1/*
2 * Copyright (C) 2009 Apple Inc. All Rights Reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef PossiblyNull_h
27#define PossiblyNull_h
28
29#include "Assertions.h"
30
31namespace WTF {
32
33template <typename T> struct PossiblyNull {
34    PossiblyNull(T data)
35        : m_data(data)
36    {
37    }
38    PossiblyNull(const PossiblyNull<T>& source)
39        : m_data(source.m_data)
40    {
41        source.m_data = 0;
42    }
43    ~PossiblyNull() { ASSERT(!m_data); }
44    bool getValue(T& out) WARN_UNUSED_RETURN;
45private:
46    mutable T m_data;
47};
48
49template <typename T> bool PossiblyNull<T>::getValue(T& out)
50{
51    out = m_data;
52    bool result = !!m_data;
53    m_data = 0;
54    return result;
55}
56
57}
58
59#endif
60