From 7b0197e6c2b2d3a6d30632f2663c2612dbda419a Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Thu, 15 Jan 2026 20:42:19 -0500
Subject: [PATCH] trace.util: add Unix_util and Mock_

---
 src/util/dune               |  5 ++++
 src/util/mock_.ml           | 46 +++++++++++++++++++++++++++++++++++++
 src/util/unix_util.dummy.ml |  1 +
 src/util/unix_util.mli      |  1 +
 src/util/unix_util.real.ml  |  1 +
 5 files changed, 54 insertions(+)
 create mode 100644 src/util/mock_.ml
 create mode 100644 src/util/unix_util.dummy.ml
 create mode 100644 src/util/unix_util.mli
 create mode 100644 src/util/unix_util.real.ml

diff --git a/src/util/dune b/src/util/dune
index 9bc0f53..68c028f 100644
--- a/src/util/dune
+++ b/src/util/dune
@@ -16,6 +16,11 @@
    (mtime mtime.clock.jsoo -> time_util.mtime.ml)
    (unix -> time_util.unix.ml)
    (-> time_util.dummy.ml))
+  (select
+    unix_util.ml
+    from
+    (unix -> unix_util.real.ml)
+    (-> unix_util.dummy.ml))
   (select
    domain_util.ml
    from
diff --git a/src/util/mock_.ml b/src/util/mock_.ml
new file mode 100644
index 0000000..b98fc70
--- /dev/null
+++ b/src/util/mock_.ml
@@ -0,0 +1,46 @@
+(** Mocking for tests *)
+
+module Inner = struct
+  let mock = ref false
+  let get_now_ns_ref = ref Time_util.get_time_ns
+  let get_tid_ref = ref Thread_util.get_tid
+  let get_pid_ref = ref Unix_util.get_pid
+
+  (** used to mock timing *)
+  let make_time_mock () : unit -> int64 =
+    let time_ = ref 0 in
+
+    let get_now_ns () : int64 =
+      let x = !time_ in
+      incr time_;
+      Int64.(mul (of_int x) 1000L)
+    in
+    get_now_ns
+end
+
+(** Now, in nanoseconds. Uses {!get_now_ns_ref} *)
+let[@inline] now_ns () : int64 =
+  if !Inner.mock then
+    !Inner.get_now_ns_ref ()
+  else
+    Time_util.get_time_ns ()
+
+(** Current thread's ID. Uses {!get_tid_ref} *)
+let[@inline] get_tid () : int =
+  if !Inner.mock then
+    !Inner.get_tid_ref ()
+  else
+    Thread_util.get_tid ()
+
+let[@inline] get_pid () : int =
+  if !Inner.mock then
+    !Inner.get_pid_ref ()
+  else
+    Unix_util.get_pid ()
+
+let mock_all () : unit =
+  Inner.mock := true;
+  (Inner.get_pid_ref := fun () -> 2);
+  (Inner.get_tid_ref := fun () -> 3);
+  Inner.get_now_ns_ref := Inner.make_time_mock ();
+  ()
diff --git a/src/util/unix_util.dummy.ml b/src/util/unix_util.dummy.ml
new file mode 100644
index 0000000..9c81b96
--- /dev/null
+++ b/src/util/unix_util.dummy.ml
@@ -0,0 +1 @@
+let get_pid () = -1
diff --git a/src/util/unix_util.mli b/src/util/unix_util.mli
new file mode 100644
index 0000000..8920e24
--- /dev/null
+++ b/src/util/unix_util.mli
@@ -0,0 +1 @@
+val get_pid : unit -> int
diff --git a/src/util/unix_util.real.ml b/src/util/unix_util.real.ml
new file mode 100644
index 0000000..8d4ec6e
--- /dev/null
+++ b/src/util/unix_util.real.ml
@@ -0,0 +1 @@
+let get_pid = Unix.getpid