Inside Bitcoin

1// Copyright (c) 2023-present 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#include <span.h>
6
7#include <boost/test/unit_test.hpp>
8#include <array>
9#include <set>
10#include <vector>
11
12namespace spannable {
13struct Ignore
14{
15    template<typename T> Ignore(T&&) {}
16};
17template<typename T>
18bool Spannable(T&& value, decltype(std::span{value})* enable = nullptr)
19{
20    return true;
21}
22bool Spannable(Ignore)
23{
24    return false;
25}
26
27struct SpannableYes
28{
29    int* data();
30    int* begin();
31    int* end();
32    size_t size();
33};
34struct SpannableNo
35{
36    void data();
37    size_t size();
38};
39} // namespace spannable
40
41using namespace spannable;
42
43BOOST_AUTO_TEST_SUITE(span_tests)
44
45// Make sure template std::span template deduction guides accurately enable calls to
46// std::span constructor overloads that work, and disable calls to constructor overloads that
47// don't work. This makes it possible to use the std::span constructor in a SFINAE
48// contexts like in the Spannable function above to detect whether types are or
49// aren't compatible with std::span at compile time.
50BOOST_AUTO_TEST_CASE(span_constructor_sfinae)
51{
52    BOOST_CHECK(Spannable(std::vector<int>{}));
53    BOOST_CHECK(!Spannable(std::set<int>{}));
54    BOOST_CHECK(!Spannable(std::vector<bool>{}));
55    BOOST_CHECK(Spannable(std::array<int, 3>{}));
56    BOOST_CHECK(Spannable(std::span<int>{}));
57    BOOST_CHECK(Spannable("char array"));
58    BOOST_CHECK(Spannable(SpannableYes{}));
59    BOOST_CHECK(!Spannable(SpannableNo{}));
60}
61
62BOOST_AUTO_TEST_SUITE_END()
63