Add all elements then sort in Node.WithLatests()

To save allocating and re-allocating the data structure by repeated
addition.

report/map_helpers.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"sort"
+	"time"
 
 	"github.com/ugorji/go/codec"
 	"github.com/weaveworks/ps"
@@ -138,3 +139,37 @@ func mapWrite(m ps.Map, encoder *codec.Encoder, encodeValue func(*codec.Encoder,
 	})
 	z.EncSendContainerState(containerMapEnd)
 }
+
+// Now follow helpers for StringLatestMap
+
+// These let us sort a StringLatestMap strings by key
+func (m StringLatestMap) Len() int           { return len(m) }
+func (m StringLatestMap) Swap(i, j int)      { m[i], m[j] = m[j], m[i] }
+func (m StringLatestMap) Less(i, j int) bool { return m[i].key < m[j].key }
+
+// sort entries and shuffle down any duplicates
+func (m StringLatestMap) fixup() {
+	sort.Sort(m)
+	for i := 1; i < len(m); {
+		if m[i-1].key == m[i].key {
+			if m[i-1].Timestamp.Before(m[i].Timestamp) {
+				m = append(m[:i-1], m[i:]...)
+			} else {
+				m = append(m[:i], m[i+1:]...)
+			}
+		} else {
+			i++
+		}
+	}
+}
+
+// add several entries at the same timestamp
+func (m StringLatestMap) addMapEntries(ts time.Time, n map[string]string) StringLatestMap {
+	out := make(StringLatestMap, len(m), len(m)+len(n))
+	copy(out, m)
+	for k, v := range n {
+		out = append(out, stringLatestEntry{key: k, Value: v, Timestamp: ts})
+	}
+	out.fixup()
+	return out
+}

report/node.go

@@ -73,9 +73,7 @@ func (n Node) After(other Node) bool {
 // WithLatests returns a fresh copy of n, with Metadata m merged in.
 func (n Node) WithLatests(m map[string]string) Node {
 	ts := mtime.Now()
-	for k, v := range m {
-		n.Latest = n.Latest.Set(k, ts, v)
-	}
+	n.Latest = n.Latest.addMapEntries(ts, m)
 	return n
 }