------------------------------------------------------------------------------ -- -- -- 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) 2006-2008, 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 2, 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. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, USA. -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- -- 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;