41 lines
61 KiB
HTML
41 lines
61 KiB
HTML
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><meta name="viewport" content="width=device-width, initial-scale=0.8"/><title>11.2.4 Buffered Asynchronous Channels</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="icons.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">►</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x">The Racket Reference</a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="model.html" class="tocviewlink" data-pltdoc="x">Language Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewlink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="tocviewselflink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr><tr><td align="right">12 </td><td><a href="Macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">13 </td><td><a href="input-and-output.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr><tr><td align="right">15 </td><td><a href="os.html" class="tocviewlink" data-pltdoc="x">Operating System</a></td></tr><tr><td align="right">16 </td><td><a href="memory.html" class="tocviewlink" data-pltdoc="x">Memory Management</a></td></tr><tr><td align="right">17 </td><td><a href="unsafe.html" class="tocviewlink" data-pltdoc="x">Unsafe Oper
|
||
|
|
values so that a send operation does not wait on a receive operation.</p><p>In addition to its use with procedures that are specific to
|
||
|
|
asynchronous channels, an asynchronous channel can be used as a
|
||
|
|
<a href="sync.html#%28tech._synchronizable._event%29" class="techoutside" data-pltdoc="x"><span class="techinside">synchronizable event</span></a> (see <a href="sync.html" data-pltdoc="x">Events</a>). An asynchronous
|
||
|
|
channel is <a href="sync.html#%28tech._ready._for._synchronization%29" class="techoutside" data-pltdoc="x"><span class="techinside">ready for synchronization</span></a> when
|
||
|
|
<span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-get%29%29" class="RktValLink" data-pltdoc="x">async-channel-get</a></span> would not block; the asynchronous channel’s
|
||
|
|
<a href="sync.html#%28tech._synchronization._result%29" class="techoutside" data-pltdoc="x"><span class="techinside">synchronization result</span></a> is the same as the
|
||
|
|
<span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-get%29%29" class="RktValLink" data-pltdoc="x">async-channel-get</a></span> result.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._async-channel~3f))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">async-channel?</a></span></span><span class="hspace"> </span><span class="RktVar">v</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._boolean~3f%29%29" class="RktValLink" data-pltdoc="x">boolean?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns <span class="RktVal">#t</span> if <span class="RktVar">v</span> is an asynchronous channel,
|
||
|
|
<span class="RktVal">#f</span> otherwise.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._make-async-channel))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._make-async-channel%29%29" class="RktValDef RktValLink" data-pltdoc="x">make-async-channel</a></span></span><span class="hspace"> </span><span class="RktOpt">[</span><span class="RktVar">limit</span><span class="RktOpt">]</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">limit</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="number-types.html#%28def._%28%28quote._~23~25kernel%29._exact-positive-integer~3f%29%29" class="RktValLink" data-pltdoc="x">exact-positive-integer?</a></span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span><span class="hspace"> </span>=<span class="hspace"> </span><span class="RktVal">#f</span></td></tr></table></blockquote></div><div class="SIntrapara">Returns an asynchronous channel with a buffer limit of <span class="RktVar">limit</span>
|
||
|
|
items. A get operation blocks when the channel is empty, and a put
|
||
|
|
operation blocks when the channel has <span class="RktVar">limit</span> items already.
|
||
|
|
If <span class="RktVar">limit</span> is <span class="RktVal">#f</span>, the channel buffer has no limit (so
|
||
|
|
a put never blocks).</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._async-channel-get))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-get%29%29" class="RktValDef RktValLink" data-pltdoc="x">async-channel-get</a></span></span><span class="hspace"> </span><span class="RktVar">ach</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">ach</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Blocks until at least one value is available in <span class="RktVar">ach</span>, and then
|
||
|
|
returns the first of the values that were put into
|
||
|
|
<span class="RktSym">async-channel</span>.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._async-channel-try-get))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-try-get%29%29" class="RktValDef RktValLink" data-pltdoc="x">async-channel-try-get</a></span></span><span class="hspace"> </span><span class="RktVar">ach</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">ach</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">If at least one value is immediately available in <span class="RktVar">ach</span>,
|
||
|
|
returns the first of the values that were put into <span class="RktVar">ach</span>. If
|
||
|
|
<span class="RktSym">async-channel</span> is empty, the result is <span class="RktVal">#f</span>.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._async-channel-put))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-put%29%29" class="RktValDef RktValLink" data-pltdoc="x">async-channel-put</a></span></span><span class="hspace"> </span><span class="RktVar">ach</span><span class="hspace"> </span><span class="RktVar">v</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="void.html#%28def._%28%28quote._~23~25kernel%29._void~3f%29%29" class="RktValLink" data-pltdoc="x">void?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">ach</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Puts <span class="RktVar">v</span> into <span class="RktVar">ach</span>, blocking if <span class="RktVar">ach</span>’s buffer
|
||
|
|
is full until space is available.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._async-channel-put-evt))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-put-evt%29%29" class="RktValDef RktValLink" data-pltdoc="x">async-channel-put-evt</a></span></span><span class="hspace"> </span><span class="RktVar">ach</span><span class="hspace"> </span><span class="RktVar">v</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="sync.html#%28def._%28%28quote._~23~25kernel%29._evt~3f%29%29" class="RktValLink" data-pltdoc="x">evt?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">ach</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns a <a href="sync.html#%28tech._synchronizable._event%29" class="techoutside" data-pltdoc="x"><span class="techinside">synchronizable event</span></a> that is <a href="sync.html#%28tech._ready._for._synchronization%29" class="techoutside" data-pltdoc="x"><span class="techinside">ready for
|
||
|
|
synchronization</span></a> when <span class="RktPn">(</span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-put%29%29" class="RktValLink" data-pltdoc="x">async-channel-put</a></span><span class="stt"> </span><span class="RktVar">ach</span><span class="stt"> </span><span class="RktVar">v</span><span class="RktPn">)</span> would return
|
||
|
|
a value (i.e., when the channel holds fewer values already than its
|
||
|
|
limit); the <a href="sync.html#%28tech._synchronization._result%29" class="techoutside" data-pltdoc="x"><span class="techinside">synchronization result</span></a> of a asynchronous channel-put event is the asynchronous channel-put event itself.</div></p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">server</span><span class="hspace"> </span><span class="RktSym">input-channel</span><span class="hspace"> </span><span class="RktSym">output-channel</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="threads.html#%28def._%28%28quote._~23~25kernel%29._thread%29%29" class="RktValLink" data-pltdoc="x">thread</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">get</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-get%29%29" class="RktValLink" data-pltdoc="x">async-channel-get</a></span><span class="hspace"> </span><span class="RktSym">input-channel</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">put</span><span class="hspace"> </span><span class="RktSym">x</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-put%29%29" class="RktValLink" data-pltdoc="x">async-channel-put</a></span><span class="hspace"> </span><span class="RktSym">output-channel</span><span class="hspace"> </span><span class="RktSym">x</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">do-large-computation</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote.
|
||
|
|
retrieved from the channel must match <span class="RktVar">c</span>.</div></p><p>If the <span class="RktVar">c</span> argument is a flat contract or a chaperone contract, then the
|
||
|
|
result will be a chaperone contract. Otherwise, the result will be an
|
||
|
|
impersonator contract.</p><p>When an <span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel%2Fc%29%29" class="RktValLink" data-pltdoc="x">async-channel/c</a></span> contract is applied to an asynchronous channel,
|
||
|
|
the result is not <span class="RktSym"><a href="Equality.html#%28def._%28%28quote._~23~25kernel%29._eq~3f%29%29" class="RktValLink" data-pltdoc="x">eq?</a></span> to the input. The result will be either a
|
||
|
|
<a href="chaperones.html#%28tech._chaperone%29" class="techoutside" data-pltdoc="x"><span class="techinside">chaperone</span></a> or <a href="chaperones.html#%28tech._impersonator%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator</span></a> of the input depending on the type of
|
||
|
|
contract.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><table cellspacing="0" cellpadding="0" class="prototype RForeground"><tr><td valign="top"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._impersonate-async-channel))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._impersonate-async-channel%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-async-channel</a></span></span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">channel</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">get-proc</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">put-proc</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">prop</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktMeta">...</span><span class="RktPn">)</span></td><td valign="top"><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span><span class="hspace"> </span><span class="RktSym"><a href="chaperones.html#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">channel</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">get-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktSym"><a href="function-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._-~3e%29%29" class="RktStxLink" data-pltdoc="x"><span class="nobreak">-></span></a></span><span class="RktPn"> .</span><span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib.
|
||
|
|
<span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-get%29%29" class="RktValLink" data-pltdoc="x">async-channel-get</a></span> and <span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-put%29%29" class="RktValLink" data-pltdoc="x">async-channel-put</a></span> operations.</div></p><p>The <span class="RktVar">get-proc</span> must accept the value that <span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-get%29%29" class="RktValLink" data-pltdoc="x">async-channel-get</a></span>
|
||
|
|
produces on <span class="RktVar">channel</span>; it must produce a replacement value, which is the
|
||
|
|
result of the get operation on the impersonator.</p><p>The <span class="RktVar">put-proc</span> must accept the value passed to <span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-put%29%29" class="RktValLink" data-pltdoc="x">async-channel-put</a></span>
|
||
|
|
called on <span class="RktVar">channel</span>; it must produce a replacement value, which is the
|
||
|
|
value passed to the put procedure called on the original channel.</p><p>The <span class="RktVar">get-proc</span> and <span class="RktVar">put-proc</span> procedures are called for all
|
||
|
|
operations that get or put values from the channel, not just
|
||
|
|
<span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-get%29%29" class="RktValLink" data-pltdoc="x">async-channel-get</a></span> and <span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel-put%29%29" class="RktValLink" data-pltdoc="x">async-channel-put</a></span>.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments to
|
||
|
|
<span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._impersonate-async-channel%29%29" class="RktValLink" data-pltdoc="x">impersonate-async-channel</a></span> must be odd) add
|
||
|
|
<a href="chaperones.html#%28tech._impersonator._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator properties</span></a> or override <a href="chaperones.html#%28tech._impersonator._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator property</span></a> values
|
||
|
|
of <span class="RktVar">channel</span>.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><table cellspacing="0" cellpadding="0" class="prototype RForeground"><tr><td valign="top"><span class="RktPn">(</span><a name="(def._((lib._racket/async-channel..rkt)._chaperone-async-channel))"></a><span title="Provided from: racket/async-channel | Package: base"><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._chaperone-async-channel%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-async-channel</a></span></span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">channel</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">get-proc</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">put-proc</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">prop</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktMeta">...</span><span class="RktPn">)</span></td><td valign="top"><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span><span class="hspace"> </span><span class="RktSym"><a href="chaperones.html#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">channel</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="async-channel.html#%28def._%28%28lib._racket%2Fasync-channel..rkt%29._async-channel~3f%29%29" class="RktValLink" data-pltdoc="x">async-channel?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">get-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktSym"><a href="function-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._-~3e%29%29" class="RktStxLink" data-pltdoc="x"><span class="nobreak">-></span></a></span><span class="RktPn"> .</span><span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#
|
||
|
|
must produce the same value or a chaperone of the original value, and
|
||
|
|
<span class="RktVar">put-proc</span> must produce the same value or a chaperone of the original
|
||
|
|
value.</div></p><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" id="searchbox" type="text" tabindex="1" placeholder="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "8.6", "../");"/></form> <a href="https://docs.racket-lang.org/index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("8.6");">top</a><span class="tocsettoggle"> <a href="javascript:void(0);" title="show/hide table of contents" onclick="TocsetToggle();">contents</a></span></span><span class="navright"> <a href="semaphore.html" title="backward to "11.2.3 Semaphores"" data-pltdoc="x">← prev</a> <a href="all-sync.html" title="up to "11.2 Synchronization"" data-pltdoc="x">up</a> <a href="thread-local-storage.html" title="forward to "11.3 Thread-Local Storage"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
|