promesa.exec.csp — funcool/promesa 11.0.678

A core.async analogous implementation of channels that uses promises instead of callbacks for all operations and are intended to be used as-is (using blocking operations) in go-blocks backed by virtual threads.

There are no macro transformations, go blocks are just alias for the promesa.core/vthread macro that launches an virtual thread.

This code is based on the same ideas as core.async but the implementation is written from scratch, for make it more simplier (and smaller, because it does not intend to solve all the corner cases that core.async does right now).

This code is implemented in CLJS for make available the channel abstraction to the CLJS, but the main use case for this ns is targeted to the JVM, where you will be able to take advantage of virtual threads and seamless blocking operations on channels.

EXPERIMENTAL API

*executor* clj/s

A defalt executor for channel callback dispatching

<! clj

(<! port)

(<! port timeout-duration)

(<! port timeout-duration timeout-value)

A convenience alias for take!.

>! clj

(>! port val)

(>! port val timeout-duration)

(>! port val timeout-duration timeout-value)

A convenience alias for put!.

alts clj/s

(alts ports & {:as opts})

Completes at most one of several operations on channel. Receives a vector of operations and optional keyword options.

A channel operation is defined as a vector of 2 elements for take, and 3 elements for put. Unless the :priority option is true and if more than one channel operation is ready, a non-deterministic choice will be made.

Returns a promise instance that will be resolved when a single operation is ready to a vector [val channel] where val is return value of the operation and channel identifies the channel where the the operation is succeeded.

alts! clj

(alts! ports & {:as opts})

A blocking variant of alts.

chan clj/s

(chan & {:keys [buf xf exh exc] :or {exh channel/close-with-exception}})

Creates a new channel instance, it optionally accepts buffer, transducer and error handler. If buffer is an integer, it will be used as initial capacity for the expanding buffer.

chan? clj/s

(chan? o)

Returns true if o is instance of Channel or satisfies IChannel protocol.

close! clj/s

(close! port)

(close! port cause)

Close the channel.

close-with-exception clj/s

(close-with-exception ch cause)

A channel exception handler that closes the channel with the cause if an exception is raised in the transducer.

closed? clj/s

(closed? port)

Returns true if channel is closed.

dropping-buffer clj/s

(dropping-buffer n)

Create a dropping buffer instance.

expanding-buffer clj/s

(expanding-buffer n)

Create a fixed size (but expanding) buffer instance.

This buffer is used by default if you pass an integer as buffer on channel constructor.

fixed-buffer clj/s

(fixed-buffer n)

Create a fixed size buffer instance.

go clj/s macro

(go & body)

Schedules the body to be executed asychronously, potentially using virtual thread if available (a normal thread will be used in other case, determined by executor dynamic var). Returns a promise instance that resolves with the return value when the asynchronous block finishes.

Forwards dynamic bindings.

go-chan clj/s macro

(go-chan & body)

A convencience go macro version that returns a channel instead of a promise instance, has the same semantics as go macro.

go-loop clj/s macro

(go-loop bindings & body)

A convencience helper macro that combines go + loop.

mult clj/s

(mult & {:as opts})

Creates an instance of multiplexer.

A multiplexer instance acts like a write-only channel what enables a broadcast-like (instead of a queue-like) behavior. Channels containing copies of this multiplexer can be attached using tap! and dettached with untap!.

Each item is forwarded to all attached channels in parallel and synchronously; use buffers to prevent slow taps from holding up the multiplexer.

If there are no taps, all received items will be dropped. Closed channels will be automatically removed from multiplexer.

Do not creates vthreads (or threads).

mult* clj/s

(mult* ch)

(mult* ch close?)

Create a multiplexer with an externally provided channel. From now, you can use the external channel or the multiplexer instace to put values in because multiplexer implements the IWriteChannel protocol.

Optionally accepts close? argument, that determines if the channel will be closed when close! is called on multiplexer o not.

offer! clj/s

(offer! port val)

Puts a val into channel if it's possible to do so immediately. Returns a resolved promise with true if the operation succeeded. Never blocks.

once-buffer clj/s

(once-buffer)

Create a once buffer instance.

onto-chan! clj/s

(onto-chan! ch coll)

(onto-chan! ch coll close?)

Puts the contents of coll into the supplied channel.

By default the channel will be closed after the items are copied, but can be determined by the close? parameter. Returns a promise that will be resolved with nil once the items are copied.

pipe clj/s

(pipe from to)

(pipe from to close?)

Takes elements from the from channel and supplies them to the to channel. By default, the to channel will be closed when the from channel closes, but can be determined by the close? parameter. Will stop consuming the from channel if the to channel closes.

pipeline clj

(pipeline & {:keys [typ in out f close? n exh] :or {typ :thread close? true}})

Create a processing pipeline with the ability to specify the process function proc-fn, the type of concurrency primitive to use (:thread or :vthread) and the parallelism.

The proc-fn should be a function that takes the value and the result channel; the result channel should be closed once the processing unit is finished.

By default the output channel is closed when pipeline is terminated, but it can be specified by user using the :close? parameter.

Returns a promise which will be resolved once the pipeline is terminated.

Example:

(def inp (sp/chan)) (def out (sp/chan (map inc)))

(sp/pipeline :typ :vthread :close? true :n 10 :in inp :out out :f proc-fn)

(sp/go (loop [] (when-let [val (sp/<! out)] (prn "RES:" val) (recur))) (prn "RES: END"))

(p/await! (sp/onto-chan! inp ["1" "2" "3" "4"] true))

Internally, uses 2 vthreads for pipeline internals processing.

EXPERIMENTAL: API subject to be changed or removed in future releases.

poll! clj/s

(poll! port)

Takes a val from port if it's possible to do so immediatelly. Returns a resolved promise with the value if succeeded, nil otherwise.

put clj/s

(put port val)

(put port val timeout-duration)

(put port val timeout-duration timeout-value)

Schedules a put operation on the channel. Returns a promise instance that will resolve to: false if channel is closed, true if put is succeed. If channel has buffer, it will return immediatelly with resolved promise.

Optionally accepts a timeout-duration and timeout-value. The timeout-duration can be a long or Duration instance measured in milliseconds.

put! clj

(put! port val)

(put! port val timeout-duration)

(put! port val timeout-duration timeout-value)

A blocking version of put.

sliding-buffer clj/s

(sliding-buffer n)

Create a sliding buffer instance.

take clj/s

(take port)

(take port timeout-duration)

(take port timeout-duration timeout-value)

Schedules a take operation on the channel. Returns a promise instance that will resolve to: nil if channel is closed, obj if value is found. If channel has non-empty buffer the take operation will succeed immediatelly with resolved promise.

Optionally accepts a timeout-duration and timeout-value. The timeout-duration can be a long or Duration instance measured in milliseconds.

take! clj

(take! port)

(take! port timeout-duration)

(take! port timeout-duration timeout-value)

Blocking version of take.

tap! clj/s

(tap! mult ch)

(tap! mult ch close?)

Copies the multiplexer source onto the provided channel.

thread-chan clj/s macro

(thread-chan & body)

A convencience thread macro version that returns a channel instead of a promise instance.

throw-uncaught clj/s

(throw-uncaught ch cause)

A channel exception handler that throws the exception to the default uncaught exception handler.

timeout clj/s

(timeout ms)

Returns a promise that will be resolved in the specified timeout. The default scheduler will be used.

timeout-chan clj/s

(timeout-chan ms)

(timeout-chan scheduler ms)

Returns a channel that will be closed in the specified timeout. The default scheduler will be used. You can provide your own as optional first argument.

untap! clj/s

(untap! mult ch)

Disconnects a channel from the multiplexer.