Invariant.h

//========================================================================================
// 
// $File$
// 
// Owner: Jesse Jones (jejones)
// 
// $Author$
// 
// $DateTime$
// 
// $Revision$
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// $Change$
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// Copyright 1997-2010 Adobe Systems Incorporated. All rights reserved.
// 
// NOTICE: Adobe permits you to use, modify, and distribute this file in accordance 
// with the terms of the Adobe license agreement accompanying it. If you have received
// this file from a source other than Adobe, then your use, modification, or 
// distribution of it requires the prior written permission of Adobe.
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// 
// ADOBE CONFIDENTIAL
// 
// Purpose: Misc debugging features
// 
//========================================================================================

#ifndef __INVARIANT__H__
#define __INVARIANT__H__

// ===================================================================================
// Design By Contract
// ===================================================================================
#ifdef DEBUG
 class InvariantCount { // $$$ Use DECLARE_HELPER_METHODS to automate adding this when interfaces are used?
 public:
 InvariantCount() {fNesting = 0;}
 void Enter() const {++fNesting; ASSERT(fNesting >= 1);}
 void Exit() const {--fNesting; ASSERT(fNesting >= 0);}
 bool16 Check() const {return fNesting == 1;}
 private:
 mutable int32 fNesting;
 };

 template<typename T> class AutoInvariantChecker {
 public:
 explicit AutoInvariantChecker(InvariantCount& invariant, T& t) : 
 fInvariant(invariant),
 fObject(t)
 {
 fInvariant.Enter();
 if (fInvariant.Check()) 
 fObject.Invariant();
 }
 ~AutoInvariantChecker()
 {
 if (fInvariant.Check())
 fObject.Invariant();
 fInvariant.Exit();
 }
 private:
 InvariantCount& fInvariant;
 T& fObject;
 };

#define PRECONDITION(p) ASSERT(p); fInvariant.Enter(); if (fInvariant.Check()) this->Invariant()
#define POSTCONDITION(p) ASSERT(p); if (fInvariant.Check()) this->Invariant(); fInvariant.Exit()

#define CHECK_INVARIANT this->Invariant
#define AUTO_INVARIANT_CHECKER(TYPE) AutoInvariantChecker<TYPE> autoInvariantChecker(fInvariant, *this)

#else
#define PRECONDITION(p) ((void) 0)
#define POSTCONDITION(p) ((void) 0)
#define CHECK_INVARIANT() ((void) 0)
#define AUTO_INVARIANT_CHECKER(TYPE) ((void) 0)
#endif 

#endif // __INVARIANT__H__