From 3adaeefbc6b3bade8c07ac49d8977a44a2503bfe Mon Sep 17 00:00:00 2001
From: Philipp Hancke <phancke@microsoft.com>
Date: Tue, 27 Jun 2023 13:08:44 +0200
Subject: [PATCH] Fix TimeUTCMicros resolution on Windows
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making it return actual microseconds instead of being limited to
millisecond resolution.

This uses GetSystemTimeAsFileTime
  https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimeasfiletime
which returns a timestamp in multiples of 100ns since January 1st 1601.

BUG=webrtc:15212

Change-Id: I293868d8f683289a9dbcf6eccb910bd9c6694e57
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/306440
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40360}
---
 rtc_base/BUILD.gn      |  3 ++-
 rtc_base/time_utils.cc | 34 ++++++++++++++++++++++------------
 rtc_base/win32.cc      |  1 -
 3 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index ac27ee8251..a6d806d066 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -551,6 +551,7 @@ rtc_library("timeutils") {
     ":stringutils",
     "system:rtc_export",
   ]
+
   if (rtc_exclude_system_time) {
     defines = [ "WEBRTC_EXCLUDE_SYSTEM_TIME" ]
   }
@@ -558,6 +559,7 @@ rtc_library("timeutils") {
   libs = []
   if (is_win) {
     libs += [ "winmm.lib" ]
+    deps += [ ":win32" ]
   }
 }
 
@@ -1070,7 +1072,6 @@ if (is_win) {
     deps = [
       ":byte_order",
       ":checks",
-      ":logging",
       ":macromagic",
       ":stringutils",
     ]
diff --git a/rtc_base/time_utils.cc b/rtc_base/time_utils.cc
index 78434536e1..9f112e49c1 100644
--- a/rtc_base/time_utils.cc
+++ b/rtc_base/time_utils.cc
@@ -14,17 +14,27 @@
 #include <sys/time.h>
 #endif
 
-#if defined(WEBRTC_WIN)
-#include <sys/timeb.h>
-#endif
-
 #include "rtc_base/checks.h"
 #include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/system_time.h"
 #include "rtc_base/time_utils.h"
+#if defined(WEBRTC_WIN)
+#include "rtc_base/win32.h"
+#endif
+#if defined(WEBRTC_WIN)
+#include <minwinbase.h>
+#endif
 
 namespace rtc {
 
+#if defined(WEBRTC_WIN) || defined(WINUWP)
+// FileTime (January 1st 1601) to Unix time (January 1st 1970)
+// offset in units of 100ns.
+static constexpr uint64_t kFileTimeToUnixTimeEpochOffset =
+    116444736000000000ULL;
+static constexpr uint64_t kFileTimeToMicroSeconds = 10LL;
+#endif
+
 ClockInterface* g_clock = nullptr;
 
 ClockInterface* SetClockForTesting(ClockInterface* clock) {
@@ -115,8 +125,6 @@ class TimeHelper final {
   }
 
  private:
-  static constexpr uint64_t kFileTimeToUnixTimeEpochOffset =
-      116444736000000000ULL;
   static constexpr uint64_t kNTPTimeToUnixTimeEpochOffset = 2208988800000L;
 
   // The number of nanoseconds since unix system epoch
@@ -231,13 +239,15 @@ int64_t TimeUTCMicros() {
   // Convert from second (1.0) and microsecond (1e-6).
   return (static_cast<int64_t>(time.tv_sec) * rtc::kNumMicrosecsPerSec +
           time.tv_usec);
-
 #elif defined(WEBRTC_WIN)
-  struct _timeb time;
-  _ftime(&time);
-  // Convert from second (1.0) and milliseconds (1e-3).
-  return (static_cast<int64_t>(time.time) * rtc::kNumMicrosecsPerSec +
-          static_cast<int64_t>(time.millitm) * rtc::kNumMicrosecsPerMillisec);
+  FILETIME ft;
+  // This will give us system file in UTC format in multiples of 100ns.
+  GetSystemTimeAsFileTime(&ft);
+  LARGE_INTEGER li;
+  li.HighPart = ft.dwHighDateTime;
+  li.LowPart = ft.dwLowDateTime;
+  return (li.QuadPart - kFileTimeToUnixTimeEpochOffset) /
+         kFileTimeToMicroSeconds;
 #endif
 }
 
diff --git a/rtc_base/win32.cc b/rtc_base/win32.cc
index b44e513026..9ce0523413 100644
--- a/rtc_base/win32.cc
+++ b/rtc_base/win32.cc
@@ -18,7 +18,6 @@
 #include "rtc_base/arraysize.h"
 #include "rtc_base/byte_order.h"
 #include "rtc_base/checks.h"
-#include "rtc_base/logging.h"
 #include "rtc_base/string_utils.h"
 
 namespace rtc {