From b37d1d71f115f6b5a0000e09c7be063994387e1a Mon Sep 17 00:00:00 2001
From: Ryan Ofsky <ryan@ofsky.org>
Date: Sat, 6 Jun 2026 18:27:03 -0400
Subject: [PATCH] type-chrono: Add CustomBuildField/CustomReadField overloads
 for std::chrono::time_point

Needed by bitcoin/bitcoin#34882 which uses NodeClock::time_point in the
Node stats struct (m_last_send, m_last_recv, m_ping_start), requiring
IPC serialization support for time_point types.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 include/mp/type-chrono.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/mp/type-chrono.h b/include/mp/type-chrono.h
index d7154986..f58adddf 100644
--- a/include/mp/type-chrono.h
+++ b/include/mp/type-chrono.h
@@ -29,6 +29,29 @@ decltype(auto) CustomReadField(TypeList<std::chrono::duration<Rep, Period>>, Pri
 {
     return read_dest.construct(input.get());
 }
+
+//! Overload CustomBuildField and CustomReadField to serialize
+//! std::chrono::time_point parameters and return values as integer tick counts.
+//! The capnp field type must be an integer type with enough range to hold the
+//! time_since_epoch() count for the given Duration (e.g. Int64 for nanoseconds).
+template <class Clock, class Duration, typename Value, typename Output>
+void CustomBuildField(TypeList<std::chrono::time_point<Clock, Duration>>, Priority<1>, InvokeContext& invoke_context,
+                      Value&& value, Output&& output)
+{
+    using Rep = typename Duration::rep;
+    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::time_point 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::time_point value");
+    output.set(value.time_since_epoch().count());
+}
+
+template <class Clock, class Duration, typename Input, typename ReadDest>
+decltype(auto) CustomReadField(TypeList<std::chrono::time_point<Clock, Duration>>, Priority<1>,
+                               InvokeContext& invoke_context, Input&& input, ReadDest&& read_dest)
+{
+    return read_dest.construct(std::chrono::time_point<Clock, Duration>{Duration{input.get()}});
+}
 } // namespace mp
 
 #endif // MP_PROXY_TYPE_CHRONO_H