Find offset by index

nel/include/nel/misc/utf_string_view.h

@@ -131,7 +131,8 @@ public:
 	inline bool empty() const { return !m_Size; }
 	const void *ptr() const { return m_Str; }
 
-	size_t count() const; // Slow count of UTF-32 characters
+	size_t count() const; //< Slow count of UTF-32 codepoints
+	ptrdiff_t offset(ptrdiff_t i); const //< Get byte offset by utf-32 codepoint index
 
 	inline CUtfStringView substr(const iterator &begin, const iterator &end) const
 	{

nel/src/misc/utf_string_view.cpp

@@ -230,6 +230,18 @@ size_t CUtfStringView::count() const
 	return res;
 }
 
+ptrdiff_t CUtfStringView::offset(ptrdiff_t i)
+{
+	size_t res = 0;
+	for (iterator it(begin()), end(this->end()); it != end; ++it)
+	{
+		if (res == i)
+			return (ptrdiff_t)it.ptr() - (ptrdiff_t)ptr();
+		++res;
+	}
+	return res;
+}
+
 u32char CUtfStringView::utf8Iterator(const void **addr)
 {
 	// Decode UTF-8