Line data    Source code

       1             : #pragma once
       2             : 
       3             : #include <compare>
       4             : #include <ostream>
       5             : #include <type_traits>
       6             : #include <utility>
       7             : 
       8             : #include "fmt/format.h"
       9             : 
      10             : namespace ipc
      11             : {
      12             : 
      13             : /**
      14             :  * Traits class that enables an enum type to be used in the typesafe enum flag.
      15             :  * Specialize for your enum and derive from std::true_type.
      16             :  * This enables usage of the enum class as flags using the usual | and & bitwise operators.
      17             :  * Example:
      18             :  * ```
      19             :  * enum class Foo { None = 0, Flag1 = 0B1, Flag2 = 0B10, Flag3 = 0B100, };
      20             :  * template<> struct EnumFlagTraits<Foo> : std::true_type { }
      21             :  * FlagType<Foo> flags = Flag1 | Flag3;
      22             :  * //...
      23             :  * if (flags & Foo::Flag1) { printf("Flag1 is set."); }
      24             :  * ```
      25             :  */
      26             : template<class E>
      27             : struct EnumFlagTraits : std::false_type
      28             : {
      29             : };
      30             : 
      31             : /**
      32             :  * A type safe bitfield based on flags defined by an enum type.
      33             :  * Ensures that only values of the specified enum type are set.
      34             :  * @tparam E an enum type whose members are flags.
      35             :  */
      36             : template<class E>
      37             : struct FlagType
      38             : {
      39             :     static_assert(std::is_enum_v<E>);
      40             : 
      41             :     /**
      42             :      * The combined values of all flags.
      43             :      */
      44          12 :     std::underlying_type_t<E> value;
      45             : 
      46             :     /**
      47             :      * Default constructor.
      48             :      * No flags are set.
      49             :      */
      50           2 :     FlagType() : value(0) { }
      51             : 
      52             :     /**
      53             :      * Constructor from the underlying type of the enum type.
      54             :      */
      55          58 :     explicit FlagType(std::underlying_type_t<E> v) : value(v) { }
      56             :     
      57             :     /**
      58             :      * Constructor to set a single flag.
      59             :      * Implicit conversion from E to FlagType<E>.
      60             :      */
      61          32 :     FlagType(E e) : value(std::underlying_type_t<E>(e)) { }
      62             : 
      63             :     /**
      64             :      * Default comparison operator.
      65             :      * Equal if the same flags are set in both operands.
      66             :      * Can also be used to compare with single flags due to implicit conversion.
      67             :      * @{
      68             :      */
      69          12 :     bool operator==(const FlagType& b) const = default;
      70             :     bool operator!=(const FlagType& b) const = default;
      71             :     /** @} */
      72             : 
      73             :     /**
      74             :      * Check if a specific flag is set.
      75             :      * `if (f.is_set(a))` is equivalent to `if (f & a)`.
      76             :      */
      77           1 :     bool is_set(E e) const { return (*this & e) != 0; }
      78             : 
      79             :     /**
      80             :      * Check if any flag is set.
      81             :      */
      82          39 :     bool any() const { return value != 0; }
      83             : 
      84             :     /**
      85             :      * Check if any flag is set.
      86             :      */
      87          37 :     operator bool() const { return any(); }
      88             : 
      89             :     /**
      90             :      * Form the union of the flags from two bitfields in place.
      91             :      */
      92           2 :     FlagType& operator|=(const FlagType& b) { return (*this = (*this | b)); }
      93             : 
      94             :     /**
      95             :      * Output the underlying flag value.
      96             :      */
      97             :     std::ostream& operator<<(std::ostream& os)
      98             :     {
      99             :         os << E(value);
     100             :         return os;
     101             :     }
     102             : };
     103             : 
     104             : /**
     105             :  * Extension for the fmt library.
     106             :  */
     107             : template<class E, class = std::enable_if_t<EnumFlagTraits<E>::value>>
     108             : auto format_as(FlagType<E> flags)
     109             : {
     110             :     return flags.value;
     111             : }
     112             : 
     113             : /**
     114             :  * Union of two flags.
     115             :  */
     116             : template<class E>
     117           7 : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator|(E a, E b)
     118             : {
     119           7 :     return FlagType<E>{std::underlying_type_t<E>(a) | std::underlying_type_t<E>(b)};
     120             : }
     121             : 
     122             : /**
     123             :  * Union of a flag and an exisiting set.
     124             :  * @{
     125             :  */
     126             : template<class E>
     127           3 : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator|(FlagType<E> a, E b)
     128             : {
     129           3 :     return FlagType<E>{a.value | std::underlying_type_t<E>(b)};
     130             : }
     131             : template<class E>
     132           1 : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator|(E a, FlagType<E> b)
     133             : {
     134           1 :     return FlagType<E>{std::underlying_type_t<E>(a) | b.value};
     135             : }
     136             : /** @} */
     137             : 
     138             : /**
     139             :  * Form the union of the flags from two bitfields.
     140             :  */
     141             : template<class E>
     142           3 : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator|(FlagType<E> a, FlagType<E> b)
     143             : {
     144           3 :     return FlagType<E>{a.value | b.value};
     145             : }
     146             : 
     147             : /**
     148             :  * Intersection of two flags.
     149             :  * Use with `FlagType::any` or `FlagType::operator bool` to check if the flag is set.
     150             :  */
     151             : template<class E>
     152             : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator&(E a, E b)
     153             : {
     154             :     return FlagType<E>{std::underlying_type_t<E>(a) & std::underlying_type_t<E>(b)};
     155             : }
     156             : 
     157             : /**
     158             :  * Intersection of a bitfield and a single flag.
     159             :  * Use with `FlagType::any` or `FlagType::operator bool` to check if the flag is set.
     160             :  * @{
     161             :  */
     162             : template<class E>
     163          36 : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator&(FlagType<E> a, E b)
     164             : {
     165          36 :     return FlagType<E>{a.value & std::underlying_type_t<E>(b)};
     166             : }
     167             : template<class E>
     168           1 : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator&(E b, FlagType<E> a)
     169             : {
     170           1 :     return FlagType<E>{a.value & std::underlying_type_t<E>(b)};
     171             : }
     172             : /** @} */
     173             : 
     174             : /**
     175             :  * Intersection of two bit fields.
     176             :  */
     177             : template<class E>
     178           1 : std::enable_if_t<EnumFlagTraits<E>::value, FlagType<E>> operator&(FlagType<E> a, FlagType<E> b)
     179             : {
     180           1 :     return FlagType<E>{a.value & std::underlying_type_t<E>(b)};
     181             : }
     182             : 
     183             : } // namespace ipc