diff --git a/src/span.h b/src/span.h index 0eb91f24f..df4d906d8 100644 --- a/src/span.h +++ b/src/span.h @@ -1,47 +1,94 @@ // 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 #include #include /** 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 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 Span(C *data, C *end) noexcept + : m_data(data), m_size(end - data) {} constexpr C *data() const noexcept { return m_data; } + constexpr C *begin() const noexcept { return m_data; } + constexpr C *end() const noexcept { return m_data + m_size; } constexpr std::ptrdiff_t size() const noexcept { return m_size; } + constexpr C &operator[](std::ptrdiff_t pos) const noexcept { + return m_data[pos]; + } + + constexpr Span subspan(std::ptrdiff_t offset) const noexcept { + return Span(m_data + offset, m_size - offset); + } + constexpr Span subspan(std::ptrdiff_t offset, std::ptrdiff_t count) const + noexcept { + return Span(m_data + offset, count); + } + constexpr Span first(std::ptrdiff_t count) const noexcept { + return Span(m_data, count); + } + constexpr Span last(std::ptrdiff_t count) const noexcept { + return Span(m_data + m_size - count, count); + } + + friend constexpr bool operator==(const Span &a, const Span &b) noexcept { + return a.size() == b.size() && + std::equal(a.begin(), a.end(), b.begin()); + } + friend constexpr bool operator!=(const Span &a, const Span &b) noexcept { + return !(a == b); + } + friend constexpr bool operator<(const Span &a, const Span &b) noexcept { + return std::lexicographical_compare(a.begin(), a.end(), b.begin(), + b.end()); + } + friend constexpr bool operator<=(const Span &a, const Span &b) noexcept { + return !(b < a); + } + friend constexpr bool operator>(const Span &a, const Span &b) noexcept { + return (b < a); + } + friend constexpr bool operator>=(const Span &a, const Span &b) noexcept { + return !(a < b); + } }; /** 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 constexpr Span MakeSpan(A (&a)[N]) { + return Span(a, N); +} + template constexpr Span< typename std::remove_pointer().data())>::type> MakeSpan(V &v) { return Span< typename std::remove_pointer().data())>::type>( v.data(), v.size()); } #endif // BITCOIN_SPAN_H