Marco Zecchini / Mbed OS Example_RTOS

Rtos API example

mbed-os/features/FEATURE_BLE/ble/SafeBool.h@0:9fca2b23d0ba, 2019-02-23 (annotated)

Committer:
marcozecchini
Date:
Sat Feb 23 12:13:36 2019 +0000
Revision:
0:9fca2b23d0ba
final commit

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marcozecchini 0:9fca2b23d0ba 1 /* mbed Microcontroller Library
marcozecchini 0:9fca2b23d0ba 2 * Copyright (c) 2006-2013 ARM Limited
marcozecchini 0:9fca2b23d0ba 3 *
marcozecchini 0:9fca2b23d0ba 4 * Licensed under the Apache License, Version 2.0 (the "License");
marcozecchini 0:9fca2b23d0ba 5 * you may not use this file except in compliance with the License.
marcozecchini 0:9fca2b23d0ba 6 * You may obtain a copy of the License at
marcozecchini 0:9fca2b23d0ba 7 *
marcozecchini 0:9fca2b23d0ba 8 * http://www.apache.org/licenses/LICENSE-2.0
marcozecchini 0:9fca2b23d0ba 9 *
marcozecchini 0:9fca2b23d0ba 10 * Unless required by applicable law or agreed to in writing, software
marcozecchini 0:9fca2b23d0ba 11 * distributed under the License is distributed on an "AS IS" BASIS,
marcozecchini 0:9fca2b23d0ba 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
marcozecchini 0:9fca2b23d0ba 13 * See the License for the specific language governing permissions and
marcozecchini 0:9fca2b23d0ba 14 * limitations under the License.
marcozecchini 0:9fca2b23d0ba 15 */
marcozecchini 0:9fca2b23d0ba 16
marcozecchini 0:9fca2b23d0ba 17 #ifndef BLE_API_SAFE_BOOL_H_
marcozecchini 0:9fca2b23d0ba 18 #define BLE_API_SAFE_BOOL_H_
marcozecchini 0:9fca2b23d0ba 19
marcozecchini 0:9fca2b23d0ba 20 /* Safe bool idiom, see: http://www.artima.com/cppsource/safebool.html */
marcozecchini 0:9fca2b23d0ba 21
marcozecchini 0:9fca2b23d0ba 22 /**
marcozecchini 0:9fca2b23d0ba 23 * @file
marcozecchini 0:9fca2b23d0ba 24 * @addtogroup ble
marcozecchini 0:9fca2b23d0ba 25 * @{
marcozecchini 0:9fca2b23d0ba 26 * @addtogroup common
marcozecchini 0:9fca2b23d0ba 27 * @{
marcozecchini 0:9fca2b23d0ba 28 */
marcozecchini 0:9fca2b23d0ba 29
marcozecchini 0:9fca2b23d0ba 30 /**
marcozecchini 0:9fca2b23d0ba 31 * Private namespace used to host details of the SafeBool implementation.
marcozecchini 0:9fca2b23d0ba 32 */
marcozecchini 0:9fca2b23d0ba 33 namespace SafeBool_ {
marcozecchini 0:9fca2b23d0ba 34 /**
marcozecchini 0:9fca2b23d0ba 35 * Base class of all SafeBool instances.
marcozecchini 0:9fca2b23d0ba 36 *
marcozecchini 0:9fca2b23d0ba 37 * This nontemplate base class exists to reduce the number of instantiation of
marcozecchini 0:9fca2b23d0ba 38 * the trueTag function.
marcozecchini 0:9fca2b23d0ba 39 */
marcozecchini 0:9fca2b23d0ba 40 class base {
marcozecchini 0:9fca2b23d0ba 41 template<typename>
marcozecchini 0:9fca2b23d0ba 42 friend class SafeBool;
marcozecchini 0:9fca2b23d0ba 43
marcozecchini 0:9fca2b23d0ba 44 protected:
marcozecchini 0:9fca2b23d0ba 45 /**
marcozecchini 0:9fca2b23d0ba 46 * The bool type is a pointer to method that can be used in boolean context.
marcozecchini 0:9fca2b23d0ba 47 */
marcozecchini 0:9fca2b23d0ba 48 typedef void (base::*BoolType_t)() const;
marcozecchini 0:9fca2b23d0ba 49
marcozecchini 0:9fca2b23d0ba 50 /**
marcozecchini 0:9fca2b23d0ba 51 * Nonimplemented call, use to disallow conversion between unrelated types.
marcozecchini 0:9fca2b23d0ba 52 */
marcozecchini 0:9fca2b23d0ba 53 void invalidTag() const;
marcozecchini 0:9fca2b23d0ba 54
marcozecchini 0:9fca2b23d0ba 55 /**
marcozecchini 0:9fca2b23d0ba 56 * Special member function that indicates a true value.
marcozecchini 0:9fca2b23d0ba 57 */
marcozecchini 0:9fca2b23d0ba 58 void trueTag() const {}
marcozecchini 0:9fca2b23d0ba 59 };
marcozecchini 0:9fca2b23d0ba 60
marcozecchini 0:9fca2b23d0ba 61
marcozecchini 0:9fca2b23d0ba 62 }
marcozecchini 0:9fca2b23d0ba 63
marcozecchini 0:9fca2b23d0ba 64 /**
marcozecchini 0:9fca2b23d0ba 65 * Safe conversion of objects in boolean context.
marcozecchini 0:9fca2b23d0ba 66 *
marcozecchini 0:9fca2b23d0ba 67 * Classes wanting evaluation of their instances in boolean context must derive
marcozecchini 0:9fca2b23d0ba 68 * publicly from this class rather than implementing the easy to misuse
marcozecchini 0:9fca2b23d0ba 69 * operator bool().
marcozecchini 0:9fca2b23d0ba 70 *
marcozecchini 0:9fca2b23d0ba 71 * Descendant classes must implement the function bool toBool() const to enable
marcozecchini 0:9fca2b23d0ba 72 * the safe conversion in boolean context.
marcozecchini 0:9fca2b23d0ba 73 *
marcozecchini 0:9fca2b23d0ba 74 * @tparam T Type of the derived class
marcozecchini 0:9fca2b23d0ba 75 *
marcozecchini 0:9fca2b23d0ba 76 * @code
marcozecchini 0:9fca2b23d0ba 77 *
marcozecchini 0:9fca2b23d0ba 78 * class A : public SafeBool<A> {
marcozecchini 0:9fca2b23d0ba 79 * public:
marcozecchini 0:9fca2b23d0ba 80 *
marcozecchini 0:9fca2b23d0ba 81 * // boolean conversion
marcozecchini 0:9fca2b23d0ba 82 * bool toBool() const {
marcozecchini 0:9fca2b23d0ba 83 *
marcozecchini 0:9fca2b23d0ba 84 * }
marcozecchini 0:9fca2b23d0ba 85 * };
marcozecchini 0:9fca2b23d0ba 86 *
marcozecchini 0:9fca2b23d0ba 87 * class B : public SafeBool<B> {
marcozecchini 0:9fca2b23d0ba 88 * public:
marcozecchini 0:9fca2b23d0ba 89 *
marcozecchini 0:9fca2b23d0ba 90 * // boolean conversion
marcozecchini 0:9fca2b23d0ba 91 * bool toBool() const {
marcozecchini 0:9fca2b23d0ba 92 *
marcozecchini 0:9fca2b23d0ba 93 * }
marcozecchini 0:9fca2b23d0ba 94 * };
marcozecchini 0:9fca2b23d0ba 95 *
marcozecchini 0:9fca2b23d0ba 96 * A a;
marcozecchini 0:9fca2b23d0ba 97 * B b;
marcozecchini 0:9fca2b23d0ba 98 *
marcozecchini 0:9fca2b23d0ba 99 * // will compile
marcozecchini 0:9fca2b23d0ba 100 * if(a) {
marcozecchini 0:9fca2b23d0ba 101 *
marcozecchini 0:9fca2b23d0ba 102 * }
marcozecchini 0:9fca2b23d0ba 103 *
marcozecchini 0:9fca2b23d0ba 104 * // compilation error
marcozecchini 0:9fca2b23d0ba 105 * if(a == b) {
marcozecchini 0:9fca2b23d0ba 106 *
marcozecchini 0:9fca2b23d0ba 107 * }
marcozecchini 0:9fca2b23d0ba 108 * @endcode
marcozecchini 0:9fca2b23d0ba 109 */
marcozecchini 0:9fca2b23d0ba 110 template <typename T>
marcozecchini 0:9fca2b23d0ba 111 class SafeBool : public SafeBool_::base {
marcozecchini 0:9fca2b23d0ba 112 public:
marcozecchini 0:9fca2b23d0ba 113 /**
marcozecchini 0:9fca2b23d0ba 114 * Bool operator implementation, derived class must provide a bool
marcozecchini 0:9fca2b23d0ba 115 * toBool() const function.
marcozecchini 0:9fca2b23d0ba 116 */
marcozecchini 0:9fca2b23d0ba 117 operator BoolType_t() const
marcozecchini 0:9fca2b23d0ba 118 {
marcozecchini 0:9fca2b23d0ba 119 return (static_cast<const T*>(this))->toBool()
marcozecchini 0:9fca2b23d0ba 120 ? &SafeBool<T>::trueTag : 0;
marcozecchini 0:9fca2b23d0ba 121 }
marcozecchini 0:9fca2b23d0ba 122 };
marcozecchini 0:9fca2b23d0ba 123
marcozecchini 0:9fca2b23d0ba 124 /**
marcozecchini 0:9fca2b23d0ba 125 * Avoid conversion to bool between different classes.
marcozecchini 0:9fca2b23d0ba 126 *
marcozecchini 0:9fca2b23d0ba 127 * @important Will generate a compile time error if instantiated.
marcozecchini 0:9fca2b23d0ba 128 */
marcozecchini 0:9fca2b23d0ba 129 template <typename T, typename U>
marcozecchini 0:9fca2b23d0ba 130 void operator==(const SafeBool<T>& lhs,const SafeBool<U>& rhs)
marcozecchini 0:9fca2b23d0ba 131 {
marcozecchini 0:9fca2b23d0ba 132 lhs.invalidTag();
marcozecchini 0:9fca2b23d0ba 133 // return false;
marcozecchini 0:9fca2b23d0ba 134 }
marcozecchini 0:9fca2b23d0ba 135
marcozecchini 0:9fca2b23d0ba 136 /**
marcozecchini 0:9fca2b23d0ba 137 * Avoid conversion to bool between different classes.
marcozecchini 0:9fca2b23d0ba 138 *
marcozecchini 0:9fca2b23d0ba 139 * @important Will generate a compile time error if instantiated.
marcozecchini 0:9fca2b23d0ba 140 */
marcozecchini 0:9fca2b23d0ba 141 template <typename T,typename U>
marcozecchini 0:9fca2b23d0ba 142 void operator!=(const SafeBool<T>& lhs,const SafeBool<U>& rhs)
marcozecchini 0:9fca2b23d0ba 143 {
marcozecchini 0:9fca2b23d0ba 144 lhs.invalidTag();
marcozecchini 0:9fca2b23d0ba 145 // return false;
marcozecchini 0:9fca2b23d0ba 146 }
marcozecchini 0:9fca2b23d0ba 147
marcozecchini 0:9fca2b23d0ba 148 /**
marcozecchini 0:9fca2b23d0ba 149 * @}
marcozecchini 0:9fca2b23d0ba 150 * @}
marcozecchini 0:9fca2b23d0ba 151 */
marcozecchini 0:9fca2b23d0ba 152
marcozecchini 0:9fca2b23d0ba 153
marcozecchini 0:9fca2b23d0ba 154 #endif /* BLE_API_SAFE_BOOL_H_ */