From 65d9f3c105fb5d799300c69a4f25a5a3021a6367 Mon Sep 17 00:00:00 2001
From: tprepscius <timprepscius@gmail.com>
Date: Thu, 30 Apr 2020 10:36:35 -0400
Subject: [PATCH] adds ability to get system time from frame, and makes
 monotonic os_time_service a possibility

---
 include/librealsense2/h/rs_frame.h     |  8 ++++++++
 include/librealsense2/hpp/rs_frame.hpp |  8 ++++++++
 src/backend.h                          | 26 +++++++++++++++++++++++++-
 src/rs.cpp                             |  8 ++++++++
 4 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/include/librealsense2/h/rs_frame.h b/include/librealsense2/h/rs_frame.h
index 35a36db2ab..43205db0c9 100644
--- a/include/librealsense2/h/rs_frame.h
+++ b/include/librealsense2/h/rs_frame.h
@@ -102,6 +102,14 @@ rs2_timestamp_domain rs2_get_frame_timestamp_domain(const rs2_frame* frameset, r
 */
 rs2_time_t rs2_get_frame_timestamp(const rs2_frame* frame, rs2_error** error);
 
+/**
+* retrieve timestamp from frame handle in milliseconds
+* \param[in] frame      handle returned from a callback
+* \param[out] error     if non-null, receives any error that occurs during this call, otherwise, errors are ignored
+* \return               the timestamp of the frame in milliseconds
+*/
+rs2_time_t rs2_get_frame_system_time(const rs2_frame* frame, rs2_error** error);
+
 /**
 * retrieve frame parent sensor from frame handle
 * \param[in] frame      handle returned from a callback
diff --git a/include/librealsense2/hpp/rs_frame.hpp b/include/librealsense2/hpp/rs_frame.hpp
index 0ecf670af9..50994ca639 100644
--- a/include/librealsense2/hpp/rs_frame.hpp
+++ b/include/librealsense2/hpp/rs_frame.hpp
@@ -472,6 +472,14 @@ namespace rs2
             return r;
         }
 
+        double get_system_time() const
+        {
+            rs2_error* e = nullptr;
+            auto r = rs2_get_frame_system_time(frame_ref, &e);
+            error::handle(e);
+            return r;
+        }
+
         /** retrieve the timestamp domain
         * \return            timestamp domain (clock name) for timestamp values
         */
diff --git a/src/backend.h b/src/backend.h
index a402e3dfb5..06d2c7a8c6 100644
--- a/src/backend.h
+++ b/src/backend.h
@@ -100,7 +100,7 @@ namespace librealsense
             virtual ~time_service() = default;
         };
 
-        class os_time_service: public time_service
+        class os_time_service_realtime: public time_service
         {
         public:
             rs2_time_t get_time() const override
@@ -109,6 +109,30 @@ namespace librealsense
             }
         };
 
+        class os_time_service_monotonic: public time_service
+        {
+        public:
+
+            typedef std::chrono::high_resolution_clock clock_type;
+            clock_type clock;
+            clock_type::time_point startTime;
+
+            os_time_service_monotonic ()
+            {
+                startTime = clock.now();
+            }
+
+            rs2_time_t get_time() const override
+            {
+                const static double microsecondsInMillisecond = 1000000 / 1000;
+                double value = std::chrono::duration_cast<std::chrono::microseconds>(clock.now() - startTime).count() / microsecondsInMillisecond;
+                
+                return value;
+            }
+        };        
+
+        typedef os_time_service_monotonic os_time_service;
+
         struct guid { uint32_t data1; uint16_t data2, data3; uint8_t data4[8]; };
         // subdevice and node fields are assigned by Host driver; unit and GUID are hard-coded in camera firmware
         struct extension_unit { int subdevice; uint8_t unit; int node; guid id; };
diff --git a/src/rs.cpp b/src/rs.cpp
index 2fced98214..f5fca4c9f6 100644
--- a/src/rs.cpp
+++ b/src/rs.cpp
@@ -781,6 +781,14 @@ rs2_time_t rs2_get_frame_timestamp(const rs2_frame* frame_ref, rs2_error** error
 }
 HANDLE_EXCEPTIONS_AND_RETURN(0, frame_ref)
 
+rs2_time_t rs2_get_frame_system_time(const rs2_frame* frame_ref, rs2_error** error) BEGIN_API_CALL
+{
+    VALIDATE_NOT_NULL(frame_ref);
+    return ((frame_interface*)frame_ref)->get_frame_system_time();
+}
+
+HANDLE_EXCEPTIONS_AND_RETURN(0, frame_ref)
+
 rs2_timestamp_domain rs2_get_frame_timestamp_domain(const rs2_frame* frame_ref, rs2_error** error) BEGIN_API_CALL
 {
     VALIDATE_NOT_NULL(frame_ref);