26269c329e
The new predicates are `progress-evt?' `thread-cell-values?', `prefab-key?', `semaphore-peek-evt?', and `channel-put-evt?'. These were used internally, and now they appear in contract error messages.
60 lines
2.1 KiB
Racket
60 lines
2.1 KiB
Racket
#lang scribble/doc
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@(require "mz.rkt")
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@title[#:tag "channel"]{Channels}
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A @deftech{channel} both synchronizes a pair of threads and passes a
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value from one to the other. Channels are synchronous; both the sender
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and the receiver must block until the (atomic) transaction is
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complete. Multiple senders and receivers can access a channel at once,
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but a single sender and receiver is selected for each transaction.
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Channel synchronization is @defterm{fair}: if a thread is blocked on a
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channel and transaction opportunities for the channel occur infinitely
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often, then the thread eventually participates in a transaction.
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For buffered asynchronous channels, see @secref["async-channel"].
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@defproc[(channel? [v any/c]) boolean?]{
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Returns @racket[#t] if @racket[v] is a @tech{channel},
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@racket[#f] otherwise.}
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@defproc[(make-channel) channel?]{
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Creates and returns a new channel. The channel can be used with
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@racket[channel-get], with @racket[channel-try-get], or as a
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@tech{synchronizable event} (see @secref["sync"]) to receive a value
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through the channel. The channel can be used with @racket[channel-put]
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or through the result of @racket[channel-put-evt] to send a value
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through the channel.}
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@defproc[(channel-get [ch channel?]) any]{
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Blocks until a sender is ready to provide a value through
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@racket[ch]. The result is the sent value.}
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@defproc[(channel-try-get [ch channel?]) any]{
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Receives and returns a value from @racket[ch] if a sender is
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immediately ready, otherwise returns @racket[#f].}
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@defproc[(channel-put [ch channel?] [v any/c]) void?]{
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Blocks until a receiver is ready to accept the value @racket[v]
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through @racket[ch].}
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@defproc[(channel-put-evt [ch channel?] [v any/c]) channel-put-evt?]{
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Returns a fresh @tech{synchronizable event} for use with
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@racket[sync]. The event is ready when @racket[(channel-put ch v)]
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would not block, and the event's synchronization result is the event
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itself.}
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@defproc[(channel-put-evt? [v any/c]) boolean?]{
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Returns @racket[#t] if @racket[v] is a channel-put event produced by
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@racket[channel-put-evt], @racket[#f] otherwise.}
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