From 68bd5fdbb6a94fd90575e2e2199365a0c2b9db68 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 18 Apr 2022 13:08:26 -0700
Subject: [PATCH 2/6] Refactor to simplify clock resolution support

* src/timefns.c (timespec_mpz, timespec_ticks):
New args HZ, RES.  All callers changed.
(timespec_clockres_to_lisp): New function,
extended from timespec_to_lisp.
(timespec_to_lisp): Use it.
(make_lisp_time_clockres): New function, extended from make_lisp_time.
(make_lisp_time): Use it.
---
 src/timefns.c | 61 ++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 43 insertions(+), 18 deletions(-)

diff --git a/src/timefns.c b/src/timefns.c
index b0b84a438c..3f8efadf54 100644
--- a/src/timefns.c
+++ b/src/timefns.c
@@ -482,30 +482,37 @@ mpz_set_time (mpz_t rop, time_t t)
     mpz_set_uintmax (rop, t);
 }
 
-/* Store into mpz[0] a clock tick count for T, assuming a
-   TIMESPEC_HZ-frequency clock.  Use mpz[1] as a temp.  */
+/* Store into mpz[0] a clock tick count for T, assuming a HZ-frequency
+   clock with resolution RES ns (so that HZ*RES = TIMESPEC_HZ).
+   Use mpz[1] as a temp.  */
 static void
-timespec_mpz (struct timespec t)
+timespec_mpz (struct timespec t, long int hz, long int res)
 {
-  /* mpz[0] = sec * TIMESPEC_HZ + nsec.  */
-  mpz_set_ui (mpz[0], t.tv_nsec);
+  /* mpz[0] = sec * hz + nsec / res.  */
+  mpz_set_ui (mpz[0], t.tv_nsec / res);
   mpz_set_time (mpz[1], t.tv_sec);
-  mpz_addmul_ui (mpz[0], mpz[1], TIMESPEC_HZ);
+  mpz_addmul_ui (mpz[0], mpz[1], hz);
 }
 
-/* Convert T to a Lisp integer counting TIMESPEC_HZ ticks.  */
+/* Convert T to a Lisp integer counting HZ ticks each consisting
+   of RES ns.  */
 static Lisp_Object
-timespec_ticks (struct timespec t)
+timespec_ticks (struct timespec t, long int hz, long int res)
 {
+  eassume (0 <= t.tv_nsec && t.tv_nsec < TIMESPEC_HZ);
+  eassume (0 < hz && hz <= TIMESPEC_HZ);
+  eassume (0 < res && res <= TIMESPEC_HZ);
+  eassume (hz * res == TIMESPEC_HZ);
+
   /* For speed, use intmax_t arithmetic if it will do.  */
   intmax_t accum;
   if (FASTER_TIMEFNS
-      && !INT_MULTIPLY_WRAPV (t.tv_sec, TIMESPEC_HZ, &accum)
-      && !INT_ADD_WRAPV (t.tv_nsec, accum, &accum))
+      && !INT_MULTIPLY_WRAPV (t.tv_sec, hz, &accum)
+      && !INT_ADD_WRAPV (t.tv_nsec / res, accum, &accum))
     return make_int (accum);
 
   /* Fall back on bignum arithmetic.  */
-  timespec_mpz (t);
+  timespec_mpz (t, hz, res);
   return make_integer_mpz ();
 }
 
@@ -565,9 +572,26 @@ lisp_time_seconds (struct lisp_time t)
   return make_integer_mpz ();
 }
 
-/* Convert T to a Lisp timestamp.  */
+/* Return (TICKS . LISPHZ) for time T, assuming a LISPHZ,HZ,RES clock.  */
+static Lisp_Object
+timespec_clockres_to_lisp (struct timespec t, Lisp_Object lisphz,
+			   long int hz, long int res)
+{
+  return Fcons (timespec_ticks (t, hz, res), lisphz);
+}
+
+/* Return (TICKS . HZ) for time T, assuming a clock resolution of 1 ns.  */
 Lisp_Object
-make_lisp_time (struct timespec t)
+timespec_to_lisp (struct timespec t)
+{
+  return timespec_clockres_to_lisp (t, timespec_hz, TIMESPEC_HZ, 1);
+}
+
+/* Convert T to a Lisp timestamp, assuming a LISPHZ or HZ-frequency
+   clock with resolution RES ns (so that HZ*RES = TIMESPEC_HZ).  */
+static Lisp_Object
+make_lisp_time_clockres (struct timespec t, Lisp_Object lisphz,
+			 long int hz, long int res)
 {
   if (CURRENT_TIME_LIST)
     {
@@ -577,14 +601,14 @@ make_lisp_time (struct timespec t)
 		    make_fixnum (ns / 1000), make_fixnum (ns % 1000 * 1000));
     }
   else
-    return timespec_to_lisp (t);
+    return timespec_clockres_to_lisp (t, lisphz, hz, res);
 }
 
-/* Return (TICKS . HZ) for time T.  */
+/* Convert T to a Lisp timestamp.  */
 Lisp_Object
-timespec_to_lisp (struct timespec t)
+make_lisp_time (struct timespec t)
 {
-  return Fcons (timespec_ticks (t), timespec_hz);
+  return make_lisp_time_clockres (t, timespec_hz, TIMESPEC_HZ, 1);
 }
 
 /* Return NUMERATOR / DENOMINATOR, rounded to the nearest double.
@@ -747,7 +771,8 @@ decode_time_components (enum timeform form,
       }
 
     case TIMEFORM_NIL:
-      return decode_ticks_hz (timespec_ticks (current_timespec ()),
+      return decode_ticks_hz (timespec_ticks (current_timespec (),
+					      TIMESPEC_HZ, 1),
 			      timespec_hz, result, dresult);
 
     default:
-- 
2.35.1