moveonly: add mp/type-chrono.h

Definitions moved from
https://github.com/bitcoin/bitcoin/blob/0a931a9787b196d7a620863cc143d9319ffd356d/src/ipc/capnp/common-types.h#L97-L115

Author: ryanofsky

CMakeLists.txt

@@ -46,6 +46,7 @@ set(MP_PUBLIC_HEADERS
   include/mp/proxy-types.h
   include/mp/proxy.h
   include/mp/type-char.h
+  include/mp/type-chrono.h
   include/mp/type-context.h
   include/mp/type-decay.h
   include/mp/type-exception.h

include/mp/type-chrono.h

@@ -0,0 +1,34 @@
+// Copyright (c) 2025 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef MP_PROXY_TYPE_CHRONO_H
+#define MP_PROXY_TYPE_CHRONO_H
+
+#include <mp/util.h>
+
+#include <chrono>
+
+namespace mp {
+//! Overload CustomBuildField and CustomReadField to serialize std::chrono
+//! parameters and return values as numbers.
+template <class Rep, class Period, typename Value, typename Output>
+void CustomBuildField(TypeList<std::chrono::duration<Rep, Period>>, Priority<1>, InvokeContext& invoke_context, Value&& value,
+                      Output&& output)
+{
+    static_assert(std::numeric_limits<decltype(output.get())>::lowest() <= std::numeric_limits<Rep>::lowest(),
+                  "capnp type does not have enough range to hold lowest std::chrono::duration value");
+    static_assert(std::numeric_limits<decltype(output.get())>::max() >= std::numeric_limits<Rep>::max(),
+                  "capnp type does not have enough range to hold highest std::chrono::duration value");
+    output.set(value.count());
+}
+
+template <class Rep, class Period, typename Input, typename ReadDest>
+decltype(auto) CustomReadField(TypeList<std::chrono::duration<Rep, Period>>, Priority<1>, InvokeContext& invoke_context,
+                               Input&& input, ReadDest&& read_dest)
+{
+    return read_dest.construct(input.get());
+}
+} // namespace mp
+
+#endif // MP_PROXY_TYPE_CHRONO_H