93 lines
2.1 KiB
C++
93 lines
2.1 KiB
C++
#ifndef NULLABLE_INCLUDED
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#define NULLABLE_INCLUDED
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/*
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Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "my_dbug.h"
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namespace Mysql{
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/**
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Class for storing value or NULL value.
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*/
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template<typename T_value> class Nullable
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{
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public:
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Nullable()
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: m_has_value(false)
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{}
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Nullable(T_value value)
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: m_has_value(true),
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m_value(value)
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{}
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Nullable(const Nullable<T_value>& other)
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: m_has_value(other.m_has_value),
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m_value(other.m_value)
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{}
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/**
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Assigns value from another Nullable<> object.
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*/
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Nullable<T_value>& operator= (const Nullable<T_value>& other)
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{
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this->m_has_value= other.m_has_value;
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if (this->m_has_value)
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{
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this->m_value= other.m_value;
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}
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return *this;
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}
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/**
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Returns true if object has not-NULL value assigned. If this is false, one
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should not try to get value by value().
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*/
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bool has_value() const
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{
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return this->m_has_value;
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}
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/**
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Returns actual value of object. Do not call this method if has_value()
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returns false.
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*/
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const T_value& value() const
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{
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DBUG_ASSERT(this->m_has_value);
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return this->m_value;
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}
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private:
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/**
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Specifies if this object represents NULL value. If this is false, one
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should not try to get value by value().
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*/
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bool m_has_value;
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/**
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Actual value, if m_has_value is true. Undefined if m_has_value is false.
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*/
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T_value m_value;
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};
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}
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#endif // NULLABLE_INCLUDED
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