1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME COMPONENTS -- 4-- -- 5-- G N A T . D E C O D E _ S T R I N G -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 2007-2013, AdaCore -- 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 3, 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. -- 17-- -- 18-- As a special exception under Section 7 of GPL version 3, you are granted -- 19-- additional permissions described in the GCC Runtime Library Exception, -- 20-- version 3.1, as published by the Free Software Foundation. -- 21-- -- 22-- You should have received a copy of the GNU General Public License and -- 23-- a copy of the GCC Runtime Library Exception along with this program; -- 24-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- 25-- <http://www.gnu.org/licenses/>. -- 26-- -- 27-- GNAT was originally developed by the GNAT team at New York University. -- 28-- Extensive contributions were provided by Ada Core Technologies Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This generic package provides utility routines for converting from an 33-- encoded string to a corresponding Wide_String or Wide_Wide_String value 34-- using a specified encoding convention, which is supplied as the generic 35-- parameter. UTF-8 is handled especially efficiently, and if the encoding 36-- method is known at compile time to be WCEM_UTF8, then the instantiation 37-- is specialized to handle only the UTF-8 case and exclude code for the 38-- other encoding methods. The package also provides positioning routines 39-- for skipping encoded characters in either direction, and for validating 40-- strings for correct encodings. 41 42-- Note: this package is only about decoding sequences of 8-bit characters 43-- into corresponding 16-bit Wide_String or 32-bit Wide_Wide_String values. 44-- It knows nothing at all about the character encodings being used for the 45-- resulting Wide_Character and Wide_Wide_Character values. Most often this 46-- will be Unicode/ISO-10646 as specified by the Ada RM, but this package 47-- does not make any assumptions about the character coding. See also the 48-- packages Ada.Wide_[Wide_]Characters.Unicode for unicode specific functions. 49 50-- In particular, in the case of UTF-8, all valid UTF-8 encodings, as listed 51-- in table 3.6 of the Unicode Standard, version 6.2.0, are recognized as 52-- legitimate. This includes the full range 16#0000_0000# .. 16#03FF_FFFF#. 53-- This includes codes in the range 16#D800# - 16#DFFF#. These codes all 54-- have UTF-8 encoding sequences that are well-defined (e.g. the encoding for 55-- 16#D800# is ED A0 80). But these codes do not correspond to defined Unicode 56-- characters and are thus considered to be "not well-formed" (see table 3.7 57-- of the Unicode Standard). If you need to exclude these codes, you must do 58-- that manually, e.g. use Decode_Wide_Character/Decode_Wide_String and check 59-- that the resulting code(s) are not in this range. 60 61-- Note on the use of brackets encoding (WCEM_Brackets). The brackets encoding 62-- method is ambiguous in the context of this package, since there is no way 63-- to tell if ["1234"] is eight unencoded characters or one encoded character. 64-- In the context of Ada sources, any sequence starting [" must be the start 65-- of an encoding (since that sequence is not valid in Ada source otherwise). 66-- The routines in this package use the same approach. If the input string 67-- contains the sequence [" then this is assumed to be the start of a brackets 68-- encoding sequence, and if it does not match the syntax, an error is raised. 69-- In the case of the Prev functions, a sequence ending with "] is assumed to 70-- be a valid brackets sequence, and an error is raised if it is not. 71 72with System.WCh_Con; 73 74generic 75 Encoding_Method : System.WCh_Con.WC_Encoding_Method; 76 77package GNAT.Decode_String is 78 pragma Pure; 79 80 function Decode_Wide_String (S : String) return Wide_String; 81 pragma Inline (Decode_Wide_String); 82 -- Decode the given String, which is encoded using the indicated coding 83 -- method, returning the corresponding decoded Wide_String value. If S 84 -- contains a character code that cannot be represented with the given 85 -- encoding, then Constraint_Error is raised. 86 87 procedure Decode_Wide_String 88 (S : String; 89 Result : out Wide_String; 90 Length : out Natural); 91 -- Similar to the above function except that the result is stored in the 92 -- given Wide_String variable Result, starting at Result (Result'First). On 93 -- return, Length is set to the number of characters stored in Result. The 94 -- caller must ensure that Result is long enough (an easy choice is to set 95 -- the length equal to the S'Length, since decoding can never increase the 96 -- string length). If the length of Result is insufficient Constraint_Error 97 -- will be raised. 98 99 function Decode_Wide_Wide_String (S : String) return Wide_Wide_String; 100 -- Same as above function but for Wide_Wide_String output 101 102 procedure Decode_Wide_Wide_String 103 (S : String; 104 Result : out Wide_Wide_String; 105 Length : out Natural); 106 -- Same as above procedure, but for Wide_Wide_String output 107 108 function Validate_Wide_String (S : String) return Boolean; 109 -- This function inspects the string S to determine if it contains only 110 -- valid encodings corresponding to Wide_Character values using the 111 -- given encoding. If a call to Decode_Wide_String (S) would return 112 -- without raising Constraint_Error, then Validate_Wide_String will 113 -- return True. If the call would have raised Constraint_Error, then 114 -- Validate_Wide_String will return False. 115 116 function Validate_Wide_Wide_String (S : String) return Boolean; 117 -- Similar to Validate_Wide_String, except that it succeeds if the string 118 -- contains only encodings corresponding to Wide_Wide_Character values. 119 120 procedure Decode_Wide_Character 121 (Input : String; 122 Ptr : in out Natural; 123 Result : out Wide_Character); 124 pragma Inline (Decode_Wide_Character); 125 -- This is a lower level procedure that decodes a single character using 126 -- the given encoding method. The encoded character is stored in Input, 127 -- starting at Input (Ptr). The resulting output character is stored in 128 -- Result, and on return Ptr is updated past the input character or 129 -- encoding sequence. Constraint_Error will be raised if the input has 130 -- has a character that cannot be represented using the given encoding, 131 -- or if Ptr is outside the bounds of the Input string. 132 133 procedure Decode_Wide_Wide_Character 134 (Input : String; 135 Ptr : in out Natural; 136 Result : out Wide_Wide_Character); 137 pragma Inline (Decode_Wide_Wide_Character); 138 -- Same as above procedure but with Wide_Wide_Character input 139 140 procedure Next_Wide_Character (Input : String; Ptr : in out Natural); 141 pragma Inline (Next_Wide_Character); 142 -- This procedure examines the input string starting at Input (Ptr), and 143 -- advances Ptr past one character in the encoded string, so that on return 144 -- Ptr points to the next encoded character. Constraint_Error is raised if 145 -- an invalid encoding is encountered, or the end of the string is reached 146 -- or if Ptr is less than String'First on entry, or if the character 147 -- skipped is not a valid Wide_Character code. 148 149 procedure Prev_Wide_Character (Input : String; Ptr : in out Natural); 150 -- This procedure is similar to Next_Encoded_Character except that it moves 151 -- backwards in the string, so that on return, Ptr is set to point to the 152 -- previous encoded character. Constraint_Error is raised if the start of 153 -- the string is encountered. It is valid for Ptr to be one past the end 154 -- of the string for this call (in which case on return it will point to 155 -- the last encoded character). 156 -- 157 -- Note: it is not generally possible to do this function efficiently with 158 -- all encodings, the current implementation is only efficient for the case 159 -- of UTF-8 (Encoding_Method = WCEM_UTF8) and Brackets (Encoding_Method = 160 -- WCEM_Brackets). For all other encodings, we work by starting at the 161 -- beginning of the string and moving forward till Ptr is reached, which 162 -- is correct but slow. 163 -- 164 -- Note: this routine assumes that the sequence prior to Ptr is correctly 165 -- encoded, it does not have a defined behavior if this is not the case. 166 167 procedure Next_Wide_Wide_Character (Input : String; Ptr : in out Natural); 168 pragma Inline (Next_Wide_Wide_Character); 169 -- Similar to Next_Wide_Character except that codes skipped must be valid 170 -- Wide_Wide_Character codes. 171 172 procedure Prev_Wide_Wide_Character (Input : String; Ptr : in out Natural); 173 -- Similar to Prev_Wide_Character except that codes skipped must be valid 174 -- Wide_Wide_Character codes. 175 176end GNAT.Decode_String; 177