Fix DateTime#sec_fraction on ruby 1.9

Previously, it had the 1.8 behavior of returning the fraction of
the second as a fraction of the day, even on 1.9.  This increases
compatibility with the 1.9 stdlib.

This also adds a spec for the :sec_fraction entry of Date._parse,
though that is the fraction of the second on both 1.8 and 1.9.

ext/date_ext/datetime.c

@@ -1400,17 +1400,27 @@ static VALUE rhrdt_sec(VALUE self) {
 /* call-seq:
  *   sec_fraction() -> Float
  *
- * Returns a +Float+ representing the fraction of the second as a
+ * On ruby 1.8, returns a +Float+ representing the fraction of the second as a
  * fraction of the day, which will always be in the range [0.0, 1/86400.0).
  * 
  *   (DateTime.civil(2009, 1, 2, 12, 13, 14) + (1.5/86400)).sec_fraction
  *   # => 0.000005787037
+ *
+ * On ruby 1.9, returns a +Float+ representing the fraction of the second, which
+ * will always be in the range [0,1).
+ * 
+ *   (DateTime.civil(2009, 1, 2, 12, 13, 14) + (1.5/86400)).sec_fraction
+ *   # => 0.5
  */
 static VALUE rhrdt_sec_fraction(VALUE self) {
   rhrdt_t *dt;
   Data_Get_Struct(self, rhrdt_t, dt);
   RHRDT_FILL_NANOS(dt)
+#ifdef RUBY19
+  return rb_float_new((double)(dt->nanos % RHR_NANOS_PER_SECOND)/RHR_NANOS_PER_SECONDD);
+#else
   return rb_float_new((double)(dt->nanos % RHR_NANOS_PER_SECOND)/RHR_NANOS_PER_DAYD);
+#endif
 } 
 
 /* call-seq:

spec/datetime/accessor_spec.rb

@@ -40,10 +40,19 @@
 end
 
 describe "DateTime#sec_fraction" do
-  it "should be the fraction of a second as a fraction of the day" do
-    DateTime.new(2008, 1, 1).sec_fraction.should == 0.0
-    DateTime.parse('12:13:15.678900').sec_fraction.should be_close(7.85763888888889e-06, 0.0000000000001)
-  end 
+  ruby_version_is "" ... "1.9" do
+    it "should be the fraction of a second as a fraction of the day" do
+      DateTime.new(2008, 1, 1).sec_fraction.should == 0.0
+      DateTime.parse('12:13:15.678900').sec_fraction.should be_close(7.85763888888889e-06, 0.0000000000001)
+    end 
+  end
+
+  ruby_version_is "1.9" do
+    it "should be the fraction of a second" do
+      DateTime.new(2008, 1, 1).sec_fraction.should == 0.0
+      DateTime.parse('12:13:15.678900').sec_fraction.should be_close(0.6789, 0.0000000000001)
+    end 
+  end
 end
 
 describe "DateTime#zone" do

spec/datetime/parse_spec.rb

@@ -1,7 +1,16 @@
 require File.expand_path('../../spec_helper', __FILE__)
 
-describe "DateTime#parse" do
+describe "DateTime._parse" do
+  it "should return a hash of values" do
+    DateTime._parse("01:02:03").should == {:hour=>1, :min=>2, :sec=>3}
+  end
+
+  it "should have :sec_fraction entry be the fraction of second" do
+    DateTime._parse('12:13:15.678900')[:sec_fraction].should be_close(0.6789, 0.0000000000001)
+  end 
+end
 
+describe "DateTime.parse" do
   it "should have defaults and an optional sg value" do
     DateTime.parse('2008-10-11').should == DateTime.civil(2008, 10, 11)
     DateTime.parse('2008-10-11', true).should == DateTime.civil(2008, 10, 11)