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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                       S Y S T E M . W C H _ C N V                        --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- 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 package contains generic subprograms used for converting between

--  sequences of Character and Wide_Character. Wide_Wide_Character values

--  are also handled, but represented using integer range types defined in

--  this package, so that this package can be used from applications that

--  are restricted to Ada 95 compatibility (such as the compiler itself).

--  All the algorithms for encoding and decoding are isolated in this package

--  and in System.WCh_JIS and should not be duplicated elsewhere. The only

--  exception to this is that GNAT.Decode_String and GNAT.Encode_String have

--  their own circuits for UTF-8 conversions, for improved efficiency.

--  This unit may be used directly from an application program by providing

--  an appropriate WITH, and the interface can be expected to remain stable.

pragma Compiler_Unit;

with System.WCh_Con;

package System.WCh_Cnv is

   pragma Pure;

   type UTF_32_Code is range 0 .. 16#7FFF_FFFF#;

   for UTF_32_Code'Size use 32;

   --  Range of allowed UTF-32 encoding values

   type UTF_32_String is array (Positive range <>) of UTF_32_Code;

   generic

      with function In_Char return Character;

   function Char_Sequence_To_Wide_Char

     (C  : Character;

      EM : System.WCh_Con.WC_Encoding_Method) return Wide_Character;

   --  C is the first character of a sequence of one or more characters which

   --  represent a wide character sequence. Calling the function In_Char for

   --  additional characters as required, Char_To_Wide_Char returns the

   --  corresponding wide character value. Constraint_Error is raised if the

   --  sequence of characters encountered is not a valid wide character

   --  sequence for the given encoding method.

   --

   --  Note on the use of brackets encoding (WCEM_Brackets). The brackets

   --  encoding method is ambiguous in the context of this function, since

   --  there is no way to tell if ["1234"] is eight unencoded characters or

   --  one encoded character. In the context of Ada sources, any sequence

   --  starting [" must be the start of an encoding (since that sequence is

   --  not valid in Ada source otherwise). The routines in this package use

   --  the same approach. If the input string contains the sequence [" then

   --  this is assumed to be the start of a brackets encoding sequence, and

   --  if it does not match the syntax, an error is raised.

   generic

      with function In_Char return Character;

   function Char_Sequence_To_UTF_32

     (C  : Character;

      EM : System.WCh_Con.WC_Encoding_Method) return UTF_32_Code;

   --  This is similar to the above, but the function returns a code from

   --  the full UTF_32 code set, which covers the full range of possible

   --  values in Wide_Wide_Character. The result can be converted to

   --  Wide_Wide_Character form using Wide_Wide_Character'Val.

   generic

      with procedure Out_Char (C : Character);

   procedure Wide_Char_To_Char_Sequence

     (WC : Wide_Character;

      EM : System.WCh_Con.WC_Encoding_Method);

   --  Given a wide character, converts it into a sequence of one or

   --  more characters, calling the given Out_Char procedure for each.

   --  Constraint_Error is raised if the given wide character value is

   --  not a valid value for the given encoding method.

   --

   --  Note on brackets encoding (WCEM_Brackets). For the input routines above,

   --  upper half characters can be represented as ["hh"] but this procedure

   --  will only use brackets encodings for codes higher than 16#FF#, so upper

   --  half characters will be output as single Character values.

   generic

      with procedure Out_Char (C : Character);

   procedure UTF_32_To_Char_Sequence

     (Val : UTF_32_Code;

      EM  : System.WCh_Con.WC_Encoding_Method);

   --  This is similar to the above, but the input value is a code from the

   --  full UTF_32 code set, which covers the full range of possible values

   --  in Wide_Wide_Character. To convert a Wide_Wide_Character value, the

   --  caller can use Wide_Wide_Character'Pos in the call.

end System.WCh_Cnv;