free_list_iterator.hpp

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// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Daniel Polo
 
#ifndef IT_D4NP_MEMORYPOOL_FREE_LIST_ITERATOR_HPP_
#define IT_D4NP_MEMORYPOOL_FREE_LIST_ITERATOR_HPP_
 
#include <it/d4np/memorypool/memory_pool.h>
 
#if PBR_MEMORY_POOL_DIAGNOSTICS
 
#include <it/d4np/memorypool/memory_pool.hpp>
 
#include <cstddef>
#include <iterator>
 
namespace it::d4np::memorypool {
 
class FreeListIterator {
public:
    using iterator_category = std::forward_iterator_tag;
    using value_type = const void*;
    using difference_type = std::ptrdiff_t;
    using pointer = const value_type*;
    using reference = const value_type&;
 
    FreeListIterator() noexcept = default;
 
    FreeListIterator(const memory_pool_t* pool, const void* current) noexcept : pool_(pool), current_(current) {}
 
    [[nodiscard]] reference operator*() const noexcept {
        return current_;
    }
 
    [[nodiscard]] pointer operator->() const noexcept {
        return &current_;
    }
 
    FreeListIterator& operator++() noexcept {
        current_ = ::memory_pool_debug_free_list_next(pool_, current_);
        return *this;
    }
 
    // NOLINTNEXTLINE(readability-const-return-type)
    const FreeListIterator operator++(int) noexcept {
        const FreeListIterator previous = *this;
        ++(*this);
        return previous;
    }
 
    [[nodiscard]] bool operator==(const FreeListIterator& rhs) const noexcept {
        return current_ == rhs.current_;
    }
 
    [[nodiscard]] bool operator!=(const FreeListIterator& rhs) const noexcept {
        return !(*this == rhs);
    }
 
private:
    const memory_pool_t* pool_ = nullptr;
    const void* current_ = nullptr;
};
 
class FreeListView {
public:
    explicit FreeListView(const memory_pool_t* pool) noexcept : pool_(pool) {}
 
    explicit FreeListView(Pool& pool) noexcept : pool_(pool.native_handle()) {}
 
    [[nodiscard]] FreeListIterator begin() const noexcept {
        return {pool_, ::memory_pool_debug_free_list_head(pool_)};
    }
 
    [[nodiscard]] FreeListIterator end() const noexcept {
        return {pool_, nullptr};
    }
 
private:
    const memory_pool_t* pool_;
};
 
}  // namespace it::d4np::memorypool
 
#endif  // PBR_MEMORY_POOL_DIAGNOSTICS
 
#endif  // IT_D4NP_MEMORYPOOL_FREE_LIST_ITERATOR_HPP_