1/* Copyright (C) 2015-2020 Free Software Foundation, Inc. 2 3 This file is part of GDB. 4 5 This program is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 17 18#ifndef COMMON_ENUM_FLAGS_H 19#define COMMON_ENUM_FLAGS_H 20 21/* Type-safe wrapper for enum flags. enum flags are enums where the 22 values are bits that are meant to be ORed together. 23 24 This allows writing code like the below, while with raw enums this 25 would fail to compile without casts to enum type at the assignments 26 to 'f': 27 28 enum some_flag 29 { 30 flag_val1 = 1 << 1, 31 flag_val2 = 1 << 2, 32 flag_val3 = 1 << 3, 33 flag_val4 = 1 << 4, 34 }; 35 DEF_ENUM_FLAGS_TYPE(enum some_flag, some_flags); 36 37 some_flags f = flag_val1 | flag_val2; 38 f |= flag_val3; 39 40 It's also possible to assign literal zero to an enum flags variable 41 (meaning, no flags), dispensing adding an awkward explicit "no 42 value" value to the enumeration. For example: 43 44 some_flags f = 0; 45 f |= flag_val3 | flag_val4; 46 47 Note that literal integers other than zero fail to compile: 48 49 some_flags f = 1; // error 50*/ 51 52#ifdef __cplusplus 53 54/* Traits type used to prevent the global operator overloads from 55 instantiating for non-flag enums. */ 56template<typename T> struct enum_flags_type {}; 57 58/* Use this to mark an enum as flags enum. It defines FLAGS as 59 enum_flags wrapper class for ENUM, and enables the global operator 60 overloads for ENUM. */ 61#define DEF_ENUM_FLAGS_TYPE(enum_type, flags_type) \ 62 typedef enum_flags<enum_type> flags_type; \ 63 template<> \ 64 struct enum_flags_type<enum_type> \ 65 { \ 66 typedef enum_flags<enum_type> type; \ 67 } 68 69/* Until we can rely on std::underlying type being universally 70 available (C++11), roll our own for enums. */ 71template<int size, bool sign> class integer_for_size { typedef void type; }; 72template<> struct integer_for_size<1, 0> { typedef uint8_t type; }; 73template<> struct integer_for_size<2, 0> { typedef uint16_t type; }; 74template<> struct integer_for_size<4, 0> { typedef uint32_t type; }; 75template<> struct integer_for_size<8, 0> { typedef uint64_t type; }; 76template<> struct integer_for_size<1, 1> { typedef int8_t type; }; 77template<> struct integer_for_size<2, 1> { typedef int16_t type; }; 78template<> struct integer_for_size<4, 1> { typedef int32_t type; }; 79template<> struct integer_for_size<8, 1> { typedef int64_t type; }; 80 81template<typename T> 82struct enum_underlying_type 83{ 84 typedef typename 85 integer_for_size<sizeof (T), static_cast<bool>(T (-1) < T (0))>::type 86 type; 87}; 88 89template <typename E> 90class enum_flags 91{ 92public: 93 typedef E enum_type; 94 typedef typename enum_underlying_type<enum_type>::type underlying_type; 95 96private: 97 /* Private type used to support initializing flag types with zero: 98 99 foo_flags f = 0; 100 101 but not other integers: 102 103 foo_flags f = 1; 104 105 The way this works is that we define an implicit constructor that 106 takes a pointer to this private type. Since nothing can 107 instantiate an object of this type, the only possible pointer to 108 pass to the constructor is the NULL pointer, or, zero. */ 109 struct zero_type; 110 111 underlying_type 112 underlying_value () const 113 { 114 return m_enum_value; 115 } 116 117public: 118 /* Allow default construction. */ 119 enum_flags () 120 : m_enum_value ((enum_type) 0) 121 {} 122 123 /* If you get an error saying these two overloads are ambiguous, 124 then you tried to mix values of different enum types. */ 125 enum_flags (enum_type e) 126 : m_enum_value (e) 127 {} 128 enum_flags (struct enum_flags::zero_type *zero) 129 : m_enum_value ((enum_type) 0) 130 {} 131 132 enum_flags &operator&= (enum_type e) 133 { 134 m_enum_value = (enum_type) (underlying_value () & e); 135 return *this; 136 } 137 enum_flags &operator|= (enum_type e) 138 { 139 m_enum_value = (enum_type) (underlying_value () | e); 140 return *this; 141 } 142 enum_flags &operator^= (enum_type e) 143 { 144 m_enum_value = (enum_type) (underlying_value () ^ e); 145 return *this; 146 } 147 148 operator enum_type () const 149 { 150 return m_enum_value; 151 } 152 153 enum_flags operator& (enum_type e) const 154 { 155 return (enum_type) (underlying_value () & e); 156 } 157 enum_flags operator| (enum_type e) const 158 { 159 return (enum_type) (underlying_value () | e); 160 } 161 enum_flags operator^ (enum_type e) const 162 { 163 return (enum_type) (underlying_value () ^ e); 164 } 165 enum_flags operator~ () const 166 { 167 // We only the underlying type to be unsigned when actually using 168 // operator~ -- if it were not unsigned, undefined behavior could 169 // result. However, asserting this in the class itself would 170 // require too many unnecessary changes to otherwise ok enum 171 // types. 172 gdb_static_assert (std::is_unsigned<underlying_type>::value); 173 return (enum_type) ~underlying_value (); 174 } 175 176private: 177 /* Stored as enum_type because GDB knows to print the bit flags 178 neatly if the enum values look like bit flags. */ 179 enum_type m_enum_value; 180}; 181 182/* Global operator overloads. */ 183 184template <typename enum_type> 185typename enum_flags_type<enum_type>::type 186operator& (enum_type e1, enum_type e2) 187{ 188 return enum_flags<enum_type> (e1) & e2; 189} 190 191template <typename enum_type> 192typename enum_flags_type<enum_type>::type 193operator| (enum_type e1, enum_type e2) 194{ 195 return enum_flags<enum_type> (e1) | e2; 196} 197 198template <typename enum_type> 199typename enum_flags_type<enum_type>::type 200operator^ (enum_type e1, enum_type e2) 201{ 202 return enum_flags<enum_type> (e1) ^ e2; 203} 204 205template <typename enum_type> 206typename enum_flags_type<enum_type>::type 207operator~ (enum_type e) 208{ 209 return ~enum_flags<enum_type> (e); 210} 211 212#else /* __cplusplus */ 213 214/* In C, the flags type is just a typedef for the enum type. */ 215 216#define DEF_ENUM_FLAGS_TYPE(enum_type, flags_type) \ 217 typedef enum_type flags_type 218 219#endif /* __cplusplus */ 220 221#endif /* COMMON_ENUM_FLAGS_H */ 222