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* 5852Kartik Agaram2020-01-015-0/+991
generated by cgit-pink 1.4.1-2-gfad0 (git 2.36.2.497.gbbea4dcf42) at 2024-12-23 08:00:43 +0000
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<pre id='vimCodeElement'>
<span class="Comment"># Mu synchronizes using channels rather than locks, like Erlang and Go.</span>
<span class="Comment">#</span>
<span class="Comment"># The two ends of a channel will usually belong to different routines, but</span>
<span class="Comment"># each end should only be used by a single one. Don't try to read from or</span>
<span class="Comment"># write to it from multiple routines at once.</span>
<span class="Comment">#</span>
<span class="Comment"># The key property of channels is that writing to a full channel or reading</span>
<span class="Comment"># from an empty one will put the current routine in 'waiting' state until the</span>
<span class="Comment"># operation can be completed.</span>

<span class="muScenario">scenario</span> channel [
  run [
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
    <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:number, <span class="Constant">34</span>
    <span class="Constant">3</span>:number, <span class="Constant">1</span>:address:source:number<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:source:number
  ]
  memory-should-contain [
    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">34</span>
  ]
]

<span class="muData">container</span> channel:_elem [
  <span class="Comment"># To avoid locking, writer and reader will never write to the same location.</span>
  <span class="Comment"># So channels will include fields in pairs, one for the writer and one for the</span>
  <span class="Comment"># reader.</span>
  first-full:number  <span class="Comment"># for write</span>
  first-free:number  <span class="Comment"># for read</span>
  <span class="Comment"># A circular buffer contains values from index first-full up to (but not</span>
  <span class="Comment"># including) index first-empty. The reader always modifies it at first-full,</span>
  <span class="Comment"># while the writer always modifies it at first-empty.</span>
  data:address:array:_elem
]

<span class="Comment"># Since channels have two ends, and since it's an error to use either end from</span>
<span class="Comment"># multiple routines, let's distinguish the ends.</span>

<span class="muData">container</span> source:_elem [
  chan:address:channel:_elem
]

<span class="muData">container</span> sink:_elem [
  chan:address:channel:_elem
]

<span class="muRecipe">def</span> new-channel capacity:number<span class="muRecipe"> -&gt; </span>in:address:source:_elem, out:address:sink:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  result:address:channel:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(channel _elem): type<span class="Delimiter">}</span>
  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">first-full:offset</span>, <span class="Constant">0</span>
  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">first-free:offset</span>, <span class="Constant">0</span>
  capacity<span class="Special"> &lt;- </span>add capacity, <span class="Constant">1</span>  <span class="Comment"># unused slot for 'full?' below</span>
  data:address:array:_elem<span class="Special"> &lt;- </span>new <span class="Constant">_elem:type</span>, capacity
  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">data:offset</span>, data
  in<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(source _elem): type<span class="Delimiter">}</span>
  *in<span class="Special"> &lt;- </span>put *in, <span class="Constant">chan:offset</span>, result
  out<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(sink _elem): type<span class="Delimiter">}</span>
  *out<span class="Special"> &lt;- </span>put *out, <span class="Constant">chan:offset</span>, result
]

<span class="muRecipe">def</span> write out:address:sink:_elem, val:_elem<span class="muRecipe"> -&gt; </span>out:address:sink:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  chan:address:channel:_elem<span class="Special"> &lt;- </span>get *out, <span class="Constant">chan:offset</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># block if chan is full</span>
    full:boolean<span class="Special"> &lt;- </span>channel-full? chan
    <span class="muControl">break-unless</span> full
    full-address:location<span class="Special"> &lt;- </span>get-location *chan, <span class="Constant">first-full:offset</span>
    wait-for-location full-address
  <span class="Delimiter">}</span>
  <span class="Comment"># store val</span>
  circular-buffer:address:array:_elem<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
  free:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-free:offset</span>
  *circular-buffer<span class="Special"> &lt;- </span>put-index *circular-buffer, free, val
  <span class="Comment"># mark its slot as filled</span>
  <span class="Comment"># todo: clear the slot itself</span>
  free<span class="Special"> &lt;- </span>add free, <span class="Constant">1</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># wrap free around to 0 if necessary</span>
    len:number<span class="Special"> &lt;- </span>length *circular-buffer
    at-end?:boolean<span class="Special"> &lt;- </span>greater-or-equal free, len
    <span class="muControl">break-unless</span> at-end?
    free<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># write back</span>
  *chan<span class="Special"> &lt;- </span>put *chan, <span class="Constant">first-free:offset</span>, free
]

<span class="muRecipe">def</span> read in:address:source:_elem<span class="muRecipe"> -&gt; </span>result:_elem, in:address:source:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  chan:address:channel:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">chan:offset</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># block if chan is empty</span>
    empty?:boolean<span class="Special"> &lt;- </span>channel-empty? chan
    <span class="muControl">break-unless</span> empty?
    free-address:location<span class="Special"> &lt;- </span>get-location *chan, <span class="Constant">first-free:offset</span>
    wait-for-location free-address
  <span class="Delimiter">}</span>
  <span class="Comment"># pull result off</span>
  full:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-full:offset</span>
  circular-buffer:address:array:_elem<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
  result<span class="Special"> &lt;- </span>index *circular-buffer, full
  <span class="Comment"># mark its slot as empty</span>
  <span class="Comment"># todo: clear the slot itself</span>
  full<span class="Special"> &lt;- </span>add full, <span class="Constant">1</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># wrap full around to 0 if necessary</span>
    len:number<span class="Special"> &lt;- </span>length *circular-buffer
    at-end?:boolean<span class="Special"> &lt;- </span>greater-or-equal full, len
    <span class="muControl">break-unless</span> at-end?
    full<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># write back</span>
  *chan<span class="Special"> &lt;- </span>put *chan, <span class="Constant">first-full:offset</span>, full
]

<span class="muRecipe">def</span> clear in:address:source:_elem<span class="muRecipe"> -&gt; </span>in:address:source:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  chan:address:channel:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">chan:offset</span>
  <span class="Delimiter">{</span>
    empty?:boolean<span class="Special"> &lt;- </span>channel-empty? chan
    <span class="muControl">break-if</span> empty?
    _, in<span class="Special"> &lt;- </span>read in
  <span class="Delimiter">}</span>
]

<span class="muScenario">scenario</span> channel-initialization [
  run [
    <span class="Constant">1</span>:address:source:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
    <span class="Constant">2</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:channel:number, <span class="Constant">first-full:offset</span>
    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:channel:number, <span class="Constant">first-free:offset</span>
  ]
  memory-should-contain [
    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first-full</span>
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first-free</span>
  ]
]

<span class="muScenario">scenario</span> channel-write-increments-free [
  run [
    _, <span class="Constant">1</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
    <span class="Constant">1</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:sink:number, <span class="Constant">34</span>
    <span class="Constant">2</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:sink:number, <span class="Constant">chan:offset</span>
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:channel:character, <span class="Constant">first-full:offset</span>
    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:channel:character, <span class="Constant">first-free:offset</span>
  ]
  memory-should-contain [
    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first-full</span>
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># first-free</span>
  ]
]

<span class="muScenario">scenario</span> channel-read-increments-full [
  run [
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
    <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:number, <span class="Constant">34</span>
    _, <span class="Constant">1</span>:address:source:number<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:source:number
    <span class="Constant">3</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:channel:number, <span class="Constant">first-full:offset</span>
    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:channel:number, <span class="Constant">first-free:offset</span>
  ]
  memory-should-contain [
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># first-full</span>
    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># first-free</span>
  ]
]

<span class="muScenario">scenario</span> channel-wrap [
  run [
    <span class="Comment"># channel with just 1 slot</span>
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
    <span class="Constant">3</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Comment"># write and read a value</span>
    <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:number, <span class="Constant">34</span>
    _, <span class="Constant">1</span>:address:source:number<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:source:number
    <span class="Comment"># first-free will now be 1</span>
    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:channel:number, <span class="Constant">first-free:offset</span>
    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:channel:number, <span class="Constant">first-free:offset</span>
    <span class="Comment"># write second value, verify that first-free wraps</span>
    <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:number, <span class="Constant">34</span>
    <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:channel:number, <span class="Constant">first-free:offset</span>
    <span class="Comment"># read second value, verify that first-full wraps</span>
    _, <span class="Constant">1</span>:address:source:number<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:source:number
    <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:channel:number, <span class="Constant">first-full:offset</span>
  ]
  memory-should-contain [
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># first-free after first write</span>
    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># first-full after first read</span>
    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first-free after second write, wrapped</span>
    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first-full after second read, wrapped</span>
  ]
]

<span class="SalientComment">## helpers</span>

<span class="Comment"># An empty channel has first-empty and first-full both at the same value.</span>
<span class="muRecipe">def</span> channel-empty? chan:address:channel:_elem<span class="muRecipe"> -&gt; </span>result:boolean [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="Comment"># return chan.first-full == chan.first-free</span>
  full:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-full:offset</span>
  free:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-free:offset</span>
  result<span class="Special"> &lt;- </span>equal full, free
]

<span class="Comment"># A full channel has first-empty just before first-full, wasting one slot.</span>
<span class="Comment"># (Other alternatives: <a href="https://en.wikipedia.org/wiki/Circular_buffer#Full_.2F_Empty_Buffer_Distinction)">https://en.wikipedia.org/wiki/Circular_buffer#Full_.2F_Empty_Buffer_Distinction)</a></span>
<span class="muRecipe">def</span> channel-full? chan:address:channel:_elem<span class="muRecipe"> -&gt; </span>result:boolean [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="Comment"># tmp = chan.first-free + 1</span>
  tmp:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-free:offset</span>
  tmp<span class="Special"> &lt;- </span>add tmp, <span class="Constant">1</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># if tmp == chan.capacity, tmp = 0</span>
    len:number<span class="Special"> &lt;- </span>capacity chan
    at-end?:boolean<span class="Special"> &lt;- </span>greater-or-equal tmp, len
    <span class="muControl">break-unless</span> at-end?
    tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># return chan.first-full == tmp</span>
  full:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-full:offset</span>
  result<span class="Special"> &lt;- </span>equal full, tmp
]

<span class="muRecipe">def</span> capacity chan:address:channel:_elem<span class="muRecipe"> -&gt; </span>result:number [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  q:address:array:_elem<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
  result<span class="Special"> &lt;- </span>length *q
]

<span class="muScenario">scenario</span> channel-new-empty-not-full [
  run [
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
    <span class="Constant">3</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">3</span>:address:channel:number
    <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">3</span>:address:channel:number
  ]
  memory-should-contain [
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># empty?</span>
    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># full?</span>
  ]
]

<span class="muScenario">scenario</span> channel-write-not-empty [
  run [
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
    <span class="Constant">3</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:number, <span class="Constant">34</span>
    <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">3</span>:address:channel:number
    <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">3</span>:address:channel:number
  ]
  memory-should-contain [
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># empty?</span>
    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># full?</span>
  ]
]

<span class="muScenario">scenario</span> channel-write-full [
  run [
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
    <span class="Constant">3</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:number, <span class="Constant">34</span>
    <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">3</span>:address:channel:number
    <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">3</span>:address:channel:number
  ]
  memory-should-contain [
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># empty?</span>
    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># full?</span>
  ]
]

<span class="muScenario">scenario</span> channel-read-not-full [
  run [
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
    <span class="Constant">3</span>:address:channel:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:number, <span class="Constant">34</span>
    _, <span class="Constant">1</span>:address:source:number<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:source:number
    <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">3</span>:address:channel:number
    <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">3</span>:address:channel:number
  ]
  memory-should-contain [
    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># empty?</span>
    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># full?</span>
  ]
]

<span class="Comment"># helper for channels of characters in particular</span>
<span class="muRecipe">def</span> buffer-lines in:address:source:character, buffered-out:address:sink:character<span class="muRecipe"> -&gt; </span>buffered-out:address:sink:character, in:address:source:character [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="Comment"># repeat forever</span>
  <span class="Delimiter">{</span>
    line:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">30</span>
    <span class="Comment"># read characters from 'in' until newline, copy into line</span>
    <span class="Delimiter">{</span>
<span class="Constant">      +next-character</span>
      c:character, in<span class="Special"> &lt;- </span>read in
      <span class="Comment"># drop a character on backspace</span>
      <span class="Delimiter">{</span>
        <span class="Comment"># special-case: if it's a backspace</span>
        backspace?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">8</span>
        <span class="muControl">break-unless</span> backspace?
        <span class="Comment"># drop previous character</span>
        <span class="Delimiter">{</span>
          buffer-length:number<span class="Special"> &lt;- </span>get *line, <span class="Constant">length:offset</span>
          buffer-empty?:boolean<span class="Special"> &lt;- </span>equal buffer-length, <span class="Constant">0</span>
          <span class="muControl">break-if</span> buffer-empty?
          buffer-length<span class="Special"> &lt;- </span>subtract buffer-length, <span class="Constant">1</span>
          *line<span class="Special"> &lt;- </span>put *line, <span class="Constant">length:offset</span>, buffer-length
        <span class="Delimiter">}</span>
        <span class="Comment"># and don't append this one</span>
        <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>
      <span class="Delimiter">}</span>
      <span class="Comment"># append anything else</span>
      line<span class="Special"> &lt;- </span>append line, c
      line-done?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
      <span class="muControl">break-if</span> line-done?
      <span class="Comment"># stop buffering on eof (currently only generated by fake console)</span>
      eof?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">0/eof</span>
      <span class="muControl">break-if</span> eof?
      <span class="muControl">loop</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># copy line into 'buffered-out'</span>
    i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
    line-contents:address:array:character<span class="Special"> &lt;- </span>get *line, <span class="Constant">data:offset</span>
    max:number<span class="Special"> &lt;- </span>get *line, <span class="Constant">length:offset</span>
    <span class="Delimiter">{</span>
      done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, max
      <span class="muControl">break-if</span> done?
      c:character<span class="Special"> &lt;- </span>index *line-contents, i
      buffered-out<span class="Special"> &lt;- </span>write buffered-out, c
      i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
      <span class="muControl">loop</span>
    <span class="Delimiter">}</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muScenario">scenario</span> buffer-lines-blocks-until-newline [
  run [
    <span class="Constant">1</span>:address:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
    _, <span class="Constant">3</span>:address:sink:number/buffered-stdin<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
    <span class="Constant">4</span>:address:channel:number/buffered-stdin<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:source:number, <span class="Constant">chan:offset</span>
    <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">4</span>:address:channel:character/buffered-stdin
    assert <span class="Constant">5</span>:boolean, <span class="Constant">[ </span>
<span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after init]</span>
    <span class="Comment"># buffer stdin into buffered-stdin, try to read from buffered-stdin</span>
    <span class="Constant">6</span>:number/buffer-routine<span class="Special"> &lt;- </span>start-running buffer-lines, <span class="Constant">1</span>:address:source:character/stdin, <span class="Constant">3</span>:address:sink:character/buffered-stdin
    wait-for-routine <span class="Constant">6</span>:number/buffer-routine
    <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">4</span>:address:channel:character/buffered-stdin
    assert <span class="Constant">7</span>:boolean, <span class="Constant">[ </span>
<span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after buffer-lines bring-up]</span>
    <span class="Comment"># write 'a'</span>
    <span class="Constant">2</span>:address:sink:character<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:character, <span class="Constant">97/a</span>
    restart <span class="Constant">6</span>:number/buffer-routine
    wait-for-routine <span class="Constant">6</span>:number/buffer-routine
    <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">4</span>:address:channel:character/buffered-stdin
    assert <span class="Constant">8</span>:boolean, <span class="Constant">[ </span>
<span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after writing 'a']</span>
    <span class="Comment"># write 'b'</span>
    <span class="Constant">2</span>:address:sink:character<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:character, <span class="Constant">98/b</span>
    restart <span class="Constant">6</span>:number/buffer-routine
    wait-for-routine <span class="Constant">6</span>:number/buffer-routine
    <span class="Constant">9</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">4</span>:address:channel:character/buffered-stdin
    assert <span class="Constant">9</span>:boolean, <span class="Constant">[ </span>
<span class="Constant">F buffer-lines-blocks-until-newline: channel should be empty after writing 'b']</span>
    <span class="Comment"># write newline</span>
    <span class="Constant">2</span>:address:sink:character<span class="Special"> &lt;- </span>write <span class="Constant">2</span>:address:sink:character, <span class="Constant">10/newline</span>
    restart <span class="Constant">6</span>:number/buffer-routine
    wait-for-routine <span class="Constant">6</span>:number/buffer-routine
    <span class="Constant">10</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">4</span>:address:channel:character/buffered-stdin
    <span class="Constant">11</span>:boolean/completed?<span class="Special"> &lt;- </span>not <span class="Constant">10</span>:boolean
    assert <span class="Constant">11</span>:boolean/completed?, <span class="Constant">[ </span>
<span class="Constant">F buffer-lines-blocks-until-newline: channel should contain data after writing newline]</span>
    trace <span class="Constant">1</span>, <span class="Constant">[test]</span>, <span class="Constant">[reached end]</span>
  ]
  trace-should-contain [
    test: reached end
  ]
]
</pre>
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