time: add support for parsing timezones denoted by sign and offset

MyChaOS87 · bradfitz · commit 9f2c611fa7cc · 2018-03-08T17:15:35.000Z
IANA Zoneinfo does not provide names for all timezones. Some are denoted by a sign and an offset only. E.g: Europe/Turkey is currently +03 or America/La_Paz which is -04 (https://data.iana.org/time-zones/releases/tzdata2018c.tar.gz) Fixes golang#24071 Change-Id: I9c230a719945e1263c5b52bab82084d22861be3e Reviewed-on: https://go-review.googlesource.com/98157 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/time/format.go b/src/time/format.go
@@ -1117,6 +1117,11 @@ func parseTimeZone(value string) (length int, ok bool) {
 		length = parseGMT(value)
 		return length, true
 	}
+	// Special Case 3: Some time zones are not named, but have +/-00 format
+	if value[0] == '+' || value[0] == '-' {
+		length = parseSignedOffset(value)
+		return length, true
+	}
 	// How many upper-case letters are there? Need at least three, at most five.
 	var nUpper int
 	for nUpper = 0; nUpper < 6; nUpper++ {
@@ -1153,21 +1158,29 @@ func parseGMT(value string) int {
 	if len(value) == 0 {
 		return 3
 	}
+
+	return 3 + parseSignedOffset(value)
+}
+
+// parseSignedOffset parses a signed timezone offset (e.g. "+03" or "-04").
+// The function checks for a signed number in the range -14 through +12 excluding zero.
+// Returns length of the found offset string or 0 otherwise
+func parseSignedOffset(value string) int {
 	sign := value[0]
 	if sign != '-' && sign != '+' {
-		return 3
+		return 0
 	}
 	x, rem, err := leadingInt(value[1:])
 	if err != nil {
-		return 3
+		return 0
 	}
 	if sign == '-' {
 		x = -x
 	}
 	if x == 0 || x < -14 || 12 < x {
-		return 3
+		return 0
 	}
-	return 3 + len(value) - len(rem)
+	return len(value) - len(rem)
 }
 
 func parseNanoseconds(value string, nbytes int) (ns int, rangeErrString string, err error) {
diff --git a/src/time/format_test.go b/src/time/format_test.go
@@ -427,6 +427,8 @@ var parseTimeZoneTests = []ParseTimeZoneTest{
 	{"ESASTT hi", 0, false}, // run of upper-case letters too long.
 	{"ESATY hi", 0, false},  // five letters must end in T.
 	{"WITA hi", 4, true},    // Issue #18251
+	{"+03 hi", 3, true},     // Issue #24071
+	{"-04 hi", 3, true},     // Issue #24071
 }
 
 func TestParseTimeZone(t *testing.T) {

Original file line number	Diff line number	Diff line change
`@@ -427,6 +427,8 @@ var parseTimeZoneTests = []ParseTimeZoneTest{`
`427`	`427`	`{"ESASTT hi", 0, false}, // run of upper-case letters too long.`
`428`	`428`	`{"ESATY hi", 0, false}, // five letters must end in T.`
`429`	`429`	`{"WITA hi", 4, true}, // Issue #18251`
	`430`	`+ {"+03 hi", 3, true}, // Issue #24071`
	`431`	`+ {"-04 hi", 3, true}, // Issue #24071`
`430`	`432`	`}`
`431`	`433`
`432`	`434`	`func TestParseTimeZone(t *testing.T) {`