From a78e24e9ebf24fb9980328b4103c8351bae23ff3 Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Thu, 26 Jun 2025 07:51:36 +0200
Subject: Add DenseHandlePool

---
 asl/handle_pool/dense_handle_pool.hpp | 162 ++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 asl/handle_pool/dense_handle_pool.hpp

(limited to 'asl/handle_pool/dense_handle_pool.hpp')

diff --git a/asl/handle_pool/dense_handle_pool.hpp b/asl/handle_pool/dense_handle_pool.hpp
new file mode 100644
index 0000000..34cd04f
--- /dev/null
+++ b/asl/handle_pool/dense_handle_pool.hpp
@@ -0,0 +1,162 @@
+// Copyright 2025 Steven Le Rouzic
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#pragma once
+
+#include "asl/handle_pool/index_pool.hpp"
+#include "asl/memory/allocator.hpp"
+#include "asl/containers/chunked_buffer.hpp"
+
+
+namespace asl
+{
+
+// @Todo If we want the allocator to be non-copyable, we could
+// introduce a reference allocator type that is copyable, and store
+// the "main" allocator in the pool.
+
+template<
+    is_object T,
+    int kIndexBits,
+    int kGenBits,
+    typename UserType = empty,
+    int kUserBits = 0,
+    isize_t kChunkSize = 32,
+    allocator Allocator = DefaultAllocator>
+requires moveable<T> && copyable<Allocator>
+class DenseHandlePool
+{
+    using ThisIndexPool = IndexPool<kIndexBits, kGenBits, UserType, kUserBits, isize_t, Allocator>;
+
+    struct Slot
+    {
+        ThisIndexPool::handle h;
+        T obj;
+
+        template<typename... Args>
+        explicit Slot(ThisIndexPool::handle h, Args&&... args)
+            : h{h}
+            , obj(std::forward<Args>(args)...)
+        {}
+    };
+
+    using Buffer = chunked_buffer<Slot, kChunkSize, Allocator>;
+
+    ThisIndexPool m_index_pool{};
+    Buffer        m_buffer{};
+
+    using config = ThisIndexPool::handle::config;
+
+    template<typename... Args>
+    isize_t push(Args&&... args)
+        requires constructible_from<T, Args&&...>
+    {
+        m_buffer.push(typename ThisIndexPool::handle{}, std::forward<Args>(args)...);
+        return m_buffer.size() - 1;
+    }
+
+public:
+    using handle = ThisIndexPool::handle;
+
+    DenseHandlePool() requires default_constructible<Allocator> = default;
+
+    explicit DenseHandlePool(const Allocator& allocator)
+        : m_index_pool(allocator)
+        , m_buffer(allocator)
+    {}
+
+    ASL_DELETE_COPY(DenseHandlePool);
+    ASL_DEFAULT_MOVE(DenseHandlePool);
+    ~DenseHandlePool() = default;
+
+    [[nodiscard]] bool is_full() const
+    {
+        return m_index_pool.is_full();
+    }
+
+    bool is_valid(handle h) const
+    {
+        return m_index_pool.is_valid(h);
+    }
+
+    template<typename... Args>
+    option<handle> acquire(config::UserType user, Args&&... args)
+        requires config::kHasUser && constructible_from<T, Args&&...>
+    {
+        if (is_full()) { return nullopt; }
+        const isize_t obj_index = push(std::forward<Args>(args)...);
+        const auto handle = m_index_pool.acquire_ensure(user, obj_index);
+        m_buffer[obj_index].h = handle;
+        return handle;
+    }
+
+    template<typename... Args>
+    option<handle> acquire(Args&&... args)
+        requires (!config::kHasUser) && constructible_from<T, Args&&...>
+    {
+        if (is_full()) { return nullopt; }
+        const isize_t obj_index = push(std::forward<Args>(args)...);
+        const auto handle = m_index_pool.acquire_ensure(obj_index);
+        m_buffer[obj_index].h = handle;
+        return handle;
+    }
+
+    template<typename... Args>
+    handle acquire_ensure(config::UserType user, Args&&... args)
+        requires config::kHasUser && constructible_from<T, Args&&...>
+    {
+        ASL_ASSERT_RELEASE(!is_full());
+        const isize_t obj_index = push(std::forward<Args>(args)...);
+        const auto handle = m_index_pool.acquire_ensure(user, obj_index);
+        m_buffer[obj_index].h = handle;
+        return handle;
+    }
+
+    template<typename... Args>
+    handle acquire_ensure(Args&&... args)
+        requires (!config::kHasUser) && constructible_from<T, Args&&...>
+    {
+        ASL_ASSERT_RELEASE(!is_full());
+        const isize_t obj_index = push(std::forward<Args>(args)...);
+        const auto handle = m_index_pool.acquire_ensure(obj_index);
+        m_buffer[obj_index].h = handle;
+        return handle;
+    }
+
+    void release(handle to_release_handle)
+    {
+        if (!is_valid(to_release_handle)) { return; }
+
+        const auto to_release_index = *m_index_pool.get_payload(to_release_handle);
+        if (to_release_index < m_buffer.size() - 1)
+        {
+            const auto to_swap_index = m_buffer.size() - 1;
+            const auto to_swap_handle = m_buffer[to_swap_index].h;
+
+            m_buffer[to_release_index] = std::move(m_buffer[to_swap_index]);
+            m_index_pool.exchange_payload(to_swap_handle, to_release_index);
+        }
+
+        m_buffer.pop();
+        m_index_pool.release(to_release_handle);
+    }
+
+    auto get(this auto&& self, handle h)
+        -> copy_const_t<un_ref_t<decltype(self)>, T>*
+    {
+        if (!self.is_valid(h)) { return nullptr; }
+        const auto index = *self.m_index_pool.get_payload(h);
+        return &self.m_buffer[index].obj;
+    }
+
+    auto get_ensure(this auto&& self, handle h)
+        -> copy_cref_t<decltype(self), T>
+    {
+        ASL_ASSERT_RELEASE(self.is_valid(h));
+        const auto index = *self.m_index_pool.get_payload(h);
+        return std::forward<decltype(self)>(self).m_buffer[index].obj;
+    }
+};
+
+} // namespace asl
-- 
cgit