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Add Slice: a (pointer, size) array view that acts like a container
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sipa authored and furszy committed Jul 3, 2021
1 parent 949f42e commit 8fef544
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1 change: 1 addition & 0 deletions src/Makefile.am
Original file line number Diff line number Diff line change
Expand Up @@ -262,6 +262,7 @@ BITCOIN_CORE_H = \
script/standard.h \
script/script_error.h \
serialize.h \
span.h \
spork.h \
sporkdb.h \
sporkid.h \
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40 changes: 40 additions & 0 deletions src/span.h
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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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