#include <array>
#include <type_traits>

template <typename T>
constexpr auto array_from_object(const T& obj) {
	std::array<unsigned char, sizeof(T)> ret;
	for (std::size_t i = 0; i < sizeof(T); ++i) {
		ret[i] = reinterpret_cast<const unsigned char*>(&obj)[i];
	}
	return ret;
}

// iterator-aware hasher
template <
    typename it,
    typename = std::enable_if_t<
        std::is_pointer<decltype(&*std::declval<it>())>::value
        // and
        // std::has_unique_object_representations<decltype(*std::declval<it>())>::value
        >>
constexpr auto FNV32a(it begin, it end) -> uint32_t {
	const uint32_t FNV_32_PRIME = 16777619;
	uint32_t hval = 2166136261;
	for (it p = begin; p != end; ++p) {
		// get *p as a reference to array of unsigned char
		auto repr = array_from_object(*p);
		for (auto ch : repr) {
			hval ^= std::uint32_t{ch};
			hval *= FNV_32_PRIME;
		}
	}
	return hval;
}