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/*
* Copyright (c) 2011-2017 Isode Limited.
* All rights reserved.
* See the COPYING file for more information.
*/
#pragma once
#include <algorithm>
#include <type_traits>
namespace Swift {
template<typename V1, typename V2, typename... Rest>
std::size_t getReserveAmount(V1 const& v1, V2 const& v2, Rest const&... rest) SWIFTEN_NOEXCEPT
{
// Total size of the concatenated output is equal to sum of sizes of all the containers that were passed in.
// Two first can be accessed directly:
std::size_t sizeSum = v1.size() + v2.size();
// While the rest needs to be calculated in parameter pack expansion:
// http://stackoverflow.com/a/25683817/61574
// Pack expansion can occur inside a braced-init-list - dummy array is used for that (with side effect of accumulating the size)
int dummy[] = {0, ((sizeSum += rest.size()), void(), 0)...};
(void)dummy; // dummy is unused - suppress compiler warning
return sizeSum;
}
template<typename V1, typename V2, typename... Rest>
typename std::decay<V1>::type concat(V1&& v1, V2&& v2, Rest&&... rest) {
// Create the output container and reserve the required amount of space
typename std::decay<V1>::type v;
v.reserve(getReserveAmount(v1, v2, rest...));
// Insert the elements from input containers to output. Directly for the first two:
v.insert(v.cend(), v1.cbegin(), v1.cend());
v.insert(v.cend(), v2.cbegin(), v2.cend());
// Use pack expansion for the others:
int dummy[] = {0, ((v.insert(v.cend(), rest.cbegin(), rest.cend())), void(), 0 )...};
(void)dummy;
return v;
}
}
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Swift