1 /*
2 * Copyright (c) 2019 Fastly
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a copy
5 * of this software and associated documentation files (the "Software"), to
6 * deal in the Software without restriction, including without limitation the
7 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
8 * sell copies of the Software, and to permit persons to whom the Software is
9 * furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice shall be included in
12 * all copies or substantial portions of the Software.
13 *
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
19 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
20 * IN THE SOFTWARE.
21 */
22 #ifndef h2o__absprio_h
23 #define h2o__absprio_h
24
25 #include <assert.h>
26 #include <stddef.h>
27 #include <stdint.h>
28
29 #define H2O_ABSPRIO_DEFAULT_URGENCY 3
30 #define H2O_ABSPRIO_NUM_URGENCY_LEVELS 8
31
32 typedef struct h2o_absprio_t {
33 uint8_t urgency : 3;
34 uint8_t incremental : 1;
35 } h2o_absprio_t;
36
37 extern h2o_absprio_t h2o_absprio_default;
38
39 void h2o_absprio_parse_priority(const char *s, size_t len, h2o_absprio_t *prio);
40 /**
41 * Convert urgency value in absolute priority header to HTTP2 weight, having Chromium as a client in mind.
42 */
43 static uint16_t h2o_absprio_urgency_to_chromium_weight(uint8_t urgency);
44
45 /* inline functions */
46
h2o_absprio_urgency_to_chromium_weight(uint8_t urgency)47 inline uint16_t h2o_absprio_urgency_to_chromium_weight(uint8_t urgency)
48 {
49 uint16_t weight;
50 assert(urgency < H2O_ABSPRIO_NUM_URGENCY_LEVELS);
51 /* formula excerpted from:
52 * https://quiche.googlesource.com/quiche/+/8cbe7bfa5c6efa7a42652e36fabf8d21879894be/spdy/core/spdy_protocol.cc#50 */
53 const float ksteps = 255.9f / (float)(H2O_ABSPRIO_NUM_URGENCY_LEVELS - 1);
54 weight = (uint16_t)(ksteps * ((H2O_ABSPRIO_NUM_URGENCY_LEVELS - 1) - urgency)) + 1;
55 return weight;
56 }
57
58 #endif
59