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#ifndef MOZC_BASE_SCOPED_PTR_H_
#define MOZC_BASE_SCOPED_PTR_H_

//  This is an implementation designed to match the anticipated future TR2
//  implementation of the scoped_ptr class, and its closely-related brethren,
//  scoped_array.
//
//  See http://wiki/Main/ScopedPointerInterface for the spec that drove this
//  file.

#include <assert.h>
#include <cstddef>

#include "base/port.h"

template <class C> class scoped_ptr;

// A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T>
// automatically deletes the pointer it holds (if any).
// That is, scoped_ptr<T> owns the T object that it points to.
// Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object.
// Also like T*, scoped_ptr<T> is thread-compatible, and once you
// dereference it, you get the threadsafety guarantees of T.
//
// The size of a scoped_ptr is small:
// sizeof(scoped_ptr<C>) == sizeof(C*)
template <class C>
class scoped_ptr {
 public:

  // The element type
  typedef C element_type;

  // Constructor.  Defaults to intializing with NULL.
  // There is no way to create an uninitialized scoped_ptr.
  // The input parameter must be allocated with new.
  explicit scoped_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.
  ~scoped_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) };
      delete ptr_;
      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 a scoped_ptr and a raw pointer refer to
  // the same object, not just to two different but equal objects.
  bool operator==(const C* p) const { return ptr_ == p; }
  bool operator!=(const C* p) const { return ptr_ != p; }

  // Swap two scoped pointers.
  void swap(scoped_ptr& 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;
  }

 private:
  C* ptr_;

  // Forbid comparison of scoped_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 scoped_ptrs.
  template <class C2> bool operator==(scoped_ptr<C2> const& p2) const;
  template <class C2> bool operator!=(scoped_ptr<C2> const& p2) const;

  DISALLOW_COPY_AND_ASSIGN(scoped_ptr);
};

// Free functions
template <class C>
inline void swap(scoped_ptr<C>& p1, scoped_ptr<C>& p2) {
  p1.swap(p2);
}

template <class C>
inline bool operator==(const C* p1, const scoped_ptr<C>& p2) {
  return p1 == p2.get();
}

template <class C>
inline bool operator==(const C* p1, const scoped_ptr<const C>& p2) {
  return p1 == p2.get();
}

template <class C>
inline bool operator!=(const C* p1, const scoped_ptr<C>& p2) {
  return p1 != p2.get();
}

template <class C>
inline bool operator!=(const C* p1, const scoped_ptr<const C>& p2) {
  return p1 != p2.get();
}

// Specialization of scoped_ptr for holding arrays.
//
// scoped_ptr<C[]> is like scoped_ptr<C>, except that the caller must allocate
// with new [] and the destructor deletes objects with delete [].
//
// As with scoped_ptr<C>, a scoped_ptr<C[]> either points to an array of objects
// or is NULL.  A scoped_ptr<C[]> owns the array that it points to.
// scoped_ptr<C[]> is thread-compatible, and once you index into it, the
// returned objects have only the threadsafety guarantees of C.
//
// Size: sizeof(scoped_ptr<C[]>) == sizeof(C*)
template <class C>
class scoped_ptr<C[]> {
 public:
  // The element type
  typedef C element_type;

  // Constructor.  Defaults to intializing with NULL.
  // There is no way to create an uninitialized scoped_ptr.
  // The input parameter must be allocated with new [].
  explicit scoped_ptr(C* p = NULL) : array_(p) { }

  // Destructor.  If there is a C object, delete it.
  // We don't need to test ptr_ == NULL because C++ does that for us.
  ~scoped_ptr() {
    enum { type_must_be_complete = sizeof(C) };
    delete[] array_;
  }

  // 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 != array_) {
      enum { type_must_be_complete = sizeof(C) };
      delete[] array_;
      array_ = p;
    }
  }

  // Get one element of the current object.
  // Will assert() if there is no current object, or index i is negative.
  C& operator[](std::ptrdiff_t i) const {
    assert(i >= 0);
    assert(array_ != NULL);
    return array_[i];
  }

  // Get a pointer to the zeroth element of the current object.
  // If there is no current object, return NULL.
  C* get() const {
    return array_;
  }

  // Comparison operators.
  // These return whether a scoped_ptr and a raw pointer refer to
  // the same array, not just to two different but equal arrays.
  bool operator==(const C* p) const { return array_ == p; }
  bool operator!=(const C* p) const { return array_ != p; }

  // Swap two scoped arrays.
  void swap(scoped_ptr& p2) {
    C* tmp = array_;
    array_ = p2.array_;
    p2.array_ = tmp;
  }

  // Release an array.
  // 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 = array_;
    array_ = NULL;
    return retVal;
  }

 private:
  C* array_;

  // Forbid comparison of different scoped_ptr types.
  template <class C2> bool operator==(scoped_ptr<C2[]> const& p2) const;
  template <class C2> bool operator!=(scoped_ptr<C2[]> const& p2) const;

  DISALLOW_COPY_AND_ASSIGN(scoped_ptr);
};

// Free functions
template <class C>
inline void swap(scoped_ptr<C[]>& p1, scoped_ptr<C[]>& p2) {
  p1.swap(p2);
}

template <class C>
inline bool operator==(const C* p1, const scoped_ptr<C[]>& p2) {
  return p1 == p2.get();
}

template <class C>
inline bool operator==(const C* p1, const scoped_ptr<const C[]>& p2) {
  return p1 == p2.get();
}

template <class C>
inline bool operator!=(const C* p1, const scoped_ptr<C[]>& p2) {
  return p1 != p2.get();
}

template <class C>
inline bool operator!=(const C* p1, const scoped_ptr<const C[]>& p2) {
  return p1 != p2.get();
}

#endif  // MOZC_BASE_SCOPED_PTR_H_