/* $Id$ Part of SWI-Prolog Author: Jan Wielemaker E-mail: wielemak@science.uva.nl WWW: http://www.swi-prolog.org Copyright (C): 1985-2007, University of Amsterdam This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT 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 along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA As a special exception, if you link this library with other files, compiled with a Free Software compiler, to produce an executable, this library 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 General Public License. */ :- module(base32, [ base32/2, % ?PlainText, ?Encoded base32//1 % ?PlainText ]). /** Base32 encoding and decoding Prolog-based base32 encoding using DCG rules. Encoding according to rfc4648. For example: == 1 ?- base32('Hello World', X). X = 'JBSWY3DPEBLW64TMMQ======' Yes 2 ?- base32(H, 'JBSWY3DPEBLW64TMMQ======'). H = 'Hello World' == @see http://en.wikipedia.org/wiki/Base32 @author Jan Wielemaker */ %% base32(+Plain, -Encoded) is det. %% base32(-Plain, +Encoded) is det. % % Translates between plaintext and base32 encoded atom or string. % See also base32//1. base32(Plain, Encoded) :- nonvar(Plain), !, atom_codes(Plain, PlainCodes), phrase(base32(PlainCodes), EncCodes), atom_codes(Encoded, EncCodes). base32(Plain, Encoded) :- nonvar(Encoded), !, atom_codes(Encoded, EncCodes), phrase(base32(PlainCodes), EncCodes), atom_codes(Plain, PlainCodes). base32(_, _) :- throw(error(instantiation_error, _)). %% base32(+PlainText)// is det. %% base32(-PlainText)// is det. % % Encode/decode list of character codes using _base32_. See also % base32/2. base32(Input) --> { nonvar(Input) }, !, encode(Input). base32(Output) --> decode(Output). /******************************* * ENCODING * *******************************/ encode([I0, I1, I2, I3, I4|Rest]) --> !, [O0, O1, O2, O3, O4, O5, O6, O7], { A is (I0<<32)+(I1<<24)+(I2<<16)+(I3<<8)+I4, O00 is (A>>35) /\ 0x1f, O01 is (A>>30) /\ 0x1f, O02 is (A>>25) /\ 0x1f, O03 is (A>>20) /\ 0x1f, O04 is (A>>15) /\ 0x1f, O05 is (A>>10) /\ 0x1f, O06 is (A>>5) /\ 0x1f, O07 is A /\ 0x1f, base32_char(O00, O0), base32_char(O01, O1), base32_char(O02, O2), base32_char(O03, O3), base32_char(O04, O4), base32_char(O05, O5), base32_char(O06, O6), base32_char(O07, O7) }, encode(Rest). encode([I0, I1, I2, I3]) --> !, [O0, O1, O2, O3, O4, O5, O6, 0'=], { A is (I0<<32)+(I1<<24)+(I2<<16)+(I3<<8), O00 is (A>>35) /\ 0x1f, O01 is (A>>30) /\ 0x1f, O02 is (A>>25) /\ 0x1f, O03 is (A>>20) /\ 0x1f, O04 is (A>>15) /\ 0x1f, O05 is (A>>10) /\ 0x1f, O06 is (A>>5) /\ 0x1f, base32_char(O00, O0), base32_char(O01, O1), base32_char(O02, O2), base32_char(O03, O3), base32_char(O04, O4), base32_char(O05, O5), base32_char(O06, O6) }. encode([I0, I1, I2]) --> !, [O0, O1, O2, O3, O4, 0'=, 0'=, 0'=], { A is (I0<<32)+(I1<<24)+(I2<<16), O00 is (A>>35) /\ 0x1f, O01 is (A>>30) /\ 0x1f, O02 is (A>>25) /\ 0x1f, O03 is (A>>20) /\ 0x1f, O04 is (A>>15) /\ 0x1f, base32_char(O00, O0), base32_char(O01, O1), base32_char(O02, O2), base32_char(O03, O3), base32_char(O04, O4) }. encode([I0, I1]) --> !, [O0, O1, O2, O3, 0'=, 0'=, 0'=, 0'=], { A is (I0<<32)+(I1<<24), O00 is (A>>35) /\ 0x1f, O01 is (A>>30) /\ 0x1f, O02 is (A>>25) /\ 0x1f, O03 is (A>>20) /\ 0x1f, base32_char(O00, O0), base32_char(O01, O1), base32_char(O02, O2), base32_char(O03, O3) }. encode([I0]) --> !, [O0, O1, 0'=, 0'=, 0'=, 0'=, 0'=, 0'=], { A is (I0<<32), O00 is (A>>35) /\ 0x1f, O01 is (A>>30) /\ 0x1f, base32_char(O00, O0), base32_char(O01, O1) }. encode([]) --> []. /******************************* * DECODE * *******************************/ decode(Text) --> [C0, C1, C2, C3, C4, C5, C6, C7], !, { base32_char(B0, C0), base32_char(B1, C1) }, !, { C7 == 0'= -> ( C6 == 0'=, C5 == 0'= -> ( C4 == 0'= -> ( C3 = 0'=, C2 = 0'= -> A is (B0<<35) + (B1<<30), I0 is (A>>32) /\ 0xff, Text = [I0|Rest] ; base32_char(B2, C2), base32_char(B3, C3), base32_char(B4, C4), A is (B0<<35) + (B1<<30) + (B2<<25) + (B3<<20) + (B4<<15), I0 is (A>>32) /\ 0xff, I1 is (A>>24) /\ 0xff, Text = [I0,I1|Rest] ) ; base32_char(B2, C2), base32_char(B3, C3), base32_char(B4, C4), base32_char(B5, C5), A is (B0<<35) + (B1<<30) + (B2<<25) + (B3<<20) + (B4<<15) + (B5<<10), I0 is (A>>32) /\ 0xff, I1 is (A>>24) /\ 0xff, I2 is (A>>16) /\ 0xff, Text = [I0,I1,I2|Rest] ) ; base32_char(B2, C2), base32_char(B3, C3), base32_char(B4, C4), base32_char(B5, C5), base32_char(B6, C6) -> A is (B0<<35) + (B1<<30) + (B2<<25) + (B3<<20) + (B4<<15) + (B5<<10) + (B6<<5), I0 is (A>>32) /\ 0xff, I1 is (A>>24) /\ 0xff, I2 is (A>>16) /\ 0xff, I3 is (A>>8) /\ 0xff, Text = [I0,I1,I2,I3|Rest] ) ; base32_char(B2, C2), base32_char(B3, C3), base32_char(B4, C4), base32_char(B5, C5), base32_char(B6, C6), base32_char(B7, C7) -> A is (B0<<35) + (B1<<30) + (B2<<25) + (B3<<20) + (B4<<15) + (B5<<10) + (B6<<5) + B7, I0 is (A>>32) /\ 0xff, I1 is (A>>24) /\ 0xff, I2 is (A>>16) /\ 0xff, I3 is (A>>8) /\ 0xff, I4 is A /\ 0xff, Text = [I0,I1,I2,I3,I4|Rest] }, decode(Rest). decode([]) --> []. /******************************* * BASIC CHARACTER ENCODING * *******************************/ base32_char(00, 0'A). base32_char(01, 0'B). base32_char(02, 0'C). base32_char(03, 0'D). base32_char(04, 0'E). base32_char(05, 0'F). base32_char(06, 0'G). base32_char(07, 0'H). base32_char(08, 0'I). base32_char(09, 0'J). base32_char(10, 0'K). base32_char(11, 0'L). base32_char(12, 0'M). base32_char(13, 0'N). base32_char(14, 0'O). base32_char(15, 0'P). base32_char(16, 0'Q). base32_char(17, 0'R). base32_char(18, 0'S). base32_char(19, 0'T). base32_char(20, 0'U). base32_char(21, 0'V). base32_char(22, 0'W). base32_char(23, 0'X). base32_char(24, 0'Y). base32_char(25, 0'Z). base32_char(26, 0'2). base32_char(27, 0'3). base32_char(28, 0'4). base32_char(29, 0'5). base32_char(30, 0'6). base32_char(31, 0'7).