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{{About-distinguish|software interprocess communication|Channel (communications)|I/O channel}}
In computing, a '''channel''' is a model for [[interprocess communication]] and [[synchronization]] via [[message passing]]. A message may be sent over a channel, and another process or thread is able to receive messages sent over a channel it has a [[reference (computer science)|reference]] to, as a [[stream (computing)|stream]]. Different implementations of channels may be buffered or not, and either synchronous or asynchronous.
== {{Proper name|libthread}} channels ==▼
▲== libthread channels ==
The [[Multithreading (computer architecture)|multithreading]] library, [[libthread]], which was first created for the operating system [[Plan 9 from Bell Labs|Plan 9]], offers inter-thread communication based on fixed-size channels.
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=== Lua Love2D ===
The [[Löve (game engine)|Love2D]] library which
-- A string containing code which will be interpreted by a function such as loadstring(),
-- but on the C side to start a native thread.
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=== XMOS XC ===
The [[XMOS]] programming language [[XC (programming language)|XC]] provides a primitive type "
In this example, two hardware threads are started on the XMOS, running the two lines in the "par" block. The first line transmits the number 42 through the channel while the second waits until it is received and sets the value of x. The XC language also allows asynchronous receiving on channels through a select statement.
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=== Go ===
This snippet of [[Go (programming language)|Go]] code performs similarly to the XC code. First the channel c is created, then a [[goroutine]] is spawned which sends 42 through the channel. When the number is put in the channel x is set to 42. Go allows channels to buffer contents, as well as non blocking receiving through the use of a select block.<ref>{{Cite web|url=https://golang.org/doc/effective_go.html#channels|title = Effective Go - the Go Programming Language}}</ref>
<syntaxhighlight lang="go">
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=== Rust ===
[[Rust (programming language)|Rust]] provides asynchronous channels for communication between threads. Channels allow a unidirectional flow of information between two
<syntaxhighlight lang="rust">
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== Applications ==
In addition to their fundamental use for interprocess communication, channels can be used as a primitive to implement various other concurrent programming constructs which can be realized as streams. For example, channels can be used to construct [[futures and promises]], where a future is a one-element channel, and a promise is a process that sends to the channel, fulfilling the future.<ref>"[https://sites.google.com/site/gopatterns/concurrency/futures Futures] {{Webarchive|url=https://web.archive.org/web/20201204060631/https://sites.google.com/site/gopatterns/concurrency/futures |date=2020-12-04 }}", ''[https://sites.google.com/site/gopatterns Go Language Patterns] {{Webarchive|url=https://web.archive.org/web/20201111222255/https://sites.google.com/site/gopatterns |date=2020-11-11 }}''</ref> Similarly, [[iterator]]s can be constructed directly from channels.<ref>"[https://sites.google.com/site/gopatterns/object-oriented/iterators Iterators] {{Webarchive|url=https://web.archive.org/web/20201015115025/https://sites.google.com/site/gopatterns/object-oriented/iterators |date=2020-10-15 }}", ''[https://sites.google.com/site/gopatterns Go Language Patterns] {{Webarchive|url=https://web.archive.org/web/20201111222255/https://sites.google.com/site/gopatterns |date=2020-11-11 }}''</ref>
== List of implementations ==
* For Scala:
** CSO -- Communicating Scala Objects<ref>{{Citation |last=Sufrin |first=Bernard |title=ThreadCSO |date=2021-07-13 |url=https://github.com/sufrin/ThreadCSO/blob/5f8ef6eebdfd8e001e45af18fea52fec36ff7ddd/Lectures/cso-paper.pdf |access-date=2023-02-17}}</ref> is a complete DSL for channel-based communication and concurrency whose semantic primitives are generalizations of the OCCAM primitives. CSO has been used since 2007 in the teaching of concurrent programming, and relevant lectures can be found with the ThreadCSO implementation.<ref>{{Citation |last=Sufrin |first=Bernard |title=ThreadCSO |date=2021-07-13 |url=https://github.com/sufrin/ThreadCSO |access-date=2023-02-17}}</ref>
▲=== List of non-standard, library based implementations of channels ===
* For C++:
** [[stlab]]<ref>{{cite web|url=https://stlab.cc/libraries/concurrency|title=stlab is the ongoing work of what was Adobe's Software Technology Lab. The Adobe Source Libraries (ASL), Platform Libraries, and new stlab libraries are hosted on github.|date=2021-01-31}}</ref> This implementation supports splits, and different merge and zip operations. Different executors can be attached to the individual nodes.
* For Rust:
** [[Tokio (software)|Tokio]]
== References ==
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