Adding utility method to test the version of the OS.

base/sys_info_ios.mm

Index: base/sys_info_ios.mm
diff --git a/base/sys_info_ios.mm b/base/sys_info_ios.mm
index 8b1ffd4521192f0f9db7e9c2b3b6621a4e6d1838..8b25ef5c631eb6d0dd4d4ff00548aacf7d216c00 100644
--- a/base/sys_info_ios.mm
+++ b/base/sys_info_ios.mm
@@ -76,4 +76,36 @@ std::string SysInfo::CPUModelName() {
   return std::string();
 }
 
+// static
+bool SysInfo::IsRunningOnIOS5OrLater() {
+  return IsRunningOnOrLater(5, 0, 0);
+}
+
+// static
+bool SysInfo::IsRunningOnIOS6OrLater() {
+  return IsRunningOnOrLater(6, 0, 0);
+}
+
+// static
+bool SysInfo::IsRunningOnOrLater(int major, int minor, int bugFix) {
+  static int32 digits[3] = { 0, 0, 0 };

[Mark Mentovai, 2012/10/05 12:49:05]

You know how I feel about these. I’d prefer to just initialize the static with a
call to a simple adapter function, like:

  static int32* digits =
OperatingSystemVersionNumbersPointerToArray_PickABetterName();

[qsr, 2012/10/05 14:53:56]

Done.

+  if (digits[0] == 0) {
+    OperatingSystemVersionNumbers(&digits[0], &digits[1], &digits[2]);

[Mark Mentovai, 2012/10/05 12:49:05]

mac_util uses uname for its runtime OS version checks like IsOSLionOrLater.
There’s a comment in base/mac/mac_util.mm DarwinMajorVersionInternal that
explains what the story is, but uname is faster and more side-effect-free than
other methods of getting the version. It’s fine if that’s not a concern on iOS,
but I thought I’d point it out.

[qsr, 2012/10/05 14:53:56]

 On iOS, we are calling: [[UIDevice currentDevice] systemVersion]

 1) I don't think this will call Getstalt, as it returns a fully constructed
version, not individual element and as this value is cached here, I'm not that
worried. 

+  }
+  if (digits[0] < major)

[Mark Mentovai, 2012/10/05 12:49:05]

Seems like this could be written as a loop. Or would a Version (base/version.h)
be appropriate?

[qsr, 2012/10/05 14:53:56]

 I'll do a loop. Version is working on string. I do not want to transform that
on string before sending that to Version that will cut it back.

+    return NO;
+  if (digits[0] > major)
+    return YES;
+  // digits[0] == major
+  if (digits[1] < minor)
+    return NO;
+  if (digits[1] > minor)
+    return YES;
+  // digits[1] == minor
+  if (digits[2] < bugFix)
+    return NO;
+  // digits[2] >= bugFix
+  return YES;
+}
+
 }  // namespace base