util/SpanCast: add FromBytesStrict()

src/util/SpanCast.hxx

@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <cassert>
 #include <cstddef>
 #include <span>
 #include <string_view>
@@ -52,6 +53,18 @@ FromBytesFloor(std::span<CopyConst<T, std::byte>> other) noexcept
 	};
 }
 
+/**
+ * Like FromBytesFloor(), but assert that rounding is not necessary.
+ */
+template<typename T>
+constexpr std::span<T>
+FromBytesStrict(std::span<CopyConst<T, std::byte>> other) noexcept
+{
+	assert(other.size() % sizeof(T) == 0);
+
+	return FromBytesFloor<T>(other);
+}
+
 constexpr std::span<const char>
 ToSpan(std::string_view sv) noexcept
 {