1 files changed, 98 insertions, 0 deletions
diff --git a/serialize/packbits.hpp b/serialize/packbits.hpp
new file mode 100644
index 00000000..6e388846
--- /dev/null
+++ b/serialize/packbits.hpp
@@ -0,0 +1,98 @@
+#pragma once
+#include "compat/assert.hpp"
+#include <type_traits>
+#include <concepts>
+
+namespace floormat::Pack {
+template<std::unsigned_integral T, uint8_t N> struct Bits_;
+} // namespace floormat::Pack
+
+namespace floormat::detail_Pack {
+
+using namespace floormat::Pack;
+template<std::unsigned_integral T, size_t Sum, typename... Xs> struct check_size_overflow;
+
+template<std::unsigned_integral T, std::unsigned_integral U, size_t Sum, uint8_t N, typename... Xs>
+struct check_size_overflow<T, Sum, Bits_<U, N>, Xs...>
+{
+    static_assert(std::is_same_v<T, U>);
+    static constexpr auto acc = Sum + size_t{N};
+    using next_check = check_size_overflow<T, acc, Xs...>;
+    static constexpr auto size = next_check::size;
+    static constexpr bool result = next_check::result;
+};
+
+template<std::unsigned_integral T, size_t Sum>
+struct check_size_overflow<T, Sum>
+{
+    static constexpr size_t size = Sum;
+    static constexpr bool result = Sum <= sizeof(T)*8;
+};
+
+template<std::unsigned_integral T, size_t Capacity>
+struct Storage
+{
+    static_assert(Capacity <= sizeof(T)*8);
+    T value;
+
+    template<size_t N>
+    constexpr T get()
+    {
+        static_assert(N <= sizeof(T)*8);
+        static_assert(N <= Capacity);
+        return T(value & (T(1) << N) - T(1));
+    }
+
+    template<size_t N>
+    constexpr T advance()
+    {
+        static_assert(N <= sizeof(T)*8);
+        static_assert(N <= Capacity);
+        return T(value >> N);
+    }
+
+    template<size_t N> [[maybe_unused]] constexpr bool check_zero() = delete;
+
+    template<size_t N>
+    using next = Storage<T, Capacity - N>;
+};
+
+template<std::unsigned_integral T>
+struct Storage<T, 0>
+{
+    T value;
+
+    template<size_t N> [[maybe_unused]] constexpr T get() = delete;
+    template<size_t N> [[maybe_unused]] constexpr T advance() = delete;
+
+    template<size_t N> constexpr inline bool check_zero()
+    {
+        fm_assert(value == T(0));
+        return true;
+    }
+
+    template<size_t N> struct next
+    {
+        static_assert(!std::is_same_v<T, void>, "reading past the end");
+        static_assert( std::is_same_v<T, void>, "can't happen!");
+    };
+};
+
+} // namespace floormat::detail_Pack
+
+namespace floormat::Pack {
+
+template<std::unsigned_integral T, uint8_t N>
+struct Bits_ final
+{
+    static_assert(std::is_fundamental_v<T>);
+    static_assert(N > 0);
+    static_assert(N < sizeof(T)*8);
+
+    using type = T;
+    static constexpr auto bits = N;
+};
+
+
+
+} // namespace floormat::Pack