add opentelemetry_ptime with a clock

src/ptime/opentelemetry_ptime.ml

@@ -0,0 +1,32 @@
+open Opentelemetry_core
+
+open struct
+  module TS = Timestamp_ns
+
+  let ns_in_a_day = Int64.(mul 1_000_000_000L (of_int (24 * 3600)))
+end
+
+(** Current unix timestamp in nanoseconds *)
+let[@inline] now_unix_ns () : TS.t =
+  let span = Ptime_clock.now () |> Ptime.to_span in
+  let d, ps = Ptime.Span.to_d_ps span in
+  let d = Int64.(mul (of_int d) ns_in_a_day) in
+  let ns = Int64.(div ps 1_000L) in
+  Int64.(add d ns)
+
+let clock : Clock.t = { now = now_unix_ns }
+
+(** Nicer pretty-printer *)
+let pp_debug out (self : TS.t) =
+  let d = Int64.(to_int (div self ns_in_a_day)) in
+  let ns = Int64.(rem self ns_in_a_day) in
+  let ps = Int64.(mul ns 1_000L) in
+  match Ptime.Span.of_d_ps (d, ps) with
+  | None -> Format.fprintf out "ts: <%Ld ns>" self
+  | Some span ->
+    (match Ptime.add_span Ptime.epoch span with
+    | None -> Format.fprintf out "ts: <%Ld ns>" self
+    | Some ptime -> Ptime.pp_human () out ptime)
+
+(** Install as main clock. *)
+let set_as_main () = Clock.Main.set clock