Add index_pool_config

1 files changed, 56 insertions, 0 deletions

diff --git a/asl/handle_pool/index_pool.hpp b/asl/handle_pool/index_pool.hpp
new file mode 100644
index 0000000..f874386
--- /dev/null
+++ b/asl/handle_pool/index_pool.hpp
@@ -0,0 +1,56 @@
+// 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
+{
+
+// @Todo Uniquely represented for the handle?
+
+template<
+    int kIndexBits_,
+    int kGenBits_,
+    typename UserType_ = empty,
+    int kUserBits_ = 0
+>
+requires (kIndexBits_ > 0 && kGenBits_ > 0 && kUserBits_ >= 0)
+struct index_pool_config
+{
+    static constexpr bool kHasUser = !same_as<UserType_, empty>;
+
+    using UserType          = UserType_;
+    using PrimitiveUserType = smallest_unsigned_integer_type_for_width<size_of<UserType> * 8>;
+
+    static_assert(trivially_copy_constructible<UserType>);
+    static_assert(size_of<UserType> == size_of<PrimitiveUserType>, "UserType should be of size 1, 2 or 4");
+
+    static constexpr int kUserBits = []() static -> int {
+        if constexpr (!kHasUser) { return 0; };
+        return kUserBits_ == 0 ? size_of<UserType> * 8 : kUserBits_;
+    }();
+
+    static_assert(kUserBits <= size_of<UserType> * 8);
+
+    static constexpr int kIndexBits = kIndexBits_;
+    static constexpr int kGenBits   = kGenBits_;
+
+    static_assert(kIndexBits + kGenBits + kUserBits <= 63);
+
+    using HandleType = smallest_unsigned_integer_type_for_width<kIndexBits + kGenBits + kUserBits + 1>;
+
+    static constexpr int kGenShift  = kIndexBits;
+    static constexpr int kUserShift = kIndexBits + kGenBits;
+
+    static constexpr HandleType kValidMask = HandleType{1} << (size_of<HandleType> * 8 - 1);
+    static constexpr HandleType kIndexMask = (HandleType{1} << kIndexBits) - 1;
+    static constexpr HandleType kGenMask   = ((HandleType{1} << kGenBits) - 1) << kGenShift;
+    static constexpr HandleType kUserMask  = ((HandleType{1} << kUserBits) - 1) << kUserShift;
+};
+
+} // namespace asl
+