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C++

// Copyright 2025 Steven Le Rouzic
//
// SPDX-License-Identifier: BSD-3-Clause
#pragma once
#include "asl/base/meta.hpp"
#include "asl/base/assert.hpp"
#include "asl/base/annotations.hpp"
#include "asl/memory/layout.hpp"
namespace asl
{
static constexpr isize_t dynamic_size = -1;
// NOLINTBEGIN(*-convert-member-functions-to-static)
template<typename T>
class contiguous_iterator
{
T* m_ptr;
public:
constexpr explicit contiguous_iterator(T* ptr) : m_ptr{ptr} {}
constexpr bool operator==(this contiguous_iterator self, contiguous_iterator other) = default;
constexpr contiguous_iterator& operator++()
{
m_ptr += 1;
return *this;
}
constexpr contiguous_iterator operator++(int)
{
return contiguous_iterator{ exchange(m_ptr, m_ptr + 1) };
}
constexpr T& operator*(this contiguous_iterator self) { return *self.m_ptr; }
constexpr T* operator->(this contiguous_iterator self) { return self.m_ptr; }
};
template<typename T>
contiguous_iterator(T) -> contiguous_iterator<T>;
template<is_object T, isize_t kSize = dynamic_size>
class span
{
static constexpr bool is_dynamic(isize_t size)
{
return size < 0;
}
static constexpr bool kIsDynamic = is_dynamic(kSize);
using SizeType = select_t<kIsDynamic, isize_t, empty>;
T* m_data{};
ASL_NO_UNIQUE_ADDRESS SizeType m_size{};
public:
constexpr span() requires (kIsDynamic || kSize == 0) = default;
constexpr span(T* data, isize_t size)
requires kIsDynamic
: m_data{data}
, m_size{size}
{}
constexpr explicit span(T* data, [[maybe_unused]] isize_t size)
requires (!kIsDynamic)
: m_data{data}
{
ASL_ASSERT(size == kSize);
}
template<isize_t N>
constexpr span(T (&array)[N]) // NOLINT(*explicit*)
requires (kIsDynamic)
: m_data{static_cast<T*>(array)}
, m_size{N}
{}
template<isize_t N>
constexpr span(T (&array)[N]) // NOLINT(*explicit*)
requires (!kIsDynamic) && (N == kSize)
: m_data{static_cast<T*>(array)}
{}
template<is_object U, isize_t kOtherSize>
constexpr explicit(!kIsDynamic)
span(const span<U, kOtherSize>& other)
requires (
(
kIsDynamic ||
is_dynamic(kOtherSize) ||
kOtherSize == kSize
) && convertible_to<U(&)[], T(&)[]>
)
: span{static_cast<U*>(other.data()), other.size()}
{
}
constexpr span(const span&) = default;
constexpr span(span&&) = default;
constexpr span& operator=(const span&) = default;
constexpr span& operator=(span&&) = default;
~span() = default;
[[nodiscard]] constexpr isize_t size(this span self)
{
if constexpr (kIsDynamic) { return self.m_size; }
else { return kSize; }
}
[[nodiscard]] constexpr isize_t size_bytes(this span self) { return self.size() * size_of<T>; }
[[nodiscard]] constexpr bool is_empty(this span self) { return self.size() == 0; }
[[nodiscard]] constexpr T* data(this span self) { return self.m_data; }
[[nodiscard]] constexpr contiguous_iterator<T> begin(this span self)
{
return contiguous_iterator{self.m_data};
}
[[nodiscard]] constexpr contiguous_iterator<T> end(this span self)
{
return contiguous_iterator{self.m_data + self.size()};
}
constexpr T& operator[](this span self, isize_t i)
{
ASL_ASSERT(i >= 0 && i < self.size());
return self.m_data[i]; // NOLINT(*-pointer-arithmetic)
}
template<isize_t kOffset, isize_t kSubSize = dynamic_size>
[[nodiscard]] constexpr auto subspan(this span self)
requires (
kOffset >= 0 &&
(kIsDynamic || kOffset <= kSize) &&
(kIsDynamic || is_dynamic(kSubSize) || kSubSize <= kSize - kOffset)
)
{
ASL_ASSERT(kOffset <= self.size());
if constexpr (is_dynamic(kSubSize))
{
if constexpr (kIsDynamic)
{
return span<T>(self.data() + kOffset, self.size() - kOffset);
}
else
{
return span<T, kSize - kOffset>(self.data() + kOffset, self.size() - kOffset);
}
}
else
{
ASL_ASSERT(kSubSize <= self.size() - kOffset);
return span<T, kSubSize>(self.data() + kOffset, kSubSize);
}
}
[[nodiscard]] constexpr span<T> subspan(this span self, isize_t offset)
{
ASL_ASSERT(offset <= self.size());
return span<T>{ self.data() + offset, self.size() - offset };
}
[[nodiscard]] constexpr span<T> subspan(this span self, isize_t offset, isize_t sub_size)
{
ASL_ASSERT(offset <= self.size() && !is_dynamic(sub_size));
ASL_ASSERT(sub_size <= self.size() - offset);
return span<T>{ self.data() + offset, sub_size };
}
template<isize_t kSubSize>
[[nodiscard]] constexpr auto first(this span self)
requires (
kSubSize >= 0 &&
(kIsDynamic || kSubSize <= kSize)
)
{
ASL_ASSERT(kSubSize <= self.size());
return span<T, kSubSize>{ self.data(), kSubSize };
}
[[nodiscard]] constexpr span<T> first(this span self, isize_t sub_size)
{
ASL_ASSERT(sub_size >= 0 && sub_size <= self.size());
return span<T>{ self.data(), sub_size };
}
template<isize_t kSubSize>
[[nodiscard]] constexpr auto last(this span self)
requires (
kSubSize >= 0 &&
(kIsDynamic || kSubSize <= kSize)
)
{
ASL_ASSERT(kSubSize <= self.size());
return span<T, kSubSize>{ self.data() + self.size() - kSubSize, kSubSize };
}
[[nodiscard]] constexpr span<T> last(this span self, isize_t sub_size)
{
ASL_ASSERT(sub_size >= 0 && sub_size <= self.size());
return span<T>{ self.data() + self.size() - sub_size, sub_size };
}
};
// NOLINTEND(*-convert-member-functions-to-static)
template<is_object T, isize_t kSize>
inline span<const byte> as_bytes(span<T, kSize> s)
{
return span<const byte>(
reinterpret_cast<const byte*>(s.data()), // NOLINT(*-reinterpret-cast)
s.size_bytes());
}
template<is_object T, isize_t kSize>
inline span<byte> as_mutable_bytes(span<T, kSize> s)
requires (!is_const<T>)
{
return span<byte>(
reinterpret_cast<byte*>(s.data()), // NOLINT(*-reinterpret-cast)
s.size_bytes());
}
template<is_object T, isize_t kSize>
span(T (&)[kSize]) -> span<T, kSize>;
} // namespace asl