Line data    Source code

       1             : /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       2             :    Copyright (c) 2024 The plumed team
       3             :    (see the PEOPLE file at the root of the distribution for a list of names)
       4             : 
       5             :    See http://www.plumed.org for more information.
       6             : 
       7             :    This file is part of plumed, version 2.
       8             : 
       9             :    plumed is free software: you can redistribute it and/or modify
      10             :    it under the terms of the GNU Lesser General Public License as published by
      11             :    the Free Software Foundation, either version 3 of the License, or
      12             :    (at your option) any later version.
      13             : 
      14             :    plumed is distributed in the hope that it will be useful,
      15             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
      16             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      17             :    GNU Lesser General Public License for more details.
      18             : 
      19             :    You should have received a copy of the GNU Lesser General Public License
      20             :    along with plumed.  If not, see <http://www.gnu.org/licenses/>.
      21             : +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
      22             : 
      23             : #ifndef __PLUMED_tools_BitmaskEnum_h
      24             : #define __PLUMED_tools_BitmaskEnum_h
      25             : #include <type_traits>
      26             : 
      27             : namespace PLMD {
      28             : namespace enum_traits {
      29             : /**  @brief struct for setting up bitmask operations on enum types
      30             : 
      31             :   example usage: specialize with extra traits (see it in action in tools/Keywords.h)
      32             :   Example:
      33             : 
      34             :   Please note that in the example the `0` is not a named value (it is reserved
      35             :   as a result of mask not matching masks) and the others values are implemented as single bit
      36             :   @code{.cpp}
      37             :   enum class argType {scalar=1,grid=1<<2,vector=1<<3,matrix=1<<4};
      38             :   template<>
      39             :   struct BitmaskEnum< argType > {
      40             :     static constexpr bool has_valid = true;
      41             :     static constexpr bool has_bit_or = true;
      42             :     static constexpr bool has_bit_and = true;
      43             :   };
      44             :   @endcode
      45             :    Currenlty we have implemented:
      46             :   @code{.cpp}
      47             :    static constexpr bool has_valid = true;
      48             :   @endcode
      49             :    that activates the ::valid(enumtype) function
      50             :   @code{.cpp}
      51             :    static constexpr bool has_bit_or = true;
      52             :   @endcode
      53             :    that activates the operator|(enumtype , enumtype )
      54             :   @code{.cpp}
      55             :    static constexpr bool has_bit_and = true;
      56             :   @endcode
      57             :    that activates the operator&(enumtype , enumtype )
      58             : 
      59             :   @see valid(enumtype) for a complete example
      60             :   @see operator&(enumtype, enumtype)
      61             :   @see operator|(enumtype, enumtype)
      62             : */
      63             : template< typename enum_type >
      64             : struct BitmaskEnum {
      65             : };
      66             : } // namespace enum_traits
      67             : 
      68             : /**
      69             :  @brief Perform a bitwise AND between two enum values.
      70             : 
      71             :  @param a The first enum value.
      72             :  @param b The second enum value.
      73             :  @return The result of performing a bitwise AND between the two values.
      74             : 
      75             :  This operator is only available for enum types that have a specialization of
      76             : enum_traits::BitmaskEnum with the `has_bit_and` trait enabled.
      77             : 
      78             : Useful for checking composed values agains masks.
      79             : 
      80             : Note that the value may be a 0, and if you do not have defined the 0 as a named
      81             : value you should use valid(enumtype) to check it.
      82             : 
      83             : @see valid(enumtype) for a complete example
      84             : @see operator|(enumtype, enumtype)
      85             : */
      86             : template< typename enumtype > // SFINAE makes function contingent on trait
      87             : constexpr typename std::enable_if_t< enum_traits::BitmaskEnum< enumtype >::has_bit_and,enumtype>
      88             : operator&( enumtype a, enumtype b ) {
      89             :   return static_cast<enumtype>(static_cast<std::underlying_type_t<enumtype>>(a) &
      90       20774 :                                static_cast<std::underlying_type_t<enumtype>>(b));
      91             : }
      92             : 
      93             : /**
      94             :  @brief Perform a bitwise OR between two enum values.
      95             : 
      96             :  @param a The first enum value.
      97             :  @param b The second enum value.
      98             :  @return The result of performing a bitwise OR between the two values.
      99             : 
     100             : This operator is only available for enum types that have a specialization of
     101             : enum_traits::BitmaskEnum with the `has_bit_or` trait enabled.
     102             : 
     103             : The principal use is to compose named enum values into masks or combined options.
     104             : 
     105             : @see valid(enumtype) for a complete example
     106             : @see operator&(enumtype, enumtype)
     107             : */
     108             : template< typename enumtype > // SFINAE makes function contingent on trait
     109             : constexpr typename std::enable_if_t< enum_traits::BitmaskEnum< enumtype >::has_bit_or,enumtype>
     110             : operator|( enumtype a, enumtype b ) {
     111             :   return static_cast<enumtype>(static_cast<std::underlying_type_t<enumtype>>(a) |
     112      107885 :                                static_cast<std::underlying_type_t<enumtype>>(b));
     113             : }
     114             : 
     115             : /**
     116             :  @brief Test if an enum value is valid.
     117             : 
     118             :  @param a The enum value to test.
     119             :  @return true if the enum value is not equal to zero, false otherwise.
     120             : 
     121             : 
     122             : This operator is only available for enum types that have a specialization of
     123             : enum_traits::BitmaskEnum with the `has_valid` trait enabled.
     124             : 
     125             :  @code
     126             :  // Note: explicit declarations of the values, and
     127             :  enum class myenum { A=1,B=1<<1,C=1<<2 };
     128             :  //then activate the functions `&`, `|` and `valid`
     129             :  template<>
     130             :  struct BitmaskEnum< myenum > {
     131             :   static constexpr bool has_valid   = true;
     132             :   static constexpr bool has_bit_or  = true;
     133             :   static constexpr bool has_bit_and = true;
     134             :  };
     135             :  //...code...
     136             :  myenum val = myenum::A | myenum::C;
     137             :  std::cout <<"val is "<< int(val) << "\n";
     138             :  if(PLMD::valid( val & myenum::A)) {
     139             :    std::cout << "val has A\n";
     140             :  }
     141             :  if(PLMD::valid(val & myenum::B)) {
     142             :    std::cout << "val has B\n";
     143             :  }
     144             :  if(PLMD::valid(val & myenum::C)) {
     145             :    std::cout << "val has C\n";
     146             :  }
     147             :  if(PLMD::valid(val & (myenum::A | myenum::C))) {
     148             :    std::cout << "val has C and A\n";
     149             :  }
     150             :  //will produce:
     151             :  ///>val is 5
     152             :  ///>val has A
     153             :  ///>val has C
     154             :  ///>val has C and A
     155             :  @endcode
     156             : 
     157             : @see operator|(enumtype, enumtype)
     158             : @see operator&(enumtype, enumtype)
     159             : */
     160             : template< typename enumtype > // SFINAE makes function contingent on trait
     161             : constexpr typename std::enable_if_t< enum_traits::BitmaskEnum< enumtype >::has_valid,bool>
     162             : valid( enumtype a) {
     163             :   return static_cast<std::underlying_type_t<enumtype>>(a)!=0;
     164             : }
     165             : } // namespace PLMD
     166             : 
     167             : #endif //__PLUMED_tools_BitmaskEnum_h