1 | use std::u32; |
2 | |
3 | /// A stream identifier, as described in [Section 5.1.1] of RFC 7540. |
4 | /// |
5 | /// Streams are identified with an unsigned 31-bit integer. Streams |
6 | /// initiated by a client MUST use odd-numbered stream identifiers; those |
7 | /// initiated by the server MUST use even-numbered stream identifiers. A |
8 | /// stream identifier of zero (0x0) is used for connection control |
9 | /// messages; the stream identifier of zero cannot be used to establish a |
10 | /// new stream. |
11 | /// |
12 | /// [Section 5.1.1]: https://tools.ietf.org/html/rfc7540#section-5.1.1 |
13 | #[derive (Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)] |
14 | pub struct StreamId(u32); |
15 | |
16 | #[derive (Debug, Copy, Clone)] |
17 | pub struct StreamIdOverflow; |
18 | |
19 | const STREAM_ID_MASK: u32 = 1 << 31; |
20 | |
21 | impl StreamId { |
22 | /// Stream ID 0. |
23 | pub const ZERO: StreamId = StreamId(0); |
24 | |
25 | /// The maximum allowed stream ID. |
26 | pub const MAX: StreamId = StreamId(u32::MAX >> 1); |
27 | |
28 | /// Parse the stream ID |
29 | #[inline ] |
30 | pub fn parse(buf: &[u8]) -> (StreamId, bool) { |
31 | let mut ubuf = [0; 4]; |
32 | ubuf.copy_from_slice(&buf[0..4]); |
33 | let unpacked = u32::from_be_bytes(ubuf); |
34 | let flag = unpacked & STREAM_ID_MASK == STREAM_ID_MASK; |
35 | |
36 | // Now clear the most significant bit, as that is reserved and MUST be |
37 | // ignored when received. |
38 | (StreamId(unpacked & !STREAM_ID_MASK), flag) |
39 | } |
40 | |
41 | /// Returns true if this stream ID corresponds to a stream that |
42 | /// was initiated by the client. |
43 | pub fn is_client_initiated(&self) -> bool { |
44 | let id = self.0; |
45 | id != 0 && id % 2 == 1 |
46 | } |
47 | |
48 | /// Returns true if this stream ID corresponds to a stream that |
49 | /// was initiated by the server. |
50 | pub fn is_server_initiated(&self) -> bool { |
51 | let id = self.0; |
52 | id != 0 && id % 2 == 0 |
53 | } |
54 | |
55 | /// Return a new `StreamId` for stream 0. |
56 | #[inline ] |
57 | pub fn zero() -> StreamId { |
58 | StreamId::ZERO |
59 | } |
60 | |
61 | /// Returns true if this stream ID is zero. |
62 | pub fn is_zero(&self) -> bool { |
63 | self.0 == 0 |
64 | } |
65 | |
66 | /// Returns the next stream ID initiated by the same peer as this stream |
67 | /// ID, or an error if incrementing this stream ID would overflow the |
68 | /// maximum. |
69 | pub fn next_id(&self) -> Result<StreamId, StreamIdOverflow> { |
70 | let next = self.0 + 2; |
71 | if next > StreamId::MAX.0 { |
72 | Err(StreamIdOverflow) |
73 | } else { |
74 | Ok(StreamId(next)) |
75 | } |
76 | } |
77 | } |
78 | |
79 | impl From<u32> for StreamId { |
80 | fn from(src: u32) -> Self { |
81 | assert_eq!(src & STREAM_ID_MASK, 0, "invalid stream ID -- MSB is set" ); |
82 | StreamId(src) |
83 | } |
84 | } |
85 | |
86 | impl From<StreamId> for u32 { |
87 | fn from(src: StreamId) -> Self { |
88 | src.0 |
89 | } |
90 | } |
91 | |
92 | impl PartialEq<u32> for StreamId { |
93 | fn eq(&self, other: &u32) -> bool { |
94 | self.0 == *other |
95 | } |
96 | } |
97 | |