1 files changed, 165 insertions, 0 deletions
diff --git a/base/win/scoped_comptr.h b/base/win/scoped_comptr.h
new file mode 100644
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--- /dev/null
+++ b/base/win/scoped_comptr.h
@@ -0,0 +1,165 @@
+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_WIN_SCOPED_COMPTR_H_
+#define BASE_WIN_SCOPED_COMPTR_H_
+#pragma once
+
+#include <unknwn.h>
+
+#include "base/logging.h"
+#include "base/ref_counted.h"
+
+namespace base {
+namespace win {
+
+// A fairly minimalistic smart class for COM interface pointers.
+// Uses scoped_refptr for the basic smart pointer functionality
+// and adds a few IUnknown specific services.
+template <class Interface, const IID* interface_id = &__uuidof(Interface)>
+class ScopedComPtr : public scoped_refptr<Interface> {
+ public:
+  // Utility template to prevent users of ScopedComPtr from calling AddRef
+  // and/or Release() without going through the ScopedComPtr class.
+  template <class Interface>
+  class BlockIUnknownMethods : public Interface {
+   private:
+    STDMETHOD(QueryInterface)(REFIID iid, void** object) = 0;
+    STDMETHOD_(ULONG, AddRef)() = 0;
+    STDMETHOD_(ULONG, Release)() = 0;
+  };
+
+  typedef scoped_refptr<Interface> ParentClass;
+
+  ScopedComPtr() {
+  }
+
+  explicit ScopedComPtr(Interface* p) : ParentClass(p) {
+  }
+
+  ScopedComPtr(const ScopedComPtr<Interface, interface_id>& p)
+      : ParentClass(p) {
+  }
+
+  ~ScopedComPtr() {
+    // We don't want the smart pointer class to be bigger than the pointer
+    // it wraps.
+    COMPILE_ASSERT(sizeof(ScopedComPtr<Interface, interface_id>) ==
+                   sizeof(Interface*), ScopedComPtrSize);
+  }
+
+  // Explicit Release() of the held object.  Useful for reuse of the
+  // ScopedComPtr instance.
+  // Note that this function equates to IUnknown::Release and should not
+  // be confused with e.g. scoped_ptr::release().
+  void Release() {
+    if (ptr_ != NULL) {
+      ptr_->Release();
+      ptr_ = NULL;
+    }
+  }
+
+  // Sets the internal pointer to NULL and returns the held object without
+  // releasing the reference.
+  Interface* Detach() {
+    Interface* p = ptr_;
+    ptr_ = NULL;
+    return p;
+  }
+
+  // Accepts an interface pointer that has already been addref-ed.
+  void Attach(Interface* p) {
+    DCHECK(ptr_ == NULL);
+    ptr_ = p;
+  }
+
+  // Retrieves the pointer address.
+  // Used to receive object pointers as out arguments (and take ownership).
+  // The function DCHECKs on the current value being NULL.
+  // Usage: Foo(p.Receive());
+  Interface** Receive() {
+    DCHECK(ptr_ == NULL) << "Object leak. Pointer must be NULL";
+    return &ptr_;
+  }
+
+  template <class Query>
+  HRESULT QueryInterface(Query** p) {
+    DCHECK(p != NULL);
+    DCHECK(ptr_ != NULL);
+    // IUnknown already has a template version of QueryInterface
+    // so the iid parameter is implicit here. The only thing this
+    // function adds are the DCHECKs.
+    return ptr_->QueryInterface(p);
+  }
+
+  // QI for times when the IID is not associated with the type.
+  HRESULT QueryInterface(const IID& iid, void** obj) {
+    DCHECK(obj != NULL);
+    DCHECK(ptr_ != NULL);
+    return ptr_->QueryInterface(iid, obj);
+  }
+
+  // Queries |other| for the interface this object wraps and returns the
+  // error code from the other->QueryInterface operation.
+  HRESULT QueryFrom(IUnknown* object) {
+    DCHECK(object != NULL);
+    return object->QueryInterface(Receive());
+  }
+
+  // Convenience wrapper around CoCreateInstance
+  HRESULT CreateInstance(const CLSID& clsid, IUnknown* outer = NULL,
+                         DWORD context = CLSCTX_ALL) {
+    DCHECK(ptr_ == NULL);
+    HRESULT hr = ::CoCreateInstance(clsid, outer, context, *interface_id,
+                                    reinterpret_cast<void**>(&ptr_));
+    return hr;
+  }
+
+  // Checks if the identity of |other| and this object is the same.
+  bool IsSameObject(IUnknown* other) {
+    if (!other && !ptr_)
+      return true;
+
+    if (!other || !ptr_)
+      return false;
+
+    ScopedComPtr<IUnknown> my_identity;
+    QueryInterface(my_identity.Receive());
+
+    ScopedComPtr<IUnknown> other_identity;
+    other->QueryInterface(other_identity.Receive());
+
+    return static_cast<IUnknown*>(my_identity) ==
+           static_cast<IUnknown*>(other_identity);
+  }
+
+  // Provides direct access to the interface.
+  // Here we use a well known trick to make sure we block access to
+  // IUknown methods so that something bad like this doesn't happen:
+  //    ScopedComPtr<IUnknown> p(Foo());
+  //    p->Release();
+  //    ... later the destructor runs, which will Release() again.
+  // and to get the benefit of the DCHECKs we add to QueryInterface.
+  // There's still a way to call these methods if you absolutely must
+  // by statically casting the ScopedComPtr instance to the wrapped interface
+  // and then making the call... but generally that shouldn't be necessary.
+  BlockIUnknownMethods<Interface>* operator->() const {
+    DCHECK(ptr_ != NULL);
+    return reinterpret_cast<BlockIUnknownMethods<Interface>*>(ptr_);
+  }
+
+  // Pull in operator=() from the parent class.
+  using scoped_refptr<Interface>::operator=;
+
+  // static methods
+
+  static const IID& iid() {
+    return *interface_id;
+  }
+};
+
+}  // namespace win
+}  // namespace base
+
+#endif  // BASE_WIN_SCOPED_COMPTR_H_