1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2007-2022, University of Amsterdam 7 VU University Amsterdam 8 SWI-Prolog Solutions b.v. 9 All rights reserved. 10 11 Redistribution and use in source and binary forms, with or without 12 modification, are permitted provided that the following conditions 13 are met: 14 15 1. Redistributions of source code must retain the above copyright 16 notice, this list of conditions and the following disclaimer. 17 18 2. Redistributions in binary form must reproduce the above copyright 19 notice, this list of conditions and the following disclaimer in 20 the documentation and/or other materials provided with the 21 distribution. 22 23 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 24 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 25 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 26 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 27 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 28 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 29 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 30 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 31 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 33 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 34 POSSIBILITY OF SUCH DAMAGE. 35*/ 36 37:- module(base64, 38 [ base64_encoded/3, % ?Plain, ?Encoded, +Options 39 base64_encoded//2, % ?Plain, +Options 40 41 base64/2, % ?PlainText, ?Encoded 42 base64//1, % ?PlainText 43 44 base64url/2, % ?PlainText, ?Encoded 45 base64url//1 % ?PlainText 46 ]). 47:- autoload(library(error), 48 [instantiation_error/1,must_be/2,syntax_error/1]). 49:- autoload(library(option),[option/3]). 50 (utf8).
classic
uses the classical rfc2045 characters. The value url uses URL
and file name friendly characters. See base64url/2.true (default), the output is padded with = characters.string (default) or
atom.utf8.101base64_encoded(Plain, Encoded, Options) :- 102 option(charset(CharSet), Options, classic), 103 option(padding(Padding), Options, true), 104 option(as(As), Options, string), 105 option(encoding(Enc), Options, utf8), 106 ( nonvar(Plain) 107 -> string_bytes(Plain, PlainBytes, Enc), 108 phrase(base64(Padding, PlainBytes, CharSet), EncCodes), 109 as(As, Encoded, EncCodes, iso_latin_1) 110 ; nonvar(Encoded) 111 -> string_bytes(Encoded, EncCodes, iso_latin_1), 112 phrase(base64(Padding, PlainBytes, CharSet), EncCodes), 113 as(As, Plain, PlainBytes, Enc) 114 ; instantiation_error(base64(Plain, Encoded)) 115 ). 116 117as(atom, Atom, Codes, Enc) :- 118 !, 119 string_bytes(String, Codes, Enc), 120 atom_string(Atom, String). 121as(string, String, Codes, Enc) :- 122 !, 123 string_bytes(String, Codes, Enc). 124as(As, _, _, _) :- 125 must_be(oneof([atom,string]), As).
as(atom) and
encoding(iso_latin_1).
136base64(Plain, Encoded) :-
137 base64_encoded(Plain, Encoded, [ as(atom), encoding(iso_latin_1) ]).
Equivalent to base64_encoded/3 using the options as(atom),
encoding(utf8) and charset(url).
151base64url(Plain, Encoded) :-
152 base64_encoded(Plain, Encoded,
153 [ as(atom),
154 encoding(utf8),
155 charset(url)
156 ]).
161base64_encoded(PlainText, Options) -->
162 { option(charset(CharSet), Options, classic),
163 option(padding(Padding), Options, true)
164 },
165 base64(Padding, PlainText, CharSet).
174base64(PlainText) -->
175 base64(true, PlainText, classic).183base64url(PlainText) --> 184 base64(false, PlainText, url). 185 186base64(Padded, Input, Charset) --> 187 { nonvar(Input) }, 188 !, 189 encode(Padded, Input, Charset). 190base64(Padded, Output, Charset) --> 191 decode(Padded, Output, Charset). 192 193 /******************************* 194 * ENCODING * 195 *******************************/
199encode(Padded, [I0, I1, I2|Rest], Charset) --> 200 !, 201 [O0, O1, O2, O3], 202 { A is (I0<<16)+(I1<<8)+I2, 203 O00 is (A>>18) /\ 0x3f, 204 O01 is (A>>12) /\ 0x3f, 205 O02 is (A>>6) /\ 0x3f, 206 O03 is A /\ 0x3f, 207 base64_char(Charset, O00, O0), 208 base64_char(Charset, O01, O1), 209 base64_char(Charset, O02, O2), 210 base64_char(Charset, O03, O3) 211 }, 212 encode(Padded, Rest, Charset). 213encode(true, [I0, I1], Charset) --> 214 !, 215 [O0, O1, O2, 0'=], 216 { A is (I0<<16)+(I1<<8), 217 O00 is (A>>18) /\ 0x3f, 218 O01 is (A>>12) /\ 0x3f, 219 O02 is (A>>6) /\ 0x3f, 220 base64_char(Charset, O00, O0), 221 base64_char(Charset, O01, O1), 222 base64_char(Charset, O02, O2) 223 }. 224encode(true, [I0], Charset) --> 225 !, 226 [O0, O1, 0'=, 0'=], 227 { A is (I0<<16), 228 O00 is (A>>18) /\ 0x3f, 229 O01 is (A>>12) /\ 0x3f, 230 base64_char(Charset, O00, O0), 231 base64_char(Charset, O01, O1) 232 }. 233encode(false, [I0, I1], Charset) --> 234 !, 235 [O0, O1, O2], 236 { A is (I0<<16)+(I1<<8), 237 O00 is (A>>18) /\ 0x3f, 238 O01 is (A>>12) /\ 0x3f, 239 O02 is (A>>6) /\ 0x3f, 240 base64_char(Charset, O00, O0), 241 base64_char(Charset, O01, O1), 242 base64_char(Charset, O02, O2) 243 }. 244encode(false, [I0], Charset) --> 245 !, 246 [O0, O1], 247 { A is (I0<<16), 248 O00 is (A>>18) /\ 0x3f, 249 O01 is (A>>12) /\ 0x3f, 250 base64_char(Charset, O00, O0), 251 base64_char(Charset, O01, O1) 252 }. 253encode(_, [], _) --> 254 []. 255 256 257 /******************************* 258 * DECODE * 259 *******************************/
263decode(true, Text, Charset) --> 264 [C0, C1, C2, C3], 265 !, 266 { base64_char(Charset, B0, C0), 267 base64_char(Charset, B1, C1) 268 }, 269 !, 270 { C3 == 0'= 271 -> ( C2 == 0'= 272 -> A is (B0<<18) + (B1<<12), 273 I0 is (A>>16) /\ 0xff, 274 Text = [I0|Rest] 275 ; base64_char(Charset, B2, C2) 276 -> A is (B0<<18) + (B1<<12) + (B2<<6), 277 I0 is (A>>16) /\ 0xff, 278 I1 is (A>>8) /\ 0xff, 279 Text = [I0,I1|Rest] 280 ) 281 ; base64_char(Charset, B2, C2), 282 base64_char(Charset, B3, C3) 283 -> A is (B0<<18) + (B1<<12) + (B2<<6) + B3, 284 I0 is (A>>16) /\ 0xff, 285 I1 is (A>>8) /\ 0xff, 286 I2 is A /\ 0xff, 287 Text = [I0,I1,I2|Rest] 288 }, 289 decode(true, Rest, Charset). 290decode(false, Text, Charset) --> 291 [C0, C1, C2, C3], 292 !, 293 { base64_char(Charset, B0, C0), 294 base64_char(Charset, B1, C1), 295 base64_char(Charset, B2, C2), 296 base64_char(Charset, B3, C3), 297 A is (B0<<18) + (B1<<12) + (B2<<6) + B3, 298 I0 is (A>>16) /\ 0xff, 299 I1 is (A>>8) /\ 0xff, 300 I2 is A /\ 0xff, 301 Text = [I0,I1,I2|Rest] 302 }, 303 decode(false, Rest, Charset). 304decode(false, Text, Charset) --> 305 [C0, C1, C2], 306 !, 307 { base64_char(Charset, B0, C0), 308 base64_char(Charset, B1, C1), 309 base64_char(Charset, B2, C2), 310 A is (B0<<18) + (B1<<12) + (B2<<6), 311 I0 is (A>>16) /\ 0xff, 312 I1 is (A>>8) /\ 0xff, 313 Text = [I0,I1] 314 }. 315decode(false, Text, Charset) --> 316 [C0, C1], 317 !, 318 { base64_char(Charset, B0, C0), 319 base64_char(Charset, B1, C1), 320 A is (B0<<18) + (B1<<12), 321 I0 is (A>>16) /\ 0xff, 322 Text = [I0] 323 }. 324decode(_, [], _) --> 325 []. 326 327 328 329 /******************************* 330 * BASIC CHARACTER ENCODING * 331 *******************************/ 332 333base64_char(00, 0'A). 334base64_char(01, 0'B). 335base64_char(02, 0'C). 336base64_char(03, 0'D). 337base64_char(04, 0'E). 338base64_char(05, 0'F). 339base64_char(06, 0'G). 340base64_char(07, 0'H). 341base64_char(08, 0'I). 342base64_char(09, 0'J). 343base64_char(10, 0'K). 344base64_char(11, 0'L). 345base64_char(12, 0'M). 346base64_char(13, 0'N). 347base64_char(14, 0'O). 348base64_char(15, 0'P). 349base64_char(16, 0'Q). 350base64_char(17, 0'R). 351base64_char(18, 0'S). 352base64_char(19, 0'T). 353base64_char(20, 0'U). 354base64_char(21, 0'V). 355base64_char(22, 0'W). 356base64_char(23, 0'X). 357base64_char(24, 0'Y). 358base64_char(25, 0'Z). 359base64_char(26, 0'a). 360base64_char(27, 0'b). 361base64_char(28, 0'c). 362base64_char(29, 0'd). 363base64_char(30, 0'e). 364base64_char(31, 0'f). 365base64_char(32, 0'g). 366base64_char(33, 0'h). 367base64_char(34, 0'i). 368base64_char(35, 0'j). 369base64_char(36, 0'k). 370base64_char(37, 0'l). 371base64_char(38, 0'm). 372base64_char(39, 0'n). 373base64_char(40, 0'o). 374base64_char(41, 0'p). 375base64_char(42, 0'q). 376base64_char(43, 0'r). 377base64_char(44, 0's). 378base64_char(45, 0't). 379base64_char(46, 0'u). 380base64_char(47, 0'v). 381base64_char(48, 0'w). 382base64_char(49, 0'x). 383base64_char(50, 0'y). 384base64_char(51, 0'z). 385base64_char(52, 0'0). 386base64_char(53, 0'1). 387base64_char(54, 0'2). 388base64_char(55, 0'3). 389base64_char(56, 0'4). 390base64_char(57, 0'5). 391base64_char(58, 0'6). 392base64_char(59, 0'7). 393base64_char(60, 0'8). 394base64_char(61, 0'9). 395base64_char(62, 0'+). 396base64_char(63, 0'/). 397 398base64url_char_x(62, 0'-). 399base64url_char_x(63, 0'_). 400 401base64_char(classic, Value, Char) :- 402 ( base64_char(Value, Char) 403 -> true 404 ; syntax_error(base64_char(Value, Char)) 405 ). 406base64_char(url, Value, Char) :- 407 ( base64url_char_x(Value, Char) 408 -> true 409 ; base64_char(Value, Char) 410 -> true 411 ; syntax_error(base64_char(Value, Char)) 412 ). 413 414 415 /******************************* 416 * MESSAGES * 417 *******************************/ 418 419:- multifile prolog:error_message//1. 420 421prologerror_message(syntax_error(base64_char(_D,E))) --> 422 { nonvar(E) }, 423 !, 424 [ 'Illegal Base64 character: "~c"'-[E] ]
Base64 encoding and decoding
Prolog-based base64 encoding using DCG rules. Encoding according to rfc2045. For example:
1 ?- base64('Hello World', X). X = 'SGVsbG8gV29ybGQ='. 2 ?- base64(H, 'SGVsbG8gV29ybGQ='). H = 'Hello World'.The Base64URL encoding provides a URL and file name friendly alternative to base64. Base64URL encoded strings do not contain white space.