time: add YearDay method for time.Time structs

YearDay provides the day in the year represented by a given time.Time
object. This value is normally computed as part of other date calculations,
but not exported.

Fixes #3932.

R=golang-dev, r, remyoudompheng
CC=golang-dev, rsc
https://golang.org/cl/6460069

diff --git a/src/pkg/time/time.go b/src/pkg/time/time.go
index ef966c3ef0e395db0a579ca7295cc9d8a71144d2..1eb17858a8c68bd08a5e556b78466194e81b77e8 100644 (file)
--- a/src/pkg/time/time.go
+++ b/src/pkg/time/time.go
@@ -412,6 +412,13 @@ func (t Time) Nanosecond() int {
        return int(t.nsec)
 }
 
+// YearDay returns the day of the year specified by t, in the range [1, 365] for non-leap years,
+// and [1,366] in leap years.
+func (t Time) YearDay() int {
+       _, _, _, yday := t.date(false)
+       return yday + 1
+}
+
 // A Duration represents the elapsed time between two instants
 // as an int64 nanosecond count.  The representation limits the
 // largest representable duration to approximately 290 years.
@@ -641,7 +648,7 @@ const (
        days1970To2001   = 31*365 + 8
 )
 
-// date computes the year and, only when full=true,
+// date computes the year, day of year, and when full=true,
 // the month and day in which t occurs.
 func (t Time) date(full bool) (year int, month Month, day int, yday int) {
        return absDate(t.abs(), full)

diff --git a/src/pkg/time/time_test.go b/src/pkg/time/time_test.go
index 0204fc29ee7292762f7736d88717708117b7a494..3311d70be55658f30e32fe430b339121997d1f3d 100644 (file)
--- a/src/pkg/time/time_test.go
+++ b/src/pkg/time/time_test.go
@@ -611,6 +611,103 @@ func TestISOWeek(t *testing.T) {
        }
 }
 
+type YearDayTest struct {
+       year, month, day int
+       yday             int
+}
+
+// Test YearDay in several different scenarios
+// and corner cases
+var yearDayTests = []YearDayTest{
+       // Non-leap-year tests
+       {2007, 1, 1, 1},
+       {2007, 1, 15, 15},
+       {2007, 2, 1, 32},
+       {2007, 2, 15, 46},
+       {2007, 3, 1, 60},
+       {2007, 3, 15, 74},
+       {2007, 4, 1, 91},
+       {2007, 12, 31, 365},
+
+       // Leap-year tests
+       {2008, 1, 1, 1},
+       {2008, 1, 15, 15},
+       {2008, 2, 1, 32},
+       {2008, 2, 15, 46},
+       {2008, 3, 1, 61},
+       {2008, 3, 15, 75},
+       {2008, 4, 1, 92},
+       {2008, 12, 31, 366},
+
+       // Looks like leap-year (but isn't) tests
+       {1900, 1, 1, 1},
+       {1900, 1, 15, 15},
+       {1900, 2, 1, 32},
+       {1900, 2, 15, 46},
+       {1900, 3, 1, 60},
+       {1900, 3, 15, 74},
+       {1900, 4, 1, 91},
+       {1900, 12, 31, 365},
+
+       // Year one tests (non-leap)
+       {1, 1, 1, 1},
+       {1, 1, 15, 15},
+       {1, 2, 1, 32},
+       {1, 2, 15, 46},
+       {1, 3, 1, 60},
+       {1, 3, 15, 74},
+       {1, 4, 1, 91},
+       {1, 12, 31, 365},
+
+       // Year minus one tests (non-leap)
+       {-1, 1, 1, 1},
+       {-1, 1, 15, 15},
+       {-1, 2, 1, 32},
+       {-1, 2, 15, 46},
+       {-1, 3, 1, 60},
+       {-1, 3, 15, 74},
+       {-1, 4, 1, 91},
+       {-1, 12, 31, 365},
+
+       // 400 BC tests (leap-year)
+       {-400, 1, 1, 1},
+       {-400, 1, 15, 15},
+       {-400, 2, 1, 32},
+       {-400, 2, 15, 46},
+       {-400, 3, 1, 61},
+       {-400, 3, 15, 75},
+       {-400, 4, 1, 92},
+       {-400, 12, 31, 366},
+
+       // Special Cases
+
+       // Gregorian calendar change (no effect)
+       {1582, 10, 4, 277},
+       {1582, 10, 15, 288},
+}
+
+// Check to see if YearDay is location sensitive
+var yearDayLocations = []*Location{
+       FixedZone("UTC-8", -8*60*60),
+       FixedZone("UTC-4", -4*60*60),
+       UTC,
+       FixedZone("UTC+4", 4*60*60),
+       FixedZone("UTC+8", 8*60*60),
+}
+
+func TestYearDay(t *testing.T) {
+       for _, loc := range yearDayLocations {
+               for _, ydt := range yearDayTests {
+                       dt := Date(ydt.year, Month(ydt.month), ydt.day, 0, 0, 0, 0, loc)
+                       yday := dt.YearDay()
+                       if yday != ydt.yday {
+                               t.Errorf("got %d, expected %d for %d-%02d-%02d in %v",
+                                       yday, ydt.yday, ydt.year, ydt.month, ydt.day, loc)
+                       }
+               }
+       }
+}
+
 var durationTests = []struct {
        str string
        d   Duration