From 8d27b407787549a90d47d273a753bb0000e5e73e Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 8 Oct 2015 13:37:37 -0400
Subject: [PATCH] cmFileTimeComparison: Port to OS X nanosecond times (#15769)

---
 Source/CMakeLists.txt           |  1 +
 Source/cmFileTimeComparison.cxx | 35 +++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
index 28a3fd143..ee690e68a 100644
--- a/Source/CMakeLists.txt
+++ b/Source/CMakeLists.txt
@@ -550,6 +550,7 @@ endforeach()
 
 foreach(check
     STAT_HAS_ST_MTIM
+    STAT_HAS_ST_MTIMESPEC
     )
   if(KWSYS_CXX_${check}_COMPILED) # abuse KWSys check cache entry
     set(CMake_${check} 1)
diff --git a/Source/cmFileTimeComparison.cxx b/Source/cmFileTimeComparison.cxx
index 8d5e08daa..279b61da9 100644
--- a/Source/cmFileTimeComparison.cxx
+++ b/Source/cmFileTimeComparison.cxx
@@ -166,6 +166,24 @@ int cmFileTimeComparisonInternal::Compare(cmFileTimeComparison_Type* s1,
     {
     return 1;
     }
+# elif CMake_STAT_HAS_ST_MTIMESPEC
+  // Compare using nanosecond resolution.
+  if(s1->st_mtimespec.tv_sec < s2->st_mtimespec.tv_sec)
+    {
+    return -1;
+    }
+  else if(s1->st_mtimespec.tv_sec > s2->st_mtimespec.tv_sec)
+    {
+    return 1;
+    }
+  else if(s1->st_mtimespec.tv_nsec < s2->st_mtimespec.tv_nsec)
+    {
+    return -1;
+    }
+  else if(s1->st_mtimespec.tv_nsec > s2->st_mtimespec.tv_nsec)
+    {
+    return 1;
+    }
 # else
   // Compare using 1 second resolution.
   if(s1->st_mtime < s2->st_mtime)
@@ -207,6 +225,23 @@ bool cmFileTimeComparisonInternal::TimesDiffer(cmFileTimeComparison_Type* s1,
     {
     return false;
     }
+# elif CMake_STAT_HAS_ST_MTIMESPEC
+  // Times are integers in units of 1ns.
+  long long bil = 1000000000;
+  long long t1 = s1->st_mtimespec.tv_sec * bil + s1->st_mtimespec.tv_nsec;
+  long long t2 = s2->st_mtimespec.tv_sec * bil + s2->st_mtimespec.tv_nsec;
+  if(t1 < t2)
+    {
+    return (t2 - t1) >= bil;
+    }
+  else if(t2 < t1)
+    {
+    return (t1 - t2) >= bil;
+    }
+  else
+    {
+    return false;
+    }
 # else
   // Times are integers in units of 1s.
   if(s1->st_mtime < s2->st_mtime)