forked from wownero/wownero
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// Copyright (c) 2017, The Monero Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF 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 CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include <cstdint>
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#include <memory>
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#include <type_traits>
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namespace epee
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{
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/*!
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\brief Non-owning sequence of data. Does not deep copy
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Inspired by `gsl::span` and/or `boost::iterator_range`. This class is
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intended to be used as a parameter type for functions that need to take a
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writable or read-only sequence of data. Most common cases are `span<char>`
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and `span<std::uint8_t>`. Using as a class member is only recommended if
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clearly documented as not doing a deep-copy. C-arrays are easily convertible
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to this type.
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\note Conversion from C string literal to `span<const char>` will include
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the NULL-terminator.
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\note Never allows derived-to-base pointer conversion; an array of derived
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types is not an array of base types.
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*/
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template<typename T>
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class span
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{
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/* Supporting class types is tricky - the {ptr,len} constructor will allow
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derived-to-base conversions. This is NOT desireable because an array of
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derived types is not an array of base types. It is possible to handle
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this case, implement when/if needed. */
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static_assert(!std::is_class<T>(), "no class types are currently allowed");
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public:
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using value_type = T;
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using size_type = std::size_t;
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using difference_type = std::ptrdiff_t;
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using pointer = T*;
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using const_pointer = const T*;
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using reference = T&;
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using const_reference = const T&;
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using iterator = pointer;
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using const_iterator = const_pointer;
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constexpr span() noexcept : ptr(nullptr), len(0) {}
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constexpr span(std::nullptr_t) noexcept : span() {}
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constexpr span(T* const src_ptr, const std::size_t count) noexcept
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: ptr(src_ptr), len(count) {}
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//! Conversion from C-array. Prevents common bugs with sizeof + arrays.
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template<std::size_t N>
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constexpr span(T (&src)[N]) noexcept : span(src, N) {}
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constexpr span(const span&) noexcept = default;
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span& operator=(const span&) noexcept = default;
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constexpr iterator begin() const noexcept { return ptr; }
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constexpr const_iterator cbegin() const noexcept { return ptr; }
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constexpr iterator end() const noexcept { return begin() + size(); }
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constexpr const_iterator cend() const noexcept { return cbegin() + size(); }
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constexpr bool empty() const noexcept { return size() == 0; }
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constexpr pointer data() const noexcept { return ptr; }
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constexpr std::size_t size() const noexcept { return len; }
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constexpr std::size_t size_bytes() const noexcept { return size() * sizeof(value_type); }
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private:
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T* ptr;
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std::size_t len;
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};
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//! \return `span<const T::value_type>` from a STL compatible `src`.
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template<typename T>
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constexpr span<const typename T::value_type> to_span(const T& src)
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{
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// compiler provides diagnostic if size() is not size_t.
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return {src.data(), src.size()};
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}
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template<typename T>
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constexpr bool has_padding() noexcept
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{
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return !std::is_pod<T>() || alignof(T) != 1;
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}
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//! \return Cast data from `src` as `span<const std::uint8_t>`.
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template<typename T>
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span<const std::uint8_t> to_byte_span(const span<const T> src) noexcept
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{
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static_assert(!has_padding<T>(), "source type may have padding");
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return {reinterpret_cast<const std::uint8_t*>(src.data()), src.size_bytes()};
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}
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//! \return `span<const std::uint8_t>` which represents the bytes at `&src`.
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template<typename T>
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span<const std::uint8_t> as_byte_span(const T& src) noexcept
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{
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static_assert(!std::is_empty<T>(), "empty types will not work -> sizeof == 1");
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static_assert(!has_padding<T>(), "source type may have padding");
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return {reinterpret_cast<const std::uint8_t*>(std::addressof(src)), sizeof(T)};
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}
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}
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@ -1,174 +0,0 @@
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// Copyright (c) 2017, The Monero Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF 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 CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include <cstddef>
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#include <memory>
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#include <type_traits>
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#include <utility>
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namespace epee
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{
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/*!
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\brief Non-owning sequence of data. Does not deep copy
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Inspired by `gsl::span`. This class is intended to be used as a parameter
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type for functions that need to take a writable or read-only sequence of
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data. Most common cases are `span<char>` and `span<std::uint8_t>`. Using as
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a class member is only recommended if clearly documented as not doing a
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deep-copy. `std::vector`, `std::string`, `std::array`, and C-arrays are all
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easily convertible to this type.
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\note Conversion from C string literal to `view<char>` will include the
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NULL-terminator.
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\note `view<T>` is an alias for `span<const T>` which is read-only.
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\note Never allows derived-to-base pointer conversion; an array of derived
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types is not an array of base types.
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*/
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template<typename T>
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class span
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{
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/* Supporting class types is tricky - the {ptr,len} and {container}
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constructors will allow derived-to-base conversions. This is NOT
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desireable because an array of derived types is not an array of base
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types. It is possible to handle this case, implement when/if needed. */
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static_assert(std::is_integral<T>::value, "only integral values currently for span");
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// Disables ADL for these calls.
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struct get {
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// we only accept pointer and size_t return types, so use noexcept aggressively
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template<std::size_t N>
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static constexpr T* data(T (&src)[N]) noexcept { return src; }
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template<typename C>
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static constexpr auto
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data(C& src) noexcept(noexcept(src.data())) -> decltype(src.data()) {
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return src.data();
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}
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template<std::size_t N>
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static constexpr std::size_t size(T (&)[N]) noexcept { return N; }
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template<typename C>
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static constexpr auto
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size(const C& src) noexcept(noexcept(src.size())) -> decltype(src.size()) {
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return src.size();
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}
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};
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public:
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using value_type = T;
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using pointer = T*;
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using reference = T&;
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using iterator = pointer;
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using const_iterator = typename std::add_const<value_type>::type *;
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constexpr span() noexcept : ptr(nullptr), len(0) {}
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constexpr span(std::nullptr_t) noexcept : span() {}
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constexpr span(T* const src_ptr, const std::size_t src_len) noexcept
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: ptr(src_ptr), len(src_len) {
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}
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/*!
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A `span` is implicitly convertible from any type where `get::data(src)`
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returns a pointer convertible to T* and `get::size(src)` returns a
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`std::size_t`. This constructor is disabled for all other types.
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*/
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template<
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typename C,
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typename U = decltype(get::data(std::declval<C&>())),
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typename S = decltype(get::size(std::declval<C&>())),
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typename = typename std::enable_if<
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// Do not allow proxy iterators, but allow valid cv conversions
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std::is_pointer<U>::value && std::is_convertible<U, pointer>::value &&
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// Prevent underflow/overflow on size storage
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std::is_same<S, std::size_t>::value
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>::type
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>
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constexpr span(C&& src) noexcept(noexcept(get::data(src), get::size(src)))
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: span(get::data(src), get::size(src)) {
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}
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constexpr span(span&&) noexcept = default;
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constexpr span(span&) noexcept = default;
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constexpr span(const span&) noexcept = default;
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span& operator=(const span&) noexcept = default;
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constexpr iterator begin() const noexcept { return ptr; }
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constexpr const_iterator cbegin() const noexcept { return ptr; }
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constexpr iterator end() const noexcept { return begin() + size(); }
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constexpr const_iterator cend() const noexcept { return cbegin() + size(); }
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constexpr bool empty() const noexcept { return size() == 0; }
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constexpr pointer data() const noexcept { return ptr; }
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constexpr std::size_t size() const noexcept { return len; }
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constexpr std::size_t size_bytes() const noexcept { return size() * sizeof(value_type); }
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private:
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T* ptr;
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std::size_t len;
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};
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//! A `view` is a `span` over immutable data. See `span` for more info.
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template<typename T>
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using view = span<typename std::add_const<T>::type>;
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//! \return `src` aliased as a view of type `T`.
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template<typename T, typename U>
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view<T> view_cast(const span<U>& src) noexcept
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{
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using normalized = typename std::remove_cv<T>::type;
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static_assert(
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std::is_same<normalized, char>::value || std::is_same<normalized, std::uint8_t>::value,
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"only valid aliasing allowed - char or unsigned char target types"
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);
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static_assert(std::is_integral<U>::value, "only integral source types");
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return {reinterpret_cast<typename std::add_const<T>::type *>(src.data()), src.size_bytes()};
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}
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//! \return `src` aliased as a span of type `T`.
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template<typename T, typename U>
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span<T> pod_cast(U&& src) noexcept
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{
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using normalized = typename std::remove_cv<T>::type;
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static_assert(
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std::is_same<normalized, char>::value || std::is_same<normalized, std::uint8_t>::value,
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"only valid aliasing allowed - char or unsigned char target types"
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);
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using decayed = typename std::decay<U>::type;
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static_assert(std::is_pod<decayed>::value, "only POD types allowed for conversion");
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static_assert(alignof(decayed) == 1, "only types with 1 byte alignment allowed for conversion");
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return {reinterpret_cast<T*>(std::addressof(src)), sizeof(decayed)};
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}
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}
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Loading…
Reference in new issue