From d485101331f5957067fb83e227e3d5aedcf24f2d Mon Sep 17 00:00:00 2001
From: Lunny Xiao <xiaolunwen@gmail.com>
Date: Fri, 22 May 2020 02:53:55 +0000
Subject: [PATCH] chore: improve snakeCasedName performance (#1688)

chore: update

chore: udpate

chore: improve snakeCasedName performance

Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Reviewed-on: https://gitea.com/xorm/xorm/pulls/1688
Reviewed-by: appleboy <appleboy.tw@gmail.com>
---
 names/mapper.go      | 20 +++++++++++++-------
 names/mapper_test.go | 11 +++++++++++
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/names/mapper.go b/names/mapper.go
index 4aaf0844..80aa48d5 100644
--- a/names/mapper.go
+++ b/names/mapper.go
@@ -7,6 +7,7 @@ package names
 import (
 	"strings"
 	"sync"
+	"unsafe"
 )
 
 // Mapper represents a name convertation between struct's fields name and table's column name
@@ -77,19 +78,24 @@ func (m SameMapper) Table2Obj(t string) string {
 type SnakeMapper struct {
 }
 
+func b2s(b []byte) string {
+	return *(*string)(unsafe.Pointer(&b))
+}
+
 func snakeCasedName(name string) string {
-	newstr := make([]rune, 0)
-	for idx, chr := range name {
-		if isUpper := 'A' <= chr && chr <= 'Z'; isUpper {
-			if idx > 0 {
+	newstr := make([]byte, 0, len(name)+1)
+	for i := 0; i < len(name); i++ {
+		c := name[i]
+		if isUpper := 'A' <= c && c <= 'Z'; isUpper {
+			if i > 0 {
 				newstr = append(newstr, '_')
 			}
-			chr -= ('A' - 'a')
+			c += 'a' - 'A'
 		}
-		newstr = append(newstr, chr)
+		newstr = append(newstr, c)
 	}
 
-	return string(newstr)
+	return b2s(newstr)
 }
 
 func (mapper SnakeMapper) Obj2Table(name string) string {
diff --git a/names/mapper_test.go b/names/mapper_test.go
index 0edfd2a8..5c6dc5d9 100644
--- a/names/mapper_test.go
+++ b/names/mapper_test.go
@@ -5,6 +5,7 @@
 package names
 
 import (
+	"strings"
 	"testing"
 )
 
@@ -47,3 +48,13 @@ func TestGonicMapperToObj(t *testing.T) {
 		}
 	}
 }
+
+func BenchmarkSnakeCasedName(b *testing.B) {
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	s := strings.Repeat("FooBar", 32)
+	for i := 0; i < b.N; i++ {
+		_ = snakeCasedName(s)
+	}
+}