------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- G N A T . D E C O D E _ S T R I N G -- -- -- -- S p e c -- -- -- -- Copyright (C) 2007-2013, AdaCore -- -- -- -- 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 -- -- . -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This generic package provides utility routines for converting from an -- encoded string to a corresponding Wide_String or Wide_Wide_String value -- using a specified encoding convention, which is supplied as the generic -- parameter. UTF-8 is handled especially efficiently, and if the encoding -- method is known at compile time to be WCEM_UTF8, then the instantiation -- is specialized to handle only the UTF-8 case and exclude code for the -- other encoding methods. The package also provides positioning routines -- for skipping encoded characters in either direction, and for validating -- strings for correct encodings. -- Note: this package is only about decoding sequences of 8-bit characters -- into corresponding 16-bit Wide_String or 32-bit Wide_Wide_String values. -- It knows nothing at all about the character encodings being used for the -- resulting Wide_Character and Wide_Wide_Character values. Most often this -- will be Unicode/ISO-10646 as specified by the Ada RM, but this package -- does not make any assumptions about the character coding. See also the -- packages Ada.Wide_[Wide_]Characters.Unicode for unicode specific functions. -- In particular, in the case of UTF-8, all valid UTF-8 encodings, as listed -- in table 3.6 of the Unicode Standard, version 6.2.0, are recognized as -- legitimate. This includes the full range 16#0000_0000# .. 16#03FF_FFFF#. -- This includes codes in the range 16#D800# - 16#DFFF#. These codes all -- have UTF-8 encoding sequences that are well-defined (e.g. the encoding for -- 16#D800# is ED A0 80). But these codes do not correspond to defined Unicode -- characters and are thus considered to be "not well-formed" (see table 3.7 -- of the Unicode Standard). If you need to exclude these codes, you must do -- that manually, e.g. use Decode_Wide_Character/Decode_Wide_String and check -- that the resulting code(s) are not in this range. -- Note on the use of brackets encoding (WCEM_Brackets). The brackets encoding -- method is ambiguous in the context of this package, 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. -- In the case of the Prev functions, a sequence ending with "] is assumed to -- be a valid brackets sequence, and an error is raised if it is not. with System.WCh_Con; generic Encoding_Method : System.WCh_Con.WC_Encoding_Method; package GNAT.Decode_String is pragma Pure; function Decode_Wide_String (S : String) return Wide_String; pragma Inline (Decode_Wide_String); -- Decode the given String, which is encoded using the indicated coding -- method, returning the corresponding decoded Wide_String value. If S -- contains a character code that cannot be represented with the given -- encoding, then Constraint_Error is raised. procedure Decode_Wide_String (S : String; Result : out Wide_String; Length : out Natural); -- Similar to the above function except that the result is stored in the -- given Wide_String variable Result, starting at Result (Result'First). On -- return, Length is set to the number of characters stored in Result. The -- caller must ensure that Result is long enough (an easy choice is to set -- the length equal to the S'Length, since decoding can never increase the -- string length). If the length of Result is insufficient Constraint_Error -- will be raised. function Decode_Wide_Wide_String (S : String) return Wide_Wide_String; -- Same as above function but for Wide_Wide_String output procedure Decode_Wide_Wide_String (S : String; Result : out Wide_Wide_String; Length : out Natural); -- Same as above procedure, but for Wide_Wide_String output function Validate_Wide_String (S : String) return Boolean; -- This function inspects the string S to determine if it contains only -- valid encodings corresponding to Wide_Character values using the -- given encoding. If a call to Decode_Wide_String (S) would return -- without raising Constraint_Error, then Validate_Wide_String will -- return True. If the call would have raised Constraint_Error, then -- Validate_Wide_String will return False. function Validate_Wide_Wide_String (S : String) return Boolean; -- Similar to Validate_Wide_String, except that it succeeds if the string -- contains only encodings corresponding to Wide_Wide_Character values. procedure Decode_Wide_Character (Input : String; Ptr : in out Natural; Result : out Wide_Character); pragma Inline (Decode_Wide_Character); -- This is a lower level procedure that decodes a single character using -- the given encoding method. The encoded character is stored in Input, -- starting at Input (Ptr). The resulting output character is stored in -- Result, and on return Ptr is updated past the input character or -- encoding sequence. Constraint_Error will be raised if the input has -- has a character that cannot be represented using the given encoding, -- or if Ptr is outside the bounds of the Input string. procedure Decode_Wide_Wide_Character (Input : String; Ptr : in out Natural; Result : out Wide_Wide_Character); pragma Inline (Decode_Wide_Wide_Character); -- Same as above procedure but with Wide_Wide_Character input procedure Next_Wide_Character (Input : String; Ptr : in out Natural); pragma Inline (Next_Wide_Character); -- This procedure examines the input string starting at Input (Ptr), and -- advances Ptr past one character in the encoded string, so that on return -- Ptr points to the next encoded character. Constraint_Error is raised if -- an invalid encoding is encountered, or the end of the string is reached -- or if Ptr is less than String'First on entry, or if the character -- skipped is not a valid Wide_Character code. procedure Prev_Wide_Character (Input : String; Ptr : in out Natural); -- This procedure is similar to Next_Encoded_Character except that it moves -- backwards in the string, so that on return, Ptr is set to point to the -- previous encoded character. Constraint_Error is raised if the start of -- the string is encountered. It is valid for Ptr to be one past the end -- of the string for this call (in which case on return it will point to -- the last encoded character). -- -- Note: it is not generally possible to do this function efficiently with -- all encodings, the current implementation is only efficient for the case -- of UTF-8 (Encoding_Method = WCEM_UTF8) and Brackets (Encoding_Method = -- WCEM_Brackets). For all other encodings, we work by starting at the -- beginning of the string and moving forward till Ptr is reached, which -- is correct but slow. -- -- Note: this routine assumes that the sequence prior to Ptr is correctly -- encoded, it does not have a defined behavior if this is not the case. procedure Next_Wide_Wide_Character (Input : String; Ptr : in out Natural); pragma Inline (Next_Wide_Wide_Character); -- Similar to Next_Wide_Character except that codes skipped must be valid -- Wide_Wide_Character codes. procedure Prev_Wide_Wide_Character (Input : String; Ptr : in out Natural); -- Similar to Prev_Wide_Character except that codes skipped must be valid -- Wide_Wide_Character codes. end GNAT.Decode_String;