1 /*
2 * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package jdk.incubator.http.internal.hpack;
26
27 import java.io.IOException;
28 import java.nio.ByteBuffer;
29
30 import static java.lang.String.format;
31
32 /**
33 * Huffman coding table.
34 *
35 * <p> Instances of this class are safe for use by multiple threads.
36 *
37 * @since 9
38 */
39 public final class Huffman {
40
41 // TODO: check if reset is done in both reader and writer
42
43 static final class Reader {
44
45 private Node curr; // position in the trie
46 private int len; // length of the path from the root to 'curr'
47 private int p; // byte probe
48
49 {
50 reset();
51 }
52
53 public void read(ByteBuffer source,
54 Appendable destination,
55 boolean isLast) throws IOException {
56 read(source, destination, true, isLast);
57 }
58
59 // Takes 'isLast' rather than returns whether the reading is done or
60 // not, for more informative exceptions.
61 void read(ByteBuffer source,
62 Appendable destination,
63 boolean reportEOS, /* reportEOS is exposed for tests */
64 boolean isLast) throws IOException {
65 Node c = curr;
66 int l = len;
67 /*
68 Since ByteBuffer is itself stateful, its position is
69 remembered here NOT as a part of Reader's state,
70 but to set it back in the case of a failure
71 */
72 int pos = source.position();
73
74 while (source.hasRemaining()) {
75 int d = source.get();
76 for (; p != 0; p >>= 1) {
77 c = c.getChild(p & d);
78 l++;
79 if (c.isLeaf()) {
80 if (reportEOS && c.isEOSPath) {
81 throw new IOException("Encountered EOS");
82 }
83 char ch;
84 try {
85 ch = c.getChar();
86 } catch (IllegalStateException e) {
87 source.position(pos); // do we need this?
88 throw new IOException(e);
89 }
90 try {
91 destination.append(ch);
92 } catch (IOException e) {
93 source.position(pos); // do we need this?
94 throw e;
95 }
96 c = INSTANCE.root;
97 l = 0;
98 }
99 curr = c;
100 len = l;
101 }
102 resetProbe();
103 pos++;
104 }
105 if (!isLast) {
106 return; // it's too early to jump to any conclusions, let's wait
107 }
108 if (c.isLeaf()) {
109 return; // it's perfectly ok, no extra padding bits
110 }
111 if (c.isEOSPath && len <= 7) {
112 return; // it's ok, some extra padding bits
113 }
114 if (c.isEOSPath) {
115 throw new IOException(
116 "Padding is too long (len=" + len + ") " +
117 "or unexpected end of data");
118 }
119 throw new IOException(
120 "Not a EOS prefix padding or unexpected end of data");
121 }
122
123 public void reset() {
124 curr = INSTANCE.root;
125 len = 0;
126 resetProbe();
127 }
128
129 private void resetProbe() {
130 p = 0x80;
131 }
132 }
133
134 static final class Writer {
135
136 private int pos; // position in 'source'
137 private int avail = 8; // number of least significant bits available in 'curr'
138 private int curr; // next byte to put to the destination
139 private int rem; // number of least significant bits in 'code' yet to be processed
140 private int code; // current code being written
141
142 private CharSequence source;
143 private int end;
144
145 public Writer from(CharSequence input, int start, int end) {
146 if (start < 0 || end < 0 || end > input.length() || start > end) {
147 throw new IndexOutOfBoundsException(
148 String.format("input.length()=%s, start=%s, end=%s",
149 input.length(), start, end));
150 }
151 pos = start;
152 this.end = end;
153 this.source = input;
154 return this;
155 }
156
157 public boolean write(ByteBuffer destination) {
158 for (; pos < end; pos++) {
159 if (rem == 0) {
160 Code desc = INSTANCE.codeOf(source.charAt(pos));
161 rem = desc.length;
162 code = desc.code;
163 }
164 while (rem > 0) {
165 if (rem < avail) {
166 curr |= (code << (avail - rem));
167 avail -= rem;
168 rem = 0;
169 } else {
170 int c = (curr | (code >>> (rem - avail)));
171 if (destination.hasRemaining()) {
172 destination.put((byte) c);
173 } else {
174 return false;
175 }
176 curr = c;
177 code <<= (32 - rem + avail); // throw written bits off the cliff (is this Sparta?)
178 code >>>= (32 - rem + avail); // return to the position
179 rem -= avail;
180 curr = 0;
181 avail = 8;
182 }
183 }
184 }
185
186 if (avail < 8) { // have to pad
187 if (destination.hasRemaining()) {
188 destination.put((byte) (curr | (INSTANCE.EOS.code >>> (INSTANCE.EOS.length - avail))));
189 avail = 8;
190 } else {
191 return false;
192 }
193 }
194
195 return true;
196 }
197
198 public Writer reset() {
199 source = null;
200 end = -1;
201 pos = -1;
202 avail = 8;
203 curr = 0;
204 code = 0;
205 return this;
206 }
207 }
208
209 /**
210 * Shared instance.
211 */
212 public static final Huffman INSTANCE = new Huffman();
213
214 private final Code EOS = new Code(0x3fffffff, 30);
215 private final Code[] codes = new Code[257];
216 private final Node root = new Node() {
217 @Override
218 public String toString() { return "root"; }
219 };
220
221 // TODO: consider builder and immutable trie
222 private Huffman() {
223 // @formatter:off
224 addChar(0, 0x1ff8, 13);
225 addChar(1, 0x7fffd8, 23);
226 addChar(2, 0xfffffe2, 28);
227 addChar(3, 0xfffffe3, 28);
228 addChar(4, 0xfffffe4, 28);
229 addChar(5, 0xfffffe5, 28);
230 addChar(6, 0xfffffe6, 28);
231 addChar(7, 0xfffffe7, 28);
232 addChar(8, 0xfffffe8, 28);
233 addChar(9, 0xffffea, 24);
234 addChar(10, 0x3ffffffc, 30);
235 addChar(11, 0xfffffe9, 28);
236 addChar(12, 0xfffffea, 28);
237 addChar(13, 0x3ffffffd, 30);
238 addChar(14, 0xfffffeb, 28);
239 addChar(15, 0xfffffec, 28);
240 addChar(16, 0xfffffed, 28);
241 addChar(17, 0xfffffee, 28);
242 addChar(18, 0xfffffef, 28);
243 addChar(19, 0xffffff0, 28);
244 addChar(20, 0xffffff1, 28);
245 addChar(21, 0xffffff2, 28);
246 addChar(22, 0x3ffffffe, 30);
247 addChar(23, 0xffffff3, 28);
248 addChar(24, 0xffffff4, 28);
249 addChar(25, 0xffffff5, 28);
250 addChar(26, 0xffffff6, 28);
251 addChar(27, 0xffffff7, 28);
252 addChar(28, 0xffffff8, 28);
253 addChar(29, 0xffffff9, 28);
254 addChar(30, 0xffffffa, 28);
255 addChar(31, 0xffffffb, 28);
256 addChar(32, 0x14, 6);
257 addChar(33, 0x3f8, 10);
258 addChar(34, 0x3f9, 10);
259 addChar(35, 0xffa, 12);
260 addChar(36, 0x1ff9, 13);
261 addChar(37, 0x15, 6);
262 addChar(38, 0xf8, 8);
263 addChar(39, 0x7fa, 11);
264 addChar(40, 0x3fa, 10);
265 addChar(41, 0x3fb, 10);
266 addChar(42, 0xf9, 8);
267 addChar(43, 0x7fb, 11);
268 addChar(44, 0xfa, 8);
269 addChar(45, 0x16, 6);
270 addChar(46, 0x17, 6);
271 addChar(47, 0x18, 6);
272 addChar(48, 0x0, 5);
273 addChar(49, 0x1, 5);
274 addChar(50, 0x2, 5);
275 addChar(51, 0x19, 6);
276 addChar(52, 0x1a, 6);
277 addChar(53, 0x1b, 6);
278 addChar(54, 0x1c, 6);
279 addChar(55, 0x1d, 6);
280 addChar(56, 0x1e, 6);
281 addChar(57, 0x1f, 6);
282 addChar(58, 0x5c, 7);
283 addChar(59, 0xfb, 8);
284 addChar(60, 0x7ffc, 15);
285 addChar(61, 0x20, 6);
286 addChar(62, 0xffb, 12);
287 addChar(63, 0x3fc, 10);
288 addChar(64, 0x1ffa, 13);
289 addChar(65, 0x21, 6);
290 addChar(66, 0x5d, 7);
291 addChar(67, 0x5e, 7);
292 addChar(68, 0x5f, 7);
293 addChar(69, 0x60, 7);
294 addChar(70, 0x61, 7);
295 addChar(71, 0x62, 7);
296 addChar(72, 0x63, 7);
297 addChar(73, 0x64, 7);
298 addChar(74, 0x65, 7);
299 addChar(75, 0x66, 7);
300 addChar(76, 0x67, 7);
301 addChar(77, 0x68, 7);
302 addChar(78, 0x69, 7);
303 addChar(79, 0x6a, 7);
304 addChar(80, 0x6b, 7);
305 addChar(81, 0x6c, 7);
306 addChar(82, 0x6d, 7);
307 addChar(83, 0x6e, 7);
308 addChar(84, 0x6f, 7);
309 addChar(85, 0x70, 7);
310 addChar(86, 0x71, 7);
311 addChar(87, 0x72, 7);
312 addChar(88, 0xfc, 8);
313 addChar(89, 0x73, 7);
314 addChar(90, 0xfd, 8);
315 addChar(91, 0x1ffb, 13);
316 addChar(92, 0x7fff0, 19);
317 addChar(93, 0x1ffc, 13);
318 addChar(94, 0x3ffc, 14);
319 addChar(95, 0x22, 6);
320 addChar(96, 0x7ffd, 15);
321 addChar(97, 0x3, 5);
322 addChar(98, 0x23, 6);
323 addChar(99, 0x4, 5);
324 addChar(100, 0x24, 6);
325 addChar(101, 0x5, 5);
326 addChar(102, 0x25, 6);
327 addChar(103, 0x26, 6);
328 addChar(104, 0x27, 6);
329 addChar(105, 0x6, 5);
330 addChar(106, 0x74, 7);
331 addChar(107, 0x75, 7);
332 addChar(108, 0x28, 6);
333 addChar(109, 0x29, 6);
334 addChar(110, 0x2a, 6);
335 addChar(111, 0x7, 5);
336 addChar(112, 0x2b, 6);
337 addChar(113, 0x76, 7);
338 addChar(114, 0x2c, 6);
339 addChar(115, 0x8, 5);
340 addChar(116, 0x9, 5);
341 addChar(117, 0x2d, 6);
342 addChar(118, 0x77, 7);
343 addChar(119, 0x78, 7);
344 addChar(120, 0x79, 7);
345 addChar(121, 0x7a, 7);
346 addChar(122, 0x7b, 7);
347 addChar(123, 0x7ffe, 15);
348 addChar(124, 0x7fc, 11);
349 addChar(125, 0x3ffd, 14);
350 addChar(126, 0x1ffd, 13);
351 addChar(127, 0xffffffc, 28);
352 addChar(128, 0xfffe6, 20);
353 addChar(129, 0x3fffd2, 22);
354 addChar(130, 0xfffe7, 20);
355 addChar(131, 0xfffe8, 20);
356 addChar(132, 0x3fffd3, 22);
357 addChar(133, 0x3fffd4, 22);
358 addChar(134, 0x3fffd5, 22);
359 addChar(135, 0x7fffd9, 23);
360 addChar(136, 0x3fffd6, 22);
361 addChar(137, 0x7fffda, 23);
362 addChar(138, 0x7fffdb, 23);
363 addChar(139, 0x7fffdc, 23);
364 addChar(140, 0x7fffdd, 23);
365 addChar(141, 0x7fffde, 23);
366 addChar(142, 0xffffeb, 24);
367 addChar(143, 0x7fffdf, 23);
368 addChar(144, 0xffffec, 24);
369 addChar(145, 0xffffed, 24);
370 addChar(146, 0x3fffd7, 22);
371 addChar(147, 0x7fffe0, 23);
372 addChar(148, 0xffffee, 24);
373 addChar(149, 0x7fffe1, 23);
374 addChar(150, 0x7fffe2, 23);
375 addChar(151, 0x7fffe3, 23);
376 addChar(152, 0x7fffe4, 23);
377 addChar(153, 0x1fffdc, 21);
378 addChar(154, 0x3fffd8, 22);
379 addChar(155, 0x7fffe5, 23);
380 addChar(156, 0x3fffd9, 22);
381 addChar(157, 0x7fffe6, 23);
382 addChar(158, 0x7fffe7, 23);
383 addChar(159, 0xffffef, 24);
384 addChar(160, 0x3fffda, 22);
385 addChar(161, 0x1fffdd, 21);
386 addChar(162, 0xfffe9, 20);
387 addChar(163, 0x3fffdb, 22);
388 addChar(164, 0x3fffdc, 22);
389 addChar(165, 0x7fffe8, 23);
390 addChar(166, 0x7fffe9, 23);
391 addChar(167, 0x1fffde, 21);
392 addChar(168, 0x7fffea, 23);
393 addChar(169, 0x3fffdd, 22);
394 addChar(170, 0x3fffde, 22);
395 addChar(171, 0xfffff0, 24);
396 addChar(172, 0x1fffdf, 21);
397 addChar(173, 0x3fffdf, 22);
398 addChar(174, 0x7fffeb, 23);
399 addChar(175, 0x7fffec, 23);
400 addChar(176, 0x1fffe0, 21);
401 addChar(177, 0x1fffe1, 21);
402 addChar(178, 0x3fffe0, 22);
403 addChar(179, 0x1fffe2, 21);
404 addChar(180, 0x7fffed, 23);
405 addChar(181, 0x3fffe1, 22);
406 addChar(182, 0x7fffee, 23);
407 addChar(183, 0x7fffef, 23);
408 addChar(184, 0xfffea, 20);
409 addChar(185, 0x3fffe2, 22);
410 addChar(186, 0x3fffe3, 22);
411 addChar(187, 0x3fffe4, 22);
412 addChar(188, 0x7ffff0, 23);
413 addChar(189, 0x3fffe5, 22);
414 addChar(190, 0x3fffe6, 22);
415 addChar(191, 0x7ffff1, 23);
416 addChar(192, 0x3ffffe0, 26);
417 addChar(193, 0x3ffffe1, 26);
418 addChar(194, 0xfffeb, 20);
419 addChar(195, 0x7fff1, 19);
420 addChar(196, 0x3fffe7, 22);
421 addChar(197, 0x7ffff2, 23);
422 addChar(198, 0x3fffe8, 22);
423 addChar(199, 0x1ffffec, 25);
424 addChar(200, 0x3ffffe2, 26);
425 addChar(201, 0x3ffffe3, 26);
426 addChar(202, 0x3ffffe4, 26);
427 addChar(203, 0x7ffffde, 27);
428 addChar(204, 0x7ffffdf, 27);
429 addChar(205, 0x3ffffe5, 26);
430 addChar(206, 0xfffff1, 24);
431 addChar(207, 0x1ffffed, 25);
432 addChar(208, 0x7fff2, 19);
433 addChar(209, 0x1fffe3, 21);
434 addChar(210, 0x3ffffe6, 26);
435 addChar(211, 0x7ffffe0, 27);
436 addChar(212, 0x7ffffe1, 27);
437 addChar(213, 0x3ffffe7, 26);
438 addChar(214, 0x7ffffe2, 27);
439 addChar(215, 0xfffff2, 24);
440 addChar(216, 0x1fffe4, 21);
441 addChar(217, 0x1fffe5, 21);
442 addChar(218, 0x3ffffe8, 26);
443 addChar(219, 0x3ffffe9, 26);
444 addChar(220, 0xffffffd, 28);
445 addChar(221, 0x7ffffe3, 27);
446 addChar(222, 0x7ffffe4, 27);
447 addChar(223, 0x7ffffe5, 27);
448 addChar(224, 0xfffec, 20);
449 addChar(225, 0xfffff3, 24);
450 addChar(226, 0xfffed, 20);
451 addChar(227, 0x1fffe6, 21);
452 addChar(228, 0x3fffe9, 22);
453 addChar(229, 0x1fffe7, 21);
454 addChar(230, 0x1fffe8, 21);
455 addChar(231, 0x7ffff3, 23);
456 addChar(232, 0x3fffea, 22);
457 addChar(233, 0x3fffeb, 22);
458 addChar(234, 0x1ffffee, 25);
459 addChar(235, 0x1ffffef, 25);
460 addChar(236, 0xfffff4, 24);
461 addChar(237, 0xfffff5, 24);
462 addChar(238, 0x3ffffea, 26);
463 addChar(239, 0x7ffff4, 23);
464 addChar(240, 0x3ffffeb, 26);
465 addChar(241, 0x7ffffe6, 27);
466 addChar(242, 0x3ffffec, 26);
467 addChar(243, 0x3ffffed, 26);
468 addChar(244, 0x7ffffe7, 27);
469 addChar(245, 0x7ffffe8, 27);
470 addChar(246, 0x7ffffe9, 27);
471 addChar(247, 0x7ffffea, 27);
472 addChar(248, 0x7ffffeb, 27);
473 addChar(249, 0xffffffe, 28);
474 addChar(250, 0x7ffffec, 27);
475 addChar(251, 0x7ffffed, 27);
476 addChar(252, 0x7ffffee, 27);
477 addChar(253, 0x7ffffef, 27);
478 addChar(254, 0x7fffff0, 27);
479 addChar(255, 0x3ffffee, 26);
480 addEOS (256, EOS.code, EOS.length);
481 // @formatter:on
482 }
483
484
485 /**
486 * Calculates the number of bytes required to represent the given {@code
487 * CharSequence} with the Huffman coding.
488 *
489 * @param value
490 * characters
491 *
492 * @return number of bytes
493 *
494 * @throws NullPointerException
495 * if the value is null
496 */
497 public int lengthOf(CharSequence value) {
498 return lengthOf(value, 0, value.length());
499 }
500
501 /**
502 * Calculates the number of bytes required to represent a subsequence of the
503 * given {@code CharSequence} with the Huffman coding.
504 *
505 * @param value
506 * characters
507 * @param start
508 * the start index, inclusive
509 * @param end
510 * the end index, exclusive
511 *
512 * @return number of bytes
513 *
514 * @throws NullPointerException
515 * if the value is null
516 * @throws IndexOutOfBoundsException
517 * if any invocation of {@code value.charAt(i)}, where
518 * {@code start <= i < end} would throw an IndexOutOfBoundsException
519 */
520 public int lengthOf(CharSequence value, int start, int end) {
521 int len = 0;
522 for (int i = start; i < end; i++) {
523 char c = value.charAt(i);
524 len += INSTANCE.codeOf(c).length;
525 }
526 // Integer division with ceiling, assumption:
527 assert (len / 8 + (len % 8 != 0 ? 1 : 0)) == (len + 7) / 8 : len;
528 return (len + 7) / 8;
529 }
530
531 private void addChar(int c, int code, int bitLength) {
532 addLeaf(c, code, bitLength, false);
533 codes[c] = new Code(code, bitLength);
534 }
535
536 private void addEOS(int c, int code, int bitLength) {
537 addLeaf(c, code, bitLength, true);
538 codes[c] = new Code(code, bitLength);
539 }
540
541 private void addLeaf(int c, int code, int bitLength, boolean isEOS) {
542 if (bitLength < 1) {
543 throw new IllegalArgumentException("bitLength < 1");
544 }
545 Node curr = root;
546 for (int p = 1 << bitLength - 1; p != 0 && !curr.isLeaf(); p = p >> 1) {
547 curr.isEOSPath |= isEOS; // If it's already true, it can't become false
548 curr = curr.addChildIfAbsent(p & code);
549 }
550 curr.isEOSPath |= isEOS; // The last one needs to have this property as well
551 if (curr.isLeaf()) {
552 throw new IllegalStateException("Specified code is already taken");
553 }
554 curr.setChar((char) c);
555 }
556
557 private Code codeOf(char c) {
558 if (c > 255) {
559 throw new IllegalArgumentException("char=" + ((int) c));
560 }
561 return codes[c];
562 }
563
564 //
565 // For debugging/testing purposes
566 //
567 Node getRoot() {
568 return root;
569 }
570
571 //
572 // Guarantees:
573 //
574 // if (isLeaf() == true) => getChar() is a legal call
575 // if (isLeaf() == false) => getChild(i) is a legal call (though it can
576 // return null)
577 //
578 static class Node {
579
580 Node left;
581 Node right;
582 boolean isEOSPath;
583
584 boolean charIsSet;
585 char c;
586
587 Node getChild(int selector) {
588 if (isLeaf()) {
589 throw new IllegalStateException("This is a leaf node");
590 }
591 Node result = selector == 0 ? left : right;
592 if (result == null) {
593 throw new IllegalStateException(format(
594 "Node doesn't have a child (selector=%s)", selector));
595 }
596 return result;
597 }
598
599 boolean isLeaf() {
600 return charIsSet;
601 }
602
603 char getChar() {
604 if (!isLeaf()) {
605 throw new IllegalStateException("This node is not a leaf node");
606 }
607 return c;
608 }
609
610 void setChar(char c) {
611 if (charIsSet) {
612 throw new IllegalStateException(
613 "This node has been taken already");
614 }
615 if (left != null || right != null) {
616 throw new IllegalStateException("The node cannot be made "
617 + "a leaf as it's already has a child");
618 }
619 this.c = c;
620 charIsSet = true;
621 }
622
623 Node addChildIfAbsent(int i) {
624 if (charIsSet) {
625 throw new IllegalStateException("The node cannot have a child "
626 + "as it's already a leaf node");
627 }
628 Node child;
629 if (i == 0) {
630 if ((child = left) == null) {
631 child = left = new Node();
632 }
633 } else {
634 if ((child = right) == null) {
635 child = right = new Node();
636 }
637 }
638 return child;
639 }
640
641 @Override
642 public String toString() {
643 if (isLeaf()) {
644 if (isEOSPath) {
645 return "EOS";
646 } else {
647 return format("char: (%3s) '%s'", (int) c, c);
648 }
649 }
650 return "/\\";
651 }
652 }
653
654 // TODO: value-based class?
655 // FIXME: can we re-use Node instead of this class?
656 private static final class Code {
657
658 final int code;
659 final int length;
660
661 private Code(int code, int length) {
662 this.code = code;
663 this.length = length;
664 }
665
666 public int getCode() {
667 return code;
668 }
669
670 public int getLength() {
671 return length;
672 }
673
674 @Override
675 public String toString() {
676 long p = 1 << length;
677 return Long.toBinaryString(code + p).substring(1)
678 + ", length=" + length;
679 }
680 }
681 }