1use super::table::{Index, Table};
2use super::{huffman, Header};
3
4use bytes::{BufMut, BytesMut};
5use http::header::{HeaderName, HeaderValue};
6
7#[derive(Debug)]
8pub struct Encoder {
9 table: Table,
10 size_update: Option<SizeUpdate>,
11}
12
13#[derive(Debug, Copy, Clone, Eq, PartialEq)]
14enum SizeUpdate {
15 One(usize),
16 Two(usize, usize), // min, max
17}
18
19impl Encoder {
20 pub fn new(max_size: usize, capacity: usize) -> Encoder {
21 Encoder {
22 table: Table::new(max_size, capacity),
23 size_update: None,
24 }
25 }
26
27 /// Queues a max size update.
28 ///
29 /// The next call to `encode` will include a dynamic size update frame.
30 pub fn update_max_size(&mut self, val: usize) {
31 match self.size_update {
32 Some(SizeUpdate::One(old)) => {
33 if val > old {
34 if old > self.table.max_size() {
35 self.size_update = Some(SizeUpdate::One(val));
36 } else {
37 self.size_update = Some(SizeUpdate::Two(old, val));
38 }
39 } else {
40 self.size_update = Some(SizeUpdate::One(val));
41 }
42 }
43 Some(SizeUpdate::Two(min, _)) => {
44 if val < min {
45 self.size_update = Some(SizeUpdate::One(val));
46 } else {
47 self.size_update = Some(SizeUpdate::Two(min, val));
48 }
49 }
50 None => {
51 if val != self.table.max_size() {
52 // Don't bother writing a frame if the value already matches
53 // the table's max size.
54 self.size_update = Some(SizeUpdate::One(val));
55 }
56 }
57 }
58 }
59
60 /// Encode a set of headers into the provide buffer
61 pub fn encode<I>(&mut self, headers: I, dst: &mut BytesMut)
62 where
63 I: IntoIterator<Item = Header<Option<HeaderName>>>,
64 {
65 let span = tracing::trace_span!("hpack::encode");
66 let _e = span.enter();
67
68 self.encode_size_updates(dst);
69
70 let mut last_index = None;
71
72 for header in headers {
73 match header.reify() {
74 // The header has an associated name. In which case, try to
75 // index it in the table.
76 Ok(header) => {
77 let index = self.table.index(header);
78 self.encode_header(&index, dst);
79
80 last_index = Some(index);
81 }
82 // The header does not have an associated name. This means that
83 // the name is the same as the previously yielded header. In
84 // which case, we skip table lookup and just use the same index
85 // as the previous entry.
86 Err(value) => {
87 self.encode_header_without_name(
88 last_index.as_ref().unwrap_or_else(|| {
89 panic!("encoding header without name, but no previous index to use for name");
90 }),
91 &value,
92 dst,
93 );
94 }
95 }
96 }
97 }
98
99 fn encode_size_updates(&mut self, dst: &mut BytesMut) {
100 match self.size_update.take() {
101 Some(SizeUpdate::One(val)) => {
102 self.table.resize(val);
103 encode_size_update(val, dst);
104 }
105 Some(SizeUpdate::Two(min, max)) => {
106 self.table.resize(min);
107 self.table.resize(max);
108 encode_size_update(min, dst);
109 encode_size_update(max, dst);
110 }
111 None => {}
112 }
113 }
114
115 fn encode_header(&mut self, index: &Index, dst: &mut BytesMut) {
116 match *index {
117 Index::Indexed(idx, _) => {
118 encode_int(idx, 7, 0x80, dst);
119 }
120 Index::Name(idx, _) => {
121 let header = self.table.resolve(index);
122
123 encode_not_indexed(idx, header.value_slice(), header.is_sensitive(), dst);
124 }
125 Index::Inserted(_) => {
126 let header = self.table.resolve(index);
127
128 assert!(!header.is_sensitive());
129
130 dst.put_u8(0b0100_0000);
131
132 encode_str(header.name().as_slice(), dst);
133 encode_str(header.value_slice(), dst);
134 }
135 Index::InsertedValue(idx, _) => {
136 let header = self.table.resolve(index);
137
138 assert!(!header.is_sensitive());
139
140 encode_int(idx, 6, 0b0100_0000, dst);
141 encode_str(header.value_slice(), dst);
142 }
143 Index::NotIndexed(_) => {
144 let header = self.table.resolve(index);
145
146 encode_not_indexed2(
147 header.name().as_slice(),
148 header.value_slice(),
149 header.is_sensitive(),
150 dst,
151 );
152 }
153 }
154 }
155
156 fn encode_header_without_name(
157 &mut self,
158 last: &Index,
159 value: &HeaderValue,
160 dst: &mut BytesMut,
161 ) {
162 match *last {
163 Index::Indexed(..)
164 | Index::Name(..)
165 | Index::Inserted(..)
166 | Index::InsertedValue(..) => {
167 let idx = self.table.resolve_idx(last);
168
169 encode_not_indexed(idx, value.as_ref(), value.is_sensitive(), dst);
170 }
171 Index::NotIndexed(_) => {
172 let last = self.table.resolve(last);
173
174 encode_not_indexed2(
175 last.name().as_slice(),
176 value.as_ref(),
177 value.is_sensitive(),
178 dst,
179 );
180 }
181 }
182 }
183}
184
185impl Default for Encoder {
186 fn default() -> Encoder {
187 Encoder::new(max_size:4096, capacity:0)
188 }
189}
190
191fn encode_size_update(val: usize, dst: &mut BytesMut) {
192 encode_int(value:val, prefix_bits:5, first_byte:0b0010_0000, dst)
193}
194
195fn encode_not_indexed(name: usize, value: &[u8], sensitive: bool, dst: &mut BytesMut) {
196 if sensitive {
197 encode_int(value:name, prefix_bits:4, first_byte:0b10000, dst);
198 } else {
199 encode_int(value:name, prefix_bits:4, first_byte:0, dst);
200 }
201
202 encode_str(val:value, dst);
203}
204
205fn encode_not_indexed2(name: &[u8], value: &[u8], sensitive: bool, dst: &mut BytesMut) {
206 if sensitive {
207 dst.put_u8(0b10000);
208 } else {
209 dst.put_u8(0);
210 }
211
212 encode_str(val:name, dst);
213 encode_str(val:value, dst);
214}
215
216fn encode_str(val: &[u8], dst: &mut BytesMut) {
217 if !val.is_empty() {
218 let idx = position(dst);
219
220 // Push a placeholder byte for the length header
221 dst.put_u8(0);
222
223 // Encode with huffman
224 huffman::encode(val, dst);
225
226 let huff_len = position(dst) - (idx + 1);
227
228 if encode_int_one_byte(huff_len, 7) {
229 // Write the string head
230 dst[idx] = 0x80 | huff_len as u8;
231 } else {
232 // Write the head to a placeholder
233 const PLACEHOLDER_LEN: usize = 8;
234 let mut buf = [0u8; PLACEHOLDER_LEN];
235
236 let head_len = {
237 let mut head_dst = &mut buf[..];
238 encode_int(huff_len, 7, 0x80, &mut head_dst);
239 PLACEHOLDER_LEN - head_dst.remaining_mut()
240 };
241
242 // This is just done to reserve space in the destination
243 dst.put_slice(&buf[1..head_len]);
244
245 // Shift the header forward
246 for i in 0..huff_len {
247 let src_i = idx + 1 + (huff_len - (i + 1));
248 let dst_i = idx + head_len + (huff_len - (i + 1));
249 dst[dst_i] = dst[src_i];
250 }
251
252 // Copy in the head
253 for i in 0..head_len {
254 dst[idx + i] = buf[i];
255 }
256 }
257 } else {
258 // Write an empty string
259 dst.put_u8(0);
260 }
261}
262
263/// Encode an integer into the given destination buffer
264fn encode_int<B: BufMut>(
265 mut value: usize, // The integer to encode
266 prefix_bits: usize, // The number of bits in the prefix
267 first_byte: u8, // The base upon which to start encoding the int
268 dst: &mut B,
269) {
270 if encode_int_one_byte(value, prefix_bits) {
271 dst.put_u8(first_byte | value as u8);
272 return;
273 }
274
275 let low: usize = (1 << prefix_bits) - 1;
276
277 value -= low;
278
279 dst.put_u8(first_byte | low as u8);
280
281 while value >= 128 {
282 dst.put_u8(0b1000_0000 | value as u8);
283
284 value >>= 7;
285 }
286
287 dst.put_u8(value as u8);
288}
289
290/// Returns true if the in the int can be fully encoded in the first byte.
291fn encode_int_one_byte(value: usize, prefix_bits: usize) -> bool {
292 value < (1 << prefix_bits) - 1
293}
294
295fn position(buf: &BytesMut) -> usize {
296 buf.len()
297}
298
299#[cfg(test)]
300mod test {
301 use super::*;
302 use http::*;
303
304 #[test]
305 fn test_encode_method_get() {
306 let mut encoder = Encoder::default();
307 let res = encode(&mut encoder, vec![method("GET")]);
308 assert_eq!(*res, [0x80 | 2]);
309 assert_eq!(encoder.table.len(), 0);
310 }
311
312 #[test]
313 fn test_encode_method_post() {
314 let mut encoder = Encoder::default();
315 let res = encode(&mut encoder, vec![method("POST")]);
316 assert_eq!(*res, [0x80 | 3]);
317 assert_eq!(encoder.table.len(), 0);
318 }
319
320 #[test]
321 fn test_encode_method_patch() {
322 let mut encoder = Encoder::default();
323 let res = encode(&mut encoder, vec![method("PATCH")]);
324
325 assert_eq!(res[0], 0b01000000 | 2); // Incremental indexing w/ name pulled from table
326 assert_eq!(res[1], 0x80 | 5); // header value w/ huffman coding
327
328 assert_eq!("PATCH", huff_decode(&res[2..7]));
329 assert_eq!(encoder.table.len(), 1);
330
331 let res = encode(&mut encoder, vec![method("PATCH")]);
332
333 assert_eq!(1 << 7 | 62, res[0]);
334 assert_eq!(1, res.len());
335 }
336
337 #[test]
338 fn test_encode_indexed_name_literal_value() {
339 let mut encoder = Encoder::default();
340 let res = encode(&mut encoder, vec![header("content-language", "foo")]);
341
342 assert_eq!(res[0], 0b01000000 | 27); // Indexed name
343 assert_eq!(res[1], 0x80 | 2); // header value w/ huffman coding
344
345 assert_eq!("foo", huff_decode(&res[2..4]));
346
347 // Same name, new value should still use incremental
348 let res = encode(&mut encoder, vec![header("content-language", "bar")]);
349 assert_eq!(res[0], 0b01000000 | 27); // Indexed name
350 assert_eq!(res[1], 0x80 | 3); // header value w/ huffman coding
351 assert_eq!("bar", huff_decode(&res[2..5]));
352 }
353
354 #[test]
355 fn test_repeated_headers_are_indexed() {
356 let mut encoder = Encoder::default();
357 let res = encode(&mut encoder, vec![header("foo", "hello")]);
358
359 assert_eq!(&[0b01000000, 0x80 | 2], &res[0..2]);
360 assert_eq!("foo", huff_decode(&res[2..4]));
361 assert_eq!(0x80 | 4, res[4]);
362 assert_eq!("hello", huff_decode(&res[5..]));
363 assert_eq!(9, res.len());
364
365 assert_eq!(1, encoder.table.len());
366
367 let res = encode(&mut encoder, vec![header("foo", "hello")]);
368 assert_eq!([0x80 | 62], *res);
369
370 assert_eq!(encoder.table.len(), 1);
371 }
372
373 #[test]
374 fn test_evicting_headers() {
375 let mut encoder = Encoder::default();
376
377 // Fill the table
378 for i in 0..64 {
379 let key = format!("x-hello-world-{:02}", i);
380 let res = encode(&mut encoder, vec![header(&key, &key)]);
381
382 assert_eq!(&[0b01000000, 0x80 | 12], &res[0..2]);
383 assert_eq!(key, huff_decode(&res[2..14]));
384 assert_eq!(0x80 | 12, res[14]);
385 assert_eq!(key, huff_decode(&res[15..]));
386 assert_eq!(27, res.len());
387
388 // Make sure the header can be found...
389 let res = encode(&mut encoder, vec![header(&key, &key)]);
390
391 // Only check that it is found
392 assert_eq!(0x80, res[0] & 0x80);
393 }
394
395 assert_eq!(4096, encoder.table.size());
396 assert_eq!(64, encoder.table.len());
397
398 // Find existing headers
399 for i in 0..64 {
400 let key = format!("x-hello-world-{:02}", i);
401 let res = encode(&mut encoder, vec![header(&key, &key)]);
402 assert_eq!(0x80, res[0] & 0x80);
403 }
404
405 // Insert a new header
406 let key = "x-hello-world-64";
407 let res = encode(&mut encoder, vec![header(key, key)]);
408
409 assert_eq!(&[0b01000000, 0x80 | 12], &res[0..2]);
410 assert_eq!(key, huff_decode(&res[2..14]));
411 assert_eq!(0x80 | 12, res[14]);
412 assert_eq!(key, huff_decode(&res[15..]));
413 assert_eq!(27, res.len());
414
415 assert_eq!(64, encoder.table.len());
416
417 // Now try encoding entries that should exist in the table
418 for i in 1..65 {
419 let key = format!("x-hello-world-{:02}", i);
420 let res = encode(&mut encoder, vec![header(&key, &key)]);
421 assert_eq!(0x80 | (61 + (65 - i)), res[0]);
422 }
423 }
424
425 #[test]
426 fn test_large_headers_are_not_indexed() {
427 let mut encoder = Encoder::new(128, 0);
428 let key = "hello-world-hello-world-HELLO-zzz";
429
430 let res = encode(&mut encoder, vec![header(key, key)]);
431
432 assert_eq!(&[0, 0x80 | 25], &res[..2]);
433
434 assert_eq!(0, encoder.table.len());
435 assert_eq!(0, encoder.table.size());
436 }
437
438 #[test]
439 fn test_sensitive_headers_are_never_indexed() {
440 use http::header::HeaderValue;
441
442 let name = "my-password".parse().unwrap();
443 let mut value = HeaderValue::from_bytes(b"12345").unwrap();
444 value.set_sensitive(true);
445
446 let header = Header::Field {
447 name: Some(name),
448 value,
449 };
450
451 // Now, try to encode the sensitive header
452
453 let mut encoder = Encoder::default();
454 let res = encode(&mut encoder, vec![header]);
455
456 assert_eq!(&[0b10000, 0x80 | 8], &res[..2]);
457 assert_eq!("my-password", huff_decode(&res[2..10]));
458 assert_eq!(0x80 | 4, res[10]);
459 assert_eq!("12345", huff_decode(&res[11..]));
460
461 // Now, try to encode a sensitive header w/ a name in the static table
462 let name = "authorization".parse().unwrap();
463 let mut value = HeaderValue::from_bytes(b"12345").unwrap();
464 value.set_sensitive(true);
465
466 let header = Header::Field {
467 name: Some(name),
468 value,
469 };
470
471 let mut encoder = Encoder::default();
472 let res = encode(&mut encoder, vec![header]);
473
474 assert_eq!(&[0b11111, 8], &res[..2]);
475 assert_eq!(0x80 | 4, res[2]);
476 assert_eq!("12345", huff_decode(&res[3..]));
477
478 // Using the name component of a previously indexed header (without
479 // sensitive flag set)
480
481 let _ = encode(
482 &mut encoder,
483 vec![self::header("my-password", "not-so-secret")],
484 );
485
486 let name = "my-password".parse().unwrap();
487 let mut value = HeaderValue::from_bytes(b"12345").unwrap();
488 value.set_sensitive(true);
489
490 let header = Header::Field {
491 name: Some(name),
492 value,
493 };
494 let res = encode(&mut encoder, vec![header]);
495
496 assert_eq!(&[0b11111, 47], &res[..2]);
497 assert_eq!(0x80 | 4, res[2]);
498 assert_eq!("12345", huff_decode(&res[3..]));
499 }
500
501 #[test]
502 fn test_content_length_value_not_indexed() {
503 let mut encoder = Encoder::default();
504 let res = encode(&mut encoder, vec![header("content-length", "1234")]);
505
506 assert_eq!(&[15, 13, 0x80 | 3], &res[0..3]);
507 assert_eq!("1234", huff_decode(&res[3..]));
508 assert_eq!(6, res.len());
509 }
510
511 #[test]
512 fn test_encoding_headers_with_same_name() {
513 let mut encoder = Encoder::default();
514 let name = "hello";
515
516 // Encode first one
517 let _ = encode(&mut encoder, vec![header(name, "one")]);
518
519 // Encode second one
520 let res = encode(&mut encoder, vec![header(name, "two")]);
521 assert_eq!(&[0x40 | 62, 0x80 | 3], &res[0..2]);
522 assert_eq!("two", huff_decode(&res[2..]));
523 assert_eq!(5, res.len());
524
525 // Encode the first one again
526 let res = encode(&mut encoder, vec![header(name, "one")]);
527 assert_eq!(&[0x80 | 63], &res[..]);
528
529 // Now the second one
530 let res = encode(&mut encoder, vec![header(name, "two")]);
531 assert_eq!(&[0x80 | 62], &res[..]);
532 }
533
534 #[test]
535 fn test_evicting_headers_when_multiple_of_same_name_are_in_table() {
536 // The encoder only has space for 2 headers
537 let mut encoder = Encoder::new(76, 0);
538
539 let _ = encode(&mut encoder, vec![header("foo", "bar")]);
540 assert_eq!(1, encoder.table.len());
541
542 let _ = encode(&mut encoder, vec![header("bar", "foo")]);
543 assert_eq!(2, encoder.table.len());
544
545 // This will evict the first header, while still referencing the header
546 // name
547 let res = encode(&mut encoder, vec![header("foo", "baz")]);
548 assert_eq!(&[0x40 | 63, 0, 0x80 | 3], &res[..3]);
549 assert_eq!(2, encoder.table.len());
550
551 // Try adding the same header again
552 let res = encode(&mut encoder, vec![header("foo", "baz")]);
553 assert_eq!(&[0x80 | 62], &res[..]);
554 assert_eq!(2, encoder.table.len());
555 }
556
557 #[test]
558 fn test_max_size_zero() {
559 // Static table only
560 let mut encoder = Encoder::new(0, 0);
561 let res = encode(&mut encoder, vec![method("GET")]);
562 assert_eq!(*res, [0x80 | 2]);
563 assert_eq!(encoder.table.len(), 0);
564
565 let res = encode(&mut encoder, vec![header("foo", "bar")]);
566 assert_eq!(&[0, 0x80 | 2], &res[..2]);
567 assert_eq!("foo", huff_decode(&res[2..4]));
568 assert_eq!(0x80 | 3, res[4]);
569 assert_eq!("bar", huff_decode(&res[5..8]));
570 assert_eq!(0, encoder.table.len());
571
572 // Encode a custom value
573 let res = encode(&mut encoder, vec![header("transfer-encoding", "chunked")]);
574 assert_eq!(&[15, 42, 0x80 | 6], &res[..3]);
575 assert_eq!("chunked", huff_decode(&res[3..]));
576 }
577
578 #[test]
579 fn test_update_max_size_combos() {
580 let mut encoder = Encoder::default();
581 assert!(encoder.size_update.is_none());
582 assert_eq!(4096, encoder.table.max_size());
583
584 encoder.update_max_size(4096); // Default size
585 assert!(encoder.size_update.is_none());
586
587 encoder.update_max_size(0);
588 assert_eq!(Some(SizeUpdate::One(0)), encoder.size_update);
589
590 encoder.update_max_size(100);
591 assert_eq!(Some(SizeUpdate::Two(0, 100)), encoder.size_update);
592
593 let mut encoder = Encoder::default();
594 encoder.update_max_size(8000);
595 assert_eq!(Some(SizeUpdate::One(8000)), encoder.size_update);
596
597 encoder.update_max_size(100);
598 assert_eq!(Some(SizeUpdate::One(100)), encoder.size_update);
599
600 encoder.update_max_size(8000);
601 assert_eq!(Some(SizeUpdate::Two(100, 8000)), encoder.size_update);
602
603 encoder.update_max_size(4000);
604 assert_eq!(Some(SizeUpdate::Two(100, 4000)), encoder.size_update);
605
606 encoder.update_max_size(50);
607 assert_eq!(Some(SizeUpdate::One(50)), encoder.size_update);
608 }
609
610 #[test]
611 fn test_resizing_table() {
612 let mut encoder = Encoder::default();
613
614 // Add a header
615 let _ = encode(&mut encoder, vec![header("foo", "bar")]);
616
617 encoder.update_max_size(1);
618 assert_eq!(1, encoder.table.len());
619
620 let res = encode(&mut encoder, vec![method("GET")]);
621 assert_eq!(&[32 | 1, 0x80 | 2], &res[..]);
622 assert_eq!(0, encoder.table.len());
623
624 let res = encode(&mut encoder, vec![header("foo", "bar")]);
625 assert_eq!(0, res[0]);
626
627 encoder.update_max_size(100);
628 let res = encode(&mut encoder, vec![header("foo", "bar")]);
629 assert_eq!(&[32 | 31, 69, 64], &res[..3]);
630
631 encoder.update_max_size(0);
632 let res = encode(&mut encoder, vec![header("foo", "bar")]);
633 assert_eq!(&[32, 0], &res[..2]);
634 }
635
636 #[test]
637 fn test_decreasing_table_size_without_eviction() {
638 let mut encoder = Encoder::default();
639
640 // Add a header
641 let _ = encode(&mut encoder, vec![header("foo", "bar")]);
642
643 encoder.update_max_size(100);
644 assert_eq!(1, encoder.table.len());
645
646 let res = encode(&mut encoder, vec![header("foo", "bar")]);
647 assert_eq!(&[32 | 31, 69, 0x80 | 62], &res[..]);
648 }
649
650 #[test]
651 fn test_nameless_header() {
652 let mut encoder = Encoder::default();
653
654 let res = encode(
655 &mut encoder,
656 vec![
657 Header::Field {
658 name: Some("hello".parse().unwrap()),
659 value: HeaderValue::from_bytes(b"world").unwrap(),
660 },
661 Header::Field {
662 name: None,
663 value: HeaderValue::from_bytes(b"zomg").unwrap(),
664 },
665 ],
666 );
667
668 assert_eq!(&[0x40, 0x80 | 4], &res[0..2]);
669 assert_eq!("hello", huff_decode(&res[2..6]));
670 assert_eq!(0x80 | 4, res[6]);
671 assert_eq!("world", huff_decode(&res[7..11]));
672
673 // Next is not indexed
674 assert_eq!(&[15, 47, 0x80 | 3], &res[11..14]);
675 assert_eq!("zomg", huff_decode(&res[14..]));
676 }
677
678 #[test]
679 fn test_large_size_update() {
680 let mut encoder = Encoder::default();
681
682 encoder.update_max_size(1912930560);
683 assert_eq!(Some(SizeUpdate::One(1912930560)), encoder.size_update);
684
685 let mut dst = BytesMut::with_capacity(6);
686 encoder.encode_size_updates(&mut dst);
687 assert_eq!([63, 225, 129, 148, 144, 7], &dst[..]);
688 }
689
690 #[test]
691 #[ignore]
692 fn test_evicted_overflow() {
693 // Not sure what the best way to do this is.
694 }
695
696 fn encode(e: &mut Encoder, hdrs: Vec<Header<Option<HeaderName>>>) -> BytesMut {
697 let mut dst = BytesMut::with_capacity(1024);
698 e.encode(hdrs, &mut dst);
699 dst
700 }
701
702 fn method(s: &str) -> Header<Option<HeaderName>> {
703 Header::Method(Method::from_bytes(s.as_bytes()).unwrap())
704 }
705
706 fn header(name: &str, val: &str) -> Header<Option<HeaderName>> {
707 let name = HeaderName::from_bytes(name.as_bytes()).unwrap();
708 let value = HeaderValue::from_bytes(val.as_bytes()).unwrap();
709
710 Header::Field {
711 name: Some(name),
712 value,
713 }
714 }
715
716 fn huff_decode(src: &[u8]) -> BytesMut {
717 let mut buf = BytesMut::new();
718 huffman::decode(src, &mut buf).unwrap()
719 }
720}
721