> struct UNION_DOESNT_CONTAIN_TYPE {};
+
+    uintptr_t getPointer() const {
+        return _value & ~3;
+    }
+    uintptr_t getTag() const {
+        return _value & 3;
+    }
+
+public:
+    explicit PointerUnion4(const std::atomic<uintptr_t> &raw)
+    : _value(raw.load(std::memory_order_relaxed))
+    { }
+    PointerUnion4(PT1 t) : _value((uintptr_t)t) { }
+    PointerUnion4(PT2 t) : _value((uintptr_t)t | 1) { }
+    PointerUnion4(PT3 t) : _value((uintptr_t)t | 2) { }
+    PointerUnion4(PT4 t) : _value((uintptr_t)t | 3) { }
+
+    void storeAt(std::atomic<uintptr_t> &raw, std::memory_order order) const {
+        raw.store(_value, order);
+    }
+
+    template <typename T>
+    bool is() const {
+        using Ty = typename PointerUnionTypeSelector<PT1, T, IsPT1,
+            PointerUnionTypeSelector<PT2, T, IsPT2,
+            PointerUnionTypeSelector<PT3, T, IsPT3,
+            PointerUnionTypeSelector<PT4, T, IsPT4,
+               UNION_DOESNT_CONTAIN_TYPE<T>>>>>::Return;
+        return getTag() == Ty::Num;
+    }
+
+    template <typename T> T get() const {
+      ASSERT(is<T>() && "Invalid accessor called");
+      return reinterpret_cast<T>(getPointer());
+    }
+
+    template <typename T> T dyn_cast() const {
+      if (is<T>())
+        return get<T>();
+      return T();
+    }
+};
+
+} // namespace objc
+
+#endif /* DENSEMAPEXTRAS_H */