erkin yucel / mbed-os

mbed os with nrf51 internal bandgap enabled to read battery level

Dependents:   BLE_file_test BLE_Blink ExternalEncoder

features/FEATURE_BLE/ble/SafeBool.h@0:f269e3021894, 2016-10-23 (annotated)

Committer:
elessair
Date:
Sun Oct 23 15:10:02 2016 +0000
Revision:
0:f269e3021894
Initial commit

Who changed what in which revision?

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elessair 0:f269e3021894 1 /* mbed Microcontroller Library
elessair 0:f269e3021894 2 * Copyright (c) 2006-2013 ARM Limited
elessair 0:f269e3021894 3 *
elessair 0:f269e3021894 4 * Licensed under the Apache License, Version 2.0 (the "License");
elessair 0:f269e3021894 5 * you may not use this file except in compliance with the License.
elessair 0:f269e3021894 6 * You may obtain a copy of the License at
elessair 0:f269e3021894 7 *
elessair 0:f269e3021894 8 * http://www.apache.org/licenses/LICENSE-2.0
elessair 0:f269e3021894 9 *
elessair 0:f269e3021894 10 * Unless required by applicable law or agreed to in writing, software
elessair 0:f269e3021894 11 * distributed under the License is distributed on an "AS IS" BASIS,
elessair 0:f269e3021894 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
elessair 0:f269e3021894 13 * See the License for the specific language governing permissions and
elessair 0:f269e3021894 14 * limitations under the License.
elessair 0:f269e3021894 15 */
elessair 0:f269e3021894 16
elessair 0:f269e3021894 17 #ifndef BLE_API_SAFE_BOOL_H_
elessair 0:f269e3021894 18 #define BLE_API_SAFE_BOOL_H_
elessair 0:f269e3021894 19
elessair 0:f269e3021894 20 /* Safe bool idiom, see : http://www.artima.com/cppsource/safebool.html */
elessair 0:f269e3021894 21
elessair 0:f269e3021894 22 namespace SafeBool_ {
elessair 0:f269e3021894 23 /**
elessair 0:f269e3021894 24 * @brief Base class for all intances of SafeBool.
elessair 0:f269e3021894 25 * This base class reduces instantiation of trueTag function.
elessair 0:f269e3021894 26 */
elessair 0:f269e3021894 27 class base {
elessair 0:f269e3021894 28 template<typename>
elessair 0:f269e3021894 29 friend class SafeBool;
elessair 0:f269e3021894 30
elessair 0:f269e3021894 31 protected:
elessair 0:f269e3021894 32 /**
elessair 0:f269e3021894 33 * The bool type is a pointer to method which can be used in boolean context.
elessair 0:f269e3021894 34 */
elessair 0:f269e3021894 35 typedef void (base::*BoolType_t)() const;
elessair 0:f269e3021894 36
elessair 0:f269e3021894 37 /**
elessair 0:f269e3021894 38 * Non implemented call, use to disallow conversion between unrelated types.
elessair 0:f269e3021894 39 */
elessair 0:f269e3021894 40 void invalidTag() const;
elessair 0:f269e3021894 41
elessair 0:f269e3021894 42 /**
elessair 0:f269e3021894 43 * Member function which indicate true value.
elessair 0:f269e3021894 44 */
elessair 0:f269e3021894 45 void trueTag() const {}
elessair 0:f269e3021894 46 };
elessair 0:f269e3021894 47
elessair 0:f269e3021894 48
elessair 0:f269e3021894 49 }
elessair 0:f269e3021894 50
elessair 0:f269e3021894 51 /**
elessair 0:f269e3021894 52 * @brief template class SafeBool use CRTP to made boolean conversion easy and correct.
elessair 0:f269e3021894 53 * Derived class should implement the function bool toBool() const to make this work. Inheritance
elessair 0:f269e3021894 54 * should be public.
elessair 0:f269e3021894 55 *
elessair 0:f269e3021894 56 * @tparam T Type of the derived class
elessair 0:f269e3021894 57 *
elessair 0:f269e3021894 58 * @code
elessair 0:f269e3021894 59 *
elessair 0:f269e3021894 60 * class A : public SafeBool<A> {
elessair 0:f269e3021894 61 * public:
elessair 0:f269e3021894 62 *
elessair 0:f269e3021894 63 * // boolean conversion
elessair 0:f269e3021894 64 * bool toBool() {
elessair 0:f269e3021894 65 *
elessair 0:f269e3021894 66 * }
elessair 0:f269e3021894 67 * };
elessair 0:f269e3021894 68 *
elessair 0:f269e3021894 69 * class B : public SafeBool<B> {
elessair 0:f269e3021894 70 * public:
elessair 0:f269e3021894 71 *
elessair 0:f269e3021894 72 * // boolean conversion
elessair 0:f269e3021894 73 * bool toBool() const {
elessair 0:f269e3021894 74 *
elessair 0:f269e3021894 75 * }
elessair 0:f269e3021894 76 * };
elessair 0:f269e3021894 77 *
elessair 0:f269e3021894 78 * A a;
elessair 0:f269e3021894 79 * B b;
elessair 0:f269e3021894 80 *
elessair 0:f269e3021894 81 * // will compile
elessair 0:f269e3021894 82 * if(a) {
elessair 0:f269e3021894 83 *
elessair 0:f269e3021894 84 * }
elessair 0:f269e3021894 85 *
elessair 0:f269e3021894 86 * // compilation error
elessair 0:f269e3021894 87 * if(a == b) {
elessair 0:f269e3021894 88 *
elessair 0:f269e3021894 89 * }
elessair 0:f269e3021894 90 *
elessair 0:f269e3021894 91 *
elessair 0:f269e3021894 92 * @endcode
elessair 0:f269e3021894 93 */
elessair 0:f269e3021894 94 template <typename T>
elessair 0:f269e3021894 95 class SafeBool : public SafeBool_::base {
elessair 0:f269e3021894 96 public:
elessair 0:f269e3021894 97 /**
elessair 0:f269e3021894 98 * Bool operator implementation, derived class has to provide bool toBool() const function.
elessair 0:f269e3021894 99 */
elessair 0:f269e3021894 100 operator BoolType_t() const {
elessair 0:f269e3021894 101 return (static_cast<const T*>(this))->toBool()
elessair 0:f269e3021894 102 ? &SafeBool<T>::trueTag : 0;
elessair 0:f269e3021894 103 }
elessair 0:f269e3021894 104 };
elessair 0:f269e3021894 105
elessair 0:f269e3021894 106 /**
elessair 0:f269e3021894 107 * Avoid conversion to bool between different classes.
elessair 0:f269e3021894 108 */
elessair 0:f269e3021894 109 template <typename T, typename U>
elessair 0:f269e3021894 110 void operator==(const SafeBool<T>& lhs,const SafeBool<U>& rhs) {
elessair 0:f269e3021894 111 lhs.invalidTag();
elessair 0:f269e3021894 112 // return false;
elessair 0:f269e3021894 113 }
elessair 0:f269e3021894 114
elessair 0:f269e3021894 115 /**
elessair 0:f269e3021894 116 * Avoid conversion to bool between different classes.
elessair 0:f269e3021894 117 */
elessair 0:f269e3021894 118 template <typename T,typename U>
elessair 0:f269e3021894 119 void operator!=(const SafeBool<T>& lhs,const SafeBool<U>& rhs) {
elessair 0:f269e3021894 120 lhs.invalidTag();
elessair 0:f269e3021894 121 // return false;
elessair 0:f269e3021894 122 }
elessair 0:f269e3021894 123
elessair 0:f269e3021894 124 #endif /* BLE_API_SAFE_BOOL_H_ */