Support arrays in nonstd::unique_ptr<>.

third_party/base/nonstd_unique_ptr.h

 // Copyright 2013 Google Inc. All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
@@ skipping 17 matching lines @@
 
 // This is a copy of breakpad's standalone scoped_ptr, which has been
 // renamed to nonstd::unique_ptr, and from which more complicated classes
 // have been removed. The reset() method has also been tweaked to more
 // closely match c++11, and an implicit conversion to bool has been added.
 
 // Scopers help you manage ownership of a pointer, helping you easily manage the
 // a pointer within a scope, and automatically destroying the pointer at the
 // end of a scope.
 //
+// A unique_ptr<T> is like a T*, except that the destructor of unique_ptr<T>
+// automatically deletes the pointer it holds (if any).
+// That is, unique_ptr<T> owns the T object that it points to.
+// Like a T*, a unique_ptr<T> may hold either NULL or a pointer to a T object.
+// Also like T*, unique_ptr<T> is thread-compatible, and once you
+// dereference it, you get the threadsafety guarantees of T.

[Lei Zhang, 2015/05/06 23:59:35]

nit: "thread safety"

[Tom Sepez, 2015/05/07 00:07:40]

Done.

+//
 // Example usage (unique_ptr):
 //   {
 //     unique_ptr<Foo> foo(new Foo("wee"));
 //   }  // foo goes out of scope, releasing the pointer with it.
 //
 //   {
 //     unique_ptr<Foo> foo;          // No pointer managed.
 //     foo.reset(new Foo("wee"));    // Now a pointer is managed.
 //     foo.reset(new Foo("wee2"));   // Foo("wee") was destroyed.
 //     foo.reset(new Foo("wee3"));   // Foo("wee2") was destroyed.
 //     foo->Method();                // Foo::Method() called.
 //     foo.get()->Method();          // Foo::Method() called.
 //     SomeFunc(foo.release());      // SomeFunc takes ownership, foo no longer
 //                                   // manages a pointer.
 //     foo.reset(new Foo("wee4"));   // foo manages a pointer again.
 //     foo.reset();                  // Foo("wee4") destroyed, foo no longer
 //                                   // manages a pointer.
 //   }  // foo wasn't managing a pointer, so nothing was destroyed.
+//
+// The size of a unique_ptr is small: sizeof(unique_ptr<C>) == sizeof(C*)
 
 #ifndef NONSTD_UNIQUE_PTR_H_
 #define NONSTD_UNIQUE_PTR_H_
 
 // This is an implementation designed to match the anticipated future TR2
 // implementation of the unique_ptr class.
 
 #include <assert.h>
 #include <stddef.h>
 #include <stdlib.h>
 
 namespace nonstd {
 
-// A unique_ptr<T> is like a T*, except that the destructor of unique_ptr<T>
-// automatically deletes the pointer it holds (if any).
-// That is, unique_ptr<T> owns the T object that it points to.
-// Like a T*, a unique_ptr<T> may hold either NULL or a pointer to a T object.
-// Also like T*, unique_ptr<T> is thread-compatible, and once you
-// dereference it, you get the threadsafety guarantees of T.
-//
-// The size of a unique_ptr is small:
-// sizeof(unique_ptr<C>) == sizeof(C*)
+// Common implementation for both pointers to elements and pointers to
+// arrays. These are diferenatiated below based on the need to invoke

[Lei Zhang, 2015/05/06 23:59:35]

typo

[Tom Sepez, 2015/05/07 00:07:40]

Done.

+ // delete vs. delete[] as appropriate.
 template <class C>
-class unique_ptr {
+class unique_ptr_base {
  public:
 
   // The element type
   typedef C element_type;
 
-  // Constructor.  Defaults to initializing with NULL.
-  // There is no way to create an uninitialized unique_ptr.
-  // The input parameter must be allocated with new.
-  explicit unique_ptr(C* p = NULL) : ptr_(p) { }
-
-  // Destructor.  If there is a C object, delete it.
-  // We don't need to test ptr_ == NULL because C++ does that for us.
-  ~unique_ptr() {
-    enum { type_must_be_complete = sizeof(C) };
-    delete ptr_;
-  }
-
-  // Reset.  Deletes the current owned object, if any.
-  // Then takes ownership of a new object, if given.
-  // this->reset(this->get()) works.
-  void reset(C* p = NULL) {
-    if (p != ptr_) {
-      enum { type_must_be_complete = sizeof(C) };
-      C* old_ptr = ptr_;
-      ptr_ = p;
-      delete old_ptr;
-    }
-  }
+  explicit unique_ptr_base(C* p) : ptr_(p) { }
 
   // Accessors to get the owned object.
   // operator* and operator-> will assert() if there is no current object.
   C& operator*() const {
     assert(ptr_ != NULL);
     return *ptr_;
   }
   C* operator->() const  {
     assert(ptr_ != NULL);
     return ptr_;
   }
   C* get() const { return ptr_; }
 
   // Comparison operators.
   // These return whether two unique_ptr refer to the same object, not just to
   // two different but equal objects.
   bool operator==(C* p) const { return ptr_ == p; }
   bool operator!=(C* p) const { return ptr_ != p; }
 
   // Swap two scoped pointers.
-  void swap(unique_ptr& p2) {
+  void swap(unique_ptr_base& p2) {
     C* tmp = ptr_;
     ptr_ = p2.ptr_;
     p2.ptr_ = tmp;
   }
 
   // Release a pointer.
   // The return value is the current pointer held by this object.
   // If this object holds a NULL pointer, the return value is NULL.
   // After this operation, this object will hold a NULL pointer,
   // and will not own the object any more.
   C* release() {
     C* retVal = ptr_;
     ptr_ = NULL;
     return retVal;
   }
 
   // Allow promotion to bool for conditional statements.
   operator bool() const { return ptr_ != NULL; }
 
- private:
+ protected:
   C* ptr_;
+};
 
+// Implementation for ordinary pointers using delete.
+template <class C>
+class unique_ptr : public unique_ptr_base<C> {
+ public:
+  using unique_ptr_base<C>::ptr_;
+  explicit unique_ptr(C* p = NULL) : unique_ptr_base<C>(p) { }
+
+  // Destructor.  If there is a C object, delete it.
+  // We don't need to test ptr_ == NULL because C++ does that for us.
+  ~unique_ptr() {
+    enum { type_must_be_complete = sizeof(C) };
+    delete ptr_;
+  }
+
+  // Reset.  Deletes the current owned object, if any.
+  // Then takes ownership of a new object, if given.
+  // this->reset(this->get()) works.
+  void reset(C* p = NULL) {
+    if (p != ptr_) {
+      enum { type_must_be_complete = sizeof(C) };
+      C* old_ptr = ptr_;
+      ptr_ = p;
+      delete old_ptr;
+    }
+  }
+
+private:
   // Forbid comparison of unique_ptr types.  If C2 != C, it totally doesn't
   // make sense, and if C2 == C, it still doesn't make sense because you should
   // never have the same object owned by two different unique_ptrs.
+  template <class C2> bool operator==(unique_ptr<C2> const& p2) const;
+  template <class C2> bool operator!=(unique_ptr<C2> const& p2) const;
+
+  // Disallow evil constructors
+  unique_ptr(const unique_ptr&);
+  void operator=(const unique_ptr&);
+};
+
+// Specialization for arrays using delete[].
+template <class C>
+class unique_ptr<C[]> : public unique_ptr_base<C> {
+ public:
+  using unique_ptr_base<C>::ptr_;
+  explicit unique_ptr(C* p = NULL) : unique_ptr_base<C>(p) { }
+
+  // Destructor.  If there is a C object, delete it.
+  // We don't need to test ptr_ == NULL because C++ does that for us.
+  ~unique_ptr() {
+    enum { type_must_be_complete = sizeof(C) };
+    delete[] ptr_;
+  }
+
+  // Reset.  Deletes the current owned object, if any.
+  // Then takes ownership of a new object, if given.
+  // this->reset(this->get()) works.
+  void reset(C* p = NULL) {
+    if (p != ptr_) {
+      enum { type_must_be_complete = sizeof(C) };
+      C* old_ptr = ptr_;
+      ptr_ = p;
+      delete[] old_ptr;
+    }
+  }
+
+  // Support indexing since it is holding array.
+  C& operator[] (size_t i) { return ptr_[i]; }
+
+private:
+  // Forbid comparison of unique_ptr types.  If C2 != C, it totally doesn't
+  // make sense, and if C2 == C, it still doesn't make sense because you should
+  // never have the same object owned by two different unique_ptrs.
   template <class C2> bool operator==(unique_ptr<C2> const& p2) const;
   template <class C2> bool operator!=(unique_ptr<C2> const& p2) const;
 
   // Disallow evil constructors
   unique_ptr(const unique_ptr&);
   void operator=(const unique_ptr&);
 };
 
 // Free functions
 template <class C>
 void swap(unique_ptr<C>& p1, unique_ptr<C>& p2) {
   p1.swap(p2);
 }
 
 template <class C>
 bool operator==(C* p1, const unique_ptr<C>& p2) {
   return p1 == p2.get();
 }
 
 template <class C>
 bool operator!=(C* p1, const unique_ptr<C>& p2) {
   return p1 != p2.get();
 }
 
 }  // namespace nonstd
 
 #endif  // NONSTD_UNIQUE_PTR_H_