Ada Programming/Libraries/Ada.Strings.UTF Encoding.Strings

is a unit of the Predefined Language Environment since Ada 2012.

Specification
Pure Strings Encode Item          String Output_Scheme Encoding_Scheme Output_BOM    Boolean   False  UTF_String Encode Item       String Output_BOM Boolean   False  UTF_8_String Encode Item       String Output_BOM Boolean   False UTF_16_Wide_String Decode Item         UTF_String Input_Scheme Encoding_Scheme  String Decode Item UTF_8_String  String Decode Item UTF_16_Wide_String  String AdaStringsUTF_EncodingStrings

Wikibook

 * Ada Programming/Libraries/Ada
 * Ada Programming/Libraries/Ada.Strings
 * Ada Programming/Libraries/Ada.Strings.UTF_Encoding