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// Copyright 2025 Steven Le Rouzic
//
// SPDX-License-Identifier: BSD-3-Clause
#include "asl/base/integers.hpp"
#include "asl/base/meta.hpp"
#include "asl/containers/chunked_buffer.hpp"
#include "asl/memory/allocator.hpp"
namespace asl
{
template<
int kIndexSize_,
int kGenSize_,
int kUserSize_ = 0
>
requires (
kUserSize_ >= 0
&& kGenSize_ > 0
&& kIndexSize_ > 0
&& (kUserSize_ + kGenSize_ + kIndexSize_ <= 63)
)
struct index_pool_config
{
static constexpr int kUserSize = kUserSize_;
static constexpr int kGenSize = kGenSize_;
static constexpr int kIndexSize = kIndexSize_;
static constexpr bool kHasUser = kUserSize > 0;
using handle_type = smallest_unsigned_integer_type_for_width<kGenSize + kIndexSize + kUserSize>;
using user_type = select_t<kHasUser, smallest_unsigned_integer_type_for_width<kUserSize>, empty>;
};
template<
int kIndexSize_,
int kGenSize_,
typename UserType = empty,
int kUserSize_ = 0
>
requires (
same_as<UserType, empty> || (kUserSize_ <= size_of<UserType> * 8 && trivially_copy_constructible<UserType>)
)
class index_pool_handle_base
{
static constexpr int kUserSizeComputed =
same_as<UserType, empty> ? 0 : (kUserSize_ == 0 ? size_of<UserType> * 8 : kUserSize_); // NOLINT
public:
using config = index_pool_config<kIndexSize_, kGenSize_, kUserSizeComputed>;
private:
using handle_type = config::handle_type;
using user_type = config::user_type;
using user_type_external = UserType;
static constexpr handle_type kHasValueMask = ~(~handle_type{0} >> 1);
static constexpr handle_type kIndexMask = (handle_type{1} << config::kIndexSize) - 1;
static constexpr int kGenShift = config::kIndexSize;
static constexpr handle_type kGenMask = ((handle_type{1} << config::kGenSize) - 1) << kGenShift;
static constexpr int kUserShift = config::kIndexSize + config::kGenSize;
static constexpr handle_type kUserMask = ((handle_type{1} << config::kUserSize) - 1) << kUserShift;
handle_type m_handle{};
public:
[[nodiscard]] constexpr bool has_value() const { return m_handle & kHasValueMask; }
[[nodiscard]] constexpr user_type_external user() const
requires config::kHasUser
{
return bit_cast<user_type_external>(
static_cast<user_type>((m_handle & kUserMask) >> kUserShift)
);
}
};
class IndexPool
{
};
} // namespace asl
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