145 lines
7.5 KiB
Ada
145 lines
7.5 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME COMPONENTS --
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-- --
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-- A D A . S T R I N G S . U T F _ E N C O D I N G --
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-- --
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-- S p e c --
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-- --
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-- This specification is derived from the Ada Reference Manual for use with --
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-- GNAT. The copyright notice above, and the license provisions that follow --
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-- apply solely to the contents of the part following the private keyword. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This is one of the Ada 2012 package defined in AI05-0137-1. It is a parent
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-- package that contains declarations used in the child packages for handling
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-- UTF encoded strings. Note: this package is consistent with Ada 95, and may
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-- be used in Ada 95 or Ada 2005 mode.
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with Interfaces;
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with Unchecked_Conversion;
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package Ada.Strings.UTF_Encoding is
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pragma Pure (UTF_Encoding);
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subtype UTF_String is String;
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-- Used to represent a string of 8-bit values containing a sequence of
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-- values encoded in one of three ways (UTF-8, UTF-16BE, or UTF-16LE).
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-- Typically used in connection with a Scheme parameter indicating which
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-- of the encodings applies. This is not strictly a String value in the
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-- sense defined in the Ada RM, but in practice type String accommodates
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-- all possible 256 codes, and can be used to hold any sequence of 8-bit
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-- codes. We use String directly rather than create a new type so that
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-- all existing facilities for manipulating type String (e.g. the child
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-- packages of Ada.Strings) are available for manipulation of UTF_Strings.
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type Encoding_Scheme is (UTF_8, UTF_16BE, UTF_16LE);
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-- Used to specify which of three possible encodings apply to a UTF_String
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subtype UTF_8_String is String;
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-- Similar to UTF_String but specifically represents a UTF-8 encoded string
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subtype UTF_16_Wide_String is Wide_String;
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-- This is similar to UTF_8_String but is used to represent a Wide_String
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-- value which is a sequence of 16-bit values encoded using UTF-16. Again
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-- this is not strictly a Wide_String in the sense of the Ada RM, but the
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-- type Wide_String can be used to represent a sequence of arbitrary 16-bit
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-- values, and it is more convenient to use Wide_String than a new type.
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Encoding_Error : exception;
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-- This exception is raised in the following situations:
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-- a) A UTF encoded string contains an invalid encoding sequence
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-- b) A UTF-16BE or UTF-16LE input string has an odd length
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-- c) An incorrect character value is present in the Input string
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-- d) The result for a Wide_Character output exceeds 16#FFFF#
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-- The exception message has the index value where the error occurred.
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-- The BOM (BYTE_ORDER_MARK) values defined here are used at the start of
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-- a string to indicate the encoding. The convention in this package is
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-- that on input a correct BOM is ignored and an incorrect BOM causes an
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-- Encoding_Error exception. On output, the output string may or may not
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-- include a BOM depending on the setting of Output_BOM.
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BOM_8 : constant UTF_8_String :=
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Character'Val (16#EF#) &
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Character'Val (16#BB#) &
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Character'Val (16#BF#);
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BOM_16BE : constant UTF_String :=
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Character'Val (16#FE#) &
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Character'Val (16#FF#);
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BOM_16LE : constant UTF_String :=
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Character'Val (16#FF#) &
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Character'Val (16#FE#);
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BOM_16 : constant UTF_16_Wide_String :=
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(1 => Wide_Character'Val (16#FEFF#));
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function Encoding
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(Item : UTF_String;
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Default : Encoding_Scheme := UTF_8) return Encoding_Scheme;
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-- This function inspects a UTF_String value to determine whether it
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-- starts with a BOM for UTF-8, UTF-16BE, or UTF_16LE. If so, the result
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-- is the scheme corresponding to the BOM. If no valid BOM is present
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-- then the result is the specified Default value.
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private
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function To_Unsigned_8 is new
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Unchecked_Conversion (Character, Interfaces.Unsigned_8);
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function To_Unsigned_16 is new
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Unchecked_Conversion (Wide_Character, Interfaces.Unsigned_16);
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function To_Unsigned_32 is new
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Unchecked_Conversion (Wide_Wide_Character, Interfaces.Unsigned_32);
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subtype UTF_XE_Encoding is Encoding_Scheme range UTF_16BE .. UTF_16LE;
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-- Subtype containing only UTF_16BE and UTF_16LE entries
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-- Utility routines for converting between UTF-16 and UTF-16LE/BE
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function From_UTF_16
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(Item : UTF_16_Wide_String;
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Output_Scheme : UTF_XE_Encoding;
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Output_BOM : Boolean := False) return UTF_String;
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-- The input string Item is encoded in UTF-16. The output is encoded using
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-- Output_Scheme (which is either UTF-16LE or UTF-16BE). There are no error
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-- cases. The output starts with BOM_16BE/LE if Output_BOM is True.
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function To_UTF_16
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(Item : UTF_String;
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Input_Scheme : UTF_XE_Encoding;
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Output_BOM : Boolean := False) return UTF_16_Wide_String;
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-- The input string Item is encoded using Input_Scheme which is either
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-- UTF-16LE or UTF-16BE. The output is the corresponding UTF_16 wide
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-- string. Encoding error is raised if the length of the input is odd.
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-- The output starts with BOM_16 if Output_BOM is True.
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procedure Raise_Encoding_Error (Index : Natural);
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pragma No_Return (Raise_Encoding_Error);
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-- Raise Encoding_Error exception for bad encoding in input item. The
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-- parameter Index is the index of the location in Item for the error.
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end Ada.Strings.UTF_Encoding;
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