From 00d9b6660240ca960585dd66f215d9e883684f4b Mon Sep 17 00:00:00 2001
From: Marco van Dijk <marco@stronk.rocks>
Date: Wed, 4 Jan 2023 11:34:24 +0100
Subject: [PATCH] Add UTC string parsing functions

Change-Id: I51cbb2274e26811d28b303375ff75a32e272adcc
---
 lib/timing.cpp | 33 +++++++++++++++++++++++++++++++++
 lib/timing.h   |  2 ++
 2 files changed, 35 insertions(+)

diff --git a/lib/timing.cpp b/lib/timing.cpp
index a2d4396f..4cd99f12 100644
--- a/lib/timing.cpp
+++ b/lib/timing.cpp
@@ -6,6 +6,8 @@
 #include <cstring>
 #include <sys/time.h> //for gettimeofday
 #include <time.h>     //for time and nanosleep
+#include <sstream>
+#include <stdlib.h>
 
 // emulate clock_gettime() for OSX compatibility
 #if defined(__APPLE__) || defined(__MACH__)
@@ -122,6 +124,37 @@ std::string Util::getUTCStringMillis(uint64_t epoch_millis){
   return std::string(result);
 }
 
+// Returns the epoch of a UTC string in the format of %Y-%m-%dT%H:%M:%S%z
+uint64_t Util::getMSFromUTCString(std::string UTCString){
+  if (UTCString.size() < 24){return 0;}
+  // Strip milliseconds
+  std::string millis = UTCString.substr(UTCString.rfind('.') + 1, 3);
+  UTCString = UTCString.substr(0, UTCString.rfind('.')) + "Z";
+  struct tm ptm;
+  memset(&ptm, 0, sizeof(struct tm));
+  strptime(UTCString.c_str(), "%Y-%m-%dT%H:%M:%S%z", &ptm);
+  time_t ts = mktime(&ptm);
+  return ts * 1000 + atoll(millis.c_str());
+}
+
+// Converts epoch_millis into UTC time and returns the diff with UTCString in seconds
+uint64_t Util::getUTCTimeDiff(std::string UTCString, uint64_t epochMillis){
+  if (!epochMillis){return 0;}
+  if (UTCString.size() < 24){return 0;}
+  // Convert epoch to UTC time
+  time_t epochSeconds = epochMillis / 1000;
+  struct tm *ptmEpoch;
+  ptmEpoch = gmtime(&epochSeconds);
+  uint64_t epochTime = mktime(ptmEpoch);
+  // Parse UTC string and strip the milliseconds
+  UTCString = UTCString.substr(0, UTCString.rfind('.')) + "Z";
+  struct tm ptmUTC;
+  memset(&ptmUTC, 0, sizeof(struct tm));
+  strptime(UTCString.c_str(), "%Y-%m-%dT%H:%M:%S%z", &ptmUTC);
+  time_t UTCTime = mktime(&ptmUTC);
+  return epochTime - UTCTime;
+}
+
 std::string Util::getDateString(uint64_t epoch){
   char buffer[80];
   time_t rawtime = epoch;
diff --git a/lib/timing.h b/lib/timing.h
index c80e8a04..886950ae 100644
--- a/lib/timing.h
+++ b/lib/timing.h
@@ -18,5 +18,7 @@ namespace Util{
   uint64_t epoch(); ///< Gets the amount of seconds since 01/01/1970.
   std::string getUTCString(uint64_t epoch = 0);
   std::string getUTCStringMillis(uint64_t epoch_millis = 0);
+  uint64_t getMSFromUTCString(std::string UTCString);
+  uint64_t getUTCTimeDiff(std::string UTCString, uint64_t epochMillis);
   std::string getDateString(uint64_t epoch = 0);
 }// namespace Util