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167 | ------------------------------------------------------------------------------
-- XML/Ada - An XML suite for Ada95 --
-- --
-- Copyright (C) 2001-2022, AdaCore --
-- --
-- This library is free software; you can redistribute it and/or modify it --
-- under terms of the GNU General Public License as published by the Free --
-- Software Foundation; either version 3, or (at your option) any later --
-- version. This library is distributed in the hope that it will be useful, --
-- but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHAN- --
-- TABILITY 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/>. --
-- --
------------------------------------------------------------------------------
-- This package provides support for Utf16 encoding of characters.
--
-- Although utf32 is simpler, it requires too much space to encode typical
-- strings. Indeed, only two bytes are currently needed to encode every
-- unicode character. Thus, utf16 was created in that purpose. Most characters
-- are encoded only on two bytes, although there is provision for a four-byte
-- encoding in some cases, using what is known as surrogate pairs.
--
-- As a result, utf16 is a variable-width encoding, and traversing a string is
-- a little bit less efficient that with Utf32.
--
-- Another inconvenient is that you can not easily search an ASCII character
-- in a string with the standard string manipulation functions, since you
-- might find the high-byte of a two-byte sequence.
with Ada.Unchecked_Deallocation;
with Unicode.CES.Utf32;
with Unicode.CCS;
package Unicode.CES.Utf16 is
-----------
-- Types --
-----------
subtype Utf16_String is String;
type Utf16_String_Access is access Utf16_String;
-- A UTF16-encoded string, undefined byte-order
subtype Utf16_LE_String is Utf16_String;
type Utf16_LE_String_Access is access Utf16_LE_String;
-- Similar, but with little-endian byte-order
subtype Utf16_BE_String is Utf16_String;
-- Similar, but with big-endian byte-order
-------------------------------------------
-- Conversion to and from byte sequences --
-------------------------------------------
procedure Encode
(Char : Unicode_Char;
Output : in out Byte_Sequence;
Index : in out Natural);
-- Return the byte sequence representing Char in the Utf16 character
-- encoding form (little-endian)
procedure Read
(Str : Utf16_LE_String;
Index : in out Positive;
Char : out Unicode_Char);
-- Return the character starting at location Index in Str
-- Invalid_Encoding is raised if not valid byte sequence starts at Index.
-- Incomplete_Encoding is raised if there is not enough characters for
-- a valid encoding.
procedure Read_BE
(Str : Utf16_BE_String;
Index : in out Positive;
Char : out Unicode_Char);
-- Return the character starting at location Index in Str (big-endian)
procedure Encode_BE
(Char : Unicode_Char;
Output : in out Byte_Sequence;
Index : in out Natural);
-- Return the byte sequence representing Char in the Utf16 character
-- encoding form (big-endian)
function Width (Char : Unicode_Char) return Natural;
-- Return the number of bytes occupied by the Utf16 representation of Char
function Length (Str : Utf16_String) return Natural;
-- Return the number of characters in Str
-------------------------------------------
-- Conversion to and from Utf32-encoding --
-------------------------------------------
function From_Utf32
(Str : Unicode.CES.Utf32.Utf32_LE_String)
return Utf16_LE_String;
-- Return a new utf16-encoded string, from a Utf32-encoded string.
function To_Utf32
(Str : Utf16_LE_String)
return Unicode.CES.Utf32.Utf32_LE_String;
-- Return a new utf32-encoded string, from a Utf16-encoded string.
---------------------------
-- Byte order conversion --
---------------------------
function To_Unicode_LE
(Str : Utf16_String;
Cs : Unicode.CCS.Character_Set := Unicode.CCS.Unicode_Character_Set;
Order : Byte_Order := Default_Byte_Order) return Utf16_LE_String;
-- Convert Str to a Unicode, little-endian utf16-encoding byte sequence.
-- Order is the order in which bytes are coded in Str. This is silently
-- overriden in case Str as a BOM (byte-order-marker) at the beginning
-- that specifies an explicit order.
-- The BOM is removed from the resulting string
-- Invalid_Encoding is raised if Str contains a BOM that indicates an
-- encoding other than Utf16.
function To_CS
(Str : Utf16_LE_String;
Cs : Unicode.CCS.Character_Set := Unicode.CCS.Unicode_Character_Set;
Order : Byte_Order := Default_Byte_Order) return Utf16_String;
-- Convert Str from Unicode to another character set, and possibly
-- another ordering.
-- No BOM is checked
---------------------
-- Encoding Scheme --
---------------------
Utf16_LE_Encoding : constant Encoding_Scheme :=
(BOM => Utf16_LE,
Read => Read'Access,
Width => Width'Access,
Encode => Encode_Function'(Encode'Access),
Length => Length'Access);
Utf16_BE_Encoding : constant Encoding_Scheme :=
(BOM => Utf16_BE,
Read => Read_BE'Access,
Width => Width'Access,
Encode => Encode_Function'(Encode_BE'Access),
Length => Length'Access);
------------------
-- Deallocation --
------------------
procedure Free is new Ada.Unchecked_Deallocation
(Utf16_String, Utf16_String_Access);
procedure Free is new Ada.Unchecked_Deallocation
(Utf16_LE_String, Utf16_LE_String_Access);
-- Free the memory occupied by a utf16-encoded string
private
pragma Inline (Width);
end Unicode.CES.Utf16;
|