101 lines
5.3 KiB
Ada
101 lines
5.3 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- G N A T . B Y T E _ O R D E R _ M A R K --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 2006-2013, AdaCore --
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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 package provides a procedure for reading and interpreting the BOM
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-- (byte order mark) used to publish the encoding method for a string (for
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-- example, a UTF-8 encoded file in windows will start with the appropriate
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-- BOM sequence to signal UTF-8 encoding.
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-- There are two cases
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-- Case 1. UTF encodings for Unicode files
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-- Here the convention is to have the first character of the file be a
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-- non-breaking zero width space character (16#0000_FEFF#). For the UTF
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-- encodings, the representation of this character can be used to uniquely
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-- determine the encoding. Furthermore, the possibility of any confusion
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-- with unencoded files is minimal, since for example the UTF-8 encoding
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-- of this character looks like the sequence:
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-- LC_I_Diaeresis
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-- Right_Angle_Quotation
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-- Fraction_One_Half
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-- which is so unlikely to occur legitimately in normal use that it can
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-- safely be ignored in most cases (for example, no legitimate Ada source
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-- file could start with this sequence of characters).
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-- Case 2. Specialized XML encodings
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-- The XML standard defines a number of other possible encodings and also
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-- defines standardized sequences for marking these encodings. This package
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-- can also optionally handle these XML defined BOM sequences. These XML
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-- cases depend on the first character of the XML file being < so that the
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-- encoding of this character can be recognized.
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pragma Compiler_Unit_Warning;
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package GNAT.Byte_Order_Mark is
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type BOM_Kind is
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(UTF8_All, -- UTF8-encoding
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UTF16_LE, -- UTF16 little-endian encoding
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UTF16_BE, -- UTF16 big-endian encoding
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UTF32_LE, -- UTF32 little-endian encoding
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UTF32_BE, -- UTF32 big-endian encoding
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-- The following cases are for XML only
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UCS4_BE, -- UCS-4, big endian machine (1234 order)
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UCS4_LE, -- UCS-4, little endian machine (4321 order)
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UCS4_2143, -- UCS-4, unusual byte order (2143 order)
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UCS4_3412, -- UCS-4, unusual byte order (3412 order)
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-- Value returned if no BOM recognized
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Unknown); -- Unknown, assumed to be ASCII compatible
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procedure Read_BOM
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(Str : String;
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Len : out Natural;
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BOM : out BOM_Kind;
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XML_Support : Boolean := False);
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-- This is the routine to read the BOM from the start of the given string
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-- Str. On return BOM is set to the appropriate BOM_Kind and Len is set to
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-- its length. The caller will typically skip the first Len characters in
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-- the string to ignore the BOM sequence. The special XML possibilities are
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-- recognized only if flag XML_Support is set to True. Note that for the
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-- XML cases, Len is always set to zero on return (not to the length of the
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-- relevant sequence) since in the XML cases, the sequence recognized is
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-- for the first real character in the file (<) which is not to be skipped.
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end GNAT.Byte_Order_Mark;
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