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120 lines
2.4 KiB
C++
120 lines
2.4 KiB
C++
/*
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* PROGRAM: Firebird aux classes.
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* MODULE: TriState.h
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* DESCRIPTION: Firebird's SQL tri-state emulation class.
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*
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* The contents of this file are subject to the Initial
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* Developer's Public License Version 1.0 (the "License");
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* you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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* http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_idpl.
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*
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* Software distributed under the License is distributed AS IS,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied.
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* See the License for the specific language governing rights
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* and limitations under the License.
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*
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* The Original Code was created by Claudio Valderrama on 28-Aug-2007
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* for the Firebird Open Source RDBMS project.
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*
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* Copyright (c) 2007 Claudio Valderrama
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* and all contributors signed below.
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*
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* All Rights Reserved.
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* Contributor(s): ______________________________________.
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*
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*
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*/
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#ifndef CLASSES_TRISTATE_H
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#define CLASSES_TRISTATE_H
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#include "firebird.h"
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class TriState
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{
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public:
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TriState();
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explicit TriState(bool input);
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void operator=(bool input);
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bool asBool() const;
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void reset();
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bool assignOnce(bool input);
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bool isUnknown() const;
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bool isAssigned() const;
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bool toggle();
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private:
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bool m_init, m_val;
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};
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// The var is left uninitialized.
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inline TriState::TriState()
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: m_init(false), m_val(false)
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{
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}
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// The var is initialized to the explicit value.
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inline TriState::TriState(bool input)
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: m_init(true), m_val(input)
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{
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}
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// The var receives a T/F value.
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inline void TriState::operator=(bool input)
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{
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m_init = true;
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m_val = input;
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}
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// The var is coerced to a T/F value as result.
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inline bool TriState::asBool() const
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{
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return m_init && m_val;
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}
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// The var is returned to its uninitialized state.
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inline void TriState::reset()
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{
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m_init = m_val = false;
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}
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// The assignment succeeds only if the var is uninitialized.
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inline bool TriState::assignOnce(bool input)
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{
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if (m_init)
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return false;
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m_init = true;
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m_val = input;
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return true;
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}
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// Tests whether the var is uninitialized.
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inline bool TriState::isUnknown() const
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{
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return !m_init;
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}
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// Tests whether the var is initialized.
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inline bool TriState::isAssigned() const
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{
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return m_init;
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}
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// The var is toggled between T and F only if it's already initialized.
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inline bool TriState::toggle()
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{
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if (!m_init)
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return false;
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m_val = !m_val;
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return true;
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}
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#endif // CLASSES_TRISTATE_H
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