maint: Replace usage of folly in clock.hpp (#1448)

Signed-off-by: Julien Jerphanion <[email protected]>
Co-authored-by: William Dealtry <[email protected]>

cpp/arcticdb/util/clock.hpp

@@ -9,29 +9,43 @@
 
 #include <arcticdb/entity/types.hpp>
 
-#include <folly/ClockGettimeWrappers.h>
-#include <folly/portability/Time.h>
-#ifndef CLOCK_REALTIME_COARSE
+#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() {
-        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();
+        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();
     }
-#else
     static entity::timestamp coarse_nanos_since_epoch() {
-        return (*folly::chrono::clock_gettime_ns)(CLOCK_REALTIME_COARSE);
-    }
+#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
+    }
 };