ThePEG/Utilities/HoldFlag.h

0001 // -*- C++ -*-
0002 //
0003 // HoldFlag.h is a part of ThePEG - Toolkit for HEP Event Generation
0004 // Copyright (C) 1999-2019 Leif Lonnblad
0005 //
0006 // ThePEG is licenced under version 3 of the GPL, see COPYING for details.
0007 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
0008 //
0009 #ifndef ThePEG_HoldFlag_H
0010 #define ThePEG_HoldFlag_H
0011 // This is the declaration of the HoldFlag class.
0012
0013 namespace ThePEG {
0014
0015 template <typename T = bool>
0016 /**
0017  * <code>HoldFlag</code> objects are used to temporarily change the value
0018  * of an object, restoring the original value when the
0019  * <code>HoldFlag</code> object is destructed.
0020  *
0021  * @see Level
0022  */
0023 class HoldFlag {
0024
0025 public:
0026
0027   /**
0028    * Constructor setting a temporary value for the given object.
0029    * @param newFlag the object which value is temporarily changed.
0030    * @param holdFlag the temporary value for the newFlag object.
0031    */
0032   HoldFlag(T & newFlag, const T & holdFlag)
0033     : theFlag(newFlag), oldFlag(holdFlag) { std::swap(theFlag, oldFlag); }
0034
0035   /**
0036    * Constructor setting the a temporary value for the given object.
0037    * @param newFlag the object which value is temporarily changed.
0038    * @param holdFlag the temporary value for the newFlag object.
0039    * @param finalFlag the newFlag object will be given the value
0040    * finalFlag when the HoldFlag object is destroyed.
0041    */
0042   HoldFlag(T & newFlag, const T & holdFlag, const T & finalFlag)
0043     : theFlag(newFlag), oldFlag(holdFlag)
0044   {
0045     std::swap(theFlag, oldFlag);
0046     oldFlag = finalFlag;
0047   }
0048
0049   /**
0050    * Destructor. Restores the corresponding object to its original
0051    * value.
0052    */
0053   ~HoldFlag() { std::swap(theFlag, oldFlag); }
0054
0055 private:
0056
0057   /**
0058    * The object to be changed.
0059    */
0060   T & theFlag;
0061
0062   /**
0063    * The value which will be restored when this is destroyed.
0064    */
0065   T oldFlag;
0066
0067   /**
0068    * Default constructor is private and not implemented.
0069    */
0070   HoldFlag();
0071
0072   /**
0073    * Copy constructor is private and not implemented.
0074    */
0075   HoldFlag(const HoldFlag &);
0076
0077   /**
0078    * Assignment is private and not implemented.
0079    */
0080   HoldFlag & operator=(const HoldFlag &) = delete;
0081
0082 };
0083
0084 /**
0085  * Specialization of HoldFlag for boolean variables.
0086  */
0087 template <>
0088 class HoldFlag<bool> {
0089
0090 public:
0091
0092   /**
0093    * Constructor setting the a temporary value for the bool variable.
0094    * @param newFlag the boolean variable which value is temporarily changed.
0095    * @param holdFlag the temporary value for the newFlag variable.
0096    */
0097   HoldFlag(bool & newFlag, bool holdFlag = true)
0098     : theFlag(newFlag), oldFlag(newFlag) { theFlag = holdFlag; }
0099
0100   /**
0101    * Constructor setting the a temporary value for the bool variable.
0102    * @param newFlag the boolean variable which value is temporarily changed.
0103    * @param holdFlag the temporary value for the newFlag variable.
0104    * @param finalFlag the newFlag variable will be given the value
0105    * finalFlag when the HoldFlag object is destroyed.
0106    */
0107   HoldFlag(bool & newFlag, bool holdFlag, bool finalFlag)
0108     : theFlag(newFlag), oldFlag(finalFlag) { theFlag = holdFlag; }
0109
0110   /**
0111    * Destructor. Restores the corresponding variable to its original
0112    * value.
0113    */
0114   ~HoldFlag() { theFlag = oldFlag; }
0115
0116 private:
0117
0118   /**
0119    * The variable to be changed.
0120    */
0121   bool & theFlag;
0122
0123   /**
0124    * The value which will be restored when this is destroyed.
0125    */
0126   bool oldFlag;
0127
0128   /**
0129    * Default constructor is private and not implemented.
0130    */
0131   HoldFlag();
0132
0133   /**
0134    * Copy constructor is private and not implemented.
0135    */
0136   HoldFlag(const HoldFlag &);
0137
0138   /**
0139    * Assignment is private and not implemented.
0140    */
0141   HoldFlag & operator=(const HoldFlag &) = delete;
0142
0143 };
0144
0145 }
0146
0147 #endif /* ThePEG_HoldFlag_H */