Bitcoin Core  27.99.0
P2P Digital Currency
vector.h
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1 // Copyright (c) 2019-2022 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 <functional>
9 #include <initializer_list>
10 #include <optional>
11 #include <type_traits>
12 #include <utility>
13 #include <vector>
14 
22 template<typename... Args>
23 inline std::vector<typename std::common_type<Args...>::type> Vector(Args&&... args)
24 {
25  std::vector<typename std::common_type<Args...>::type> ret;
26  ret.reserve(sizeof...(args));
27  // The line below uses the trick from https://www.experts-exchange.com/articles/32502/None-recursive-variadic-templates-with-std-initializer-list.html
28  (void)std::initializer_list<int>{(ret.emplace_back(std::forward<Args>(args)), 0)...};
29  return ret;
30 }
31 
33 template<typename V>
34 inline V Cat(V v1, V&& v2)
35 {
36  v1.reserve(v1.size() + v2.size());
37  for (auto& arg : v2) {
38  v1.push_back(std::move(arg));
39  }
40  return v1;
41 }
42 
44 template<typename V>
45 inline V Cat(V v1, const V& v2)
46 {
47  v1.reserve(v1.size() + v2.size());
48  for (const auto& arg : v2) {
49  v1.push_back(arg);
50  }
51  return v1;
52 }
53 
55 template<typename V>
56 inline void ClearShrink(V& v) noexcept
57 {
58  // There are various ways to clear a vector and release its memory:
59  //
60  // 1. V{}.swap(v)
61  // 2. v = V{}
62  // 3. v = {}; v.shrink_to_fit();
63  // 4. v.clear(); v.shrink_to_fit();
64  //
65  // (2) does not appear to release memory in glibc debug mode, even if v.shrink_to_fit()
66  // follows. (3) and (4) rely on std::vector::shrink_to_fit, which is only a non-binding
67  // request. Therefore, we use method (1).
68 
69  V{}.swap(v);
70 }
71 
72 template<typename V, typename L>
73 inline std::optional<V> FindFirst(const std::vector<V>& vec, const L fnc)
74 {
75  for (const auto& el : vec) {
76  if (fnc(el)) {
77  return el;
78  }
79  }
80  return std::nullopt;
81 }
82 
83 #endif // BITCOIN_UTIL_VECTOR_H
int ret
ArgsManager & args
Definition: bitcoind.cpp:268
std::vector< typename std::common_type< Args... >::type > Vector(Args &&... args)
Construct a vector with the specified elements.
Definition: vector.h:23
std::optional< V > FindFirst(const std::vector< V > &vec, const L fnc)
Definition: vector.h:73
V Cat(V v1, V &&v2)
Concatenate two vectors, moving elements.
Definition: vector.h:34
void ClearShrink(V &v) noexcept
Clear a vector (or std::deque) and release its allocated memory.
Definition: vector.h:56