comparison osx/include/kj/memory.h @ 134:41e769c91eca

Add Capnp and KJ builds for OSX

+// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
+// Licensed under the MIT License:
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#ifndef KJ_MEMORY_H_
+#define KJ_MEMORY_H_
+
+#if defined(__GNUC__) && !KJ_HEADER_WARNINGS
+#pragma GCC system_header
+#endif
+
+#include "common.h"
+
+namespace kj {
+
+// =======================================================================================
+// Disposer -- Implementation details.
+
+class Disposer {
+  // Abstract interface for a thing that "disposes" of objects, where "disposing" usually means
+  // calling the destructor followed by freeing the underlying memory.  `Own<T>` encapsulates an
+  // object pointer with corresponding Disposer.
+  //
+  // Few developers will ever touch this interface.  It is primarily useful for those implementing
+  // custom memory allocators.
+
+protected:
+  // Do not declare a destructor, as doing so will force a global initializer for each HeapDisposer
+  // instance.  Eww!
+
+  virtual void disposeImpl(void* pointer) const = 0;
+  // Disposes of the object, given a pointer to the beginning of the object.  If the object is
+  // polymorphic, this pointer is determined by dynamic_cast<void*>().  For non-polymorphic types,
+  // Own<T> does not allow any casting, so the pointer exactly matches the original one given to
+  // Own<T>.
+
+public:
+
+  template <typename T>
+  void dispose(T* object) const;
+  // Helper wrapper around disposeImpl().
+  //
+  // If T is polymorphic, calls `disposeImpl(dynamic_cast<void*>(object))`, otherwise calls
+  // `disposeImpl(implicitCast<void*>(object))`.
+  //
+  // Callers must not call dispose() on the same pointer twice, even if the first call throws
+  // an exception.
+
+private:
+  template <typename T, bool polymorphic = __is_polymorphic(T)>
+  struct Dispose_;
+};
+
+template <typename T>
+class DestructorOnlyDisposer: public Disposer {
+  // A disposer that merely calls the type's destructor and nothing else.
+
+public:
+  static const DestructorOnlyDisposer instance;
+
+  void disposeImpl(void* pointer) const override {
+    reinterpret_cast<T*>(pointer)->~T();
+  }
+};
+
+template <typename T>
+const DestructorOnlyDisposer<T> DestructorOnlyDisposer<T>::instance = DestructorOnlyDisposer<T>();
+
+class NullDisposer: public Disposer {
+  // A disposer that does nothing.
+
+public:
+  static const NullDisposer instance;
+
+  void disposeImpl(void* pointer) const override {}
+};
+
+// =======================================================================================
+// Own<T> -- An owned pointer.
+
+template <typename T>
+class Own {
+  // A transferrable title to a T.  When an Own<T> goes out of scope, the object's Disposer is
+  // called to dispose of it.  An Own<T> can be efficiently passed by move, without relocating the
+  // underlying object; this transfers ownership.
+  //
+  // This is much like std::unique_ptr, except:
+  // - You cannot release().  An owned object is not necessarily allocated with new (see next
+  //   point), so it would be hard to use release() correctly.
+  // - The deleter is made polymorphic by virtual call rather than by template.  This is much
+  //   more powerful -- it allows the use of custom allocators, freelists, etc.  This could
+  //   _almost_ be accomplished with unique_ptr by forcing everyone to use something like
+  //   std::unique_ptr<T, kj::Deleter>, except that things get hairy in the presence of multiple
+  //   inheritance and upcasting, and anyway if you force everyone to use a custom deleter
+  //   then you've lost any benefit to interoperating with the "standard" unique_ptr.
+
+public:
+  KJ_DISALLOW_COPY(Own);
+  inline Own(): disposer(nullptr), ptr(nullptr) {}
+  inline Own(Own&& other) noexcept
+      : disposer(other.disposer), ptr(other.ptr) { other.ptr = nullptr; }
+  inline Own(Own<RemoveConstOrDisable<T>>&& other) noexcept
+      : disposer(other.disposer), ptr(other.ptr) { other.ptr = nullptr; }
+  template <typename U, typename = EnableIf<canConvert<U*, T*>()>>
+  inline Own(Own<U>&& other) noexcept
+      : disposer(other.disposer), ptr(other.ptr) {
+    static_assert(__is_polymorphic(T),
+        "Casting owned pointers requires that the target type is polymorphic.");
+    other.ptr = nullptr;
+  }
+  inline Own(T* ptr, const Disposer& disposer) noexcept: disposer(&disposer), ptr(ptr) {}
+
+  ~Own() noexcept(false) { dispose(); }
+
+  inline Own& operator=(Own&& other) {
+    // Move-assingnment operator.
+
+    // Careful, this might own `other`.  Therefore we have to transfer the pointers first, then
+    // dispose.
+    const Disposer* disposerCopy = disposer;
+    T* ptrCopy = ptr;
+    disposer = other.disposer;
+    ptr = other.ptr;
+    other.ptr = nullptr;
+    if (ptrCopy != nullptr) {
+      disposerCopy->dispose(const_cast<RemoveConst<T>*>(ptrCopy));
+    }
+    return *this;
+  }
+
+  inline Own& operator=(decltype(nullptr)) {
+    dispose();
+    return *this;
+  }
+
+  template <typename U>
+  Own<U> downcast() {
+    // Downcast the pointer to Own<U>, destroying the original pointer.  If this pointer does not
+    // actually point at an instance of U, the results are undefined (throws an exception in debug
+    // mode if RTTI is enabled, otherwise you're on your own).
+
+    Own<U> result;
+    if (ptr != nullptr) {
+      result.ptr = &kj::downcast<U>(*ptr);
+      result.disposer = disposer;
+      ptr = nullptr;
+    }
+    return result;
+  }
+
+#define NULLCHECK KJ_IREQUIRE(ptr != nullptr, "null Own<> dereference")
+  inline T* operator->() { NULLCHECK; return ptr; }
+  inline const T* operator->() const { NULLCHECK; return ptr; }
+  inline T& operator*() { NULLCHECK; return *ptr; }
+  inline const T& operator*() const { NULLCHECK; return *ptr; }
+#undef NULLCHECK
+  inline T* get() { return ptr; }
+  inline const T* get() const { return ptr; }
+  inline operator T*() { return ptr; }
+  inline operator const T*() const { return ptr; }
+
+private:
+  const Disposer* disposer;  // Only valid if ptr != nullptr.
+  T* ptr;
+
+  inline explicit Own(decltype(nullptr)): disposer(nullptr), ptr(nullptr) {}
+
+  inline bool operator==(decltype(nullptr)) { return ptr == nullptr; }
+  inline bool operator!=(decltype(nullptr)) { return ptr != nullptr; }
+  // Only called by Maybe<Own<T>>.
+
+  inline void dispose() {
+    // Make sure that if an exception is thrown, we are left with a null ptr, so we won't possibly
+    // dispose again.
+    T* ptrCopy = ptr;
+    if (ptrCopy != nullptr) {
+      ptr = nullptr;
+      disposer->dispose(const_cast<RemoveConst<T>*>(ptrCopy));
+    }
+  }
+
+  template <typename U>
+  friend class Own;
+  friend class Maybe<Own<T>>;
+};
+
+namespace _ {  // private
+
+template <typename T>
+class OwnOwn {
+public:
+  inline OwnOwn(Own<T>&& value) noexcept: value(kj::mv(value)) {}
+
+  inline Own<T>& operator*() & { return value; }
+  inline const Own<T>& operator*() const & { return value; }
+  inline Own<T>&& operator*() && { return kj::mv(value); }
+  inline const Own<T>&& operator*() const && { return kj::mv(value); }
+  inline Own<T>* operator->() { return &value; }
+  inline const Own<T>* operator->() const { return &value; }
+  inline operator Own<T>*() { return value ? &value : nullptr; }
+  inline operator const Own<T>*() const { return value ? &value : nullptr; }
+
+private:
+  Own<T> value;
+};
+
+template <typename T>
+OwnOwn<T> readMaybe(Maybe<Own<T>>&& maybe) { return OwnOwn<T>(kj::mv(maybe.ptr)); }
+template <typename T>
+Own<T>* readMaybe(Maybe<Own<T>>& maybe) { return maybe.ptr ? &maybe.ptr : nullptr; }
+template <typename T>
+const Own<T>* readMaybe(const Maybe<Own<T>>& maybe) { return maybe.ptr ? &maybe.ptr : nullptr; }
+
+}  // namespace _ (private)
+
+template <typename T>
+class Maybe<Own<T>> {
+public:
+  inline Maybe(): ptr(nullptr) {}
+  inline Maybe(Own<T>&& t) noexcept: ptr(kj::mv(t)) {}
+  inline Maybe(Maybe&& other) noexcept: ptr(kj::mv(other.ptr)) {}
+
+  template <typename U>
+  inline Maybe(Maybe<Own<U>>&& other): ptr(mv(other.ptr)) {}
+
+  inline Maybe(decltype(nullptr)) noexcept: ptr(nullptr) {}
+
+  inline operator Maybe<T&>() { return ptr.get(); }
+  inline operator Maybe<const T&>() const { return ptr.get(); }
+
+  inline Maybe& operator=(Maybe&& other) { ptr = kj::mv(other.ptr); return *this; }
+
+  inline bool operator==(decltype(nullptr)) const { return ptr == nullptr; }
+  inline bool operator!=(decltype(nullptr)) const { return ptr != nullptr; }
+
+  Own<T>& orDefault(Own<T>& defaultValue) {
+    if (ptr == nullptr) {
+      return defaultValue;
+    } else {
+      return ptr;
+    }
+  }
+  const Own<T>& orDefault(const Own<T>& defaultValue) const {
+    if (ptr == nullptr) {
+      return defaultValue;
+    } else {
+      return ptr;
+    }
+  }
+
+  template <typename Func>
+  auto map(Func&& f) & -> Maybe<decltype(f(instance<Own<T>&>()))> {
+    if (ptr == nullptr) {
+      return nullptr;
+    } else {
+      return f(ptr);
+    }
+  }
+
+  template <typename Func>
+  auto map(Func&& f) const & -> Maybe<decltype(f(instance<const Own<T>&>()))> {
+    if (ptr == nullptr) {
+      return nullptr;
+    } else {
+      return f(ptr);
+    }
+  }
+
+  template <typename Func>
+  auto map(Func&& f) && -> Maybe<decltype(f(instance<Own<T>&&>()))> {
+    if (ptr == nullptr) {
+      return nullptr;
+    } else {
+      return f(kj::mv(ptr));
+    }
+  }
+
+  template <typename Func>
+  auto map(Func&& f) const && -> Maybe<decltype(f(instance<const Own<T>&&>()))> {
+    if (ptr == nullptr) {
+      return nullptr;
+    } else {
+      return f(kj::mv(ptr));
+    }
+  }
+
+private:
+  Own<T> ptr;
+
+  template <typename U>
+  friend class Maybe;
+  template <typename U>
+  friend _::OwnOwn<U> _::readMaybe(Maybe<Own<U>>&& maybe);
+  template <typename U>
+  friend Own<U>* _::readMaybe(Maybe<Own<U>>& maybe);
+  template <typename U>
+  friend const Own<U>* _::readMaybe(const Maybe<Own<U>>& maybe);
+};
+
+namespace _ {  // private
+
+template <typename T>
+class HeapDisposer final: public Disposer {
+public:
+  virtual void disposeImpl(void* pointer) const override { delete reinterpret_cast<T*>(pointer); }
+
+  static const HeapDisposer instance;
+};
+
+template <typename T>
+const HeapDisposer<T> HeapDisposer<T>::instance = HeapDisposer<T>();
+
+}  // namespace _ (private)
+
+template <typename T, typename... Params>
+Own<T> heap(Params&&... params) {
+  // heap<T>(...) allocates a T on the heap, forwarding the parameters to its constructor.  The
+  // exact heap implementation is unspecified -- for now it is operator new, but you should not
+  // assume this.  (Since we know the object size at delete time, we could actually implement an
+  // allocator that is more efficient than operator new.)
+
+  return Own<T>(new T(kj::fwd<Params>(params)...), _::HeapDisposer<T>::instance);
+}
+
+template <typename T>
+Own<Decay<T>> heap(T&& orig) {
+  // Allocate a copy (or move) of the argument on the heap.
+  //
+  // The purpose of this overload is to allow you to omit the template parameter as there is only
+  // one argument and the purpose is to copy it.
+
+  typedef Decay<T> T2;
+  return Own<T2>(new T2(kj::fwd<T>(orig)), _::HeapDisposer<T2>::instance);
+}
+
+// =======================================================================================
+// SpaceFor<T> -- assists in manual allocation
+
+template <typename T>
+class SpaceFor {
+  // A class which has the same size and alignment as T but does not call its constructor or
+  // destructor automatically.  Instead, call construct() to construct a T in the space, which
+  // returns an Own<T> which will take care of calling T's destructor later.
+
+public:
+  inline SpaceFor() {}
+  inline ~SpaceFor() {}
+
+  template <typename... Params>
+  Own<T> construct(Params&&... params) {
+    ctor(value, kj::fwd<Params>(params)...);
+    return Own<T>(&value, DestructorOnlyDisposer<T>::instance);
+  }
+
+private:
+  union {
+    T value;
+  };
+};
+
+// =======================================================================================
+// Inline implementation details
+
+template <typename T>
+struct Disposer::Dispose_<T, true> {
+  static void dispose(T* object, const Disposer& disposer) {
+    // Note that dynamic_cast<void*> does not require RTTI to be enabled, because the offset to
+    // the top of the object is in the vtable -- as it obviously needs to be to correctly implement
+    // operator delete.
+    disposer.disposeImpl(dynamic_cast<void*>(object));
+  }
+};
+template <typename T>
+struct Disposer::Dispose_<T, false> {
+  static void dispose(T* object, const Disposer& disposer) {
+    disposer.disposeImpl(static_cast<void*>(object));
+  }
+};
+
+template <typename T>
+void Disposer::dispose(T* object) const {
+  Dispose_<T>::dispose(object, *this);
+}
+
+}  // namespace kj
+
+#endif  // KJ_MEMORY_H_