LogDog: Implement StreamName.Split.

logdog/common/types/streamname.go

Index: logdog/common/types/streamname.go
diff --git a/logdog/common/types/streamname.go b/logdog/common/types/streamname.go
index 7dd0365c84c4f6d96366cb5aef5e2a4d05bb1374..e91cce33426ed5cc857c2a1dd132d404b21ad827 100644
--- a/logdog/common/types/streamname.go
+++ b/logdog/common/types/streamname.go
@@ -233,6 +233,28 @@ func (s StreamName) SegmentCount() int {
 	return segmentCount(string(s))
 }
 
+// Split splits a StreamName on its last path element, into a base (everything

[nodir, 2017/02/18 05:01:51]

"base" is somewhat confusing here. Term base is usually used for the last
element, e.g. https://godoc.org/path#Base

[dnj, 2017/02/18 06:09:31]

Change to "prefix".

+// before that element) and the last element.
+//
+// Split assumes that s is a valid stream name.
+//
+// If there is only one element in the stream name, base will be empty.
+//
+// For example:
+//
+//	- Split("foo/bar/baz") ("foo/bar", "baz")
+//	- Split("foo") ("", "foo")
+//	- Split("") ("", "")
+func (s StreamName) Split() (base StreamName, last StreamName) {

[nodir, 2017/02/18 05:01:51]

(base, last StreamName)

[dnj, 2017/02/18 06:09:31]

Done.

+	lidx := strings.LastIndex(string(s), StreamNameSepStr)
+	if lidx < 0 {
+		last = s
+		return
+	}
+	base, last = s[:lidx], s[lidx+len(StreamNameSepStr):]
+	return
+}
+
 // UnmarshalJSON implements json.Unmarshaler.
 func (s *StreamName) UnmarshalJSON(data []byte) error {
 	v := ""