1 files changed, 56 insertions, 0 deletions
diff --git a/fsa/src/vespa/fsa/unaligned.h b/fsa/src/vespa/fsa/unaligned.h
new file mode 100644
index 00000000000..ff645194e4f
--- /dev/null
+++ b/fsa/src/vespa/fsa/unaligned.h
@@ -0,0 +1,56 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <cstring>
+
+namespace fsa {
+
+template <typename T>
+class Unaligned {
+private:
+    char _data[sizeof(T)];
+
+public:
+    Unaligned() = delete;
+    Unaligned(const Unaligned &) = delete;
+    Unaligned(Unaligned &&) = delete;
+
+    Unaligned &operator=(const Unaligned &) = default;
+    Unaligned &operator=(Unaligned &&) = default;
+
+    static_assert(std::is_trivial_v<T>);
+    static_assert(alignof(T) > 1, "value is always aligned");
+
+    constexpr static Unaligned &at(void *p) noexcept {
+        return *reinterpret_cast<Unaligned*>(p);
+    }
+    constexpr static const Unaligned &at(const void *p) noexcept {
+        return *reinterpret_cast<const Unaligned*>(p);
+    }
+
+    constexpr static Unaligned *ptr(void *p) noexcept {
+        return reinterpret_cast<Unaligned*>(p);
+    }
+    constexpr static const Unaligned *ptr(const void *p) noexcept {
+        return reinterpret_cast<const Unaligned*>(p);
+    }
+
+    T read() const noexcept {
+        T value;
+        static_assert(sizeof(_data) == sizeof(value));
+        memcpy(&value, _data, sizeof(value));
+        return value;
+    }
+    void write(const T &value) noexcept {
+        static_assert(sizeof(_data) == sizeof(value));
+        memcpy(_data, &value, sizeof(value));
+    }
+    operator T () const noexcept { return read(); }
+    Unaligned &operator=(const T &value) noexcept {
+        write(value);
+        return *this;
+    }
+};
+
+}