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;; Copyright (c) Rich Hickey and contributors. All rights reserved.
;; The use and distribution terms for this software are covered by the
;; Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;; which can be found in the file epl-v10.html at the root of this distribution.
;; By using this software in any fashion, you are agreeing to be bound by
;; the terms of this license.
;; You must not remove this notice, or any other, from this software.
(ns clojure.core.async
"Facilities for async programming and communication.
Set Java system property `clojure.core.async.go-checking` to true
to validate go blocks do not invoke core.async blocking operations.
Property is read once, at namespace load time. Recommended for use
primarily during development. Invalid blocking calls will throw in
go block threads - use Thread.setDefaultUncaughtExceptionHandler()
to catch and handle.
Use the Java system property `clojure.core.async.executor-factory`
to specify a function that will provide ExecutorServices for
application-wide use by core.async in lieu of its defaults. The
property value should name a fully qualified var. The function
will be passed a keyword indicating the context of use of the
executor, and should return either an ExecutorService, or nil to
use the default. Results per keyword will be cached and used for
the remainder of the application. Possible context arguments are:
:io - used in async/io-thread, for :io workloads in flow/process,
and for dispatch handling if no explicit dispatch handler is
provided (see below)
:mixed - used by async/thread and for :mixed workloads in
flow/process
:compute - used for :compute workloads in flow/process
:core-async-dispatch - used for completion fn handling (e.g. in put!
and take!, as well as go block IOC thunk processing) throughout
core.async. If not supplied the ExecutorService for :io will be
used instead.
The set of contexts may grow in the future so the function should
return nil for unexpected contexts."
(:refer-clojure :exclude [reduce transduce into merge map take partition
partition-by bounded-count])
(:require [clojure.core.async.impl.protocols :as impl]
[clojure.core.async.impl.channels :as channels]
[clojure.core.async.impl.buffers :as buffers]
[clojure.core.async.impl.timers :as timers]
[clojure.core.async.impl.dispatch :as dispatch]
[clojure.core.async.impl.ioc-macros :as ioc]
clojure.core.async.impl.go ;; TODO: make conditional
[clojure.core.async.impl.mutex :as mutex]
)
(:import [java.util.concurrent.atomic AtomicLong]
[java.util.concurrent.locks Lock]
[java.util.concurrent ThreadLocalRandom]
[java.util Arrays ArrayList]))
(alias 'core 'clojure.core)
(set! *warn-on-reflection* false)
(defn fn-handler
([f]
(fn-handler f true))
([f blockable]
(reify
Lock
(lock [_])
(unlock [_])
impl/Handler
(active? [_] true)
(blockable? [_] blockable)
(lock-id [_] 0)
(commit [_] f))))
(defn- on-caller [f]
(with-meta f {:on-caller? true}))
(defn buffer
"Returns a fixed buffer of size n. When full, puts will block/park."
[n]
(assert (pos? n) "fixed buffers must have size > 0")
(buffers/fixed-buffer n))
(defn dropping-buffer
"Returns a buffer of size n. When full, puts will complete but
val will be dropped (no transfer)."
[n]
(buffers/dropping-buffer n))
(defn sliding-buffer
"Returns a buffer of size n. When full, puts will complete, and be
buffered, but oldest elements in buffer will be dropped (not
transferred)."
[n]
(buffers/sliding-buffer n))
(defn unblocking-buffer?
"Returns true if a channel created with buff will never block. That is to say,
puts into this buffer will never cause the buffer to be full. "
[buff]
(extends? impl/UnblockingBuffer (class buff)))
(defn chan
"Creates a channel with an optional buffer, an optional transducer
(like (map f), (filter p) etc or a composition thereof), and an
optional exception-handler. If buf-or-n is a number, will create
and use a fixed buffer of that size. If a transducer is supplied a
buffer must be specified. ex-handler must be a fn of one argument -
if an exception occurs during transformation it will be called with
the Throwable as an argument, and any non-nil return value will be
placed in the channel."
([] (chan nil))
([buf-or-n] (chan buf-or-n nil))
([buf-or-n xform] (chan buf-or-n xform nil))
([buf-or-n xform ex-handler]
(when xform (assert buf-or-n "buffer must be supplied when transducer is"))
(channels/chan (if (number? buf-or-n) (buffer buf-or-n) buf-or-n) xform ex-handler)))
(defn promise-chan
"Creates a promise channel with an optional transducer, and an optional
exception-handler. A promise channel can take exactly one value that consumers
will receive. Once full, puts complete but val is dropped (no transfer).
Consumers will block until either a value is placed in the channel or the
channel is closed, then return the value (or nil) forever. See chan for the
semantics of xform and ex-handler."
([] (promise-chan nil))
([xform] (promise-chan xform nil))
([xform ex-handler]
(chan (buffers/promise-buffer) xform ex-handler)))
(defn timeout
"Returns a channel that will close after msecs"
[^long msecs]
(timers/timeout msecs))
(defmacro defblockingop
[op doc arglist & body]
(let [as (mapv #(list 'quote %) arglist)]
`(def ~(with-meta op {:arglists `(list ~as) :doc doc})
(if (Boolean/getBoolean "clojure.core.async.go-checking")
(fn ~arglist
(dispatch/check-blocking-in-dispatch)
~@body)
(fn ~arglist
~@body)))))
(defblockingop !!
"puts a val into port. nil values are not allowed. Will block if no
buffer space is available. Returns true unless port is already closed.
Not intended for use in direct or transitive calls from (go ...) blocks.
Use the clojure.core.async.go-checking flag to detect invalid use (see
namespace docs)."
[port val]
(let [p (promise)
ret (impl/put! port val (fn-handler (on-caller #(deliver p %))))]
(if ret
@ret
(deref p))))
(defn >!
"puts a val into port. nil values are not allowed. Must be called
inside a (go ...) block. Will park if no buffer space is available.
Returns true unless port is already closed."
[port val]
(assert nil ">! used not in (go ...) block"))
(defn- nop [_])
(def ^:private fhnop (fn-handler nop))
(defn put!
"Asynchronously puts a val into port, calling fn1 (if supplied) when
complete, passing false iff port is already closed. nil values are
not allowed. If on-caller? (default true) is true, and the put is
immediately accepted, will call fn1 on calling thread.
fn1 may be run in a fixed-size dispatch thread pool and should not
perform blocking IO, including core.async blocking ops (those that
end in !!).
Returns true unless port is already closed."
([port val]
(if-let [ret (impl/put! port val fhnop)]
@ret
true))
([port val fn1] (put! port val fn1 true))
([port val fn1 on-caller?]
(if-let [retb (impl/put! port val (fn-handler (if on-caller? (on-caller fn1) fn1)))]
(let [ret @retb]
(if on-caller?
(fn1 ret)
(dispatch/run #(fn1 ret)))
ret)
true)))
(defn close!
"Closes a channel. The channel will no longer accept any puts (they
will be ignored). Data in the channel remains available for taking, until
exhausted, after which takes will return nil. If there are any
pending takes, they will be dispatched with nil. Closing a closed
channel is a no-op. Returns nil.
Logically closing happens after all puts have been delivered. Therefore, any
blocked or parked puts will remain blocked/parked until a taker releases them."
[chan]
(impl/close! chan))
(defonce ^:private ^AtomicLong id-gen (AtomicLong.))
(defn- random-array
[n]
(let [rand (ThreadLocalRandom/current)
a (int-array n)]
(loop [i 1]
(if (= i n)
a
(let [j (.nextInt rand (inc i))]
(aset a i (aget a j))
(aset a j i)
(recur (inc i)))))))
(defn- alt-flag []
(let [^Lock m (mutex/mutex)
flag (atom true)
id (.incrementAndGet id-gen)]
(reify
Lock
(lock [_] (.lock m))
(unlock [_] (.unlock m))
impl/Handler
(active? [_] @flag)
(blockable? [_] true)
(lock-id [_] id)
(commit [_]
(reset! flag nil)
true))))
(defn- alt-handler [^Lock flag cb]
(reify
Lock
(lock [_] (.lock flag))
(unlock [_] (.unlock flag))
impl/Handler
(active? [_] (impl/active? flag))
(blockable? [_] true)
(lock-id [_] (impl/lock-id flag))
(commit [_]
(impl/commit flag)
cb)))
(defn do-alts
"returns derefable [val port] if immediate, nil if enqueued"
[fret ports opts]
(assert (pos? (count ports)) "alts must have at least one channel operation")
(let [flag (alt-flag)
ports (vec ports) ;; ensure vector for indexed nth
n (count ports)
_ (loop [i 0] ;; check for invalid write op
(when (< i n)
(let [port (nth ports i)]
(when (vector? port)
(assert (some? (port 1)) "can't put nil on channel")))
(recur (unchecked-inc i))))
^ints idxs (random-array n)
priority (:priority opts)
ret
(loop [i 0]
(when (< i n)
(let [idx (if priority i (aget idxs i))
port (nth ports idx)
wport (when (vector? port) (port 0))
vbox (if wport
(let [val (port 1)]
(impl/put! wport val (alt-handler flag #(fret [% wport]))))
(impl/take! port (alt-handler flag #(fret [% port]))))]
(if vbox
(channels/box [@vbox (or wport port)])
(recur (inc i))))))]
(or
ret
(when (contains? opts :default)
(.lock ^Lock flag)
(let [got (and (impl/active? flag) (impl/commit flag))]
(.unlock ^Lock flag)
(when got
(channels/box [(:default opts) :default])))))))
(defblockingop alts!!
"Like alts!, except takes will be made as if by !!, will block until completed.
Not intended for use in direct or transitive calls from (go ...) blocks.
Use the clojure.core.async.go-checking flag to detect invalid use (see
namespace docs)."
[ports & opts]
(let [p (promise)
ret (do-alts (on-caller (^:once fn* [v] (deliver p v))) ports (apply hash-map opts))]
(if ret
@ret
(deref p))))
(defn alts!
"Completes at most one of several channel operations. Must be called
inside a (go ...) block. ports is a vector of channel endpoints,
which can be either a channel to take from or a vector of
[channel-to-put-to val-to-put], in any combination. Takes will be
made as if by !. Unless
the :priority option is true, if more than one port operation is
ready a non-deterministic choice will be made. If no operation is
ready and a :default value is supplied, [default-val :default] will
be returned, otherwise alts! will park until the first operation to
become ready completes. Returns [val port] of the completed
operation, where val is the value taken for takes, and a
boolean (true unless already closed, as per put!) for puts.
opts are passed as :key val ... Supported options:
:default val - the value to use if none of the operations are immediately ready
:priority true - (default nil) when true, the operations will be tried in order.
Note: there is no guarantee that the port exps or val exprs will be
used, nor in what order should they be, so they should not be
depended upon for side effects."
[ports & {:as opts}]
(assert nil "alts! used not in (go ...) block"))
(defn do-alt [alts clauses]
(assert (even? (count clauses)) "unbalanced clauses")
(let [clauses (core/partition 2 clauses)
opt? #(keyword? (first %))
opts (filter opt? clauses)
clauses (remove opt? clauses)
[clauses bindings]
(core/reduce
(fn [[clauses bindings] [ports expr]]
(let [ports (if (vector? ports) ports [ports])
[ports bindings]
(core/reduce
(fn [[ports bindings] port]
(if (vector? port)
(let [[port val] port
gp (gensym)
gv (gensym)]
[(conj ports [gp gv]) (conj bindings [gp port] [gv val])])
(let [gp (gensym)]
[(conj ports gp) (conj bindings [gp port])])))
[[] bindings] ports)]
[(conj clauses [ports expr]) bindings]))
[[] []] clauses)
gch (gensym "ch")
gret (gensym "ret")]
`(let [~@(mapcat identity bindings)
[val# ~gch :as ~gret] (~alts [~@(apply concat (core/map first clauses))] ~@(apply concat opts))]
(cond
~@(mapcat (fn [[ports expr]]
[`(or ~@(core/map (fn [port]
`(= ~gch ~(if (vector? port) (first port) port)))
ports))
(if (and (seq? expr) (vector? (first expr)))
`(let [~(first expr) ~gret] ~@(rest expr))
expr)])
clauses)
(= ~gch :default) val#))))
(defmacro alt!!
"Like alt!, except as if by alts!!, will block until completed, and
not intended for use in (go ...) blocks."
[& clauses]
(do-alt `alts!! clauses))
(defmacro alt!
"Makes a single choice between one of several channel operations,
as if by alts!, returning the value of the result expr corresponding
to the operation completed. Must be called inside a (go ...) block.
Each clause takes the form of:
channel-op[s] result-expr
where channel-ops is one of:
take-port - a single port to take
[take-port | [put-port put-val] ...] - a vector of ports as per alts!
:default | :priority - an option for alts!
and result-expr is either a list beginning with a vector, whereupon that
vector will be treated as a binding for the [val port] return of the
operation, else any other expression.
(alt!
[c t] ([val ch] (foo ch val))
x ([v] v)
[[out val]] :wrote
:default 42)
Each option may appear at most once. The choice and parking
characteristics are those of alts!."
[& clauses]
(do-alt `alts! clauses))
(defn ioc-alts! [state cont-block ports & {:as opts}]
(ioc/aset-all! state ioc/STATE-IDX cont-block)
(when-let [cb (clojure.core.async/do-alts
(^:once fn* [val]
(ioc/aset-all! state ioc/VALUE-IDX val)
(ioc/run-state-machine-wrapped state))
ports
opts)]
(ioc/aset-all! state ioc/VALUE-IDX @cb)
:recur))
(defn offer!
"Puts a val into port if it's possible to do so immediately.
nil values are not allowed. Never blocks. Returns true if offer succeeds."
[port val]
(let [ret (impl/put! port val (fn-handler nop false))]
(when ret @ret)))
(defn poll!
"Takes a val from port if it's possible to do so immediately.
Never blocks. Returns value if successful, nil otherwise."
[port]
(let [ret (impl/take! port (fn-handler nop false))]
(when ret @ret)))
(defmacro go
"Asynchronously executes the body, returning immediately to the
calling thread. Additionally, any visible calls to ! and alt!/alts!
channel operations within the body will block (if necessary) by
'parking' the calling thread rather than tying up an OS thread (or
the only JS thread when in ClojureScript). Upon completion of the
operation, the body will be resumed.
go blocks should not (either directly or indirectly) perform operations
that may block indefinitely. Doing so risks depleting the fixed pool of
go block threads, causing all go block processing to stop. This includes
core.async blocking ops (those ending in !!) and other blocking IO.
Returns a channel which will receive the result of the body when
completed"
[& body]
(#'clojure.core.async.impl.go/go-impl &env body))
(defonce ^:private thread-macro-executor nil)
(defn thread-call
"Executes f in another thread, returning immediately to the calling
thread. Returns a channel which will receive the result of calling
f when completed, then close. workload is a keyword that describes
the work performed by f, where:
:io - may do blocking I/O but must not do extended computation
:compute - must not ever block
:mixed - anything else (default)
when workload not supplied, defaults to :mixed"
([f] (thread-call f :mixed))
([f workload]
(let [c (chan 1)
returning-to-chan (fn [bf]
#(try
(when-some [ret (bf)]
(>!! c ret))
(finally (close! c))))]
(-> f bound-fn* returning-to-chan (dispatch/exec workload))
c)))
(defmacro thread
"Executes the body in another thread, returning immediately to the
calling thread. Returns a channel which will receive the result of
the body when completed, then close."
[& body]
`(thread-call (^:once fn* [] ~@body) :mixed))
(defmacro io-thread
"Executes the body in a thread, returning immediately to the calling
thread. The body may do blocking I/O but must not do extended computation.
Returns a channel which will receive the result of the body when completed,
then close."
[& body]
`(thread-call (^:once fn* [] ~@body) :io))
;;;;;;;;;;;;;;;;;;;; ops ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defmacro go-loop
"Like (go (loop ...))"
[bindings & body]
`(go (loop ~bindings ~@body)))
(defn pipe
"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"
([from to] (pipe from to true))
([from to close?]
(go-loop []
(let [v (! to v)
(recur)))))
to))
(defn- pipeline*
([n to xf from close? ex-handler type]
(assert (pos? n))
(let [ex-handler (or ex-handler dispatch/ex-handler)
jobs (chan n)
results (chan n)
process (fn [[v p :as job]]
(if (nil? job)
(do (close! results) nil)
(let [res (chan 1 xf ex-handler)]
(>!! res v)
(close! res)
(put! p res)
true)))
async (fn [[v p :as job]]
(if (nil? job)
(do (close! results) nil)
(let [res (chan 1)]
(xf v res)
(put! p res)
true)))]
(dotimes [_ n]
(case type
(:blocking :compute) (thread
(let [job (! jobs [v p])
(>! results p)
(recur)))))
(go-loop []
(let [p (! to v))
(recur))))
(recur))))))))
;;todo - switch pipe arg order to match these (to/from)
(defn pipeline
"Takes elements from the from channel and supplies them to the to
channel, subject to the transducer xf, with parallelism n. Because
it is parallel, the transducer will be applied independently to each
element, not across elements, and may produce zero or more outputs
per input. Outputs will be returned in order relative to the
inputs. 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. Note this
should be used for computational parallelism. If you have multiple
blocking operations to put in flight, use pipeline-blocking instead,
If you have multiple asynchronous operations to put in flight, use
pipeline-async instead. See chan for semantics of ex-handler."
([n to xf from] (pipeline n to xf from true))
([n to xf from close?] (pipeline n to xf from close? nil))
([n to xf from close? ex-handler] (pipeline* n to xf from close? ex-handler :compute)))
(defn pipeline-blocking
"Like pipeline, for blocking operations."
([n to xf from] (pipeline-blocking n to xf from true))
([n to xf from close?] (pipeline-blocking n to xf from close? nil))
([n to xf from close? ex-handler] (pipeline* n to xf from close? ex-handler :blocking)))
(defn pipeline-async
"Takes elements from the from channel and supplies them to the to
channel, subject to the async function af, with parallelism n. af
must be a function of two arguments, the first an input value and
the second a channel on which to place the result(s). The
presumption is that af will return immediately, having launched some
asynchronous operation whose completion/callback will put results on
the channel, then close! it. Outputs will be returned in order
relative to the inputs. 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. See also pipeline, pipeline-blocking."
([n to af from] (pipeline-async n to af from true))
([n to af from close?] (pipeline* n to af from close? nil :async)))
(defn split
"Takes a predicate and a source channel and returns a vector of two
channels, the first of which will contain the values for which the
predicate returned true, the second those for which it returned
false.
The out channels will be unbuffered by default, or two buf-or-ns can
be supplied. The channels will close after the source channel has
closed."
([p ch] (split p ch nil nil))
([p ch t-buf-or-n f-buf-or-n]
(let [tc (chan t-buf-or-n)
fc (chan f-buf-or-n)]
(go-loop []
(let [v (! (if (p v) tc fc) v)
(recur)))))
[tc fc])))
(defn reduce
"f should be a function of 2 arguments. Returns a channel containing
the single result of applying f to init and the first item from the
channel, then applying f to that result and the 2nd item, etc. If
the channel closes without yielding items, returns init and f is not
called. ch must close before reduce produces a result."
[f init ch]
(go-loop [ret init]
(let [v (! ch (first vs)))
(recur (next vs))
(when close?
(close! ch))))))
(defn to-chan!
"Creates and returns a channel which contains the contents of coll,
closing when exhausted.
If accessing coll might block, use to-chan!! instead"
[coll]
(let [c (bounded-count 100 coll)]
(if (pos? c)
(let [ch (chan c)]
(onto-chan! ch coll)
ch)
(let [ch (chan)]
(close! ch)
ch))))
(defn onto-chan
"Deprecated - use onto-chan! or onto-chan!!"
{:deprecated "1.2"}
([ch coll] (onto-chan! ch coll true))
([ch coll close?] (onto-chan! ch coll close?)))
(defn to-chan
"Deprecated - use to-chan! or to-chan!!"
{:deprecated "1.2"}
[coll]
(to-chan! coll))
(defn onto-chan!!
"Like onto-chan! for use when accessing coll might block,
e.g. a lazy seq of blocking operations"
([ch coll] (onto-chan!! ch coll true))
([ch coll close?]
(thread
(loop [vs (seq coll)]
(if (and vs (>!! ch (first vs)))
(recur (next vs))
(when close?
(close! ch)))))))
(defn to-chan!!
"Like to-chan! for use when accessing coll might block,
e.g. a lazy seq of blocking operations"
[coll]
(let [c (bounded-count 100 coll)]
(if (pos? c)
(let [ch (chan c)]
(onto-chan!! ch coll)
ch)
(let [ch (chan)]
(close! ch)
ch))))
(defprotocol Mux
(muxch* [_]))
(defprotocol Mult
(tap* [m ch close?])
(untap* [m ch])
(untap-all* [m]))
(defn mult
"Creates and returns a mult(iple) of the supplied channel. Channels
containing copies of the channel can be created with 'tap', and
detached with 'untap'.
Each item is distributed to all taps in parallel and synchronously,
i.e. each tap must accept before the next item is distributed. Use
buffering/windowing to prevent slow taps from holding up the mult.
Items received when there are no taps get dropped.
If a tap puts to a closed channel, it will be removed from the mult."
[ch]
(let [cs (atom {}) ;;ch->close?
m (reify
Mux
(muxch* [_] ch)
Mult
(tap* [_ ch close?] (swap! cs assoc ch close?) nil)
(untap* [_ ch] (swap! cs dissoc ch) nil)
(untap-all* [_] (reset! cs {}) nil))
dchan (chan 1)
dctr (atom nil)
done (fn [_] (when (zero? (swap! dctr dec))
(put! dchan true)))]
(go-loop []
(let [val (attrs-map
solo-modes #{:mute :pause}
attrs (conj solo-modes :solo)
solo-mode (atom :mute)
change (chan (sliding-buffer 1))
changed #(put! change true)
pick (fn [attr chs]
(reduce-kv
(fn [ret c v]
(if (attr v)
(conj ret c)
ret))
#{} chs))
calc-state (fn []
(let [chs @cs
mode @solo-mode
solos (pick :solo chs)
pauses (pick :pause chs)]
{:solos solos
:mutes (pick :mute chs)
:reads (conj
(if (and (= mode :pause) (seq solos))
(vec solos)
(vec (remove pauses (keys chs))))
change)}))
m (reify
Mux
(muxch* [_] out)
Mix
(admix* [_ ch] (swap! cs assoc ch {}) (changed))
(unmix* [_ ch] (swap! cs dissoc ch) (changed))
(unmix-all* [_] (reset! cs {}) (changed))
(toggle* [_ state-map] (swap! cs (partial merge-with core/merge) state-map) (changed))
(solo-mode* [_ mode]
(assert (solo-modes mode) (str "mode must be one of: " solo-modes))
(reset! solo-mode mode)
(changed)))]
(go-loop [{:keys [solos mutes reads] :as state} (calc-state)]
(let [[v c] (alts! reads)]
(if (or (nil? v) (= c change))
(do (when (nil? v)
(swap! cs dissoc c))
(recur (calc-state)))
(if (or (solos c)
(and (empty? solos) (not (mutes c))))
(when (>! out v)
(recur state))
(recur state)))))
m))
(defn admix
"Adds ch as an input to the mix"
[mix ch]
(admix* mix ch))
(defn unmix
"Removes ch as an input to the mix"
[mix ch]
(unmix* mix ch))
(defn unmix-all
"removes all inputs from the mix"
[mix]
(unmix-all* mix))
(defn toggle
"Atomically sets the state(s) of one or more channels in a mix. The
state map is a map of channels -> channel-state-map. A
channel-state-map is a map of attrs -> boolean, where attr is one or
more of :mute, :pause or :solo. Any states supplied are merged with
the current state.
Note that channels can be added to a mix via toggle, which can be
used to add channels in a particular (e.g. paused) state."
[mix state-map]
(toggle* mix state-map))
(defn solo-mode
"Sets the solo mode of the mix. mode must be one of :mute or :pause"
[mix mode]
(solo-mode* mix mode))
(defprotocol Pub
(sub* [p v ch close?])
(unsub* [p v ch])
(unsub-all* [p] [p v]))
(defn pub
"Creates and returns a pub(lication) of the supplied channel,
partitioned into topics by the topic-fn. topic-fn will be applied to
each value on the channel and the result will determine the 'topic'
on which that value will be put. Channels can be subscribed to
receive copies of topics using 'sub', and unsubscribed using
'unsub'. Each topic will be handled by an internal mult on a
dedicated channel. By default these internal channels are
unbuffered, but a buf-fn can be supplied which, given a topic,
creates a buffer with desired properties.
Each item is distributed to all subs in parallel and synchronously,
i.e. each sub must accept before the next item is distributed. Use
buffering/windowing to prevent slow subs from holding up the pub.
Items received when there are no matching subs get dropped.
Note that if buf-fns are used then each topic is handled
asynchronously, i.e. if a channel is subscribed to more than one
topic it should not expect them to be interleaved identically with
the source."
([ch topic-fn] (pub ch topic-fn (constantly nil)))
([ch topic-fn buf-fn]
(let [mults (atom {}) ;;topic->mult
ensure-mult (fn [topic]
(or (get @mults topic)
(get (swap! mults
#(if (% topic) % (assoc % topic (mult (chan (buf-fn topic))))))
topic)))
p (reify
Mux
(muxch* [_] ch)
Pub
(sub* [_p topic ch close?]
(let [m (ensure-mult topic)]
(tap m ch close?)))
(unsub* [_p topic ch]
(when-let [m (get @mults topic)]
(untap m ch)))
(unsub-all* [_] (reset! mults {}))
(unsub-all* [_ topic] (swap! mults dissoc topic)))]
(go-loop []
(let [val (! (muxch* m) val)
(swap! mults dissoc topic)))
(recur)))))
p)))
(defn sub
"Subscribes a channel to a topic of a pub.
By default the channel will be closed when the source closes,
but can be determined by the close? parameter."
([p topic ch] (sub p topic ch true))
([p topic ch close?] (sub* p topic ch close?)))
(defn unsub
"Unsubscribes a channel from a topic of a pub"
[p topic ch]
(unsub* p topic ch))
(defn unsub-all
"Unsubscribes all channels from a pub, or a topic of a pub"
([p] (unsub-all* p))
([p topic] (unsub-all* p topic)))
;;; these are down here because they alias core fns, don't want accidents above
(defn map
"Takes a function and a collection of source channels, and returns a
channel which contains the values produced by applying f to the set
of first items taken from each source channel, followed by applying
f to the set of second items from each channel, until any one of the
channels is closed, at which point the output channel will be
closed. The returned channel will be unbuffered by default, or a
buf-or-n can be supplied"
([f chs] (map f chs nil))
([f chs buf-or-n]
(let [chs (vec chs)
out (chan buf-or-n)
cnt (count chs)
rets (object-array cnt)
dchan (chan 1)
dctr (atom nil)
done (mapv (fn [i]
(fn [ret]
(aset rets i ret)
(when (zero? (swap! dctr dec))
(put! dchan (Arrays/copyOf rets cnt)))))
(range cnt))]
(if (zero? cnt)
(close! out)
(go-loop []
(reset! dctr cnt)
(dotimes [i cnt]
(try
(take! (chs i) (done i))
(catch Exception _
(swap! dctr dec))))
(let [rets (! out (apply f rets))
(recur))))))
out)))
(defn merge
"Takes a collection of source channels and returns a channel which
contains all values taken from them. The returned channel will be
unbuffered by default, or a buf-or-n can be supplied. The channel
will close after all the source channels have closed."
([chs] (merge chs nil))
([chs buf-or-n]
(let [out (chan buf-or-n)]
(go-loop [cs (vec chs)]
(if (pos? (count cs))
(let [[v c] (alts! cs)]
(if (nil? v)
(recur (filterv #(not= c %) cs))
(do (>! out v)
(recur cs))))
(close! out)))
out)))
(defn into
"Returns a channel containing the single (collection) result of the
items taken from the channel conjoined to the supplied
collection. ch must close before into produces a result."
[coll ch]
(reduce conj coll ch))
(defn take
"Returns a channel that will return, at most, n items from ch. After n items
have been returned, or ch has been closed, the return channel will close.
The output channel is unbuffered by default, unless buf-or-n is given."
([n ch]
(take n ch nil))
([n ch buf-or-n]
(let [out (chan buf-or-n)]
(go (loop [x 0]
(when (< x n)
(let [v (! out v)
(recur (inc x))))))
(close! out))
out)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; deprecated - do not use ;;;;;;;;;;;;;;;;;;;;;;;;;
(defn map<
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
[f ch]
(reify
impl/Channel
(close! [_] (impl/close! ch))
(closed? [_] (impl/closed? ch))
impl/ReadPort
(take! [_ fn1]
(let [ret
(impl/take! ch
(reify
Lock
(lock [_] (.lock ^Lock fn1))
(unlock [_] (.unlock ^Lock fn1))
impl/Handler
(active? [_] (impl/active? fn1))
(blockable? [_] true)
(lock-id [_] (impl/lock-id fn1))
(commit [_]
(let [f1 (impl/commit fn1)]
#(f1 (if (nil? %) nil (f %)))))))]
(if (and ret (not (nil? @ret)))
(channels/box (f @ret))
ret)))
impl/WritePort
(put! [_ val fn1] (impl/put! ch val fn1))))
(defn map>
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
[f ch]
(reify
impl/Channel
(close! [_] (impl/close! ch))
(closed? [_] (impl/closed? ch))
impl/ReadPort
(take! [_ fn1] (impl/take! ch fn1))
impl/WritePort
(put! [_ val fn1]
(impl/put! ch (f val) fn1))))
(defn filter>
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
[p ch]
(reify
impl/Channel
(close! [_] (impl/close! ch))
(closed? [_] (impl/closed? ch))
impl/ReadPort
(take! [_ fn1] (impl/take! ch fn1))
impl/WritePort
(put! [_ val fn1]
(if (p val)
(impl/put! ch val fn1)
(channels/box (not (impl/closed? ch)))))))
(defn remove>
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
[p ch]
(filter> (complement p) ch))
(defn filter<
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
([p ch] (filter< p ch nil))
([p ch buf-or-n]
(let [out (chan buf-or-n)]
(go-loop []
(let [val (! out val))
(recur)))))
out)))
(defn remove<
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
([p ch] (remove< p ch nil))
([p ch buf-or-n] (filter< (complement p) ch buf-or-n)))
(defn- mapcat* [f in out]
(go-loop []
(let [val (! out v))
(when-not (impl/closed? out)
(recur)))))))
(defn mapcat<
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
([f in] (mapcat< f in nil))
([f in buf-or-n]
(let [out (chan buf-or-n)]
(mapcat* f in out)
out)))
(defn mapcat>
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
([f out] (mapcat> f out nil))
([f out buf-or-n]
(let [in (chan buf-or-n)]
(mapcat* f in out)
in)))
(defn unique
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
([ch]
(unique ch nil))
([ch buf-or-n]
(let [out (chan buf-or-n)]
(go (loop [last nil]
(let [v (! out v)
(recur v))))))
(close! out))
out)))
(defn partition
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
([n ch]
(partition n ch nil))
([n ch buf-or-n]
(let [out (chan buf-or-n)]
(go (loop [arr (make-array Object n)
idx 0]
(let [v (! out (vec arr))
(recur (make-array Object n) 0)))))
(do (when (> idx 0)
(let [narray (make-array Object idx)]
(System/arraycopy arr 0 narray 0 idx)
(>! out (vec narray))))
(close! out))))))
out)))
(defn partition-by
"Deprecated - this function will be removed. Use transducer instead"
{:deprecated "0.1.319.0-6b1aca-alpha", :skip-wiki true}
([f ch]
(partition-by f ch nil))
([f ch buf-or-n]
(let [out (chan buf-or-n)]
(go (loop [lst (ArrayList.)
last ::nothing]
(let [v (! out (vec lst))
(let [new-lst (ArrayList.)]
(.add ^ArrayList new-lst v)
(recur new-lst new-itm)))))
(do (when (> (.size ^ArrayList lst) 0)
(>! out (vec lst)))
(close! out))))))
out)))
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