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) 2007-2023, 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. The value
openbsd uses the OpenBSD password-file alphabet.true (default), the output is padded with = characters.string (default) or
atom.utf8.102base64_encoded(Plain, Encoded, Options) :- 103 option(charset(CharSet), Options, classic), 104 option(padding(Padding), Options, true), 105 option(as(As), Options, string), 106 option(encoding(Enc), Options, utf8), 107 ( nonvar(Plain) 108 -> string_bytes(Plain, PlainBytes, Enc), 109 phrase(base64(Padding, PlainBytes, CharSet), EncCodes), 110 as(As, Encoded, EncCodes, iso_latin_1) 111 ; nonvar(Encoded) 112 -> string_bytes(Encoded, EncCodes, iso_latin_1), 113 phrase(base64(Padding, PlainBytes, CharSet), EncCodes), 114 as(As, Plain, PlainBytes, Enc) 115 ; instantiation_error(base64(Plain, Encoded)) 116 ). 117 118as(atom, Atom, Codes, Enc) :- 119 !, 120 string_bytes(String, Codes, Enc), 121 atom_string(Atom, String). 122as(string, String, Codes, Enc) :- 123 !, 124 string_bytes(String, Codes, Enc). 125as(As, _, _, _) :- 126 must_be(oneof([atom,string]), As).
as(atom) and
encoding(iso_latin_1).
137base64(Plain, Encoded) :-
138 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).
152base64url(Plain, Encoded) :-
153 base64_encoded(Plain, Encoded,
154 [ as(atom),
155 encoding(utf8),
156 charset(url)
157 ]).
162base64_encoded(PlainText, Options) -->
163 { option(charset(CharSet), Options, classic),
164 option(padding(Padding), Options, true)
165 },
166 base64(Padding, PlainText, CharSet).
175base64(PlainText) -->
176 base64(true, PlainText, classic).184base64url(PlainText) --> 185 base64(false, PlainText, url). 186 187base64(Padded, Input, Charset) --> 188 { nonvar(Input) }, 189 !, 190 encode(Padded, Input, Charset). 191base64(Padded, Output, Charset) --> 192 decode(Padded, Output, Charset). 193 194 /******************************* 195 * ENCODING * 196 *******************************/
200encode(Padded, [I0, I1, I2|Rest], Charset) --> 201 !, 202 [O0, O1, O2, O3], 203 { A is (I0<<16)+(I1<<8)+I2, 204 O00 is (A>>18) /\ 0x3f, 205 O01 is (A>>12) /\ 0x3f, 206 O02 is (A>>6) /\ 0x3f, 207 O03 is A /\ 0x3f, 208 base64_char(Charset, O00, O0), 209 base64_char(Charset, O01, O1), 210 base64_char(Charset, O02, O2), 211 base64_char(Charset, O03, O3) 212 }, 213 encode(Padded, Rest, Charset). 214encode(true, [I0, I1], Charset) --> 215 !, 216 [O0, O1, O2, 0'=], 217 { A is (I0<<16)+(I1<<8), 218 O00 is (A>>18) /\ 0x3f, 219 O01 is (A>>12) /\ 0x3f, 220 O02 is (A>>6) /\ 0x3f, 221 base64_char(Charset, O00, O0), 222 base64_char(Charset, O01, O1), 223 base64_char(Charset, O02, O2) 224 }. 225encode(true, [I0], Charset) --> 226 !, 227 [O0, O1, 0'=, 0'=], 228 { A is (I0<<16), 229 O00 is (A>>18) /\ 0x3f, 230 O01 is (A>>12) /\ 0x3f, 231 base64_char(Charset, O00, O0), 232 base64_char(Charset, O01, O1) 233 }. 234encode(false, [I0, I1], Charset) --> 235 !, 236 [O0, O1, O2], 237 { A is (I0<<16)+(I1<<8), 238 O00 is (A>>18) /\ 0x3f, 239 O01 is (A>>12) /\ 0x3f, 240 O02 is (A>>6) /\ 0x3f, 241 base64_char(Charset, O00, O0), 242 base64_char(Charset, O01, O1), 243 base64_char(Charset, O02, O2) 244 }. 245encode(false, [I0], Charset) --> 246 !, 247 [O0, O1], 248 { A is (I0<<16), 249 O00 is (A>>18) /\ 0x3f, 250 O01 is (A>>12) /\ 0x3f, 251 base64_char(Charset, O00, O0), 252 base64_char(Charset, O01, O1) 253 }. 254encode(_, [], _) --> 255 []. 256 257 258 /******************************* 259 * DECODE * 260 *******************************/
264decode(true, Text, Charset) --> 265 [C0, C1, C2, C3], 266 !, 267 { base64_char(Charset, B0, C0), 268 base64_char(Charset, B1, C1) 269 }, 270 !, 271 { C3 == 0'= 272 -> ( C2 == 0'= 273 -> A is (B0<<18) + (B1<<12), 274 I0 is (A>>16) /\ 0xff, 275 Text = [I0|Rest] 276 ; base64_char(Charset, B2, C2) 277 -> A is (B0<<18) + (B1<<12) + (B2<<6), 278 I0 is (A>>16) /\ 0xff, 279 I1 is (A>>8) /\ 0xff, 280 Text = [I0,I1|Rest] 281 ) 282 ; base64_char(Charset, B2, C2), 283 base64_char(Charset, B3, C3) 284 -> A is (B0<<18) + (B1<<12) + (B2<<6) + B3, 285 I0 is (A>>16) /\ 0xff, 286 I1 is (A>>8) /\ 0xff, 287 I2 is A /\ 0xff, 288 Text = [I0,I1,I2|Rest] 289 }, 290 decode(true, Rest, Charset). 291decode(false, Text, Charset) --> 292 [C0, C1, C2, C3], 293 !, 294 { base64_char(Charset, B0, C0), 295 base64_char(Charset, B1, C1), 296 base64_char(Charset, B2, C2), 297 base64_char(Charset, B3, C3), 298 A is (B0<<18) + (B1<<12) + (B2<<6) + B3, 299 I0 is (A>>16) /\ 0xff, 300 I1 is (A>>8) /\ 0xff, 301 I2 is A /\ 0xff, 302 Text = [I0,I1,I2|Rest] 303 }, 304 decode(false, Rest, Charset). 305decode(false, Text, Charset) --> 306 [C0, C1, C2], 307 !, 308 { base64_char(Charset, B0, C0), 309 base64_char(Charset, B1, C1), 310 base64_char(Charset, B2, C2), 311 A is (B0<<18) + (B1<<12) + (B2<<6), 312 I0 is (A>>16) /\ 0xff, 313 I1 is (A>>8) /\ 0xff, 314 Text = [I0,I1] 315 }. 316decode(false, Text, Charset) --> 317 [C0, C1], 318 !, 319 { base64_char(Charset, B0, C0), 320 base64_char(Charset, B1, C1), 321 A is (B0<<18) + (B1<<12), 322 I0 is (A>>16) /\ 0xff, 323 Text = [I0] 324 }. 325decode(_, [], _) --> 326 []. 327 328 329 330 /******************************* 331 * BASIC CHARACTER ENCODING * 332 *******************************/ 333 334base64_char(00, 0'A). 335base64_char(01, 0'B). 336base64_char(02, 0'C). 337base64_char(03, 0'D). 338base64_char(04, 0'E). 339base64_char(05, 0'F). 340base64_char(06, 0'G). 341base64_char(07, 0'H). 342base64_char(08, 0'I). 343base64_char(09, 0'J). 344base64_char(10, 0'K). 345base64_char(11, 0'L). 346base64_char(12, 0'M). 347base64_char(13, 0'N). 348base64_char(14, 0'O). 349base64_char(15, 0'P). 350base64_char(16, 0'Q). 351base64_char(17, 0'R). 352base64_char(18, 0'S). 353base64_char(19, 0'T). 354base64_char(20, 0'U). 355base64_char(21, 0'V). 356base64_char(22, 0'W). 357base64_char(23, 0'X). 358base64_char(24, 0'Y). 359base64_char(25, 0'Z). 360base64_char(26, 0'a). 361base64_char(27, 0'b). 362base64_char(28, 0'c). 363base64_char(29, 0'd). 364base64_char(30, 0'e). 365base64_char(31, 0'f). 366base64_char(32, 0'g). 367base64_char(33, 0'h). 368base64_char(34, 0'i). 369base64_char(35, 0'j). 370base64_char(36, 0'k). 371base64_char(37, 0'l). 372base64_char(38, 0'm). 373base64_char(39, 0'n). 374base64_char(40, 0'o). 375base64_char(41, 0'p). 376base64_char(42, 0'q). 377base64_char(43, 0'r). 378base64_char(44, 0's). 379base64_char(45, 0't). 380base64_char(46, 0'u). 381base64_char(47, 0'v). 382base64_char(48, 0'w). 383base64_char(49, 0'x). 384base64_char(50, 0'y). 385base64_char(51, 0'z). 386base64_char(52, 0'0). 387base64_char(53, 0'1). 388base64_char(54, 0'2). 389base64_char(55, 0'3). 390base64_char(56, 0'4). 391base64_char(57, 0'5). 392base64_char(58, 0'6). 393base64_char(59, 0'7). 394base64_char(60, 0'8). 395base64_char(61, 0'9). 396base64_char(62, 0'+). 397base64_char(63, 0'/). 398 399base64url_char_x(62, 0'-). 400base64url_char_x(63, 0'_). 401 402base64bsd_char_x(00, 0'.). 403base64bsd_char_x(01, 0'/). 404 405base64_char(classic, Value, Char) :- 406 ( base64_char(Value, Char) 407 -> true 408 ; syntax_error(base64_char(Value, Char)) 409 ). 410base64_char(url, Value, Char) :- 411 ( base64url_char_x(Value, Char) 412 -> true 413 ; base64_char(Value, Char) 414 -> true 415 ; syntax_error(base64_char(Value, Char)) 416 ). 417base64_char(openbsd, Value, Char) :- 418 ( base64bsd_char_x(Value, Char) 419 -> true 420 ; nonvar(Value) 421 -> Value0 is Value - 2, 422 ( base64_char(Value0, Char) 423 -> true 424 ; syntax_error(base64_char(Value, Char)) 425 ) 426 ; ( base64_char(Value0, Char) 427 -> Value0 < 62, Value is Value0 + 2 428 ; syntax_error(base64_char(Value, Char)) 429 ) 430 ). 431 432 /******************************* 433 * MESSAGES * 434 *******************************/ 435 436:- multifile prolog:error_message//1. 437 438prologerror_message(syntax_error(base64_char(_D,E))) --> 439 { nonvar(E) }, 440 !, 441 [ '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.