LogDog: Implement StreamName.Split.

logdog/common/types/streamname.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package types
 
 import (
         "encoding/json"
         "errors"
         "fmt"
@@ skipping 215 matching lines @@
                 return nil
         }
         return strings.Split(string(s), string(StreamNameSep))
 }
 
 // SegmentCount returns the total number of segments in the StreamName.
 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 := ""
         if err := json.Unmarshal(data, &v); err != nil {
                 return err
         }
         if err := StreamName(v).Validate(); err != nil {
                 return err
         }
         *s = StreamName(v)
@@ skipping 191 matching lines @@
 
         return s
 }
 
 func segmentCount(s string) int {
         if len(s) == 0 {
                 return 0
         }
         return strings.Count(s, string(StreamNameSep)) + 1
 }