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<a href='https://github.com/akkartik/mu/blob/master/075channel.mu'>https://github.com/akkartik/mu/blob/master/075channel.mu</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr">  1 </span><span class="Comment"># Mu synchronizes between routines using channels rather than locks, like</span>
<span id="L2" class="LineNr">  2 </span><span class="Comment"># Erlang and Go.</span>
<span id="L3" class="LineNr">  3 </span><span class="Comment">#</span>
<span id="L4" class="LineNr">  4 </span><span class="Comment"># The key property of channels: Writing to a full channel or reading from an</span>
<span id="L5" class="LineNr">  5 </span><span class="Comment"># empty one will put the current routine in 'waiting' state until the</span>
<span id="L6" class="LineNr">  6 </span><span class="Comment"># operation can be completed.</span>
<span id="L7" class="LineNr">  7 </span><span class="Comment">#</span>
<span id="L8" class="LineNr">  8 </span><span class="Comment"># Beware of addresses passed into channels. They can cause race conditions.</span>
<span id="L9" class="LineNr">  9 </span>
<span id="L10" class="LineNr"> 10 </span><span class="muScenario">scenario</span> channel [
<span id="L11" class="LineNr"> 11 </span>  run [
<span id="L12" class="LineNr"> 12 </span>    <span class="Constant">local-scope</span>
<span id="L13" class="LineNr"> 13 </span>    <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">3/capacity</span>
<span id="L14" class="LineNr"> 14 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L15" class="LineNr"> 15 </span>    10:num/<span class="Special">raw</span>, 11:bool/<span class="Special">raw</span>, <a href='075channel.mu.html#L36'>source</a> <span class="Special">&lt;-</span> read <a href='075channel.mu.html#L36'>source</a>
<span id="L16" class="LineNr"> 16 </span>  ]
<span id="L17" class="LineNr"> 17 </span>  memory-should-contain [
<span id="L18" class="LineNr"> 18 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 34</span>
<span id="L19" class="LineNr"> 19 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># read was successful</span>
<span id="L20" class="LineNr"> 20 </span>  ]
<span id="L21" class="LineNr"> 21 </span>]
<span id="L22" class="LineNr"> 22 </span>
<span id="L23" class="LineNr"> 23 </span><span class="muData">container</span> channel:_elem [
<span id="L24" class="LineNr"> 24 </span>  lock:bool  <span class="Comment"># inefficient but simple: serialize all reads as well as writes</span>
<span id="L25" class="LineNr"> 25 </span>  first-full:num  <span class="Comment"># for write</span>
<span id="L26" class="LineNr"> 26 </span>  first-free:num  <span class="Comment"># for read</span>
<span id="L27" class="LineNr"> 27 </span>  <span class="Comment"># A circular buffer contains values from index first-full up to (but not</span>
<span id="L28" class="LineNr"> 28 </span>  <span class="Comment"># including) index first-free. The reader always modifies it at first-full,</span>
<span id="L29" class="LineNr"> 29 </span>  <span class="Comment"># while the writer always modifies it at first-free.</span>
<span id="L30" class="LineNr"> 30 </span>  data:&amp;:@:_elem
<span id="L31" class="LineNr"> 31 </span>]
<span id="L32" class="LineNr"> 32 </span>
<span id="L33" class="LineNr"> 33 </span><span class="Comment"># Since channels have two ends, and since it's an error to use either end from</span>
<span id="L34" class="LineNr"> 34 </span><span class="Comment"># multiple routines, let's distinguish the ends.</span>
<span id="L35" class="LineNr"> 35 </span>
<span id="L36" class="LineNr"> 36 </span><span class="muData">container</span> <a href='075channel.mu.html#L36'>source</a>:_elem [
<span id="L37" class="LineNr"> 37 </span>  chan:&amp;:channel:_elem
<span id="L38" class="LineNr"> 38 </span>]
<span id="L39" class="LineNr"> 39 </span>
<span id="L40" class="LineNr"> 40 </span><span class="muData">container</span> <a href='075channel.mu.html#L40'>sink</a>:_elem [
<span id="L41" class="LineNr"> 41 </span>  chan:&amp;:channel:_elem
<span id="L42" class="LineNr"> 42 </span>]
<span id="L43" class="LineNr"> 43 </span>
<span id="L44" class="LineNr"> 44 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L44'>new-channel</a> <a href='075channel.mu.html#L391'>capacity</a>:num<span class="muRecipe"> -&gt; </span>in:&amp;:<a href='075channel.mu.html#L36'>source</a>:_elem, out:&amp;:<a href='075channel.mu.html#L40'>sink</a>:_elem [
<span id="L45" class="LineNr"> 45 </span>  <span class="Constant">local-scope</span>
<span id="L46" class="LineNr"> 46 </span>  <span class="Constant">load-inputs</span>
<span id="L47" class="LineNr"> 47 </span>  result:&amp;:channel:_elem <span class="Special">&lt;-</span> new <span class="Delimiter">{</span>(channel _elem): type<span class="Delimiter">}</span>
<span id="L48" class="LineNr"> 48 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">first-full:offset</span>,<span class="Constant"> 0</span>
<span id="L49" class="LineNr"> 49 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">first-free:offset</span>,<span class="Constant"> 0</span>
<span id="L50" class="LineNr"> 50 </span>  <a href='075channel.mu.html#L391'>capacity</a> <span class="Special">&lt;-</span> add <a href='075channel.mu.html#L391'>capacity</a>,<span class="Constant"> 1</span>  <span class="Comment"># unused slot for 'full?' below</span>
<span id="L51" class="LineNr"> 51 </span>  data:&amp;:@:_elem <span class="Special">&lt;-</span> new <span class="Constant">_elem:type</span>, <a href='075channel.mu.html#L391'>capacity</a>
<span id="L52" class="LineNr"> 52 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">data:offset</span>, data
<span id="L53" class="LineNr"> 53 </span>  in <span class="Special">&lt;-</span> new <span class="Delimiter">{</span>(source _elem): type<span class="Delimiter">}</span>
<span id="L54" class="LineNr"> 54 </span>  *in <span class="Special">&lt;-</span> put *in, <span class="Constant">chan:offset</span>, result
<span id="L55" class="LineNr"> 55 </span>  out <span class="Special">&lt;-</span> new <span class="Delimiter">{</span>(sink _elem): type<span class="Delimiter">}</span>
<span id="L56" class="LineNr"> 56 </span>  *out <span class="Special">&lt;-</span> put *out, <span class="Constant">chan:offset</span>, result
<span id="L57" class="LineNr"> 57 </span>]
<span id="L58" class="LineNr"> 58 </span>
<span id="L59" class="LineNr"> 59 </span><span class="Comment"># write a value to a channel</span>
<span id="L60" class="LineNr"> 60 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L60'>write</a> out:&amp;:<a href='075channel.mu.html#L40'>sink</a>:_elem, val:_elem<span class="muRecipe"> -&gt; </span>out:&amp;:<a href='075channel.mu.html#L40'>sink</a>:_elem [
<span id="L61" class="LineNr"> 61 </span>  <span class="Constant">local-scope</span>
<span id="L62" class="LineNr"> 62 </span>  <span class="Constant">load-inputs</span>
<span id="L63" class="LineNr"> 63 </span>  assert out, <span class="Constant">[write to null channel]</span>
<span id="L64" class="LineNr"> 64 </span>  chan:&amp;:channel:_elem <span class="Special">&lt;-</span> get *out, <span class="Constant">chan:offset</span>
<span id="L65" class="LineNr"> 65 </span><span class="Constant">  <a href='075channel.mu.html#L65'>&lt;channel-write-initial&gt;</a></span>
<span id="L66" class="LineNr"> 66 </span>  <span class="Comment"># block until lock is acquired AND queue has room</span>
<span id="L67" class="LineNr"> 67 </span>  lock:location <span class="Special">&lt;-</span> get-location *chan, <span class="Constant">lock:offset</span>
<span id="L68" class="LineNr"> 68 </span><span class="CommentedCode">#?   $print [write], 10/newline</span>
<span id="L69" class="LineNr"> 69 </span>  <span class="Delimiter">{</span>
<span id="L70" class="LineNr"> 70 </span><span class="CommentedCode">#?     $print [trying to acquire lock for writing], 10/newline</span>
<span id="L71" class="LineNr"> 71 </span>    wait-for-reset-then-set lock
<span id="L72" class="LineNr"> 72 </span><span class="CommentedCode">#?     $print [lock acquired for writing], 10/newline</span>
<span id="L73" class="LineNr"> 73 </span>    full?:bool <span class="Special">&lt;-</span> <a href='075channel.mu.html#L373'>channel-full?</a> chan
<span id="L74" class="LineNr"> 74 </span>    <span class="muControl">break-unless</span> full?
<span id="L75" class="LineNr"> 75 </span><span class="CommentedCode">#?     $print [but channel is full; relinquishing lock], 10/newline</span>
<span id="L76" class="LineNr"> 76 </span>    <span class="Comment"># channel is full; relinquish lock and give a reader the opportunity to</span>
<span id="L77" class="LineNr"> 77 </span>    <span class="Comment"># create room on it</span>
<span id="L78" class="LineNr"> 78 </span>    reset lock
<span id="L79" class="LineNr"> 79 </span>    current-routine-is-blocked
<span id="L80" class="LineNr"> 80 </span>    switch  <span class="Comment"># avoid spinlocking</span>
<span id="L81" class="LineNr"> 81 </span>   <span class="muControl"> loop</span>
<span id="L82" class="LineNr"> 82 </span>  <span class="Delimiter">}</span>
<span id="L83" class="LineNr"> 83 </span>  current-routine-is-unblocked
<span id="L84" class="LineNr"> 84 </span><span class="CommentedCode">#?   $print [performing write], 10/newline</span>
<span id="L85" class="LineNr"> 85 </span>  <span class="Comment"># store a deep copy of val</span>
<span id="L86" class="LineNr"> 86 </span>  circular-buffer:&amp;:@:_elem <span class="Special">&lt;-</span> get *chan, <span class="Constant">data:offset</span>
<span id="L87" class="LineNr"> 87 </span>  free:num <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L88" class="LineNr"> 88 </span>  *circular-buffer <span class="Special">&lt;-</span> put-index *circular-buffer, free, val
<span id="L89" class="LineNr"> 89 </span>  <span class="Comment"># mark its slot as filled</span>
<span id="L90" class="LineNr"> 90 </span>  free <span class="Special">&lt;-</span> add free,<span class="Constant"> 1</span>
<span id="L91" class="LineNr"> 91 </span>  <span class="Delimiter">{</span>
<span id="L92" class="LineNr"> 92 </span>    <span class="Comment"># wrap free around to 0 if necessary</span>
<span id="L93" class="LineNr"> 93 </span>    len:num <span class="Special">&lt;-</span> length *circular-buffer
<span id="L94" class="LineNr"> 94 </span>    at-end?:bool <span class="Special">&lt;-</span> greater-or-equal free, len
<span id="L95" class="LineNr"> 95 </span>    <span class="muControl">break-unless</span> at-end?
<span id="L96" class="LineNr"> 96 </span>    free <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
<span id="L97" class="LineNr"> 97 </span>  <span class="Delimiter">}</span>
<span id="L98" class="LineNr"> 98 </span>  <span class="Comment"># write back</span>
<span id="L99" class="LineNr"> 99 </span>  *chan <span class="Special">&lt;-</span> put *chan, <span class="Constant">first-free:offset</span>, free
<span id="L100" class="LineNr">100 </span><span class="CommentedCode">#?   $print [relinquishing lock after writing], 10/newline</span>
<span id="L101" class="LineNr">101 </span>  reset lock
<span id="L102" class="LineNr">102 </span>]
<span id="L103" class="LineNr">103 </span>
<span id="L104" class="LineNr">104 </span><span class="Comment"># read a value from a channel</span>
<span id="L105" class="LineNr">105 </span><span class="muRecipe">def</span> read in:&amp;:<a href='075channel.mu.html#L36'>source</a>:_elem<span class="muRecipe"> -&gt; </span>result:_elem, eof?:bool, in:&amp;:<a href='075channel.mu.html#L36'>source</a>:_elem [
<span id="L106" class="LineNr">106 </span>  <span class="Constant">local-scope</span>
<span id="L107" class="LineNr">107 </span>  <span class="Constant">load-inputs</span>
<span id="L108" class="LineNr">108 </span>  assert in, <span class="Constant">[read on null channel]</span>
<span id="L109" class="LineNr">109 </span>  eof? <span class="Special">&lt;-</span> copy<span class="Constant"> false</span>  <span class="Comment"># default result</span>
<span id="L110" class="LineNr">110 </span>  chan:&amp;:channel:_elem <span class="Special">&lt;-</span> get *in, <span class="Constant">chan:offset</span>
<span id="L111" class="LineNr">111 </span>  <span class="Comment"># block until lock is acquired AND queue has data</span>
<span id="L112" class="LineNr">112 </span>  lock:location <span class="Special">&lt;-</span> get-location *chan, <span class="Constant">lock:offset</span>
<span id="L113" class="LineNr">113 </span><span class="CommentedCode">#?   $print [read], 10/newline</span>
<span id="L114" class="LineNr">114 </span>  <span class="Delimiter">{</span>
<span id="L115" class="LineNr">115 </span><span class="CommentedCode">#?     $print [trying to acquire lock for reading], 10/newline</span>
<span id="L116" class="LineNr">116 </span>    wait-for-reset-then-set lock
<span id="L117" class="LineNr">117 </span><span class="CommentedCode">#?     $print [lock acquired for reading], 10/newline</span>
<span id="L118" class="LineNr">118 </span>    empty?:bool <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan
<span id="L119" class="LineNr">119 </span>    <span class="muControl">break-unless</span> empty?
<span id="L120" class="LineNr">120 </span><span class="CommentedCode">#?     $print [but channel is empty; relinquishing lock], 10/newline</span>
<span id="L121" class="LineNr">121 </span>    <span class="Comment"># channel is empty; relinquish lock and give a writer the opportunity to</span>
<span id="L122" class="LineNr">122 </span>    <span class="Comment"># add to it</span>
<span id="L123" class="LineNr">123 </span>    reset lock
<span id="L124" class="LineNr">124 </span>    current-routine-is-blocked
<span id="L125" class="LineNr">125 </span><span class="Constant">    <a href='075channel.mu.html#L125'>&lt;channel-read-empty&gt;</a></span>
<span id="L126" class="LineNr">126 </span>    switch  <span class="Comment"># avoid spinlocking</span>
<span id="L127" class="LineNr">127 </span>   <span class="muControl"> loop</span>
<span id="L128" class="LineNr">128 </span>  <span class="Delimiter">}</span>
<span id="L129" class="LineNr">129 </span>  current-routine-is-unblocked
<span id="L130" class="LineNr">130 </span>  <span class="Comment"># pull result off</span>
<span id="L131" class="LineNr">131 </span>  full:num <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-full:offset</span>
<span id="L132" class="LineNr">132 </span>  circular-buffer:&amp;:@:_elem <span class="Special">&lt;-</span> get *chan, <span class="Constant">data:offset</span>
<span id="L133" class="LineNr">133 </span>  result <span class="Special">&lt;-</span> index *circular-buffer, full
<span id="L134" class="LineNr">134 </span>  <span class="Comment"># clear the slot</span>
<span id="L135" class="LineNr">135 </span>  empty:&amp;:_elem <span class="Special">&lt;-</span> new <span class="Constant">_elem:type</span>
<span id="L136" class="LineNr">136 </span>  *circular-buffer <span class="Special">&lt;-</span> put-index *circular-buffer, full, *empty
<span id="L137" class="LineNr">137 </span>  <span class="Comment"># mark its slot as empty</span>
<span id="L138" class="LineNr">138 </span>  full <span class="Special">&lt;-</span> add full,<span class="Constant"> 1</span>
<span id="L139" class="LineNr">139 </span>  <span class="Delimiter">{</span>
<span id="L140" class="LineNr">140 </span>    <span class="Comment"># wrap full around to 0 if necessary</span>
<span id="L141" class="LineNr">141 </span>    len:num <span class="Special">&lt;-</span> length *circular-buffer
<span id="L142" class="LineNr">142 </span>    at-end?:bool <span class="Special">&lt;-</span> greater-or-equal full, len
<span id="L143" class="LineNr">143 </span>    <span class="muControl">break-unless</span> at-end?
<span id="L144" class="LineNr">144 </span>    full <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
<span id="L145" class="LineNr">145 </span>  <span class="Delimiter">}</span>
<span id="L146" class="LineNr">146 </span>  <span class="Comment"># write back</span>
<span id="L147" class="LineNr">147 </span>  *chan <span class="Special">&lt;-</span> put *chan, <span class="Constant">first-full:offset</span>, full
<span id="L148" class="LineNr">148 </span><span class="CommentedCode">#?   $print [relinquishing lock after reading], 10/newline</span>
<span id="L149" class="LineNr">149 </span>  reset lock
<span id="L150" class="LineNr">150 </span>]
<span id="L151" class="LineNr">151 </span>
<span id="L152" class="LineNr">152 </span><span class="Comment"># todo: create a notion of iterator and iterable so we can read/write whole</span>
<span id="L153" class="LineNr">153 </span><span class="Comment"># aggregates (arrays, lists, ..) of _elems at once.</span>
<span id="L154" class="LineNr">154 </span>
<span id="L155" class="LineNr">155 </span><span class="muScenario">scenario</span> channel-initialization [
<span id="L156" class="LineNr">156 </span>  run [
<span id="L157" class="LineNr">157 </span>    <span class="Constant">local-scope</span>
<span id="L158" class="LineNr">158 </span>    <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">3/capacity</span>
<span id="L159" class="LineNr">159 </span>    chan:&amp;:channel:num <span class="Special">&lt;-</span> get *source, <span class="Constant">chan:offset</span>
<span id="L160" class="LineNr">160 </span>    10:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-full:offset</span>
<span id="L161" class="LineNr">161 </span>    11:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L162" class="LineNr">162 </span>  ]
<span id="L163" class="LineNr">163 </span>  memory-should-contain [
<span id="L164" class="LineNr">164 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># first-full</span>
<span id="L165" class="LineNr">165 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># first-free</span>
<span id="L166" class="LineNr">166 </span>  ]
<span id="L167" class="LineNr">167 </span>]
<span id="L168" class="LineNr">168 </span>
<span id="L169" class="LineNr">169 </span><span class="muScenario">scenario</span> channel-write-increments-free [
<span id="L170" class="LineNr">170 </span>  <span class="Constant">local-scope</span>
<span id="L171" class="LineNr">171 </span>  _, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">3/capacity</span>
<span id="L172" class="LineNr">172 </span>  run [
<span id="L173" class="LineNr">173 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L174" class="LineNr">174 </span>    chan:&amp;:channel:num <span class="Special">&lt;-</span> get *sink, <span class="Constant">chan:offset</span>
<span id="L175" class="LineNr">175 </span>    10:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-full:offset</span>
<span id="L176" class="LineNr">176 </span>    11:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L177" class="LineNr">177 </span>  ]
<span id="L178" class="LineNr">178 </span>  memory-should-contain [
<span id="L179" class="LineNr">179 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># first-full</span>
<span id="L180" class="LineNr">180 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># first-free</span>
<span id="L181" class="LineNr">181 </span>  ]
<span id="L182" class="LineNr">182 </span>]
<span id="L183" class="LineNr">183 </span>
<span id="L184" class="LineNr">184 </span><span class="muScenario">scenario</span> channel-read-increments-full [
<span id="L185" class="LineNr">185 </span>  <span class="Constant">local-scope</span>
<span id="L186" class="LineNr">186 </span>  <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">3/capacity</span>
<span id="L187" class="LineNr">187 </span>  <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L188" class="LineNr">188 </span>  run [
<span id="L189" class="LineNr">189 </span>    _, _, <a href='075channel.mu.html#L36'>source</a> <span class="Special">&lt;-</span> read <a href='075channel.mu.html#L36'>source</a>
<span id="L190" class="LineNr">190 </span>    chan:&amp;:channel:num <span class="Special">&lt;-</span> get *source, <span class="Constant">chan:offset</span>
<span id="L191" class="LineNr">191 </span>    10:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-full:offset</span>
<span id="L192" class="LineNr">192 </span>    11:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L193" class="LineNr">193 </span>  ]
<span id="L194" class="LineNr">194 </span>  memory-should-contain [
<span id="L195" class="LineNr">195 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># first-full</span>
<span id="L196" class="LineNr">196 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># first-free</span>
<span id="L197" class="LineNr">197 </span>  ]
<span id="L198" class="LineNr">198 </span>]
<span id="L199" class="LineNr">199 </span>
<span id="L200" class="LineNr">200 </span><span class="muScenario">scenario</span> channel-wrap [
<span id="L201" class="LineNr">201 </span>  <span class="Constant">local-scope</span>
<span id="L202" class="LineNr">202 </span>  <span class="Comment"># channel with just 1 slot</span>
<span id="L203" class="LineNr">203 </span>  <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">1/capacity</span>
<span id="L204" class="LineNr">204 </span>  chan:&amp;:channel:num <span class="Special">&lt;-</span> get *source, <span class="Constant">chan:offset</span>
<span id="L205" class="LineNr">205 </span>  <span class="Comment"># write and read a value</span>
<span id="L206" class="LineNr">206 </span>  <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L207" class="LineNr">207 </span>  _, _, <a href='075channel.mu.html#L36'>source</a> <span class="Special">&lt;-</span> read <a href='075channel.mu.html#L36'>source</a>
<span id="L208" class="LineNr">208 </span>  run [
<span id="L209" class="LineNr">209 </span>    <span class="Comment"># first-free will now be 1</span>
<span id="L210" class="LineNr">210 </span>    10:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L211" class="LineNr">211 </span>    11:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L212" class="LineNr">212 </span>    <span class="Comment"># write second value, verify that first-free wraps</span>
<span id="L213" class="LineNr">213 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L214" class="LineNr">214 </span>    20:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L215" class="LineNr">215 </span>    <span class="Comment"># read second value, verify that first-full wraps</span>
<span id="L216" class="LineNr">216 </span>    _, _, <a href='075channel.mu.html#L36'>source</a> <span class="Special">&lt;-</span> read <a href='075channel.mu.html#L36'>source</a>
<span id="L217" class="LineNr">217 </span>    30:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-full:offset</span>
<span id="L218" class="LineNr">218 </span>  ]
<span id="L219" class="LineNr">219 </span>  memory-should-contain [
<span id="L220" class="LineNr">220 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># first-free after first write</span>
<span id="L221" class="LineNr">221 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># first-full after first read</span>
<span id="L222" class="LineNr">222 </span>   <span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># first-free after second write, wrapped</span>
<span id="L223" class="LineNr">223 </span>   <span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># first-full after second read, wrapped</span>
<span id="L224" class="LineNr">224 </span>  ]
<span id="L225" class="LineNr">225 </span>]
<span id="L226" class="LineNr">226 </span>
<span id="L227" class="LineNr">227 </span><span class="muScenario">scenario</span> channel-new-empty-not-full [
<span id="L228" class="LineNr">228 </span>  run [
<span id="L229" class="LineNr">229 </span>    <span class="Constant">local-scope</span>
<span id="L230" class="LineNr">230 </span>    <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">3/capacity</span>
<span id="L231" class="LineNr">231 </span>    chan:&amp;:channel:num <span class="Special">&lt;-</span> get *source, <span class="Constant">chan:offset</span>
<span id="L232" class="LineNr">232 </span>    10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan
<span id="L233" class="LineNr">233 </span>    11:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L373'>channel-full?</a> chan
<span id="L234" class="LineNr">234 </span>  ]
<span id="L235" class="LineNr">235 </span>  memory-should-contain [
<span id="L236" class="LineNr">236 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># empty?</span>
<span id="L237" class="LineNr">237 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># full?</span>
<span id="L238" class="LineNr">238 </span>  ]
<span id="L239" class="LineNr">239 </span>]
<span id="L240" class="LineNr">240 </span>
<span id="L241" class="LineNr">241 </span><span class="muScenario">scenario</span> channel-write-not-empty [
<span id="L242" class="LineNr">242 </span>  <span class="Constant">local-scope</span>
<span id="L243" class="LineNr">243 </span>  <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">3/capacity</span>
<span id="L244" class="LineNr">244 </span>  chan:&amp;:channel:num <span class="Special">&lt;-</span> get *source, <span class="Constant">chan:offset</span>
<span id="L245" class="LineNr">245 </span>  run [
<span id="L246" class="LineNr">246 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L247" class="LineNr">247 </span>    10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan
<span id="L248" class="LineNr">248 </span>    11:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L373'>channel-full?</a> chan
<span id="L249" class="LineNr">249 </span>  ]
<span id="L250" class="LineNr">250 </span>  memory-should-contain [
<span id="L251" class="LineNr">251 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># empty?</span>
<span id="L252" class="LineNr">252 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># full?</span>
<span id="L253" class="LineNr">253 </span>  ]
<span id="L254" class="LineNr">254 </span>]
<span id="L255" class="LineNr">255 </span>
<span id="L256" class="LineNr">256 </span><span class="muScenario">scenario</span> channel-write-full [
<span id="L257" class="LineNr">257 </span>  <span class="Constant">local-scope</span>
<span id="L258" class="LineNr">258 </span>  <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">1/capacity</span>
<span id="L259" class="LineNr">259 </span>  chan:&amp;:channel:num <span class="Special">&lt;-</span> get *source, <span class="Constant">chan:offset</span>
<span id="L260" class="LineNr">260 </span>  run [
<span id="L261" class="LineNr">261 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L262" class="LineNr">262 </span>    10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan
<span id="L263" class="LineNr">263 </span>    11:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L373'>channel-full?</a> chan
<span id="L264" class="LineNr">264 </span>  ]
<span id="L265" class="LineNr">265 </span>  memory-should-contain [
<span id="L266" class="LineNr">266 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># empty?</span>
<span id="L267" class="LineNr">267 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># full?</span>
<span id="L268" class="LineNr">268 </span>  ]
<span id="L269" class="LineNr">269 </span>]
<span id="L270" class="LineNr">270 </span>
<span id="L271" class="LineNr">271 </span><span class="muScenario">scenario</span> channel-read-not-full [
<span id="L272" class="LineNr">272 </span>  <span class="Constant">local-scope</span>
<span id="L273" class="LineNr">273 </span>  <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">1/capacity</span>
<span id="L274" class="LineNr">274 </span>  chan:&amp;:channel:num <span class="Special">&lt;-</span> get *source, <span class="Constant">chan:offset</span>
<span id="L275" class="LineNr">275 </span>  <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 34</span>
<span id="L276" class="LineNr">276 </span>  run [
<span id="L277" class="LineNr">277 </span>    _, _, <a href='075channel.mu.html#L36'>source</a> <span class="Special">&lt;-</span> read <a href='075channel.mu.html#L36'>source</a>
<span id="L278" class="LineNr">278 </span>    10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan
<span id="L279" class="LineNr">279 </span>    11:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L373'>channel-full?</a> chan
<span id="L280" class="LineNr">280 </span>  ]
<span id="L281" class="LineNr">281 </span>  memory-should-contain [
<span id="L282" class="LineNr">282 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># empty?</span>
<span id="L283" class="LineNr">283 </span>   <span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># full?</span>
<span id="L284" class="LineNr">284 </span>  ]
<span id="L285" class="LineNr">285 </span>]
<span id="L286" class="LineNr">286 </span>
<span id="L287" class="LineNr">287 </span><span class="muScenario">scenario</span> channel-clear [
<span id="L288" class="LineNr">288 </span>  <span class="Constant">local-scope</span>
<span id="L289" class="LineNr">289 </span>  <span class="Comment"># create a channel with a few items</span>
<span id="L290" class="LineNr">290 </span>  <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:num, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">3/capacity</span>
<span id="L291" class="LineNr">291 </span>  chan:&amp;:channel:num <span class="Special">&lt;-</span> get *sink, <span class="Constant">chan:offset</span>
<span id="L292" class="LineNr">292 </span>  <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 30</span>
<span id="L293" class="LineNr">293 </span>  <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 31</span>
<span id="L294" class="LineNr">294 </span>  <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>,<span class="Constant"> 32</span>
<span id="L295" class="LineNr">295 </span>  run [
<span id="L296" class="LineNr">296 </span>    <a href='075channel.mu.html#L304'>clear</a> <a href='075channel.mu.html#L36'>source</a>
<span id="L297" class="LineNr">297 </span>    10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan
<span id="L298" class="LineNr">298 </span>  ]
<span id="L299" class="LineNr">299 </span>  memory-should-contain [
<span id="L300" class="LineNr">300 </span>   <span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># after the call to 'clear', the channel should be empty</span>
<span id="L301" class="LineNr">301 </span>  ]
<span id="L302" class="LineNr">302 </span>]
<span id="L303" class="LineNr">303 </span>
<span id="L304" class="LineNr">304 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L304'>clear</a> in:&amp;:<a href='075channel.mu.html#L36'>source</a>:_elem<span class="muRecipe"> -&gt; </span>in:&amp;:<a href='075channel.mu.html#L36'>source</a>:_elem [
<span id="L305" class="LineNr">305 </span>  <span class="Constant">local-scope</span>
<span id="L306" class="LineNr">306 </span>  <span class="Constant">load-inputs</span>
<span id="L307" class="LineNr">307 </span>  chan:&amp;:channel:_elem <span class="Special">&lt;-</span> get *in, <span class="Constant">chan:offset</span>
<span id="L308" class="LineNr">308 </span>  <span class="Delimiter">{</span>
<span id="L309" class="LineNr">309 </span>    empty?:bool <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan
<span id="L310" class="LineNr">310 </span>    <span class="muControl">break-if</span> empty?
<span id="L311" class="LineNr">311 </span>    _, _, in <span class="Special">&lt;-</span> read in
<span id="L312" class="LineNr">312 </span>   <span class="muControl"> loop</span>
<span id="L313" class="LineNr">313 </span>  <span class="Delimiter">}</span>
<span id="L314" class="LineNr">314 </span>]
<span id="L315" class="LineNr">315 </span>
<span id="L316" class="LineNr">316 </span><span class="SalientComment">## cancelling channels</span>
<span id="L317" class="LineNr">317 </span>
<span id="L318" class="LineNr">318 </span><span class="Comment"># every channel comes with a boolean signifying if it's been closed</span>
<span id="L319" class="LineNr">319 </span><span class="Comment"># initially this boolean is false</span>
<span id="L320" class="LineNr">320 </span><span class="muData">container</span> channel:_elem [
<span id="L321" class="LineNr">321 </span>  closed?:bool
<span id="L322" class="LineNr">322 </span>]
<span id="L323" class="LineNr">323 </span>
<span id="L324" class="LineNr">324 </span><span class="Comment"># a channel can be closed from either the source or the sink</span>
<span id="L325" class="LineNr">325 </span><span class="Comment"># both routines can modify the 'closed?' bit, but they can only ever set it, so this is a benign race</span>
<span id="L326" class="LineNr">326 </span><span class="muRecipe">def</span> close x:&amp;:<a href='075channel.mu.html#L36'>source</a>:_elem<span class="muRecipe"> -&gt; </span>x:&amp;:<a href='075channel.mu.html#L36'>source</a>:_elem [
<span id="L327" class="LineNr">327 </span>  <span class="Constant">local-scope</span>
<span id="L328" class="LineNr">328 </span>  <span class="Constant">load-inputs</span>
<span id="L329" class="LineNr">329 </span>  chan:&amp;:channel:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant">chan:offset</span>
<span id="L330" class="LineNr">330 </span>  *chan <span class="Special">&lt;-</span> put *chan, <span class="Constant">closed?:offset</span>,<span class="Constant"> true</span>
<span id="L331" class="LineNr">331 </span>]
<span id="L332" class="LineNr">332 </span><span class="muRecipe">def</span> close x:&amp;:<a href='075channel.mu.html#L40'>sink</a>:_elem<span class="muRecipe"> -&gt; </span>x:&amp;:<a href='075channel.mu.html#L40'>sink</a>:_elem [
<span id="L333" class="LineNr">333 </span>  <span class="Constant">local-scope</span>
<span id="L334" class="LineNr">334 </span>  <span class="Constant">load-inputs</span>
<span id="L335" class="LineNr">335 </span>  chan:&amp;:channel:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant">chan:offset</span>
<span id="L336" class="LineNr">336 </span>  *chan <span class="Special">&lt;-</span> put *chan, <span class="Constant">closed?:offset</span>,<span class="Constant"> true</span>
<span id="L337" class="LineNr">337 </span>]
<span id="L338" class="LineNr">338 </span>
<span id="L339" class="LineNr">339 </span><span class="Comment"># once a channel is closed from one side, no further operations are expected from that side</span>
<span id="L340" class="LineNr">340 </span><span class="Comment"># if a channel is closed for reading,</span>
<span id="L341" class="LineNr">341 </span><span class="Comment">#   no further writes will be let through</span>
<span id="L342" class="LineNr">342 </span><span class="Comment"># if a channel is closed for writing,</span>
<span id="L343" class="LineNr">343 </span><span class="Comment">#   future reads continue until the channel empties,</span>
<span id="L344" class="LineNr">344 </span><span class="Comment">#   then the channel is also closed for reading</span>
<span id="L345" class="LineNr">345 </span><span class="muRecipe">after</span> <span class="Constant"><a href='075channel.mu.html#L65'>&lt;channel-write-initial&gt;</a></span> [
<span id="L346" class="LineNr">346 </span>  closed?:bool <span class="Special">&lt;-</span> get *chan, <span class="Constant">closed?:offset</span>
<span id="L347" class="LineNr">347 </span>  <span class="muControl">return-if</span> closed?
<span id="L348" class="LineNr">348 </span>]
<span id="L349" class="LineNr">349 </span><span class="muRecipe">after</span> <span class="Constant"><a href='075channel.mu.html#L125'>&lt;channel-read-empty&gt;</a></span> [
<span id="L350" class="LineNr">350 </span>  closed?:bool <span class="Special">&lt;-</span> get *chan, <span class="Constant">closed?:offset</span>
<span id="L351" class="LineNr">351 </span>  <span class="Delimiter">{</span>
<span id="L352" class="LineNr">352 </span>    <span class="muControl">break-unless</span> closed?
<span id="L353" class="LineNr">353 </span>    empty-result:&amp;:_elem <span class="Special">&lt;-</span> new <span class="Constant">_elem:type</span>
<span id="L354" class="LineNr">354 </span>    current-routine-is-unblocked
<span id="L355" class="LineNr">355 </span>   <span class="muControl"> return</span> *empty-result,<span class="Constant"> true</span>
<span id="L356" class="LineNr">356 </span>  <span class="Delimiter">}</span>
<span id="L357" class="LineNr">357 </span>]
<span id="L358" class="LineNr">358 </span>
<span id="L359" class="LineNr">359 </span><span class="SalientComment">## helpers</span>
<span id="L360" class="LineNr">360 </span>
<span id="L361" class="LineNr">361 </span><span class="Comment"># An empty channel has first-free and first-full both at the same value.</span>
<span id="L362" class="LineNr">362 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L362'>channel-empty?</a> chan:&amp;:channel:_elem<span class="muRecipe"> -&gt; </span>result:bool [
<span id="L363" class="LineNr">363 </span>  <span class="Constant">local-scope</span>
<span id="L364" class="LineNr">364 </span>  <span class="Constant">load-inputs</span>
<span id="L365" class="LineNr">365 </span>  <span class="Comment"># return chan.first-full == chan.first-free</span>
<span id="L366" class="LineNr">366 </span>  full:num <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-full:offset</span>
<span id="L367" class="LineNr">367 </span>  free:num <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L368" class="LineNr">368 </span>  result <span class="Special">&lt;-</span> equal full, free
<span id="L369" class="LineNr">369 </span>]
<span id="L370" class="LineNr">370 </span>
<span id="L371" class="LineNr">371 </span><span class="Comment"># A full channel has first-free just before first-full, wasting one slot.</span>
<span id="L372" class="LineNr">372 </span><span class="Comment"># (Other alternatives: <a href="https://www.snellman.net/blog/archive/2016-12-13-ring-buffers">https://www.snellman.net/blog/archive/2016-12-13-ring-buffers</a>)</span>
<span id="L373" class="LineNr">373 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L373'>channel-full?</a> chan:&amp;:channel:_elem<span class="muRecipe"> -&gt; </span>result:bool [
<span id="L374" class="LineNr">374 </span>  <span class="Constant">local-scope</span>
<span id="L375" class="LineNr">375 </span>  <span class="Constant">load-inputs</span>
<span id="L376" class="LineNr">376 </span>  <span class="Comment"># tmp = chan.first-free + 1</span>
<span id="L377" class="LineNr">377 </span>  tmp:num <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-free:offset</span>
<span id="L378" class="LineNr">378 </span>  tmp <span class="Special">&lt;-</span> add tmp,<span class="Constant"> 1</span>
<span id="L379" class="LineNr">379 </span>  <span class="Delimiter">{</span>
<span id="L380" class="LineNr">380 </span>    <span class="Comment"># if tmp == chan.capacity, tmp = 0</span>
<span id="L381" class="LineNr">381 </span>    len:num <span class="Special">&lt;-</span> <a href='075channel.mu.html#L391'>capacity</a> chan
<span id="L382" class="LineNr">382 </span>    at-end?:bool <span class="Special">&lt;-</span> greater-or-equal tmp, len
<span id="L383" class="LineNr">383 </span>    <span class="muControl">break-unless</span> at-end?
<span id="L384" class="LineNr">384 </span>    tmp <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
<span id="L385" class="LineNr">385 </span>  <span class="Delimiter">}</span>
<span id="L386" class="LineNr">386 </span>  <span class="Comment"># return chan.first-full == tmp</span>
<span id="L387" class="LineNr">387 </span>  full:num <span class="Special">&lt;-</span> get *chan, <span class="Constant">first-full:offset</span>
<span id="L388" class="LineNr">388 </span>  result <span class="Special">&lt;-</span> equal full, tmp
<span id="L389" class="LineNr">389 </span>]
<span id="L390" class="LineNr">390 </span>
<span id="L391" class="LineNr">391 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L391'>capacity</a> chan:&amp;:channel:_elem<span class="muRecipe"> -&gt; </span>result:num [
<span id="L392" class="LineNr">392 </span>  <span class="Constant">local-scope</span>
<span id="L393" class="LineNr">393 </span>  <span class="Constant">load-inputs</span>
<span id="L394" class="LineNr">394 </span>  q:&amp;:@:_elem <span class="Special">&lt;-</span> get *chan, <span class="Constant">data:offset</span>
<span id="L395" class="LineNr">395 </span>  result <span class="Special">&lt;-</span> length *q
<span id="L396" class="LineNr">396 </span>]
<span id="L397" class="LineNr">397 </span>
<span id="L398" class="LineNr">398 </span><span class="SalientComment">## helpers for channels of characters in particular</span>
<span id="L399" class="LineNr">399 </span>
<span id="L400" class="LineNr">400 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L400'>buffer-lines</a> in:&amp;:<a href='075channel.mu.html#L36'>source</a>:char, buffered-out:&amp;:<a href='075channel.mu.html#L40'>sink</a>:char<span class="muRecipe"> -&gt; </span>buffered-out:&amp;:<a href='075channel.mu.html#L40'>sink</a>:char, in:&amp;:<a href='075channel.mu.html#L36'>source</a>:char [
<span id="L401" class="LineNr">401 </span>  <span class="Constant">local-scope</span>
<span id="L402" class="LineNr">402 </span>  <span class="Constant">load-inputs</span>
<span id="L403" class="LineNr">403 </span>  <span class="Comment"># repeat forever</span>
<span id="L404" class="LineNr">404 </span>  eof?:bool <span class="Special">&lt;-</span> copy<span class="Constant"> false</span>
<span id="L405" class="LineNr">405 </span>  <span class="Delimiter">{</span>
<span id="L406" class="LineNr">406 </span>    line:&amp;:<a href='061text.mu.html#L120'>buffer</a>:char <span class="Special">&lt;-</span> <a href='061text.mu.html#L125'>new-buffer</a><span class="Constant"> 30</span>
<span id="L407" class="LineNr">407 </span>    <span class="Comment"># read characters from 'in' until newline, copy into line</span>
<span id="L408" class="LineNr">408 </span>    <span class="Delimiter">{</span>
<span id="L409" class="LineNr">409 </span><span class="Constant">      +next-character</span>
<span id="L410" class="LineNr">410 </span>      c:char, eof?:bool, in <span class="Special">&lt;-</span> read in
<span id="L411" class="LineNr">411 </span>      <span class="muControl">break-if</span> eof?
<span id="L412" class="LineNr">412 </span>      <span class="Comment"># drop a character on backspace</span>
<span id="L413" class="LineNr">413 </span>      <span class="Delimiter">{</span>
<span id="L414" class="LineNr">414 </span>        <span class="Comment"># special-case: if it's a backspace</span>
<span id="L415" class="LineNr">415 </span>        backspace?:bool <span class="Special">&lt;-</span> equal c,<span class="Constant"> 8</span>
<span id="L416" class="LineNr">416 </span>        <span class="muControl">break-unless</span> backspace?
<span id="L417" class="LineNr">417 </span>        <span class="Comment"># drop previous character</span>
<span id="L418" class="LineNr">418 </span>        <span class="Delimiter">{</span>
<span id="L419" class="LineNr">419 </span>          buffer-length:num <span class="Special">&lt;-</span> get *line, <span class="Constant">length:offset</span>
<span id="L420" class="LineNr">420 </span>          buffer-empty?:bool <span class="Special">&lt;-</span> equal buffer-length,<span class="Constant"> 0</span>
<span id="L421" class="LineNr">421 </span>          <span class="muControl">break-if</span> buffer-empty?
<span id="L422" class="LineNr">422 </span>          buffer-length <span class="Special">&lt;-</span> subtract buffer-length,<span class="Constant"> 1</span>
<span id="L423" class="LineNr">423 </span>          *line <span class="Special">&lt;-</span> put *line, <span class="Constant">length:offset</span>, buffer-length
<span id="L424" class="LineNr">424 </span>        <span class="Delimiter">}</span>
<span id="L425" class="LineNr">425 </span>        <span class="Comment"># and don't append this one</span>
<span id="L426" class="LineNr">426 </span>       <span class="muControl"> loop</span> <span class="Constant">+next-character</span>
<span id="L427" class="LineNr">427 </span>      <span class="Delimiter">}</span>
<span id="L428" class="LineNr">428 </span>      <span class="Comment"># append anything else</span>
<span id="L429" class="LineNr">429 </span>      line <span class="Special">&lt;-</span> append line, c
<span id="L430" class="LineNr">430 </span>      line-done?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
<span id="L431" class="LineNr">431 </span>      <span class="muControl">break-if</span> line-done?
<span id="L432" class="LineNr">432 </span>     <span class="muControl"> loop</span>
<span id="L433" class="LineNr">433 </span>    <span class="Delimiter">}</span>
<span id="L434" class="LineNr">434 </span>    <span class="Comment"># copy line into 'buffered-out'</span>
<span id="L435" class="LineNr">435 </span>    i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
<span id="L436" class="LineNr">436 </span>    line-contents:text <span class="Special">&lt;-</span> get *line, <span class="Constant">data:offset</span>
<span id="L437" class="LineNr">437 </span>    max:num <span class="Special">&lt;-</span> get *line, <span class="Constant">length:offset</span>
<span id="L438" class="LineNr">438 </span>    <span class="Delimiter">{</span>
<span id="L439" class="LineNr">439 </span>      done?:bool <span class="Special">&lt;-</span> greater-or-equal i, max
<span id="L440" class="LineNr">440 </span>      <span class="muControl">break-if</span> done?
<span id="L441" class="LineNr">441 </span>      c:char <span class="Special">&lt;-</span> index *line-contents, i
<span id="L442" class="LineNr">442 </span>      buffered-out <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> buffered-out, c
<span id="L443" class="LineNr">443 </span>      i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
<span id="L444" class="LineNr">444 </span>     <span class="muControl"> loop</span>
<span id="L445" class="LineNr">445 </span>    <span class="Delimiter">}</span>
<span id="L446" class="LineNr">446 </span>    <span class="Delimiter">{</span>
<span id="L447" class="LineNr">447 </span>      <span class="muControl">break-unless</span> eof?
<span id="L448" class="LineNr">448 </span>      buffered-out <span class="Special">&lt;-</span> close buffered-out
<span id="L449" class="LineNr">449 </span>     <span class="muControl"> return</span>
<span id="L450" class="LineNr">450 </span>    <span class="Delimiter">}</span>
<span id="L451" class="LineNr">451 </span>   <span class="muControl"> loop</span>
<span id="L452" class="LineNr">452 </span>  <span class="Delimiter">}</span>
<span id="L453" class="LineNr">453 </span>]
<span id="L454" class="LineNr">454 </span>
<span id="L455" class="LineNr">455 </span><span class="muScenario">scenario</span> buffer-lines-blocks-until-newline [
<span id="L456" class="LineNr">456 </span>  run [
<span id="L457" class="LineNr">457 </span>    <span class="Constant">local-scope</span>
<span id="L458" class="LineNr">458 </span>    <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:char, <a href='075channel.mu.html#L40'>sink</a>:&amp;:<a href='075channel.mu.html#L40'>sink</a>:char <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">10/capacity</span>
<span id="L459" class="LineNr">459 </span>    _, buffered-stdin:&amp;:<a href='075channel.mu.html#L40'>sink</a>:char/buffered-stdin <span class="Special">&lt;-</span> <a href='075channel.mu.html#L44'>new-channel</a> <span class="Constant">10/capacity</span>
<span id="L460" class="LineNr">460 </span>    buffered-chan:&amp;:channel:char <span class="Special">&lt;-</span> get *buffered-stdin, <span class="Constant">chan:offset</span>
<span id="L461" class="LineNr">461 </span>    empty?:bool <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> buffered-chan
<span id="L462" class="LineNr">462 </span>    assert empty?, <span class="Constant">[ </span>
<span id="L463" class="LineNr">463 </span><span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after init]</span>
<span id="L464" class="LineNr">464 </span>    <span class="Comment"># buffer stdin into buffered-stdin, try to read from buffered-stdin</span>
<span id="L465" class="LineNr">465 </span>    buffer-routine:num <span class="Special">&lt;-</span> <span class="muControl">start-running</span> <a href='075channel.mu.html#L400'>buffer-lines</a>, <a href='075channel.mu.html#L36'>source</a>, buffered-stdin
<span id="L466" class="LineNr">466 </span>    wait-for-routine-to-block buffer-routine
<span id="L467" class="LineNr">467 </span>    empty? <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> buffered-chan
<span id="L468" class="LineNr">468 </span>    assert empty?:bool, <span class="Constant">[ </span>
<span id="L469" class="LineNr">469 </span><span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after <a href='075channel.mu.html#L400'>buffer-lines</a> bring-up]</span>
<span id="L470" class="LineNr">470 </span>    <span class="Comment"># write 'a'</span>
<span id="L471" class="LineNr">471 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>, <span class="Constant">97/a</span>
<span id="L472" class="LineNr">472 </span>    restart buffer-routine
<span id="L473" class="LineNr">473 </span>    wait-for-routine-to-block buffer-routine
<span id="L474" class="LineNr">474 </span>    empty? <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> buffered-chan
<span id="L475" class="LineNr">475 </span>    assert empty?:bool, <span class="Constant">[ </span>
<span id="L476" class="LineNr">476 </span><span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after writing 'a']</span>
<span id="L477" class="LineNr">477 </span>    <span class="Comment"># write 'b'</span>
<span id="L478" class="LineNr">478 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>, <span class="Constant">98/b</span>
<span id="L479" class="LineNr">479 </span>    restart buffer-routine
<span id="L480" class="LineNr">480 </span>    wait-for-routine-to-block buffer-routine
<span id="L481" class="LineNr">481 </span>    empty? <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> buffered-chan
<span id="L482" class="LineNr">482 </span>    assert empty?:bool, <span class="Constant">[ </span>
<span id="L483" class="LineNr">483 </span><span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after writing 'b']</span>
<span id="L484" class="LineNr">484 </span>    <span class="Comment"># write newline</span>
<span id="L485" class="LineNr">485 </span>    <a href='075channel.mu.html#L40'>sink</a> <span class="Special">&lt;-</span> <a href='075channel.mu.html#L60'>write</a> <a href='075channel.mu.html#L40'>sink</a>, <span class="Constant">10/newline</span>
<span id="L486" class="LineNr">486 </span>    restart buffer-routine
<span id="L487" class="LineNr">487 </span>    wait-for-routine-to-block buffer-routine
<span id="L488" class="LineNr">488 </span>    empty? <span class="Special">&lt;-</span> <a href='075channel.mu.html#L362'>channel-empty?</a> buffered-chan
<span id="L489" class="LineNr">489 </span>    data-emitted?:bool <span class="Special">&lt;-</span> not empty?
<span id="L490" class="LineNr">490 </span>    assert data-emitted?, <span class="Constant">[ </span>
<span id="L491" class="LineNr">491 </span><span class="Constant">F buffer-lines-blocks-until-newline: channel should contain data after writing newline]</span>
<span id="L492" class="LineNr">492 </span>    trace<span class="Constant"> 1</span>, <span class="Constant">[test]</span>, <span class="Constant">[reached end]</span>
<span id="L493" class="LineNr">493 </span>  ]
<span id="L494" class="LineNr">494 </span>  trace-should-contain [
<span id="L495" class="LineNr">495 </span>    test: reached end
<span id="L496" class="LineNr">496 </span>  ]
<span id="L497" class="LineNr">497 </span>]
<span id="L498" class="LineNr">498 </span>
<span id="L499" class="LineNr">499 </span><span class="muRecipe">def</span> <a href='075channel.mu.html#L499'>drain</a> <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:char<span class="muRecipe"> -&gt; </span>result:text, <a href='075channel.mu.html#L36'>source</a>:&amp;:<a href='075channel.mu.html#L36'>source</a>:char [
<span id="L500" class="LineNr">500 </span>  <span class="Constant">local-scope</span>
<span id="L501" class="LineNr">501 </span>  <span class="Constant">load-inputs</span>
<span id="L502" class="LineNr">502 </span>  buf:&amp;:<a href='061text.mu.html#L120'>buffer</a>:char <span class="Special">&lt;-</span> <a href='061text.mu.html#L125'>new-buffer</a><span class="Constant"> 30</span>
<span id="L503" class="LineNr">503 </span>  <span class="Delimiter">{</span>
<span id="L504" class="LineNr">504 </span>    c:char, done?:bool <span class="Special">&lt;-</span> read <a href='075channel.mu.html#L36'>source</a>
<span id="L505" class="LineNr">505 </span>    <span class="muControl">break-if</span> done?
<span id="L506" class="LineNr">506 </span>    buf <span class="Special">&lt;-</span> append buf, c
<span id="L507" class="LineNr">507 </span>   <span class="muControl"> loop</span>
<span id="L508" class="LineNr">508 </span>  <span class="Delimiter">}</span>
<span id="L509" class="LineNr">509 </span>  result <span class="Special">&lt;-</span> <a href='061text.mu.html#L338'>buffer-to-array</a> buf
<span id="L510" class="LineNr">510 </span>]
</pre>
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