h2/frame/
stream_id.rs

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1use 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)]
14pub struct StreamId(u32);
15
16#[derive(Debug, Copy, Clone)]
17pub struct StreamIdOverflow;
18
19const STREAM_ID_MASK: u32 = 1 << 31;
20
21impl 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
79impl 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
86impl From<StreamId> for u32 {
87    fn from(src: StreamId) -> Self {
88        src.0
89    }
90}
91
92impl PartialEq<u32> for StreamId {
93    fn eq(&self, other: &u32) -> bool {
94        self.0 == *other
95    }
96}
h2/frame/stream_id.rs

h2/frame/
stream_id.rs
