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+------------------------------------------------------------------------------
+-- --
+-- GNAT COMPILER COMPONENTS --
+-- --
+-- G N A T . B Y T E _ O R D E R _ M A R K --
+-- --
+-- S p e c --
+-- --
+-- Copyright (C) 2006-2010, 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 package provides a procedure for reading and interpreting the BOM
+-- (byte order mark) used to publish the encoding method for a string (for
+-- example, a UTF-8 encoded file in windows will start with the appropriate
+-- BOM sequence to signal UTF-8 encoding.
+
+-- There are two cases
+
+-- Case 1. UTF encodings for Unicode files
+
+-- Here the convention is to have the first character of the file be a
+-- non-breaking zero width space character (16#0000_FEFF#). For the UTF
+-- encodings, the representation of this character can be used to uniquely
+-- determine the encoding. Furthermore, the possibility of any confusion
+-- with unencoded files is minimal, since for example the UTF-8 encoding
+-- of this character looks like the sequence:
+
+-- LC_I_Diaeresis
+-- Right_Angle_Quotation
+-- Fraction_One_Half
+
+-- which is so unlikely to occur legitimately in normal use that it can
+-- safely be ignored in most cases (for example, no legitimate Ada source
+-- file could start with this sequence of characters).
+
+-- Case 2. Specialized XML encodings
+
+-- The XML standard defines a number of other possible encodings and also
+-- defines standardized sequences for marking these encodings. This package
+-- can also optionally handle these XML defined BOM sequences. These XML
+-- cases depend on the first character of the XML file being < so that the
+-- encoding of this character can be recognized.
+
+pragma Compiler_Unit;
+
+package GNAT.Byte_Order_Mark is
+
+ type BOM_Kind is
+ (UTF8_All, -- UTF8-encoding
+ UTF16_LE, -- UTF16 little-endian encoding
+ UTF16_BE, -- UTF16 big-endian encoding
+ UTF32_LE, -- UTF32 little-endian encoding
+ UTF32_BE, -- UTF32 big-endian encoding
+
+ -- The following cases are for XML only
+
+ UCS4_BE, -- UCS-4, big endian machine (1234 order)
+ UCS4_LE, -- UCS-4, little endian machine (4321 order)
+ UCS4_2143, -- UCS-4, unusual byte order (2143 order)
+ UCS4_3412, -- UCS-4, unusual byte order (3412 order)
+
+ -- Value returned if no BOM recognized
+
+ Unknown); -- Unknown, assumed to be ASCII compatible
+
+ procedure Read_BOM
+ (Str : String;
+ Len : out Natural;
+ BOM : out BOM_Kind;
+ XML_Support : Boolean := False);
+ -- This is the routine to read the BOM from the start of the given string
+ -- Str. On return BOM is set to the appropriate BOM_Kind and Len is set to
+ -- its length. The caller will typically skip the first Len characters in
+ -- the string to ignore the BOM sequence. The special XML possibilities are
+ -- recognized only if flag XML_Support is set to True. Note that for the
+ -- XML cases, Len is always set to zero on return (not to the length of the
+ -- relevant sequence) since in the XML cases, the sequence recognized is
+ -- for the first real character in the file (<) which is not to be skipped.
+
+end GNAT.Byte_Order_Mark;