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// Copyright 2014 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 Nullable_h
#define Nullable_h
#include "platform/heap/Handle.h"
#include "wtf/Assertions.h"
namespace blink {
template <typename T>
class Nullable {
DISALLOW_ALLOCATION();
public:
Nullable()
: m_value()
, m_isNull(true) { }
Nullable(std::nullptr_t)
: m_value()
, m_isNull(true) { }
Nullable(const T& value)
: m_value(value)
, m_isNull(false) { }
Nullable(const Nullable& other)
: m_value(other.m_value)
, m_isNull(other.m_isNull) { }
Nullable& operator=(const Nullable& other)
{
m_value = other.m_value;
m_isNull = other.m_isNull;
return *this;
}
Nullable& operator=(std::nullptr_t)
{
m_value = T();
m_isNull = true;
return *this;
}
void set(const T& value)
{
m_value = value;
m_isNull = false;
}
void set(std::nullptr_t)
{
m_value = T();
m_isNull = true;
}
const T& get() const { ASSERT(!m_isNull); return m_value; }
T& get() { ASSERT(!m_isNull); return m_value; }
bool isNull() const { return m_isNull; }
// See comment in RefPtr.h about what UnspecifiedBoolType is.
typedef const T* UnspecifiedBoolType;
operator UnspecifiedBoolType() const { return m_isNull ? 0 : &m_value; }
bool operator==(const Nullable& other) const
{
return (m_isNull && other.m_isNull) || (!m_isNull && !other.m_isNull && m_value == other.m_value);
}
void trace(Visitor* visitor)
{
TraceIfNeeded<T>::trace(visitor, &m_value);
}
private:
T m_value;
bool m_isNull;
};
} // namespace blink
#endif // Nullable_h
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