text: ////////////////////////////////////////////////////////////////////////////////
  // The Loki Library
  // Copyright (c) 2009 by Fedor Pikus & Rich Sposato
  // The copyright on this file is protected under the terms of the MIT license.
  //
  // Permission to use, copy, modify, distribute and sell this software for any
  //     purpose is hereby granted without fee, provided that the above copyright
  //     notice appear in all copies and that both that copyright notice and this
  //     permission notice appear in supporting documentation.
  //
  // The author makes no claims about the suitability of this software for any
  //     purpose. It is provided "as is" without express or implied warranty.
  ////////////////////////////////////////////////////////////////////////////////
  
  // $Id$
  
  
  #ifndef LOKI_INCLUDED_SAFE_BIT_FIELDS_H
  #define LOKI_INCLUDED_SAFE_BIT_FIELDS_H
  
  #include <cstdlib>
  #include <assert.h>
  #include <loki/static_check.h>
  
  
  namespace Loki
  {
  
  /*
   ==========================================================================================================================================
     SafeBitField                    - type-safe class for bit fields.
     SafeBitConst                    - type-safe class for bit constants.
     SafeBitField is designed to be a [almost] drop-in replacement for integer flags and bit fields where individual bits are set and checked
     using symbolic names for flags:
  
        typedef unsigned long Labels_t;
        Labels_t labels;
        const Labels_t Label_A = 0x00000001;
        const Labels_t Label_B = 0x00000002;
        ...
        labels |= Label_B;
        if ( labels & Label_A ) { ... }
  
     Such code offers no protection against mismatching bit constants and bit fields:
  
        typedef unsigned long Kinds_t;
        Kinds_t kinds;
        const Kinds_t Kind_A = 0x00000004;
        ...
        if ( kinds & Label_A ) { ... } // Error but compiles
  
     SafeBitField is a drop-in replacement which generates a unique type for each bit field. Bit fields of different types cannot be applied
     to each other:
  
        LOKI_BIT_FIELD( unsigned long ) Labels_t;
        Labels_t labels;
        LOKI_BIT_CONST( Labels_t, Label_A, 1 );                                // 0x0001 - 1st bit is set
        LOKI_BIT_CONST( Labels_t, Label_B, 2 );                                // 0x0002 - 1st bit is set
        ...
        LOKI_BIT_FIELD( unsigned long ) Kinds_t;
        Kinds_t kinds;
        LOKI_BIT_CONST( Kinds_t, Kind_A, 3 );                                  // 0x0004 - 1st bit is set
        ...
        if ( kinds & Label_A ) { ... } // Does not compile
  
     Several other kinds of bit field misuse are caught by safe bit fields:
  
        if ( kinds & Kind_A == 0 ) { ... }
        if ( kinds && Kind_A ) { ... }
  
     There are few cases where drop-in replacement does not work:
  
     1. Operations involving bit fields and unnamed integers. Usually the integer in question is 0:
  
           Labels_t labels = 0;  // No longer compiles
           if ( ( labels & Label_A ) == 0 ) { ... } // Also does not compile
  
        The solution is to use named bit constants, including the one for 0:
  
           LOKI_BIT_CONST( Labels_t, Label_None, 0 );                               // 0x0000 - No bit is set
           Labels_t labels = Label_None; // Or just Labels_t labels; - constructor initializes to 0
           if ( ( labels & Label_A ) == Label_None ) { ... } // // Or just if ( labels & Label_A ) { ... }
  
     2. I/O and other operations which require integer variables and cannot be modified:
  
           void write_to_db( unsigned int word );
           Labels_t labels;
           write_to_db( labels ); // No longer compiles
  
        This problem is solved by reinterpreting the bit fields as an integer, the user is responsible for using the right
        type of integer:
  
           write_to_db( *((Labels_t::bit_word_t*)(&labels)) );
  
     ==========================================================================================================================================
  */
  
  /// @par Non-Templated Initialization.
  /// Not all compilers support template member functions where the template
  /// arguments are not deduced but explicitly specified.  For these broken
  /// compilers, a non-template make_bit_const() function is provided instead of
  /// the template one. The only downside is that instead of compile-time checking
  /// of the index argument, it does runtime checking.
  #if defined(__SUNPRO_CC) || ( defined(__GNUC__) && (__GNUC__ < 3) )
      #define LOKI_BIT_FIELD_NONTEMPLATE_INIT
  #endif
  
  /// @par Forbidding Conversions.
  /// This incomplete type prevents compilers from instantiating templates for
  /// type conversions which should not happen. This incomplete type must be a
  /// template: if the type is incomplete at the point of template definition,
  /// the  template is illegal (although the standard allows compilers to accept
  /// or reject such code, §14.6/, so some compilers will not issue diagnostics
  /// unless template is instantiated). The standard-compliant way is to defer
  /// binding to the point of instantiation by making the incomplete type itself
  /// a template.
  template < typename > struct Forbidden_conversion;  // This struct must not be defined!
  
  /// Forward declaration of the field type.
  template <
      unsigned int unique_index,
      typename word_t = unsigned long
  > class SafeBitField;
  
  ////////////////////////////////////////////////////////////////////////////////
  /// \class SafeBitConst Bit constants.
  ///  This class defines a bit-field constant - a collection of unchanging bits
  ///  used to compare to bit-fields.  Instances of this class are intended to act
  ///  as labels for bit-fields.
  ///
  /// \par Safety
  ///  - This class provides operations used for comparisons and conversions, but
  ///    no operations which may modify the value.
  ///  - As a templated class, it provides type-safety so bit values and constants
  ///    used for different reasons may not be unknowingly compared to each other.
  ///  - The unique_index template parameter insures the unique type of each bit
  ///    bit-field.  It shares the unique_index with a similar SafeBitField.
  ///  - Its operations only allow comparisons to other bit-constants and
  ///    bit-fields of the same type.
  ////////////////////////////////////////////////////////////////////////////////
  
  template
  <
      unsigned int unique_index,
      typename word_t = unsigned long
  >
  class SafeBitConst
  {
  public:
  
      /// Type of the bit field is available if needed.
      typedef word_t bit_word_t;
      /// Corresponding field type.
      typedef SafeBitField< unique_index, word_t > field_t;
      /// Typedef is not allowed in friendship declaration.
      friend class SafeBitField< unique_index, word_t >;
  
      // Static factory constructor, creates a bit constant with one bit set. The position of the bit is given by the template parameter,
      // bit 1 is the junior bit, i.e. make_bit_const<1>() returns 1. Bit index 0 is a special case and returns 0.
      // This function should be used only to initialize the static bit constant objects.
      // This function will not compile if the bit index is outside the vaild range.
      // There is also a compile-time assert to make sure the size of the class is the same as the size of the underlaying integer type.
      // This assert could go into the constructor, but aCC does not seem to understand sizeof(SafeBitConst) in the constructor.
      //
  #ifndef LOKI_BIT_FIELD_NONTEMPLATE_INIT
      template < unsigned int i > static SafeBitConst make_bit_const()
      {
          LOKI_STATIC_CHECK( i <= ( 8 * sizeof(word_t) ), Index_is_beyond_size_of_data );
          LOKI_STATIC_CHECK( sizeof(SafeBitConst) == sizeof(word_t), Object_size_does_not_match_data_size );
          // Why check for ( i > 0 ) again inside the shift if the shift
          // can never be evaluated for i == 0? Some compilers see shift by ( i - 1 )
          // and complain that for i == 0 the number is invalid, without
          // checking that shift needs evaluating.
          return SafeBitConst( ( i > 0 ) ? ( word_t(1) << ( ( i > 0 ) ? ( i - 1 ) : 0 ) ) : 0 );
      }
  #else
      static SafeBitConst make_bit_const( unsigned int i )
      {
          LOKI_STATIC_CHECK( sizeof(SafeBitConst) == sizeof(word_t), Object_size_does_not_match_data_size );
          assert( i <= ( 8 * sizeof(word_t) ) ); // Index is beyond size of data.
          // Why check for ( i > 0 ) again inside the shift if the shift
          // can never be evaluated for i == 0? Some compilers see shift by ( i - 1 )
          // and complain that for i == 0 the number is invalid, without
          // checking that shift needs evaluating.
          return SafeBitConst( ( i > 0 ) ? ( word_t(1) << ( ( i > 0 ) ? ( i - 1 ) : 0 ) ) : 0 );
      }
  #endif
  
      /// Default constructor allows client code to construct bit fields on the stack.
      SafeBitConst() : word( 0 ) {}
  
      /// Copy constructor.
      SafeBitConst( const SafeBitConst& rhs ) : word( rhs.word ) {}
  
      /// Comparison operators which take a constant bit value.
      bool operator == ( const SafeBitConst & rhs ) const { return word == rhs.word; }
      bool operator != ( const SafeBitConst & rhs ) const { return word != rhs.word; }
      bool operator <  ( const SafeBitConst & rhs ) const { return word <  rhs.word; }
      bool operator >  ( const SafeBitConst & rhs ) const { return word >  rhs.word; }
      bool operator <= ( const SafeBitConst & rhs ) const { return word <= rhs.word; }
      bool operator >= ( const SafeBitConst & rhs ) const { return word >= rhs.word; }
  
      /// Comparision operators for mutable bit fields.
      bool operator == ( const field_t & rhs ) const { return word == rhs.word; }
      bool operator != ( const field_t & rhs ) const { return word != rhs.word; }
      bool operator <  ( const field_t & rhs ) const { return word <  rhs.word; }
      bool operator >  ( const field_t & rhs ) const { return word >  rhs.word; }
      bool operator <= ( const field_t & rhs ) const { return word <= rhs.word; }
      bool operator >= ( const field_t & rhs ) const { return word >= rhs.word; }
  
      /// Bitwise operations.  Operation-assignment operators are not needed,
      /// since bit constants cannot be changed after they are initialized.
      const SafeBitConst operator | ( const SafeBitConst & rhs ) const { return SafeBitConst( word | rhs.word ); }
      const SafeBitConst operator & ( const SafeBitConst & rhs ) const { return SafeBitConst( word & rhs.word ); }
      const SafeBitConst operator ^ ( const SafeBitConst & rhs ) const { return SafeBitConst( word ^ rhs.word ); }
      const SafeBitConst operator ~ ( void ) const { return SafeBitConst( ~word ); }
  
      /// These bitwise operators return a bit-field instead of a bit-const.
      field_t operator | ( const field_t & rhs ) const { return field_t( word | rhs.word ); }
      field_t operator & ( const field_t & rhs ) const { return field_t( word & rhs.word ); }
      field_t operator ^ ( const field_t & rhs ) const { return field_t( word ^ rhs.word ); }
  
      /// The shift operators move bits inside the bit field.  These are useful in
      /// loops which act over bit fields and increment them.
      const SafeBitConst operator << ( unsigned int s ) const { return SafeBitConst( word << s ); }
      const SafeBitConst operator >> ( unsigned int s ) const { return SafeBitConst( word >> s ); }
  
      /// Word size is also the maximum number of different bit fields for a given word type.
      static size_t size() { return ( 8 * sizeof( word_t ) ); }
  
  private:
  
      /// Copy-assignment operator is not implemented since it does not make sense
      /// for a constant object.
      SafeBitConst operator = ( const SafeBitConst & rhs );
  
      // Private constructor from an integer type.
      explicit SafeBitConst( word_t init ) : word( init ) {}
  
      /// This data stores a single bit value.  It is declared const to enforce
      // constness for all functions of this class.
      const word_t word;
  
      // Here comes the interesting stuff: all the operators designed to
      // trap unintended conversions and make them not compile.
      // Operators below handle code like this:
      //    SafeBitField<1> label1;
      //    SafeBitField<2> label2;
      //    if ( label1 & label2 ) { ... }
  
      // These operators are private, and will not instantiate in any
      // event because of the incomplete Forbidden_conversion struct.
      template < typename T > SafeBitConst operator|( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitConst operator&( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitConst operator^( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitConst operator|=( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitConst operator&=( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitConst operator^=( T ) const { Forbidden_conversion< T > wrong; return *this; }
  
      // And the same thing for comparisons: private and unusable.
      //    if ( label1 == label2 ) { ... }
      template < typename T > bool operator==( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator!=( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator<( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator>( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator<=( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator>=( const T ) const { Forbidden_conversion< T > wrong; return true; }
  };
  
  
  ////////////////////////////////////////////////////////////////////////////////
  /// \class SafeBitConst Bit constants.
  ///  This class defines a bit-field constant - a collection of unchanging bits
  ///  used to compare to bit-fields.  Instances of this class are intended to
  ///  store bit values.
  ///
  /// \par Safety
  ///  - This class provides operations used for comparisons and conversions, and
  ///    also operations which may safely modify the value.
  ///  - As a templated class, it provides type-safety so bit values and constants
  ///    used for different reasons may not be unknowingly compared to each other.
  ///  - The unique_index template parameter insures the unique type of each bit
  ///    bit-field.  It shares the unique_index with a similar SafeBitConst.
  ///  - Its operations only allow comparisons to other bit-constants and
  ///    bit-fields of the same type.
  ////////////////////////////////////////////////////////////////////////////////
  
  template
  <
      unsigned int unique_index,
      typename word_t
  >
  class SafeBitField
  {
  public:
  
      /// Type of the bit field is available if needed.
      typedef word_t bit_word_t;
      /// Corresponding field type.
      typedef SafeBitConst< unique_index, word_t > const_t;
      /// Typedef is not allowed in friendship declaration.
      friend class SafeBitConst<unique_index, word_t>;
  
      /// Default constructor allows client code to construct bit fields on the stack.
      SafeBitField() : word( 0 ) {}
  
      /// Copy constructor and assignment operators.
      SafeBitField( const SafeBitField & rhs ) : word( rhs.word ) {}
      SafeBitField & operator = ( const SafeBitField & rhs ) { word = rhs.word; return *this; }
  
      /// Copy constructor and assignment operators from constant bit fields.
      SafeBitField( const const_t & rhs ) : word( rhs.word ) {}
      SafeBitField & operator = ( const const_t & rhs ) { word = rhs.word; return *this; }
  
      /// These comparison operators act on bit-fields of the same type.
      bool operator == ( const SafeBitField & rhs ) const { return word == rhs.word; }
      bool operator != ( const SafeBitField & rhs ) const { return word != rhs.word; }
      bool operator <  ( const SafeBitField & rhs ) const { return word <  rhs.word; }
      bool operator >  ( const SafeBitField & rhs ) const { return word >  rhs.word; }
      bool operator <= ( const SafeBitField & rhs ) const { return word <= rhs.word; }
      bool operator >= ( const SafeBitField & rhs ) const { return word >= rhs.word; }
  
      /// These comparison operators act on bit-constants of a similar type.
      bool operator == ( const const_t & rhs ) const { return word == rhs.word; }
      bool operator != ( const const_t & rhs ) const { return word != rhs.word; }
      bool operator <  ( const const_t & rhs ) const { return word <  rhs.word; }
      bool operator >  ( const const_t & rhs ) const { return word >  rhs.word; }
      bool operator <= ( const const_t & rhs ) const { return word <= rhs.word; }
      bool operator >= ( const const_t & rhs ) const { return word >= rhs.word; }
  
      /// Bitwise operations that use bit-fields.
      SafeBitField operator |  ( const SafeBitField & rhs ) const { return SafeBitField( word | rhs.word ); }
      SafeBitField operator &  ( const SafeBitField & rhs ) const { return SafeBitField( word & rhs.word ); }
      SafeBitField operator ^  ( const SafeBitField & rhs ) const { return SafeBitField( word ^ rhs.word ); }
      SafeBitField operator ~  ( void ) const { return SafeBitField( ~word ); }
      SafeBitField operator |= ( const SafeBitField & rhs ) { word |= rhs.word; return SafeBitField( *this ); }
      SafeBitField operator &= ( const SafeBitField & rhs ) { word &= rhs.word; return SafeBitField( *this ); }
      SafeBitField operator ^= ( const SafeBitField & rhs ) { word ^= rhs.word; return SafeBitField( *this ); }
  
      /// Bitwise operators that use bit-constants.
      SafeBitField operator |  ( const_t rhs ) const { return SafeBitField( word | rhs.word ); }
      SafeBitField operator &  ( const_t rhs ) const { return SafeBitField( word & rhs.word ); }
      SafeBitField operator ^  ( const_t rhs ) const { return SafeBitField( word ^ rhs.word ); }
      SafeBitField operator |= ( const_t rhs ) { word |= rhs.word; return SafeBitField( *this ); }
      SafeBitField operator &= ( const_t rhs ) { word &= rhs.word; return SafeBitField( *this ); }
      SafeBitField operator ^= ( const_t rhs ) { word ^= rhs.word; return SafeBitField( *this ); }
  
      // Conversion to bool.
      // This is a major source of headaches, but it's required to support code like this:
      //    const static SafeBitConst<1> Label_value = SafeBitConst<1>::make_bit_const<1>();
      //    SafeBitField<1> label;
      //    if ( label & Label_value ) { ... } // Nice...
      //
      // The downside is that this allows all sorts of nasty conversions. Without additional precautions, bit fields of different types
      // can be converted to bool and then compared or operated on:
      //    SafeBitField<1> label1;
      //    SafeBitField<2> label2;
      //    if ( label1 == label2 ) { ... } // Yuck!
      //    if ( label1 & label2 ) { ... } // Blech!
      //
      // It is somewhat safer to convert to a pointer, at least pointers to different types cannot be readilly compared, and there are no
      // bitwise operations on pointers, but the conversion from word_t to a pointer can have run-time cost if they are of different size.
      //
      operator const bool() const { return ( 0 != word ); }
  
      // Shift operators shift bits inside the bit field. Does not make
      // sense, most of the time, except perhaps to loop over labels and
      // increment them.
      SafeBitField operator <<  ( unsigned int s ) { return SafeBitField( word << s ); }
      SafeBitField operator >>  ( unsigned int s ) { return SafeBitField( word >> s ); }
      SafeBitField operator <<= ( unsigned int s ) { word <<= s; return *this; }
      SafeBitField operator >>= ( unsigned int s ) { word >>= s; return *this; }
  
      // Word size is also the maximum number of different bit fields for
      // a given word type.
      static size_t size( void ) { return ( 8 * sizeof( word_t ) ); }
  
  private:
  
      /// Private constructor from an integer type. Don't put too much stock into
      /// explicit declaration, it's better than nothing but does not solve all
      /// problems with undesired conversions because SafeBitField coverts to bool.
      explicit SafeBitField( word_t init ) : word( init ) {}
  
      /// This stores the bits.
      word_t word;
  
      // Here comes the interesting stuff: all the operators designed to
      // trap unintended conversions and make them not compile.
      // Operators below handle code like this:
      //    SafeBitField<1> label1;
      //    SafeBitField<2> label2;
      //    if ( label1 & label2 ) { ... }
  
      // These operators are private, and will not instantiate in any
      // event because of the incomplete Forbidden_conversion struct.
      template < typename T > SafeBitField operator |  ( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitField operator &  ( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitField operator ^  ( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitField operator |= ( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitField operator &= ( T ) const { Forbidden_conversion< T > wrong; return *this; }
      template < typename T > SafeBitField operator ^= ( T ) const { Forbidden_conversion< T > wrong; return *this; }
  
      // And the same thing for comparisons:
      //    if ( label1 == label2 ) { ... }
      template < typename T > bool operator == ( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator != ( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator <  ( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator >  ( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator <= ( const T ) const { Forbidden_conversion< T > wrong; return true; }
      template < typename T > bool operator >= ( const T ) const { Forbidden_conversion< T > wrong; return true; }
  };
  
  // The above template member operators catch errors when the first
  // argument to a binary operator is a label, but they don't work when
  // the first argument is an integer and the second one is a label: the
  // label converts to bool and the operator is performed on two integers.
  // These operators catch errors like this:
  //    SafeBitField<1> label1;
  //    SafeBitField<2> label2;
  //    if ( !label1 & label2 ) { ... }
  // where the first label is converted to bool (these errors cannot be
  // caught by member operators of SafeBitField class because the first
  // argument is not SafeBitField but bool.
  //
  // If used, these operators will not instantiate because of the
  // incomplete Forbidden_conversion struct.
  
  template < unsigned int unique_index, typename word_t >
  inline SafeBitField< unique_index, word_t > operator & ( bool, SafeBitField< unique_index, word_t > rhs )
  {
      Forbidden_conversion<word_t> wrong;
      return rhs;
  }
  
  template < unsigned int unique_index, typename word_t >
  inline SafeBitField< unique_index, word_t > operator | ( bool, SafeBitField< unique_index, word_t > rhs )
  {
      Forbidden_conversion< word_t > wrong;
      return rhs;
  }
  
  template < unsigned int unique_index, typename word_t >
  inline SafeBitField< unique_index, word_t > operator ^ ( bool, SafeBitField< unique_index, word_t > rhs )
  {
      Forbidden_conversion< word_t > wrong;
      return rhs;
  }
  
  template < unsigned int unique_index, typename word_t >
  inline SafeBitField< unique_index, word_t > operator == ( bool, SafeBitField< unique_index, word_t > rhs )
  {
      Forbidden_conversion< word_t > wrong;
      return rhs;
  }
  
  template < unsigned int unique_index, typename word_t >
  inline SafeBitField< unique_index, word_t > operator != ( bool, SafeBitField< unique_index, word_t > rhs )
  {
      Forbidden_conversion< word_t > wrong;
      return rhs;
  }
  
  // Finally, few macros. All macros are conditionally defined to use the SafeBitField classes if LOKI_SAFE_BIT_FIELD is defined. Otherwise,
  // the macros fall back on the use of typedefs and integer constants. This provides no addititonal safety but allows the code to support the
  // mixture of compilers which are broken to different degrees.
  #define LOKI_SAFE_BIT_FIELD
  
  // The first macro helps to declare new bit field types:
  // LOKI_BIT_FIELD( ulong ) field_t;
  // This creates a typedef field_t for SafeBitField<unique_index, ulong> where index is the current line number. Since line numbers __LINE__ are counted
  // separately for all header files, this ends up being the same type in all files using the header which defines field_t.
  #ifdef LOKI_SAFE_BIT_FIELD
      #define LOKI_BIT_FIELD( word_t ) typedef SafeBitField<__LINE__, word_t>
  #else
      #define LOKI_BIT_FIELD( word_t ) typedef word_t
  #endif // LOKI_SAFE_BIT_FIELD
  
  // The second macro helps to declare static bit constants:
  // LOKI_BIT_CONST( field_t, Label_1, 1 );
  // creates new bit field object named Label_1 of type field_t which represents the field with the 1st (junior) bit set.
  #ifdef LOKI_SAFE_BIT_FIELD
      #ifndef LOKI_BIT_FIELD_NONTEMPLATE_INIT
          #define LOKI_BIT_CONST( field_t, label, bit_index ) \
              static const field_t::const_t label = field_t::const_t::make_bit_const<bit_index>()
      #else
          #define LOKI_BIT_CONST( field_t, label, bit_index ) \
              static const field_t::const_t label = field_t::const_t::make_bit_const( bit_index )
      #endif // LOKI_BIT_FIELD_NONTEMPLATE_INIT
  #else
      inline size_t make_bit_const( size_t i ) { return ( i > 0 ) ? ( size_t(1) << ( ( i > 0 ) ? ( i - 1 ) : 0 ) ) : 0; }
      #define LOKI_BIT_CONST( field_t, label, bit_index ) static const field_t label = make_bit_const( bit_index )
  #endif // LOKI_SAFE_BIT_FIELD
  
  // The third macro helps to declare complex bit constants which are combination of several bits:
  // LOKI_BIT_CONSTS( field_t, Label12 ) = Label_1 | Label_2;
  #ifdef LOKI_SAFE_BIT_FIELD
      #define LOKI_BIT_CONSTS( field_t, label ) static const field_t::const_t label
  #else
      #define LOKI_BIT_CONSTS( field_t, label ) static const field_t label
  #endif // LOKI_SAFE_BIT_FIELD
  
  // The fourth macro helps to declare the maximum number of bit constants for a given type:
  // static const size_t count = LOKI_BIT_FIELD_COUNT( field_t );
  // declared a variable "count" initialized to field_t::size()
  #ifdef LOKI_SAFE_BIT_FIELD
      #define LOKI_BIT_FIELD_COUNT( field_t ) field_t::size()
  #else
      #define LOKI_BIT_FIELD_COUNT( field_t ) ( 8 * sizeof(field_t) )
  #endif // LOKI_SAFE_BIT_FIELD
  
  } // namespace Loki
  
  #endif // LOKI_INCLUDED_SAFE_BIT_FIELDS_H
  