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67 lines
1.5 KiB
C++
67 lines
1.5 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef Nullable_h
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#define Nullable_h
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#include "platform/heap/Handle.h"
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#include "wtf/Assertions.h"
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namespace blink {
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template <typename T>
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class Nullable {
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DISALLOW_ALLOCATION();
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public:
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Nullable()
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: m_value()
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, m_isNull(true) { }
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Nullable(const T& value)
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: m_value(value)
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, m_isNull(false) { }
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Nullable(const Nullable& other)
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: m_value(other.m_value)
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, m_isNull(other.m_isNull) { }
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Nullable& operator=(const Nullable& other)
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{
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m_value = other.m_value;
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m_isNull = other.m_isNull;
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return *this;
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}
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void set(const T& value)
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{
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m_value = value;
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m_isNull = false;
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}
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const T& get() const { ASSERT(!m_isNull); return m_value; }
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T& get() { ASSERT(!m_isNull); return m_value; }
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bool isNull() const { return m_isNull; }
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// See comment in RefPtr.h about what UnspecifiedBoolType is.
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typedef const T* UnspecifiedBoolType;
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operator UnspecifiedBoolType() const { return m_isNull ? 0 : &m_value; }
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bool operator==(const Nullable& other) const
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{
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return (m_isNull && other.m_isNull) || (!m_isNull && !other.m_isNull && m_value == other.m_value);
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}
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void trace(Visitor* visitor)
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{
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TraceIfNeeded<T>::trace(visitor, &m_value);
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}
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private:
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T m_value;
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bool m_isNull;
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};
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} // namespace blink
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#endif // Nullable_h
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