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------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- A D A . S T R I N G S . U T F _ E N C O D I N G -- -- -- -- S p e c -- -- -- -- This specification is derived from the Ada Reference Manual for use with -- -- GNAT. The copyright notice above, and the license provisions that follow -- -- apply solely to the contents of the part following the private keyword. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- <http://www.gnu.org/licenses/>. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This is one of the Ada 2012 package defined in AI05-0137-1. It is a parent -- package that contains declarations used in the child packages for handling -- UTF encoded strings. Note: this package is consistent with Ada 95, and may -- be used in Ada 95 or Ada 2005 mode. with Interfaces; with Unchecked_Conversion; package Ada.Strings.UTF_Encoding is pragma Pure (UTF_Encoding); subtype UTF_String is String; -- Used to represent a string of 8-bit values containing a sequence of -- values encoded in one of three ways (UTF-8, UTF-16BE, or UTF-16LE). -- Typically used in connection with a Scheme parameter indicating which -- of the encodings applies. This is not strictly a String value in the -- sense defined in the Ada RM, but in practice type String accommodates -- all possible 256 codes, and can be used to hold any sequence of 8-bit -- codes. We use String directly rather than create a new type so that -- all existing facilities for manipulating type String (e.g. the child -- packages of Ada.Strings) are available for manipulation of UTF_Strings. type Encoding_Scheme is (UTF_8, UTF_16BE, UTF_16LE); -- Used to specify which of three possible encodings apply to a UTF_String subtype UTF_8_String is String; -- Similar to UTF_String but specifically represents a UTF-8 encoded string subtype UTF_16_Wide_String is Wide_String; -- This is similar to UTF_8_String but is used to represent a Wide_String -- value which is a sequence of 16-bit values encoded using UTF-16. Again -- this is not strictly a Wide_String in the sense of the Ada RM, but the -- type Wide_String can be used to represent a sequence of arbitrary 16-bit -- values, and it is more convenient to use Wide_String than a new type. Encoding_Error : exception; -- This exception is raised in the following situations: -- a) A UTF encoded string contains an invalid encoding sequence -- b) A UTF-16BE or UTF-16LE input string has an odd length -- c) An incorrect character value is present in the Input string -- d) The result for a Wide_Character output exceeds 16#FFFF# -- The exception message has the index value where the error occurred. -- The BOM (BYTE_ORDER_MARK) values defined here are used at the start of -- a string to indicate the encoding. The convention in this package is -- that on input a correct BOM is ignored and an incorrect BOM causes an -- Encoding_Error exception. On output, the output string may or may not -- include a BOM depending on the setting of Output_BOM. BOM_8 : constant UTF_8_String := Character'Val (16#EF#) & Character'Val (16#BB#) & Character'Val (16#BF#); BOM_16BE : constant UTF_String := Character'Val (16#FE#) & Character'Val (16#FF#); BOM_16LE : constant UTF_String := Character'Val (16#FF#) & Character'Val (16#FE#); BOM_16 : constant UTF_16_Wide_String := (1 => Wide_Character'Val (16#FEFF#)); function Encoding (Item : UTF_String; Default : Encoding_Scheme := UTF_8) return Encoding_Scheme; -- This function inspects a UTF_String value to determine whether it -- starts with a BOM for UTF-8, UTF-16BE, or UTF_16LE. If so, the result -- is the scheme corresponding to the BOM. If no valid BOM is present -- then the result is the specified Default value. private function To_Unsigned_8 is new Unchecked_Conversion (Character, Interfaces.Unsigned_8); function To_Unsigned_16 is new Unchecked_Conversion (Wide_Character, Interfaces.Unsigned_16); function To_Unsigned_32 is new Unchecked_Conversion (Wide_Wide_Character, Interfaces.Unsigned_32); subtype UTF_XE_Encoding is Encoding_Scheme range UTF_16BE .. UTF_16LE; -- Subtype containing only UTF_16BE and UTF_16LE entries -- Utility routines for converting between UTF-16 and UTF-16LE/BE function From_UTF_16 (Item : UTF_16_Wide_String; Output_Scheme : UTF_XE_Encoding; Output_BOM : Boolean := False) return UTF_String; -- The input string Item is encoded in UTF-16. The output is encoded using -- Output_Scheme (which is either UTF-16LE or UTF-16BE). There are no error -- cases. The output starts with BOM_16BE/LE if Output_BOM is True. function To_UTF_16 (Item : UTF_String; Input_Scheme : UTF_XE_Encoding; Output_BOM : Boolean := False) return UTF_16_Wide_String; -- The input string Item is encoded using Input_Scheme which is either -- UTF-16LE or UTF-16BE. The output is the corresponding UTF_16 wide -- string. Encoding error is raised if the length of the input is odd. -- The output starts with BOM_16 if Output_BOM is True. procedure Raise_Encoding_Error (Index : Natural); pragma No_Return (Raise_Encoding_Error); -- Raise Encoding_Error exception for bad encoding in input item. The -- parameter Index is the index of the location in Item for the error. end Ada.Strings.UTF_Encoding;
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