| use std::u32; |
| |
| /// A stream identifier, as described in [Section 5.1.1] of RFC 7540. |
| /// |
| /// Streams are identified with an unsigned 31-bit integer. Streams |
| /// initiated by a client MUST use odd-numbered stream identifiers; those |
| /// initiated by the server MUST use even-numbered stream identifiers. A |
| /// stream identifier of zero (0x0) is used for connection control |
| /// messages; the stream identifier of zero cannot be used to establish a |
| /// new stream. |
| /// |
| /// [Section 5.1.1]: https://tools.ietf.org/html/rfc7540#section-5.1.1 |
| #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)] |
| pub struct StreamId(u32); |
| |
| #[derive(Debug, Copy, Clone)] |
| pub struct StreamIdOverflow; |
| |
| const STREAM_ID_MASK: u32 = 1 << 31; |
| |
| impl StreamId { |
| /// Stream ID 0. |
| pub const ZERO: StreamId = StreamId(0); |
| |
| /// The maximum allowed stream ID. |
| pub const MAX: StreamId = StreamId(u32::MAX >> 1); |
| |
| /// Parse the stream ID |
| #[inline] |
| pub fn parse(buf: &[u8]) -> (StreamId, bool) { |
| let mut ubuf = [0; 4]; |
| ubuf.copy_from_slice(&buf[0..4]); |
| let unpacked = u32::from_be_bytes(ubuf); |
| let flag = unpacked & STREAM_ID_MASK == STREAM_ID_MASK; |
| |
| // Now clear the most significant bit, as that is reserved and MUST be |
| // ignored when received. |
| (StreamId(unpacked & !STREAM_ID_MASK), flag) |
| } |
| |
| /// Returns true if this stream ID corresponds to a stream that |
| /// was initiated by the client. |
| pub fn is_client_initiated(&self) -> bool { |
| let id = self.0; |
| id != 0 && id % 2 == 1 |
| } |
| |
| /// Returns true if this stream ID corresponds to a stream that |
| /// was initiated by the server. |
| pub fn is_server_initiated(&self) -> bool { |
| let id = self.0; |
| id != 0 && id % 2 == 0 |
| } |
| |
| /// Return a new `StreamId` for stream 0. |
| #[inline] |
| pub fn zero() -> StreamId { |
| StreamId::ZERO |
| } |
| |
| /// Returns true if this stream ID is zero. |
| pub fn is_zero(&self) -> bool { |
| self.0 == 0 |
| } |
| |
| /// Returns the next stream ID initiated by the same peer as this stream |
| /// ID, or an error if incrementing this stream ID would overflow the |
| /// maximum. |
| pub fn next_id(&self) -> Result<StreamId, StreamIdOverflow> { |
| let next = self.0 + 2; |
| if next > StreamId::MAX.0 { |
| Err(StreamIdOverflow) |
| } else { |
| Ok(StreamId(next)) |
| } |
| } |
| } |
| |
| impl From<u32> for StreamId { |
| fn from(src: u32) -> Self { |
| assert_eq!(src & STREAM_ID_MASK, 0, "invalid stream ID -- MSB is set"); |
| StreamId(src) |
| } |
| } |
| |
| impl From<StreamId> for u32 { |
| fn from(src: StreamId) -> Self { |
| src.0 |
| } |
| } |
| |
| impl PartialEq<u32> for StreamId { |
| fn eq(&self, other: &u32) -> bool { |
| self.0 == *other |
| } |
| } |