/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2006-2011, University of Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(utf8, [ utf8_codes//1 % ?String ]). /** UTF-8 encoding/decoding on lists of character codes. */ %! utf8_codes(?Codes)// is det. % % DCG translating between a Unicode code-list and its UTF-8 % encoded byte-string. The DCG works two ways. Encoding a % code-list to a UTF-8 byte string is achieved using % % phrase(utf8_codes(Codes), UTF8) % % The algorithm is a close copy of the C-algorithm used % internally and defined in src/pl-utf8.c % % NOTE: in many cases you can avoid this library and leave % encoding and decoding to I/O streams. If only part of the data % is to be encoded the encoding of a stream can be switched % temporary using set_stream(Stream, encoding(utf8)) % % @see set_stream/2. utf8_codes([H|T]) --> utf8_code(H), !, utf8_codes(T). utf8_codes([]) --> []. utf8_code(C) --> [C0], { nonvar(C0) }, % decoding version !, ( {C0 < 0x80} -> {C = C0} ; {C0/\0xe0 =:= 0xc0} -> utf8_cont(C1, 0), {C is (C0/\0x1f)<<6\/C1} ; {C0/\0xf0 =:= 0xe0} -> utf8_cont(C1, 6), utf8_cont(C2, 0), {C is ((C0/\0xf)<<12)\/C1\/C2} ; {C0/\0xf8 =:= 0xf0} -> utf8_cont(C1, 12), utf8_cont(C2, 6), utf8_cont(C3, 0), {C is ((C0/\0x7)<<18)\/C1\/C2\/C3} ; {C0/\0xfc =:= 0xf8} -> utf8_cont(C1, 18), utf8_cont(C2, 12), utf8_cont(C3, 6), utf8_cont(C4, 0), {C is ((C0/\0x3)<<24)\/C1\/C2\/C3\/C4} ; {C0/\0xfe =:= 0xfc} -> utf8_cont(C1, 24), utf8_cont(C2, 18), utf8_cont(C3, 12), utf8_cont(C4, 6), utf8_cont(C5, 0), {C is ((C0/\0x1)<<30)\/C1\/C2\/C3\/C4\/C5} ). utf8_code(C) --> { nonvar(C) }, % encoding version !, ( { C < 0x80 } -> [C] ; { C < 0x800 } -> { C0 is 0xc0\/((C>>6)/\0x1f), C1 is 0x80\/(C/\0x3f) }, [C0,C1] ; { C < 0x10000 } -> { C0 is 0xe0\/((C>>12)/\0x0f), C1 is 0x80\/((C>>6)/\0x3f), C2 is 0x80\/(C/\0x3f) }, [C0,C1,C2] ; { C < 0x200000 } -> { C0 is 0xf0\/((C>>18)/\0x07), C1 is 0x80\/((C>>12)/\0x3f), C2 is 0x80\/((C>>6)/\0x3f), C3 is 0x80\/(C/\0x3f) }, [C0,C1,C2,C3] ; { C < 0x4000000 } -> { C0 is 0xf8\/((C>>24)/\0x03), C1 is 0x80\/((C>>18)/\0x3f), C2 is 0x80\/((C>>12)/\0x3f), C3 is 0x80\/((C>>6)/\0x3f), C4 is 0x80\/(C/\0x3f) }, [C0,C1,C2,C3,C4] ; { C < 0x80000000 } -> { C0 is 0xfc\/((C>>30)/\0x01), C1 is 0x80\/((C>>24)/\0x3f), C2 is 0x80\/((C>>18)/\0x3f), C3 is 0x80\/((C>>12)/\0x3f), C4 is 0x80\/((C>>6)/\0x3f), C5 is 0x80\/(C/\0x3f) }, [C0,C1,C2,C3,C4,C5] ). utf8_cont(Val, Shift) --> [C], { C/\0xc0 =:= 0x80, Val is (C/\0x3f)<