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//! Data structures representing the mux protocol. //! //! Package mux implements a generic RPC multiplexer with a rich protocol. //! Mux is itself encoding independent, so it is meant to use as the //! transport for other RPC systems (eg. thrift). In OSI terminology, it //! is a pure session layer. extern crate byteorder; mod dtab; pub mod codec; pub mod types; pub use dtab::*; use std::time::Duration; /// Headers for a `Treq`. pub type Headers = Vec<(u8, Vec<u8>)>; /// Contexts of dispatch and init messages. pub type Contexts = Vec<(Vec<u8>, Vec<u8>)>; /// Maximum value of a mux Tag pub const MAX_TAG: u32 = (1 << 23) - 1; /// Id number and end flag for message frames. /// /// Every message has an associated `Tag` following the frame length and frame /// type on the wire. The frame id represents the stream identifier and is limited /// to 23 bits of precision while bit 24 signals if the message stream is ending. /// This only applies to the `Tdispatch` and `Rdispatch` frames. #[derive(PartialEq, Eq, Debug, Clone)] pub struct Tag { /// Signal that this frame is the end of the stream of fragments. /// /// Currently, only Tdispatch and Rdispatch messages may be split into an /// ordered sequence of fragments. TdispatchError message ends a Tdispatch /// sequence and an Rerr ends an Rdispatch sequence. pub end: bool, /// Identification number associated with this stream. pub id: u32, } /// Representation of an entire mux packet. #[derive(Debug, PartialEq, Eq)] pub struct Message { /// Identification and termination information about the associated stream. pub tag: Tag, /// Payload of the message. The length is determined from the payload. pub frame: MessageFrame, } /// Type wrapper for the mux packet representations. #[derive(Debug, PartialEq, Eq)] pub enum MessageFrame { Treq(Treq), Rreq(Rmsg), Tdispatch(Tdispatch), Rdispatch(Rdispatch), Tinit(Init), Rinit(Init), Tdrain, Rdrain, Tping, Rping, Tdiscarded(Tdiscarded), Tlease(Tlease), Rerr(Rerr), } // Structs that model the message frame types of the mux protocol /// Representation of the mux `Treq` types. #[derive(PartialEq, Eq, Debug)] pub struct Treq { /// Request headers. pub headers: Headers, /// Body of the request. pub body: Vec<u8>, } /// Representation of a mux `Rreq` and `Rdispatch` message body. #[derive(PartialEq, Eq, Debug)] pub enum Rmsg { /// Successful response containing a body. Ok(Vec<u8>), /// Response failed. The `String` describes the error. Error(String), /// Negative acknowledgment. The `String` describes the reason. Nack(String), } /// Representation of a mux `Tdispatch` frame. #[derive(PartialEq, Eq, Debug)] pub struct Tdispatch { /// Context information associated with this request. pub contexts: Contexts, /// Destination of this request. pub dest: String, /// Table of delegation rules for 'rewriting' the destination. pub dtab: Dtab, /// Message payload. pub body: Vec<u8>, } /// Representation of a mux `Rdispatch` frame. #[derive(PartialEq, Eq, Debug)] pub struct Rdispatch { /// Context information associated with this request. pub contexts: Contexts, /// Response of the dispatch request. pub msg: Rmsg, } /// Representation of a mux `Tinit` and `Rinit` frame. /// /// `Tinit` and `Rinit` frames are used for negotiation of the mux protocol /// version and behavior. A `Tinit` is typically sent by the client at the /// beginning of the session. Until a `Rinit` is received the client cannot /// issue any more T messages. Once the `Rinit` is received, the session state /// is considered reset. The version return in `Rinit` is the accepted protocol /// version and may be lower than that of the issued `Tinit`. #[derive(PartialEq, Eq, Debug)] pub struct Init { /// Mux protocol version. pub version: u16, /// Additional negotiation related information. pub headers: Contexts, } /// Representation of a mux `Tdiscarded` frame. /// /// A `Tdiscarded` frame is a marker message alerting the server that the /// client has discarded the `Tdispatch` issued with the associated id. This /// does not free the server from the obligation of replying to the origional /// request. #[derive(PartialEq, Eq, Debug)] pub struct Tdiscarded { /// Stream id of the discarded `Tdispatch` request. pub id: u32, /// Reason for discarding the request. pub msg: String, } /// Representation of a mux `Tlease` frame. /// /// A `Tlease` is a marker message that is issued to alert the client that /// it has been allocated resources for a specific duration. In the abscence /// of a `Tlease`, the client assumes it holds an indefinate lease. /// Adhering to the lease is optional but the server may reject requests or /// operate at a degraded capacity under and expired lease. #[derive(PartialEq, Eq, Debug)] pub struct Tlease { /// `Duration` of the lease allocated to the client. pub duration: Duration, } /// Representation of a mux `Rerr` frame. /// /// An `Rerr` is sent from the server in the even that the server failed to /// interpret or act on a request T message. #[derive(PartialEq, Eq, Debug)] pub struct Rerr { /// Description of the error. pub msg: String, } impl Tag { #[inline] /// Construct a new `Tag`. pub fn new(end: bool, id: u32) -> Tag { assert!(id <= MAX_TAG); Tag { end: end, id: id, } } } impl MessageFrame { /// Get the `i8` value coresponding the a `MessageFrame`. pub fn frame_id(&self) -> i8 { match *self { MessageFrame::Treq(_) => types::TREQ, MessageFrame::Rreq(_) => types::RREQ, MessageFrame::Tdispatch(_) => types::TDISPATCH, MessageFrame::Rdispatch(_) => types::RDISPATCH, MessageFrame::Tinit(_) => types::TINIT, MessageFrame::Rinit(_) => types::RINIT, MessageFrame::Tdrain => types::TDRAIN, MessageFrame::Rdrain => types::RDRAIN, MessageFrame::Tping => types::TPING, MessageFrame::Rping => types::RPING, MessageFrame::Tdiscarded(_) => types::TDISCARDED, MessageFrame::Tlease(_) => types::TLEASE, MessageFrame::Rerr(_) => types::RERR, } } } impl Tdispatch { /// Construct a new `Tdispatch` frame with the provided destination and body. pub fn new(dest: String, body: Vec<u8>) -> Tdispatch { Tdispatch { contexts: Vec::new(), dest: dest, dtab: Dtab::new(), body: body, } } }