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// Copyright (c) 2019-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_UTIL_VECTOR_H
#define BITCOIN_UTIL_VECTOR_H
#include <initializer_list>
#include <type_traits>
#include <utility>
#include <vector>
/** Construct a vector with the specified elements.
*
* This is preferable over the list initializing constructor of std::vector:
* - It automatically infers the element type from its arguments.
* - If any arguments are rvalue references, they will be moved into the vector
* (list initialization always copies).
*/
template<typename... Args>
inline std::vector<typename std::common_type<Args...>::type> Vector(Args&&... args)
{
std::vector<typename std::common_type<Args...>::type> ret;
ret.reserve(sizeof...(args));
// The line below uses the trick from https://www.experts-exchange.com/articles/32502/None-recursive-variadic-templates-with-std-initializer-list.html
(void)std::initializer_list<int>{(ret.emplace_back(std::forward<Args>(args)), 0)...};
return ret;
}
/** Concatenate two vectors, moving elements. */
template<typename V>
inline V Cat(V v1, V&& v2)
{
v1.reserve(v1.size() + v2.size());
for (auto& arg : v2) {
v1.push_back(std::move(arg));
}
return v1;
}
/** Concatenate two vectors. */
template<typename V>
inline V Cat(V v1, const V& v2)
{
v1.reserve(v1.size() + v2.size());
for (const auto& arg : v2) {
v1.push_back(arg);
}
return v1;
}
/** Clear a vector (or std::deque) and release its allocated memory. */
template<typename V>
inline void ClearShrink(V& v) noexcept
{
// There are various ways to clear a vector and release its memory:
//
// 1. V{}.swap(v)
// 2. v = V{}
// 3. v = {}; v.shrink_to_fit();
// 4. v.clear(); v.shrink_to_fit();
//
// (2) does not appear to release memory in glibc debug mode, even if v.shrink_to_fit()
// follows. (3) and (4) rely on std::vector::shrink_to_fit, which is only a non-binding
// request. Therefore, we use method (1).
V{}.swap(v);
}
#endif // BITCOIN_UTIL_VECTOR_H
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