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Diff: ble/SafeBool.h
- Revision:
- 1148:0340d5bbbeba
- Parent:
- 948:1bb402105289
- Child:
- 1149:c188d5238d62
--- a/ble/SafeBool.h Wed Apr 06 19:14:15 2016 +0100 +++ b/ble/SafeBool.h Wed Apr 06 19:14:16 2016 +0100 @@ -1,114 +1,114 @@ -/* mbed Microcontroller Library - * Copyright (c) 2006-2013 ARM Limited - * - * Licensed under the Apache License, Version 2.0 (the "License"); - * you may not use this file except in compliance with the License. - * You may obtain a copy of the License at - * - * http://www.apache.org/licenses/LICENSE-2.0 - * - * Unless required by applicable law or agreed to in writing, software - * distributed under the License is distributed on an "AS IS" BASIS, - * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - * See the License for the specific language governing permissions and - * limitations under the License. - */ - -#ifndef BLE_API_SAFE_BOOL_H_ -#define BLE_API_SAFE_BOOL_H_ - -//safe bool idiom, see : http://www.artima.com/cppsource/safebool.html - -namespace SafeBool_ { -/** - * @brief Base class for all intances of SafeBool, - * This base class reduce instantiation of trueTag function - */ -class base { - template<typename> - friend class SafeBool; - -protected: - //the bool type is a pointer to method which can be used in boolean context - typedef void (base::*BoolType_t)() const; - - // non implemented call, use to disallow conversion between unrelated types - void invalidTag() const; - - // member function which indicate true value - void trueTag() const {} -}; - - -} - -/** - * @brief template class SafeBool use CRTP to made boolean conversion easy and correct. - * Derived class should implement the function bool toBool() const to make this work. Inheritance - * should be public. - * - * @tparam T Type of the derived class - * - * \code - * - * class A : public SafeBool<A> { - * public: - * - * // boolean conversion - * bool toBool() { - * - * } - * }; - * - * class B : public SafeBool<B> { - * public: - * - * // boolean conversion - * bool toBool() const { - * - * } - * }; - * - * A a; - * B b; - * - * // will compile - * if(a) { - * - * } - * - * // compilation error - * if(a == b) { - * - * } - * - * - * \endcode - */ -template <typename T> -class SafeBool : public SafeBool_::base { -public: - /** - * bool operator implementation, derived class has to provide bool toBool() const function. - */ - operator BoolType_t() const { - return (static_cast<const T*>(this))->toBool() - ? &SafeBool<T>::trueTag : 0; - } -}; - -//Avoid conversion to bool between different classes -template <typename T, typename U> -void operator==(const SafeBool<T>& lhs,const SafeBool<U>& rhs) { - lhs.invalidTag(); -// return false; -} - -//Avoid conversion to bool between different classes -template <typename T,typename U> -void operator!=(const SafeBool<T>& lhs,const SafeBool<U>& rhs) { - lhs.invalidTag(); -// return false; -} - +/* mbed Microcontroller Library + * Copyright (c) 2006-2013 ARM Limited + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#ifndef BLE_API_SAFE_BOOL_H_ +#define BLE_API_SAFE_BOOL_H_ + +//safe bool idiom, see : http://www.artima.com/cppsource/safebool.html + +namespace SafeBool_ { +/** + * @brief Base class for all intances of SafeBool, + * This base class reduce instantiation of trueTag function + */ +class base { + template<typename> + friend class SafeBool; + +protected: + //the bool type is a pointer to method which can be used in boolean context + typedef void (base::*BoolType_t)() const; + + // non implemented call, use to disallow conversion between unrelated types + void invalidTag() const; + + // member function which indicate true value + void trueTag() const {} +}; + + +} + +/** + * @brief template class SafeBool use CRTP to made boolean conversion easy and correct. + * Derived class should implement the function bool toBool() const to make this work. Inheritance + * should be public. + * + * @tparam T Type of the derived class + * + * \code + * + * class A : public SafeBool<A> { + * public: + * + * // boolean conversion + * bool toBool() { + * + * } + * }; + * + * class B : public SafeBool<B> { + * public: + * + * // boolean conversion + * bool toBool() const { + * + * } + * }; + * + * A a; + * B b; + * + * // will compile + * if(a) { + * + * } + * + * // compilation error + * if(a == b) { + * + * } + * + * + * \endcode + */ +template <typename T> +class SafeBool : public SafeBool_::base { +public: + /** + * bool operator implementation, derived class has to provide bool toBool() const function. + */ + operator BoolType_t() const { + return (static_cast<const T*>(this))->toBool() + ? &SafeBool<T>::trueTag : 0; + } +}; + +//Avoid conversion to bool between different classes +template <typename T, typename U> +void operator==(const SafeBool<T>& lhs,const SafeBool<U>& rhs) { + lhs.invalidTag(); +// return false; +} + +//Avoid conversion to bool between different classes +template <typename T,typename U> +void operator!=(const SafeBool<T>& lhs,const SafeBool<U>& rhs) { + lhs.invalidTag(); +// return false; +} + #endif /* BLE_API_SAFE_BOOL_H_ */ \ No newline at end of file