NSProcessInfo: implement getting system uptime

Introduce the systemUptime property to NSProcessInfo, which can compute
platform-independently what is the uptime of the system.

Headers/Foundation/NSProcessInfo.h

@@ -83,6 +83,14 @@ enum {
  */
 + (NSProcessInfo*) processInfo;
 
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_6,GS_API_LATEST) 
+#if GS_HAS_DECLARED_PROPERTIES
+@property (readonly) NSUInteger systemUptime;
+#else
+- (NSUInteger) systemUptime;
+#endif
+#endif
+
 /**
  * Returns an array containing the arguments supplied to start this
  * process.<br />

Source/NSProcessInfo.m

@@ -1465,6 +1465,43 @@ static void determineOperatingSystem()
   return availMem;
 }
 
+- (NSUInteger) systemUptime
+{
+  NSUInteger uptime = 0;
+
+#if	defined(_WIN32)
+  uptime = GetTickCount64() / 1000;
+#elif	defined(HAVE_SYSCTLBYNAME)
+  struct timeval	tval;
+  size_t		len = sizeof(tval);
+
+  if (sysctlbyname("kern.boottime", &tval, &len, 0, 0) == 0)
+    {
+      uptime = tval.tv_sec;
+    }
+#elif	defined(HAVE_PROCFS)
+  NSFileManager *fileManager = [NSFileManager defaultManager];
+
+  if ([fileManager fileExistsAtPath: @"/proc/uptime"])
+    {
+      NSString *uptimeContent = [NSString
+	stringWithContentsOfFile: @"/proc/uptime"];
+      NSString *uptimeString = [[uptimeContent
+	componentsSeparatedByString:@" "] objectAtIndex:0];
+      uptime = [uptimeString intValue];
+    }
+#else
+#warning	"no known way to determine uptime on this system"
+#endif
+
+  if (uptime == 0)
+    {
+      NSLog(@"Cannot determine uptime.");
+    }
+
+  return uptime;
+}
+
 @end
 
 void

Tests/base/NSProcessInfo/general.m

@@ -39,8 +39,14 @@ int main()
   PASS((obj != nil && [obj isKindOfClass:[NSString class]] && [obj length] > 0),
     "-operatingSystemName works");
   NSLog(@"operatingSystemName %@", obj);
+  
   val = [info operatingSystem];
   PASS(val != 0, "-operatingSystem works"); 
+  
+  val = [info systemUptime];
+  NSLog(@"systemUptime %lu", val);
+  PASS(val != 0, "-systemUptime works");
+  
   obj = [info hostName];
   PASS((obj != nil && [obj isKindOfClass:[NSString class]] && [obj length] > 0),
     "-hostName works");