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githubcrates-iodocs-rs


Mpstthree (also called MultiCrusty) is a library to write and check communication protocols based on Multiparty Session Types.

Currently this library is geared toward use with Scribble and New Scribble for full checking of protocols.


Example

Assume a simple protocol involving 3 participants, A, B and C. A sends a payload to B, then receives another payload from C. Upon receiving the payload from A, B sends a payload to C. This protocol can be written as A!B.A?C.B!C.0. To implement this example, first, get the right components from the library.

Here is the full working example, detailed afterwards:

// Used for the functions that will process the protocol
use std::boxed::Box;
use std::error::Error;

// Used for creating the types
use mpstthree::binary::struct_trait::{end::End, recv::Recv, send::Send};
use mpstthree::meshedchannels::MeshedChannels;

// Used for creating the stack and the name of each role
use mpstthree::role::a::RoleA;
use mpstthree::role::b::RoleB;
use mpstthree::role::c::RoleC;
use mpstthree::role::end::RoleEnd;

// Used inside the functions which process the protocol for receiving one payload
use mpstthree::functionmpst::recv::recv_mpst_a_from_c;
use mpstthree::functionmpst::recv::recv_mpst_b_from_a;
use mpstthree::functionmpst::recv::recv_mpst_c_from_b;

// Used inside the functions which process the protocol for sending one payload
use mpstthree::functionmpst::send::send_mpst_a_to_b;
use mpstthree::functionmpst::send::send_mpst_b_to_c;
use mpstthree::functionmpst::send::send_mpst_c_to_a;

// Used inside the functions which process the protocol for closing the connexion
use mpstthree::functionmpst::close::close_mpst;

// Used for connecting all the roles, represented as MeshedChannels, together
use mpstthree::functionmpst::fork::fork_mpst;

// Creating the binary sessions
// for A
type AtoB<N> = Send<N, End>;
type AtoC<N> = Recv<N, End>;

// for B
type BtoA<N> = Recv<N, End>;
type BtoC<N> = Send<N, End>;

// for C
type CtoA<N> = Send<N, End>;
type CtoB<N> = Recv<N, End>;

// Stacks
// for A
type StackA = RoleB<RoleC<RoleEnd>>;
// for B
type StackB = RoleA<RoleC<RoleEnd>>;
// for C
type StackC = RoleA<RoleB<RoleEnd>>;

// Creating the MP sessions
// for A
type EndpointA<N> = MeshedChannels<AtoB<N>, AtoC<N>, StackA, RoleA<RoleEnd>>;
// for B
type EndpointB<N> = MeshedChannels<BtoA<N>, BtoC<N>, StackB, RoleB<RoleEnd>>;
// for C
type EndpointC<N> = MeshedChannels<CtoA<N>, CtoB<N>, StackC, RoleC<RoleEnd>>;

// Function to process Endpoint of A
fn endpoint_a(s: EndpointA<i32>) -> Result<(), Box<dyn Error>> {
    let s = send_mpst_a_to_b(1, s);
    let (_x, s) = recv_mpst_a_from_c(s)?;

    close_mpst(s)
}

// Function to process Endpoint of B
fn endpoint_b(s: EndpointB<i32>) -> Result<(), Box<dyn Error>> {
    let (_x, s) = recv_mpst_b_from_a(s)?;
    let s = send_mpst_b_to_c(2, s);

    close_mpst(s)
}

// Function to process Endpoint of C
fn endpoint_c(s: EndpointC<i32>) -> Result<(), Box<dyn Error>> {
    let s = send_mpst_c_to_a(3, s);
    let (_x, s) = recv_mpst_c_from_b(s)?;

    close_mpst(s)
}

// Fork all endpoints
fn main() {
    let (thread_a, thread_b, thread_c) = fork_mpst(endpoint_a, endpoint_b, endpoint_c);

    thread_a.join().unwrap();
    thread_b.join().unwrap();
    thread_c.join().unwrap();
}

Here is the full description. First, you import the correct functions and types.

// Used for the functions that will process the protocol
use std::boxed::Box;
use std::error::Error;

// Used for creating the types
use mpstthree::binary::struct_trait::{end::End, recv::Recv, send::Send};
use mpstthree::meshedchannels::MeshedChannels;

// Used for creating the stack and the name of each role
use mpstthree::role::a::RoleA;
use mpstthree::role::b::RoleB;
use mpstthree::role::c::RoleC;
use mpstthree::role::end::RoleEnd;

// Used inside the functions which process the protocol for receiving one payload
use mpstthree::functionmpst::recv::recv_mpst_a_from_c;
use mpstthree::functionmpst::recv::recv_mpst_b_from_a;
use mpstthree::functionmpst::recv::recv_mpst_c_from_b;

// Used inside the functions which process the protocol for sending one payload
use mpstthree::functionmpst::send::send_mpst_a_to_b;
use mpstthree::functionmpst::send::send_mpst_b_to_c;
use mpstthree::functionmpst::send::send_mpst_c_to_a;

// Used inside the functions which process the protocol for closing the connexion
use mpstthree::functionmpst::close::close_mpst;

// Used for connecting all the roles, represented as MeshedChannels, together
use mpstthree::functionmpst::fork::fork_mpst;

Then, you have to create the binary session types defining the interactions for each pair of participants. Note that each created type can be reused as many time as needed. For our example, we create several times the same binary session type for clarity, but we could use only two of those types for the whole protocol instead.

// Creating the binary sessions
// for A
type AtoB<N> = Send<N, End>;
type AtoC<N> = Recv<N, End>;

// for B
type BtoA<N> = Recv<N, End>;
type BtoC<N> = Send<N, End>;

// for C
type CtoA<N> = Send<N, End>;
type CtoB<N> = Recv<N, End>;

Add the stacks which give the correct order of the operations for each participant.

// Stacks
// for A
type StackA = RoleB<RoleC<RoleEnd>>;
// for B
type StackB = RoleA<RoleC<RoleEnd>>;
// for C
type StackC = RoleA<RoleB<RoleEnd>>;

You can now encapsulate those binary session types and stacks into MeshedChannels for each participant. We also add the names of the related roles.

// Creating the MP sessions
// for A
type EndpointA<N> = MeshedChannels<AtoB<N>, AtoC<N>, StackA, RoleA<RoleEnd>>;
// for B
type EndpointB<N> = MeshedChannels<BtoA<N>, BtoC<N>, StackB, RoleB<RoleEnd>>;
// for C
type EndpointC<N> = MeshedChannels<CtoA<N>, CtoB<N>, StackC, RoleC<RoleEnd>>;

To run the protocol, we need to detail the behaviour of the participants with functions that input the Endpoints defined above.

// Function to process Endpoint of A
fn simple_triple_endpoint_a(s: EndpointA<i32>) -> Result<(), Box<dyn Error>> {
    let s = send_mpst_a_to_b(1, s);
    let (x, s) = recv_mpst_a_from_c(s)?;

    close_mpst(s)
}

// Function to process Endpoint of B
fn simple_triple_endpoint_b(s: EndpointB<i32>) -> Result<(), Box<dyn Error>> {
    let (x, s) = recv_mpst_b_from_a(s)?;
    let s = send_mpst_b_to_c(2, s);

    close_mpst(s)
}

// Function to process Endpoint of C
fn simple_triple_endpoint_c(s: EndpointC<i32>) -> Result<(), Box<dyn Error>> {
    let s = send_mpst_c_to_a(3, s);
    let (x, s) = recv_mpst_c_from_b(s)?;

    close_mpst(s)
}

In the end, you have to link/fork the threads, related to the functions above, together with fork_mpst(). Do not forget to unwrap() the returned threads.

// Fork all endpoints
fn main() {
    let (thread_a, thread_b, thread_c) = fork_mpst(
        endpoint_a,
        endpoint_b,
        endpoint_c,
    );

    thread_a.join().unwrap();
    thread_b.join().unwrap();
    thread_c.join().unwrap();
}

The different features available are:

  1. default: default features, for implementing the basic example above.
  2. macros_simple: feature for implementing protocols with three participants, whatever are their name.
  3. macros_multiple: feature for implementing protocols with any number of participants. Contains macros_simple.
  4. baking: feature for implementing protocols with any number of participants and using associated functions instead of functions. Contains macros_multiple.
  5. transport_tcp: feature containing primitives for communicating with TCP. Requires openssl, pkg-config and libssl-dev installed on your machine.
  6. transport_udp: feature containing primitives for communicating with UDP. Requires openssl, pkg-config and libssl-dev installed on your machine.
  7. transport_http: feature containing primitives for communicating with HTTP/HTTPS. Requires openssl, pkg-config and libssl-dev installed on your machine.
  8. transport: feature containing transport_tcp, transport_udp and transport_http.
  9. checking: feature for the top-down approach. Needs the KMC tool.
  10. full: feature containing checking, baking and transport.

Modules

This module contains the macro for attempting to run a block of code.

bakingbaking

This module contains the macros for creating the different structures and associated functions for any number of participants to simplify send/recv.

The slightly modified binary session type library.

checkingchecking

This module contains the macros and the functions for checking whether a protocol is well written or not, according to a bottom-up method.

This module contains all the functions that are used for consuming MeshedChannels.

interleavedinterleaved

This module contains all the macros that are used for the interleaved sessions.

macros_multiplemacros_multiple

This module contains all the macros that are used for the parametrisation on the number of participants.

macros_simplemacros_simple

This module contains all the macros that are used for the parametrisation on the name of the participants.

The main structure used for representing a participant, also named a party, within a protocol.

The main trait used for representing an ordering or the name of a participant.

The module for interacting with different modes of transport such as HTTP or TCP

Macros

Try to run the first block of code and, upon error, run the second block of code. Each step in the block of code must return Result<Ok(_), Err(e)>.

broadcast_cancelmacros_multiple

Indefinitely loops to check all sessions if there is a Cancel signal and broadcast if it present. Will also close correctly if a Stop signal is received.

Create a new SessionMST structure, new roles and the baking environment. This macro creates the related fork_mpst function.

Create a new SessionMST structuren, new roles and the baking environment, with send functions that can fail. Also create the macros needed for choosing branches. Each macro is linked to a role X and are called as followed: choose_mpst_x_to_all!( s, # the current session enum_1::variant_1, # the first branch for the first passive role enum_2::variant_2, # the first branch for the second passive role … enum_n::variant_n, # the first branch for the n-th passive role ). This macro does NOT create the related fork_mpst function to avoid conflicts for interleaved functions.

Create a new SessionMST structure, new roles and the baking environment, with send functions that can fail. This macro creates the related fork_mpst function.

Create a new SessionMST structuren, new roles and the baking environment. Also create the macros needed for choosing branches. Each macro is linked to a role X and are called as followed: choose_mpst_x_to_all!( s, # the current session enum_1::variant_1, # the first branch for the first passive role enum_2::variant_2, # the first branch for the second passive role … enum_n::variant_n, # the first branch for the n-th passive role ) This macro creates the related fork_mpst function.

Create a new SessionMST structuren, new roles and the baking environment, with send functions that can fail. Also create the macros needed for choosing branches. Each macro is linked to a role X and are called as followed: choose_mpst_x_to_all!( s, # the current session enum_1::variant_1, # the first branch for the first passive role enum_2::variant_2, # the first branch for the second passive role … enum_n::variant_n, # the first branch for the n-th passive role ) This macro creates the related fork_mpst function.

Creates the structure MeshedChannels create_meshedchannels, the close_mpst and fork_mpst_multi.

Creates the structure MeshedChannels create_meshedchannels, the close_mpst_cancel and fork_mpst_multi functions to be used with more than 2 participants. It checks the send sides of the channels along the recv sides.

The macro that allows to create digraphs from each endpoint, along with enum if needed. You can also provide the name of a file for running the KMC tool and checking the properties of the provided protocol: it will return the minimal k according to this tool if it exists, and None if k is bigger than 50 or does not exist.

Choose between many different sessions wrapped in an enum

Choose, for A, among two different sessions

Choose, for B, among two different sessions

Choose, for C, among two different sessions

Create a macro that simplifies the usage of choose_mpst_multi_to_all.

Choose among different sessions that are provided, may fail because of a canceled session. Need to exclude the first participant

choose_mpst_multi_http_to_alltransport or transport_http

Choose among different sessions that are provided.

Choose among different sessions that are provided.

choose_mpst_to_allmacros_simple

Choose among two different sessions. Must be used with MeshedChannels.

choose_tcptransport or transport_tcp

Choose between many different sessions wrapped in an enum

choose_udptransport or transport_udp

Choose between many different sessions wrapped in an enum

close_mpstmacros_multiple

Create the close function to be used with more than 3 participants.

close_mpst_cancelmacros_multiple

Create the close function to be used with more than 3 participants. It is used for checking the send sides upon closing.

Create the close function to be used with more than 3 participants.

Create a new broadcast Role and its dual. A broadcast Role is used for sending a choice. Its dual is used for receving this choice.

Create a new broadcast Role and its dual. A broadcast Role is used for sending a choice. Its dual is used for receving this choice. When a name X is given, the Roles created are

Create the ChooseMpst function to send a Choose left branch from the first role to the others. Must be used with MeshedChannels.

Create the ChooseMpst function to send a Choose left branch from the second role to the others. Must be used with MeshedChannels.

Create the ChooseMpst function to send a Choose left branch from the third role to the others. Must be used with MeshedChannels.

Create the two ChooseMpst functions to send a Choose on each branch to be used with more than 3 participants. Only works when active role is the last one.

Create the ChooseMpst function to send a Choose left branch to be used with more than 3 participants. Only works when active role is the last one.

Create the ChooseMpst function to send a Choose right branch to be used with more than 3 participants. Only works when active role is the last one.

Create the ChooseMpst function to send a Choose right branch from the first role to the others. Must be used with MeshedChannels.

Create the ChooseMpst function to send a Choose right branch from the second role to the others. Must be used with MeshedChannels.

Create the ChooseMpst function to send a Choose right branch from the third role to the others. Must be used with MeshedChannels.

Create the ChooseMpst type to be used with more than 3 participants.

Create choose fuunctions, to choose among different sessions that are provided.

Create choose fuunctions, to choose among different sessions that are provided.

create_meshedchannelsmacros_multiple

Creates a MeshedChannels for more than 3 participants.

Create multiple new broadcast Role and its dual. A broadcast Role is used for sending a choice. Its dual is used for receving this choice.

Create multiple new broadcast Role and its dual. A broadcast Role is used for sending a choice. Its dual is used for receving this choice. When a name X is given, the Roles created are

Create multiple new Role and its dual.

Create multiple new Role and its dual. When a name X is given, the Roles created are

create_normal_rolemacros_simple

Create a new Role and its dual.

Create a new Role and its dual. When a name X is given, the Roles created are

Create an offer function to recv on the first binary session from any kind of role. Must be used with MeshedChannels.

Create an offer function to recv on the second binary session from any kind of role. Must be used with MeshedChannels.

Creates an OfferMpst function to receive an offer on a given binary session type of a MeshedChannels.

Create the OfferMpst type to be used with more than 3 participants.

create_recv_http_sessiontransport or transport_http

Creates a recv function to receive from a simple role on a given binary session type of a MeshedChannels.

create_recv_http_session_bundletransport or transport_http

Creates multiple recv functions to receive from a simple role on a given binary session type of a MeshedChannels.

Creates a recv function to receive from a simple role on a given binary session type of a MeshedChannels.

Create a recv function to recv on the first binary session from any kind of role. Must be used with MeshedChannels.

Create a recv function to recv on the second binary session from any kind of role. Must be used with MeshedChannels.

Creates multiple recv functions to receive from a simple role on a given binary session type of a MeshedChannels.

Creates a send function to send from a given binary session type of a MeshedChannels with more than 3 participants. Checks if the first binary session has a “cancel” signal and panic if yes. The send function will try to send and panic if not possible (canceled session).

Creates multiple send functions to send from a given binary session type of a MeshedChannels with more than 3 participants.

create_send_http_sessiontransport or transport_http

Creates a send function to send from a given binary session type of a MeshedChannels with more than 3 participants.

Creates a send function to send from a given binary session type of a MeshedChannels with more than 3 participants. The send function will try to send and panic if not possible (canceled session).

Creates multiple send functions to send from a given binary session type of a MeshedChannels with more than 3 participants.

create_send_mpst_http_bundletransport or transport_http

Creates multiple send functions to send from a given binary session type of a MeshedChannels with more than 3 participants.

Creates a send function to send from a given binary session type of a MeshedChannels with more than 3 participants.

Create a send function to send on the first binary session from any kind of role. Must be used with MeshedChannels.

Create a send function to send on the second binary session from any kind of role. Must be used with MeshedChannels.

Creates multiple send functions to send from a given binary session type of a MeshedChannels with more than 3 participants.

fork_mpst_multimacros_multiple

Creates the fork function to be used with more than 3 participants.

Offer a choice between many different sessions wrapped in an enum

offer_cancel_mpstmacros_multiple

Offer a choice and send the session to the broadcaster

offer_http_mpstmacros_multiple

Offer a choice between many different sessions wrapped in an enum. Used with http functions

offer_mpstmacros_multiple

Offer a choice between many different sessions wrapped in an enum

Offer a choice to A from B between many different sessions wrapped in an enum

Offer a choice to A from C between many different sessions wrapped in an enum

Offer a choice to B from A between many different sessions wrapped in an enum

Offer a choice to B from C between many different sessions wrapped in an enum

Offer a choice to C from A between many different sessions wrapped in an enum

Offer a choice to C from B between many different sessions wrapped in an enum

offer_tcptransport or transport_tcp

Offer a choice between many different sessions wrapped in an enum.

offer_udptransport or transport_udp

Offer a choice between many different sessions wrapped in an enum.

send_cancelmacros_multiple

Creates a function that will cancel a session and send a Cancel signal to the broadcasting role.