From dac008b9c42e133f6902997d37534e770c27680d Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Mon, 9 Jul 2018 08:14:47 +0000
Subject: [PATCH] Early return from LatestMap merge loop

If we run out of things to look at in the other map, return quickly.
Also move the equal-key case above the less-than case, since maps with
equal keys are the common case when merging.
---
 extras/generate_latest_map     | 15 ++++++++++-----
 report/latest_map_generated.go | 30 ++++++++++++++++++++----------
 2 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/extras/generate_latest_map b/extras/generate_latest_map
index 0f831799c..3ae35b398 100755
--- a/extras/generate_latest_map
+++ b/extras/generate_latest_map
@@ -96,14 +96,16 @@ function generate_latest_map() {
     loop:
         for i < len(m) {
             switch {
-            case j >= len(n) || m[i].key < n[j].key:
-                i++
+            case j >= len(n):
+                return m
             case m[i].key == n[j].key:
                 if m[i].Timestamp.Before(n[j].Timestamp) {
                     break loop
                 }
                 i++
                 j++
+            case m[i].key < n[j].key:
+                i++
             default:
                 break loop
             }
@@ -117,9 +119,9 @@ function generate_latest_map() {
 
         for i < len(m) {
             switch {
-            case j >= len(n) || m[i].key < n[j].key:
-                out = append(out, m[i])
-                i++
+            case j >= len(n):
+                out = append(out, m[i:]...)
+                return out
             case m[i].key == n[j].key:
                 if m[i].Timestamp.Before(n[j].Timestamp) {
                     out = append(out, n[j])
@@ -128,6 +130,9 @@ function generate_latest_map() {
                 }
                 i++
                 j++
+            case m[i].key < n[j].key:
+                out = append(out, m[i])
+                i++
             default:
                 out = append(out, n[j])
                 j++
diff --git a/report/latest_map_generated.go b/report/latest_map_generated.go
index 626b80988..97ce72382 100644
--- a/report/latest_map_generated.go
+++ b/report/latest_map_generated.go
@@ -64,14 +64,16 @@ func (m StringLatestMap) Merge(n StringLatestMap) StringLatestMap {
 loop:
 	for i < len(m) {
 		switch {
-		case j >= len(n) || m[i].key < n[j].key:
-			i++
+		case j >= len(n):
+			return m
 		case m[i].key == n[j].key:
 			if m[i].Timestamp.Before(n[j].Timestamp) {
 				break loop
 			}
 			i++
 			j++
+		case m[i].key < n[j].key:
+			i++
 		default:
 			break loop
 		}
@@ -85,9 +87,9 @@ loop:
 
 	for i < len(m) {
 		switch {
-		case j >= len(n) || m[i].key < n[j].key:
-			out = append(out, m[i])
-			i++
+		case j >= len(n):
+			out = append(out, m[i:]...)
+			return out
 		case m[i].key == n[j].key:
 			if m[i].Timestamp.Before(n[j].Timestamp) {
 				out = append(out, n[j])
@@ -96,6 +98,9 @@ loop:
 			}
 			i++
 			j++
+		case m[i].key < n[j].key:
+			out = append(out, m[i])
+			i++
 		default:
 			out = append(out, n[j])
 			j++
@@ -311,14 +316,16 @@ func (m NodeControlDataLatestMap) Merge(n NodeControlDataLatestMap) NodeControlD
 loop:
 	for i < len(m) {
 		switch {
-		case j >= len(n) || m[i].key < n[j].key:
-			i++
+		case j >= len(n):
+			return m
 		case m[i].key == n[j].key:
 			if m[i].Timestamp.Before(n[j].Timestamp) {
 				break loop
 			}
 			i++
 			j++
+		case m[i].key < n[j].key:
+			i++
 		default:
 			break loop
 		}
@@ -332,9 +339,9 @@ loop:
 
 	for i < len(m) {
 		switch {
-		case j >= len(n) || m[i].key < n[j].key:
-			out = append(out, m[i])
-			i++
+		case j >= len(n):
+			out = append(out, m[i:]...)
+			return out
 		case m[i].key == n[j].key:
 			if m[i].Timestamp.Before(n[j].Timestamp) {
 				out = append(out, n[j])
@@ -343,6 +350,9 @@ loop:
 			}
 			i++
 			j++
+		case m[i].key < n[j].key:
+			out = append(out, m[i])
+			i++
 		default:
 			out = append(out, n[j])
 			j++