stem-mqtt-proto 0.8.3

MQTT 3.1.1 / 5.0 wire protocol: a pure, runtime-free packet codec (no async, no TLS), shared by stem-mqtt-client and stem-mqtt-broker and usable on embedded targets.
Documentation 
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//! MQTT wire protocol: packet encoding/decoding for both MQTT 3.1.1 and
//! MQTT 5.0.
//!
//! This crate has no networking, async or TLS dependencies: it is a pure,
//! synchronous codec so it can be unit-tested byte-for-byte and reused by the
//! `stem-mqtt-client` connection loop, the `stem-mqtt-broker`, and firmware on
//! embedded targets that bring their own transport.

#[cfg(doctest)]
#[doc = include_str!("../README.md")]
struct ReadmeDoctests;

pub mod ack;
pub mod connect;
pub mod error;
mod macros;
pub mod packet;
pub mod properties;
pub mod publish;
pub mod subscribe;
pub mod support;
pub mod topic;
pub mod varint;

pub use ack::*;
pub use connect::*;
pub use error::{MqttError, MqttResult};
pub use packet::*;
pub use properties::*;
pub use publish::*;
pub use subscribe::*;

/// The MQTT protocol version negotiated for a connection.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum MqttVersion {
    /// MQTT 3.1.1 (protocol level 4).
    V311,
    /// MQTT 5.0 (protocol level 5).
    V5,
}

impl MqttVersion {
    pub fn protocol_level(self) -> u8 {
        match self {
            MqttVersion::V311 => 4,
            MqttVersion::V5 => 5,
        }
    }

    pub fn from_protocol_level(level: u8) -> Option<Self> {
        match level {
            4 => Some(MqttVersion::V311),
            5 => Some(MqttVersion::V5),
            _ => None,
        }
    }

    pub fn is_v5(self) -> bool {
        matches!(self, MqttVersion::V5)
    }
}

/// MQTT Quality of Service level.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum QoS {
    /// QoS 0 — fire and forget, no acknowledgement.
    AtMostOnce,
    /// QoS 1 — acknowledged delivery, may be duplicated.
    AtLeastOnce,
    /// QoS 2 — exactly-once delivery via a four-part handshake.
    ExactlyOnce,
}

impl QoS {
    pub fn as_u8(self) -> u8 {
        match self {
            QoS::AtMostOnce => 0,
            QoS::AtLeastOnce => 1,
            QoS::ExactlyOnce => 2,
        }
    }

    pub fn from_u8(v: u8) -> Option<Self> {
        match v {
            0 => Some(QoS::AtMostOnce),
            1 => Some(QoS::AtLeastOnce),
            2 => Some(QoS::ExactlyOnce),
            _ => None,
        }
    }
}