// 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
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// 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 thread safety guarantees of T.
//
// 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 {
// Common implementation for both pointers to elements and pointers to
// arrays. These are differentiated below based on the need to invoke
// delete vs. delete[] as appropriate.
template <class C>
class unique_ptr_base {
public:
// The element type
typedef C element_type;
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_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; }
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_;
// Constructor. Defaults to initializing with NULL. There is no way
// to create an uninitialized unique_ptr. The input parameter must be
// allocated with new (not new[] - see below).
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_;
// Constructor. Defaults to initializing with NULL. There is no way
// to create an uninitialized unique_ptr. The input parameter must be
// allocated with new[] (not new - see above).
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_