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// Copyright (c) 2018 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_SPAN_H
#define BITCOIN_SPAN_H
#include <type_traits>
#include <cstddef>
/** A Span is an object that can refer to a contiguous sequence of objects.
*
* It implements a subset of C++20's std::span.
*/
template<typename C>
class Span
{
C* m_data;
std::ptrdiff_t m_size;
public:
constexpr Span() noexcept : m_data(nullptr), m_size(0) {}
constexpr Span(C* data, std::ptrdiff_t size) noexcept : m_data(data), m_size(size) {}
constexpr C* data() const noexcept { return m_data; }
constexpr std::ptrdiff_t size() const noexcept { return m_size; }
};
/** Create a span to a container exposing data() and size().
*
* This correctly deals with constness: the returned Span's element type will be
* whatever data() returns a pointer to. If either the passed container is const,
* or its element type is const, the resulting span will have a const element type.
*
* std::span will have a constructor that implements this functionality directly.
*/
template<typename V>
constexpr Span<typename std::remove_pointer<decltype(std::declval<V>().data())>::type> MakeSpan(V& v) { return Span<typename std::remove_pointer<decltype(std::declval<V>().data())>::type>(v.data(), v.size()); }
#endif
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