191 lines
6.3 KiB
C++
191 lines
6.3 KiB
C++
/*
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Copyright (c) 2016, Arvid Norberg
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef TORRENT_SPAN_HPP_INCLUDED
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#define TORRENT_SPAN_HPP_INCLUDED
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#include <array>
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#include <type_traits>
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#include "libtorrent/assert.hpp"
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namespace libtorrent {
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namespace aux {
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template <typename From, typename To>
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struct compatible_type
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{
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// conversions that are OK
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// int -> int
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// int const -> int const
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// int -> int const
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// int -> int volatile
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// int -> int const volatile
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// int volatile -> int const volatile
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// int const -> int const volatile
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static const bool value = std::is_same<From, To>::value
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|| std::is_same<From, typename std::remove_const<To>::type>::value
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|| std::is_same<From, typename std::remove_volatile<To>::type>::value
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|| std::is_same<From, typename std::remove_cv<To>::type>::value
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;
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};
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}
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template <typename T>
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struct span
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{
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using difference_type = std::ptrdiff_t;
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using index_type = std::ptrdiff_t;
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span() noexcept : m_ptr(nullptr), m_len(0) {}
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template <typename U, typename
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= typename std::enable_if<aux::compatible_type<U, T>::value>::type>
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span(span<U> const& v) noexcept // NOLINT
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: m_ptr(v.data()), m_len(v.size()) {}
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span(T& p) noexcept : m_ptr(&p), m_len(1) {} // NOLINT
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span(T* p, difference_type const l) noexcept : m_ptr(p), m_len(l) // NOLINT
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{ TORRENT_ASSERT(l >= 0); }
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template <typename U, std::size_t N>
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span(std::array<U, N>& arr) noexcept // NOLINT
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: m_ptr(arr.data()), m_len(static_cast<difference_type>(arr.size())) {}
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// this is necessary until C++17, where data() returns a non-const pointer
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template <typename U>
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span(std::basic_string<U>& str) noexcept // NOLINT
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: m_ptr(&str[0]), m_len(static_cast<difference_type>(str.size())) {}
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template <typename U, difference_type N>
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span(U (&arr)[N]) noexcept // NOLINT
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: m_ptr(&arr[0]), m_len(N) {}
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// anything with a .data() member function is considered a container
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// but only if the value type is compatible with T
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template <typename Cont
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, typename U = typename std::remove_reference<decltype(*std::declval<Cont>().data())>::type
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, typename = typename std::enable_if<aux::compatible_type<U, T>::value>::type>
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span(Cont& c) // NOLINT
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: m_ptr(c.data()), m_len(static_cast<difference_type>(c.size())) {}
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// allow construction from const containers if T is const
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// this allows const spans to be constructed from a temporary container
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template <typename Cont
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, typename U = typename std::remove_reference<decltype(*std::declval<Cont>().data())>::type
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, typename = typename std::enable_if<aux::compatible_type<U, T>::value
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&& std::is_const<T>::value>::type>
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span(Cont const& c) // NOLINT
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: m_ptr(c.data()), m_len(static_cast<difference_type>(c.size())) {}
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template <typename U, typename
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= typename std::enable_if<aux::compatible_type<U, T>::value>::type>
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span& operator=(span<U> const& rhs) noexcept
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{
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m_ptr = rhs.data();
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m_len = rhs.size();
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return *this;
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}
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index_type size() const noexcept { return m_len; }
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bool empty() const noexcept { return m_len == 0; }
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T* data() const noexcept { return m_ptr; }
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using const_iterator = T const*;
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using const_reverse_iterator = std::reverse_iterator<T const*>;
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using iterator = T*;
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using reverse_iterator = std::reverse_iterator<T*>;
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T* begin() const noexcept { return m_ptr; }
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T* end() const noexcept { return m_ptr + m_len; }
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reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
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reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
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T& front() const noexcept { TORRENT_ASSERT(m_len > 0); return m_ptr[0]; }
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T& back() const noexcept { TORRENT_ASSERT(m_len > 0); return m_ptr[m_len - 1]; }
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span<T> first(difference_type const n) const
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{
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TORRENT_ASSERT(size() >= n);
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return { data(), n };
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}
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span<T> last(difference_type const n) const
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{
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TORRENT_ASSERT(size() >= n);
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return { data() + size() - n, n };
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}
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span<T> subspan(index_type const offset) const
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{
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TORRENT_ASSERT(size() >= offset);
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return { data() + offset, size() - offset };
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}
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span<T> subspan(index_type const offset, difference_type const count) const
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{
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TORRENT_ASSERT(count >= 0);
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TORRENT_ASSERT(size() >= offset);
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TORRENT_ASSERT(size() >= offset + count);
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return { data() + offset, count };
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}
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T& operator[](index_type const idx) const
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{
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TORRENT_ASSERT(idx < m_len);
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TORRENT_ASSERT(idx >= 0);
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return m_ptr[idx];
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}
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private:
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T* m_ptr;
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difference_type m_len;
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};
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template <class T, class U>
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inline bool operator==(span<T> const& lhs, span<U> const& rhs)
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{
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return lhs.size() == rhs.size()
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&& (lhs.data() == rhs.data() || std::equal(lhs.begin(), lhs.end(), rhs.begin()));
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}
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template <class T, class U>
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inline bool operator!=(span<T> const& lhs, span<U> const& rhs)
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{
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return lhs.size() != rhs.size()
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|| (lhs.data() != rhs.data() && !std::equal(lhs.begin(), lhs.end(), rhs.begin()));
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}
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}
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#endif // TORRENT_SPAN_HPP_INCLUDED
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