Add GetSystemTimeAsTicks to System.Native (#17484)

* Add GetSystemTimeAsTicks to System.Native

* Use reinterpret_cast

* Use clock_gettime(CLOCK_REALTIME) if possible

* Fix names and include pal_config.h

* Another missing header

* Fix unused variable warning

Author: alexperovich

src/Native/Unix/Common/pal_config.h.in

@@ -54,6 +54,7 @@
 #cmakedefine01 HAVE_GETDOMAINNAME_SIZET
 #cmakedefine01 HAVE_INOTIFY
 #cmakedefine01 HAVE_CLOCK_MONOTONIC
+#cmakedefine01 HAVE_CLOCK_REALTIME
 #cmakedefine01 HAVE_MACH_ABSOLUTE_TIME
 #cmakedefine01 HAVE_MACH_TIMEBASE_INFO
 #cmakedefine01 HAVE_CURLM_ADDED_ALREADY

src/Native/Unix/System.Native/CMakeLists.txt

@@ -18,6 +18,7 @@ set(NATIVE_SOURCES
     pal_tcpstate.cpp
     pal_time.cpp
     pal_uid.cpp
+    pal_datetime.cpp
 )
 
 if (CMAKE_SYSTEM_NAME STREQUAL Linux)

src/Native/Unix/System.Native/pal_datetime.cpp

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "pal_config.h"
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <time.h>
+#include <sys/time.h>
+
+static const int64_t TICKS_PER_SECOND = 10000000; /* 10^7 */
+#if HAVE_CLOCK_REALTIME
+static const int64_t NANOSECONDS_PER_TICK = 100;
+#else
+static const int64_t TICKS_PER_MICROSECOND = 10; /* 1000 / 100 */
+#endif
+
+//
+// SystemNative_GetSystemTimeAsTicks return the system time as ticks (100 nanoseconds) 
+// since 00:00 01 January 1970 UTC (Unix epoch) 
+//
+extern "C" int64_t SystemNative_GetSystemTimeAsTicks()
+{
+#if HAVE_CLOCK_REALTIME
+    struct timespec time;
+    if (clock_gettime(CLOCK_REALTIME, &time) == 0)
+    {
+        return static_cast<int64_t>(time.tv_sec) * TICKS_PER_SECOND + (time.tv_nsec / NANOSECONDS_PER_TICK); 
+    }
+#else
+    struct timeval time;
+    if (gettimeofday(&time, NULL) == 0)
+    {
+        return static_cast<int64_t>(time.tv_sec) * TICKS_PER_SECOND + (time.tv_usec * TICKS_PER_MICROSECOND); 
+    }
+#endif
+    // in failure we return 00:00 01 January 1970 UTC (Unix epoch)
+    return 0;
+}

src/Native/Unix/configure.cmake

@@ -339,6 +339,21 @@ check_cxx_source_runs(
     "
     HAVE_CLOCK_MONOTONIC)
 
+check_cxx_source_runs(
+    "
+    #include <stdlib.h>
+    #include <time.h>
+    #include <sys/time.h>
+    int main()
+    {
+        int ret;
+        struct timespec ts;
+        ret = clock_gettime(CLOCK_REALTIME, &ts);
+        exit(ret);
+    }
+    "
+    HAVE_CLOCK_REALTIME)
+
 check_function_exists(
     mach_absolute_time
     HAVE_MACH_ABSOLUTE_TIME)