Module toad::step

The Step trait

The Step trait defines a powerful but simple API that allows the CoAP runtime to be a composition of “steps,” stored as a type-level linked list.

e.g.

Gather Ingredients
  -> Mix Wet Ingredients
  -> Mix Dry Ingredients
  -> Mix Everything together
  -> Pour into cake tin
  -> Bake

as Steps:

Bake<PourIntoCakeTin<MixEverything<MixDry<MixWet<GatherIngredients<Empty>>>>>>

Capabilities

• May read system state (time, dgram on the socket, platform configuration)
  • platform::Snapshot
• May maintain internal state
  • Must be managed with interior mutability (e.g. RwLock)
• May perform side effects
  • platform::Effect provides deterministic API for logging and sending bytes over the wire
• May participate in client role, server role, or both roles in the CoAP runtime
  • step::Step::poll_req (server)
  • step::Step::poll_resp (client)
• May modify messages before they are sent
  • step::Step::before_message_sent
• May be notified whenever a message is sent
  • step::Step::on_message_sent
• May yield data to the outer step
  • step::Step::PollReq
  • step::Step::PollResp

Determinism

Steps provided by this crate will never perform any observable IO, aside from managing their own internal state and appending to the list of effects provided in the poll_req/poll_resp fns.

Logging

Steps provided by this crate will never log to any streams directly, and will provide them via platform::Effect::Log.

It is strongly recommended that log::Level::Warn and log::Level::Error messages are not ignored.

Re-exports

• pub use log;
• pub use log;

Modules

• ack
  ACK incoming messages
• buffer_responses
  Ensure clients only receive relevant response
• handle_acks
  Ignore ACKs we don’t recognize
• observe
  Observe
• parse
  Parse messages from dgrams
• provision_ids
  Assign message Ids to those with Id(0)
• provision_tokens
  Assign message tokens to those with Token(0)
• retry
  Buffer & resend messages until they get a sufficient response
• runtime
  Standard set of Steps
• set_standard_options
  Set standard options on outbound messages

Macros

• _try
  Specialized ? operator for use in step bodies, allowing early-exit for Result, Option<Result> and Option<nb::Result>.
• exec_inner_step
  Macro to execute inner steps, converting the Option<nb::Result<T, E>> to Option<T> by returning the inner step’s Errors & WouldBlock
• log
  Issue an Effect::Log

Traits

• Error
  An error that can be returned by a Step.
• Step
  A step in the message-handling CoAP runtime.

Type Definitions

• StepOutput