From d7a64bbc8a2486700895f5cf1c4088af5e3758a4 Mon Sep 17 00:00:00 2001
From: ChAoS_UnItY <43753315+ChAoSUnItY@users.noreply.github.com>
Date: Mon, 12 Apr 2021 10:58:03 +0800
Subject: [PATCH] encoding.utf8: fix len and ulen and optimize raw_index
 (#9682)

---
 vlib/encoding/utf8/utf8_util.v      | 10 ++++++++++
 vlib/encoding/utf8/utf8_util_test.v |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/vlib/encoding/utf8/utf8_util.v b/vlib/encoding/utf8/utf8_util.v
index 0d8eff6746..5184c57e6b 100644
--- a/vlib/encoding/utf8/utf8_util.v
+++ b/vlib/encoding/utf8/utf8_util.v
@@ -15,6 +15,10 @@ Utility functions
 
 // len return the length as number of unicode chars from a string
 pub fn len(s string) int {
+	if s.len == 0 {
+		return 0
+	}
+
 	mut count := 0
 	mut index := 0
 
@@ -82,10 +86,16 @@ pub fn get_uchar(s string, index int) int {
 // raw_index - get the raw chracter from the string by the given index value.
 // example: '我是V Lang'.raw_index(1) => '是'
 
+// raw_index - get the raw chracter from the string by the given index value.
+// example: utf8.raw_index('我是V Lang', 1) => '是'
 pub fn raw_index(s string, index int) string {
 	mut r := []rune{}
 
 	for i := 0; i < s.len; i++ {
+		if r.len - 1 == index {
+			break
+		}
+
 		b := s[i]
 		ch_len := ((0xe5000000 >> ((b >> 3) & 0x1e)) & 3)
 
diff --git a/vlib/encoding/utf8/utf8_util_test.v b/vlib/encoding/utf8/utf8_util_test.v
index e2cbb8ea43..4ab3f96513 100644
--- a/vlib/encoding/utf8/utf8_util_test.v
+++ b/vlib/encoding/utf8/utf8_util_test.v
@@ -21,10 +21,12 @@ fn test_utf8_util() {
 	assert lower1 == (src_lower.ustring())
 
 	// test len function
+	assert utf8.len('') == 0
 	assert utf8.len('pippo') == 5
 	assert utf8.len(src) == 15 // 29
 	assert src.len == 24 // 49
 	// test u_len function
+	assert utf8.u_len(''.ustring()) == 0
 	assert utf8.u_len(src1) == 15 // 29
 	assert utf8.u_len('pippo'.ustring()) == 5