| ------------------------------------------------------------------------------ |
| -- -- |
| -- 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 -- |
| -- <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 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; |
