1 // Copyright (c) 2019 The Bitcoin Core developers 2 // Distributed under the MIT software license, see the accompanying 3 // file COPYING or http://www.opensource.org/licenses/mit-license.php. 4 5 #ifndef BITCOIN_UTIL_VECTOR_H 6 #define BITCOIN_UTIL_VECTOR_H 7 8 #include <initializer_list> 9 #include <type_traits> 10 #include <vector> 11 12 /** Construct a vector with the specified elements. 13 * 14 * This is preferable over the list initializing constructor of std::vector: 15 * - It automatically infers the element type from its arguments. 16 * - If any arguments are rvalue references, they will be moved into the vector 17 * (list initialization always copies). 18 */ 19 template<typename... Args> Vector(Args &&...args)20inline std::vector<typename std::common_type<Args...>::type> Vector(Args&&... args) 21 { 22 std::vector<typename std::common_type<Args...>::type> ret; 23 ret.reserve(sizeof...(args)); 24 // The line below uses the trick from https://www.experts-exchange.com/articles/32502/None-recursive-variadic-templates-with-std-initializer-list.html 25 (void)std::initializer_list<int>{(ret.emplace_back(std::forward<Args>(args)), 0)...}; 26 return ret; 27 } 28 29 /** Concatenate two vectors, moving elements. */ 30 template<typename V> Cat(V v1,V && v2)31inline V Cat(V v1, V&& v2) 32 { 33 v1.reserve(v1.size() + v2.size()); 34 for (auto& arg : v2) { 35 v1.push_back(std::move(arg)); 36 } 37 return v1; 38 } 39 40 /** Concatenate two vectors. */ 41 template<typename V> Cat(V v1,const V & v2)42inline V Cat(V v1, const V& v2) 43 { 44 v1.reserve(v1.size() + v2.size()); 45 for (const auto& arg : v2) { 46 v1.push_back(arg); 47 } 48 return v1; 49 } 50 51 #endif // BITCOIN_UTIL_VECTOR_H 52