Line data    Source code

       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>
      20      418687 : inline std::vector<typename std::common_type<Args...>::type> Vector(Args&&... args)
      21             : {
      22      418687 :     std::vector<typename std::common_type<Args...>::type> ret;
      23      418687 :     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      418687 :     (void)std::initializer_list<int>{(ret.emplace_back(std::forward<Args>(args)), 0)...};
      26             :     return ret;
      27      418687 : }
      28             : 
      29             : /** Concatenate two vectors, moving elements. */
      30             : template<typename V>
      31        1909 : inline V Cat(V v1, V&& v2)
      32             : {
      33        1909 :     v1.reserve(v1.size() + v2.size());
      34       96919 :     for (auto& arg : v2) {
      35       95010 :         v1.push_back(std::move(arg));
      36             :     }
      37        1909 :     return v1;
      38             : }
      39             : 
      40             : /** Concatenate two vectors. */
      41             : template<typename V>
      42      102678 : inline V Cat(V v1, const V& v2)
      43             : {
      44      102678 :     v1.reserve(v1.size() + v2.size());
      45     2459121 :     for (const auto& arg : v2) {
      46     2356443 :         v1.push_back(arg);
      47             :     }
      48      102678 :     return v1;
      49             : }
      50             : 
      51             : #endif // BITCOIN_UTIL_VECTOR_H