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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . W C H _ C N V --
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6 -- --
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7 -- S p e c --
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8 -- --
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145
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9 -- Copyright (C) 1992-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- This package contains generic subprograms used for converting between
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33 -- sequences of Character and Wide_Character. Wide_Wide_Character values
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34 -- are also handled, but represented using integer range types defined in
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35 -- this package, so that this package can be used from applications that
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36 -- are restricted to Ada 95 compatibility (such as the compiler itself).
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37
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38 -- All the algorithms for encoding and decoding are isolated in this package
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39 -- and in System.WCh_JIS and should not be duplicated elsewhere. The only
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40 -- exception to this is that GNAT.Decode_String and GNAT.Encode_String have
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41 -- their own circuits for UTF-8 conversions, for improved efficiency.
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42
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43 -- This unit may be used directly from an application program by providing
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44 -- an appropriate WITH, and the interface can be expected to remain stable.
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45
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46 pragma Compiler_Unit_Warning;
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47
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48 with System.WCh_Con;
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49
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50 package System.WCh_Cnv is
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51 pragma Pure;
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52
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53 type UTF_32_Code is range 0 .. 16#7FFF_FFFF#;
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54 for UTF_32_Code'Size use 32;
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55 -- Range of allowed UTF-32 encoding values
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56
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57 type UTF_32_String is array (Positive range <>) of UTF_32_Code;
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58
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59 generic
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60 with function In_Char return Character;
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61 function Char_Sequence_To_Wide_Char
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62 (C : Character;
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63 EM : System.WCh_Con.WC_Encoding_Method) return Wide_Character;
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64 -- C is the first character of a sequence of one or more characters which
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65 -- represent a wide character sequence. Calling the function In_Char for
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66 -- additional characters as required, Char_To_Wide_Char returns the
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67 -- corresponding wide character value. Constraint_Error is raised if the
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68 -- sequence of characters encountered is not a valid wide character
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69 -- sequence for the given encoding method.
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70 --
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71 -- Note on the use of brackets encoding (WCEM_Brackets). The brackets
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72 -- encoding method is ambiguous in the context of this function, since
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73 -- there is no way to tell if ["1234"] is eight unencoded characters or
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74 -- one encoded character. In the context of Ada sources, any sequence
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75 -- starting [" must be the start of an encoding (since that sequence is
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76 -- not valid in Ada source otherwise). The routines in this package use
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77 -- the same approach. If the input string contains the sequence [" then
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78 -- this is assumed to be the start of a brackets encoding sequence, and
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79 -- if it does not match the syntax, an error is raised.
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80
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81 generic
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82 with function In_Char return Character;
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83 function Char_Sequence_To_UTF_32
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84 (C : Character;
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85 EM : System.WCh_Con.WC_Encoding_Method) return UTF_32_Code;
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86 -- This is similar to the above, but the function returns a code from
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87 -- the full UTF_32 code set, which covers the full range of possible
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88 -- values in Wide_Wide_Character. The result can be converted to
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89 -- Wide_Wide_Character form using Wide_Wide_Character'Val.
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90
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91 generic
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92 with procedure Out_Char (C : Character);
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93 procedure Wide_Char_To_Char_Sequence
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94 (WC : Wide_Character;
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95 EM : System.WCh_Con.WC_Encoding_Method);
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96 -- Given a wide character, converts it into a sequence of one or
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97 -- more characters, calling the given Out_Char procedure for each.
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98 -- Constraint_Error is raised if the given wide character value is
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99 -- not a valid value for the given encoding method.
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100 --
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101 -- Note on brackets encoding (WCEM_Brackets). For the input routines above,
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102 -- upper half characters can be represented as ["hh"] but this procedure
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103 -- will only use brackets encodings for codes higher than 16#FF#, so upper
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104 -- half characters will be output as single Character values.
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105
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106 generic
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107 with procedure Out_Char (C : Character);
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108 procedure UTF_32_To_Char_Sequence
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109 (Val : UTF_32_Code;
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110 EM : System.WCh_Con.WC_Encoding_Method);
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111 -- This is similar to the above, but the input value is a code from the
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112 -- full UTF_32 code set, which covers the full range of possible values
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113 -- in Wide_Wide_Character. To convert a Wide_Wide_Character value, the
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114 -- caller can use Wide_Wide_Character'Pos in the call.
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115
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116 end System.WCh_Cnv;
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