From cc74a8854a1a42919a9650cfe280d015d9374a1a Mon Sep 17 00:00:00 2001
From: Bo-Yi Wu <appleboy.tw@gmail.com>
Date: Thu, 21 May 2020 21:00:33 +0800
Subject: [PATCH] chore: improve snakeCasedName performance

---
 names/mapper.go      | 21 +++++++++++++++++++++
 names/mapper_test.go | 21 +++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/names/mapper.go b/names/mapper.go
index 4aaf0844..b720479e 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
@@ -92,6 +93,26 @@ func snakeCasedName(name string) string {
 	return string(newstr)
 }
 
+func b2s(b []byte) string {
+	return *(*string)(unsafe.Pointer(&b))
+}
+
+func snakeCasedNameNew(name string) string {
+	newstr := make([]byte, 0)
+	for i := 0; i < len(name); i++ {
+		c := name[i]
+		if isUpper := 'A' <= c && c <= 'Z'; isUpper {
+			if i > 0 {
+				newstr = append(newstr, '_')
+			}
+			c += 'a' - 'A'
+		}
+		newstr = append(newstr, c)
+	}
+
+	return b2s(newstr)
+}
+
 func (mapper SnakeMapper) Obj2Table(name string) string {
 	return snakeCasedName(name)
 }
diff --git a/names/mapper_test.go b/names/mapper_test.go
index 0edfd2a8..6945b84c 100644
--- a/names/mapper_test.go
+++ b/names/mapper_test.go
@@ -5,6 +5,7 @@
 package names
 
 import (
+	"strings"
 	"testing"
 )
 
@@ -47,3 +48,23 @@ 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)
+	}
+}
+
+func BenchmarkSnakeCasedNameNew(b *testing.B) {
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	s := strings.Repeat("FooBar", 32)
+	for i := 0; i < b.N; i++ {
+		_ = snakeCasedNameNew(s)
+	}
+}