From 948ea8c7eefa8cab81b8b6cddd2b5582c71b1047 Mon Sep 17 00:00:00 2001
From: Bart Meuris <bart.meuris@gmail.com>
Date: Thu, 25 Aug 2022 14:22:52 +0200
Subject: [PATCH] Improve UUID (#107)

Improvements to UUID:
* uuid now works with upper and lowercase
* sped up UUID.String() using stringbuilder, added benchmark
* UUID.String(): grow builder to prevent allocs
* make test in cicd happy
---
 uuid.go      | 23 ++++++++++++++---------
 uuid_test.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/uuid.go b/uuid.go
index 97fe11b..b632fbc 100644
--- a/uuid.go
+++ b/uuid.go
@@ -3,7 +3,10 @@ package bluetooth
 // This file implements 16-bit and 128-bit UUIDs as defined in the Bluetooth
 // specification.
 
-import "errors"
+import (
+	"errors"
+	"strings"
+)
 
 // UUID is a single UUID as used in the Bluetooth stack. It is represented as a
 // [4]uint32 instead of a [16]byte for efficiency.
@@ -90,6 +93,8 @@ func ParseUUID(s string) (uuid UUID, err error) {
 			nibble = c - '0' + 0x0
 		} else if c >= 'a' && c <= 'f' {
 			nibble = c - 'a' + 0xa
+		} else if c >= 'A' && c <= 'F' {
+			nibble = c - 'A' + 0xa
 		} else {
 			err = errInvalidUUID
 			return
@@ -112,13 +117,13 @@ func ParseUUID(s string) (uuid UUID, err error) {
 // String returns a human-readable version of this UUID, such as
 // 00001234-0000-1000-8000-00805f9b34fb.
 func (uuid UUID) String() string {
-	// TODO: make this more efficient.
-	s := ""
+	var s strings.Builder
+	s.Grow(36)
 	raw := uuid.Bytes()
 	for i := range raw {
 		// Insert a hyphen at the correct locations.
 		if i == 4 || i == 6 || i == 8 || i == 10 {
-			s += "-"
+			s.WriteRune('-')
 		}
 
 		// The character to convert to hex.
@@ -127,19 +132,19 @@ func (uuid UUID) String() string {
 		// First nibble.
 		nibble := c >> 4
 		if nibble <= 9 {
-			s += string(nibble + '0')
+			s.WriteByte(nibble + '0')
 		} else {
-			s += string(nibble + 'a' - 10)
+			s.WriteByte(nibble + 'a' - 10)
 		}
 
 		// Second nibble.
 		nibble = c & 0x0f
 		if nibble <= 9 {
-			s += string(nibble + '0')
+			s.WriteByte(nibble + '0')
 		} else {
-			s += string(nibble + 'a' - 10)
+			s.WriteByte(nibble + 'a' - 10)
 		}
 	}
 
-	return s
+	return s.String()
 }
diff --git a/uuid_test.go b/uuid_test.go
index 5e47409..5cf35f4 100644
--- a/uuid_test.go
+++ b/uuid_test.go
@@ -1,6 +1,7 @@
 package bluetooth
 
 import (
+	"strings"
 	"testing"
 )
 
@@ -38,3 +39,35 @@ func TestStringUUID(t *testing.T) {
 		t.Errorf("expected %s but got %s", uuidString, u.String())
 	}
 }
+
+func TestStringUUIDUpperCase(t *testing.T) {
+	uuidString := strings.ToUpper("00001234-0000-1000-8000-00805f9b34fb")
+	u, e := ParseUUID(uuidString)
+	if e != nil {
+		t.Errorf("expected nil but got %v", e)
+	}
+	if !strings.EqualFold(u.String(), uuidString) {
+		t.Errorf("%s does not match %s ignoring case", uuidString, u.String())
+	}
+}
+
+func TestStringUUIDLowerCase(t *testing.T) {
+	uuidString := strings.ToLower("00001234-0000-1000-8000-00805f9b34fb")
+	u, e := ParseUUID(uuidString)
+	if e != nil {
+		t.Errorf("expected nil but got %v", e)
+	}
+	if !strings.EqualFold(u.String(), uuidString) {
+		t.Errorf("%s does not match %s ignoring case", uuidString, u.String())
+	}
+}
+
+func BenchmarkUUIDToString(b *testing.B) {
+	uuid, e := ParseUUID("00001234-0000-1000-8000-00805f9b34fb")
+	if e != nil {
+		b.Errorf("expected nil but got %v", e)
+	}
+	for i := 0; i < b.N; i++ {
+		_ = uuid.String()
+	}
+}