From 12d767123fea2f605c5adc57ffe80d40c6d11449 Mon Sep 17 00:00:00 2001
From: Julien Jerphanion <git@jjerphan.xyz>
Date: Wed, 20 Mar 2024 17:24:39 +0100
Subject: [PATCH 1/2] maint: Replace usage of folly in `clock.hpp`

Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>
---
 cpp/arcticdb/util/clock.hpp | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/cpp/arcticdb/util/clock.hpp b/cpp/arcticdb/util/clock.hpp
index 0ddc5481cc..a1da36b68b 100644
--- a/cpp/arcticdb/util/clock.hpp
+++ b/cpp/arcticdb/util/clock.hpp
@@ -9,29 +9,20 @@
 
 #include <arcticdb/entity/types.hpp>
 
-#include <folly/ClockGettimeWrappers.h>
-#include <folly/portability/Time.h>
-#ifndef CLOCK_REALTIME_COARSE
 #include <chrono>
-#endif
 
 namespace arcticdb::util {
 
 class SysClock {
   public:
     static entity::timestamp nanos_since_epoch() {
-        return (*folly::chrono::clock_gettime_ns)(CLOCK_REALTIME);
-    }
-#if defined(_WIN32) || defined(__APPLE__)
-    static entity::timestamp coarse_nanos_since_epoch() {
         auto t = std::chrono::system_clock::now();
         return std::chrono::duration_cast<std::chrono::nanoseconds>(t.time_since_epoch()).count();
     }
-#else
     static entity::timestamp coarse_nanos_since_epoch() {
-        return (*folly::chrono::clock_gettime_ns)(CLOCK_REALTIME_COARSE);
+        auto t = std::chrono::system_clock::now();
+        return std::chrono::duration_cast<std::chrono::nanoseconds>(t.time_since_epoch()).count();
     }
-#endif
 };
 
 

From 58d55ff3b588ba21060c981275a220bd4252b6aa Mon Sep 17 00:00:00 2001
From: Julien Jerphanion <git@jjerphan.xyz>
Date: Thu, 4 Apr 2024 14:48:44 +0200
Subject: [PATCH 2/2] OS-specific implementations for coarse grained version

Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>

Co-authored-by: William Dealtry <willdealtry@users.noreply.github.com>
---
 cpp/arcticdb/util/clock.hpp | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/cpp/arcticdb/util/clock.hpp b/cpp/arcticdb/util/clock.hpp
index a1da36b68b..af9a66277b 100644
--- a/cpp/arcticdb/util/clock.hpp
+++ b/cpp/arcticdb/util/clock.hpp
@@ -9,19 +9,42 @@
 
 #include <arcticdb/entity/types.hpp>
 
+#include <cstdint>
+#if defined(_WIN32)
 #include <chrono>
+#elif defined(__linux__)
+#include <time.h>
+#elif defined(__APPLE__)
+#include <mach/mach_time.h>
+#endif
+
 
 namespace arcticdb::util {
 
 class SysClock {
   public:
     static entity::timestamp nanos_since_epoch() {
-        auto t = std::chrono::system_clock::now();
-        return std::chrono::duration_cast<std::chrono::nanoseconds>(t.time_since_epoch()).count();
+        auto now = std::chrono::system_clock::now();
+        auto now_ns = std::chrono::time_point_cast<std::chrono::nanoseconds>(now);
+        return now_ns.time_since_epoch().count();
     }
     static entity::timestamp coarse_nanos_since_epoch() {
-        auto t = std::chrono::system_clock::now();
-        return std::chrono::duration_cast<std::chrono::nanoseconds>(t.time_since_epoch()).count();
+#if defined(__linux__)
+        timespec ts;
+        clock_gettime(CLOCK_REALTIME_COARSE, &ts);
+        return static_cast<uint64_t>(ts.tv_sec) * 1000000000LL + ts.tv_nsec;
+#elif defined(_WIN32)
+        return nanos_since_epoch();
+#elif defined(__APPLE__)
+        static mach_timebase_info_data_t info = {0, 0};
+        if (info.denom == 0) {
+            mach_timebase_info(&info);
+        }
+        uint64_t now = mach_absolute_time();
+        now *= info.numer;
+        now /= info.denom;
+        return now;
+#endif
     }
 };