gcc/ada/s-wchcnv.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . W C H _ C N V                        --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2007, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package contains generic subprograms used for converting between
  35 --  sequences of Character and Wide_Character. Wide_Wide_Character values
  36 --  are also handled, but represented using integer range types defined in
  37 --  this package, so that this package can be used from applications that
  38 --  are restricted to Ada 95 compatibility (such as the compiler itself).
  39
  40 --  All the algorithms for encoding and decoding are isolated in this package
  41 --  and in System.WCh_JIS and should not be duplicated elsewhere. The only
  42 --  exception to this is that GNAT.Decode_String and GNAT.Encode_String have
  43 --  their own circuits for UTF-8 conversions, for improved efficiency.
  44
  45 --  This unit may be used directly from an application program by providing
  46 --  an appropriate WITH, and the interface can be expected to remain stable.
  47
  48 pragma Warnings (Off);
  49 pragma Compiler_Unit;
  50 pragma Warnings (On);
  51
  52 with System.WCh_Con;
  53
  54 package System.WCh_Cnv is
  55    pragma Pure;
  56
  57    type UTF_32_Code is range 0 .. 16#7FFF_FFFF#;
  58    for UTF_32_Code'Size use 32;
  59    --  Range of allowed UTF-32 encoding values
  60
  61    type UTF_32_String is array (Positive range <>) of UTF_32_Code;
  62
  63    generic
  64       with function In_Char return Character;
  65    function Char_Sequence_To_Wide_Char
  66      (C  : Character;
  67       EM : System.WCh_Con.WC_Encoding_Method) return Wide_Character;
  68    --  C is the first character of a sequence of one or more characters which
  69    --  represent a wide character sequence. Calling the function In_Char for
  70    --  additional characters as required, Char_To_Wide_Char returns the
  71    --  corresponding wide character value. Constraint_Error is raised if the
  72    --  sequence of characters encountered is not a valid wide character
  73    --  sequence for the given encoding method.
  74    --
  75    --  Note on the use of brackets encoding (WCEM_Brackets). The brackets
  76    --  encoding method is ambiguous in the context of this function, since
  77    --  there is no way to tell if ["1234"] is eight unencoded characters or
  78    --  one encoded character. In the context of Ada sources, any sequence
  79    --  starting [" must be the start of an encoding (since that sequence is
  80    --  not valid in Ada source otherwise). The routines in this package use
  81    --  the same approach. If the input string contains the sequence [" then
  82    --  this is assumed to be the start of a brackets encoding sequence, and
  83    --  if it does not match the syntax, an error is raised.
  84
  85    generic
  86       with function In_Char return Character;
  87    function Char_Sequence_To_UTF_32
  88      (C  : Character;
  89       EM : System.WCh_Con.WC_Encoding_Method) return UTF_32_Code;
  90    --  This is similar to the above, but the function returns a code from
  91    --  the full UTF_32 code set, which covers the full range of possible
  92    --  values in Wide_Wide_Character. The result can be converted to
  93    --  Wide_Wide_Character form using Wide_Wide_Character'Val.
  94
  95    generic
  96       with procedure Out_Char (C : Character);
  97    procedure Wide_Char_To_Char_Sequence
  98      (WC : Wide_Character;
  99       EM : System.WCh_Con.WC_Encoding_Method);
 100    --  Given a wide character, converts it into a sequence of one or
 101    --  more characters, calling the given Out_Char procedure for each.
 102    --  Constraint_Error is raised if the given wide character value is
 103    --  not a valid value for the given encoding method.
 104    --
 105    --  Note on brackets encoding (WCEM_Brackets). For the input routines above,
 106    --  upper half characters can be represented as ["hh"] but this procedure
 107    --  will only use brackets encodings for codes higher than 16#FF#, so upper
 108    --  half characters will be output as single Character values.
 109
 110    generic
 111       with procedure Out_Char (C : Character);
 112    procedure UTF_32_To_Char_Sequence
 113      (Val : UTF_32_Code;
 114       EM  : System.WCh_Con.WC_Encoding_Method);
 115    --  This is similar to the above, but the input value is a code from the
 116    --  full UTF_32 code set, which covers the full range of possible values
 117    --  in Wide_Wide_Character. To convert a Wide_Wide_Character value, the
 118    --  caller can use Wide_Wide_Character'Pos in the call.
 119
 120 end System.WCh_Cnv;