4840

New helper: printing a string to a buffered file.

11 files changed, 533 insertions, 22 deletions

diff --git a/html/subx/059read-byte.subx.html b/html/subx/059read-byte.subx.html
index fd8af4bf..07822a01 100644
--- a/html/subx/059read-byte.subx.html
+++ b/html/subx/059read-byte.subx.html
@@ -147,7 +147,7 @@ if ('onhashchange' in window) {
 <span id="L81" class="LineNr"> 81 </span>    <span class="subxComment"># read byte from stream</span>
 <span id="L82" class="LineNr"> 82 </span>    <span class="subxComment"># AL = f-&gt;data[f-&gt;read]</span>
 <span id="L83" class="LineNr"> 83 </span>    31/xor                          3/mod/direct    0/rm32/EAX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          0/r32/EAX  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># clear EAX</span>
-<span id="L84" class="LineNr"> 84 </span>    8a/copy-byte                    1/mod/*+disp8   4/rm32/sib    6/base/ESI  1/index/ECX  <span class="CommentedCode"> . </span>          0/r32/AL    0x10/disp8     <span class="CommentedCode"> . </span>                <span class="subxComment"># copy *(ESI+ECX+16) to AL</span>
+<span id="L84" class="LineNr"> 84 </span>    8a/copy-byte                    1/mod/*+disp8   4/rm32/sib    6/base/ESI  1/index/ECX  <span class="CommentedCode"> . </span>          0/r32/AL    0x10/disp8     <span class="CommentedCode"> . </span>                <span class="subxComment"># copy byte at *(ESI+ECX+16) to AL</span>
 <span id="L85" class="LineNr"> 85 </span>    <span class="subxComment"># ++f-&gt;read</span>
 <span id="L86" class="LineNr"> 86 </span>    ff          0/subop/increment   1/mod/*+disp8   6/rm32/ESI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>          8/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># increment *(ESI+8)</span>
 <span id="L87" class="LineNr"> 87 </span><span class="Constant">$read-byte:end</span>:
@@ -300,19 +300,20 @@ if ('onhashchange' in window) {
 <span id="L234" class="LineNr">234 </span>
 <span id="L235" class="LineNr">235 </span>== data
 <span id="L236" class="LineNr">236 </span>
-<span id="L237" class="LineNr">237 </span><span class="subxMinorFunction">_test-buffered-file</span>:
-<span id="L238" class="LineNr">238 </span>    <span class="subxComment"># file descriptor or (address stream)</span>
-<span id="L239" class="LineNr">239 </span>    _test-stream/imm32
-<span id="L240" class="LineNr">240 </span>    <span class="subxComment"># current write index</span>
-<span id="L241" class="LineNr">241 </span>    00 00 00 00
-<span id="L242" class="LineNr">242 </span>    <span class="subxComment"># current read index</span>
-<span id="L243" class="LineNr">243 </span>    00 00 00 00
-<span id="L244" class="LineNr">244 </span>    <span class="subxComment"># length (8)</span>
-<span id="L245" class="LineNr">245 </span>    08 00 00 00
-<span id="L246" class="LineNr">246 </span>    <span class="subxComment"># data</span>
-<span id="L247" class="LineNr">247 </span>    00 00 00 00 00 00 00 00  <span class="subxComment"># 8 bytes</span>
-<span id="L248" class="LineNr">248 </span>
-<span id="L249" class="LineNr">249 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
+<span id="L237" class="LineNr">237 </span><span class="subxComment"># a test buffered file for _test-stream</span>
+<span id="L238" class="LineNr">238 </span><span class="subxMinorFunction">_test-buffered-file</span>:
+<span id="L239" class="LineNr">239 </span>    <span class="subxComment"># file descriptor or (address stream)</span>
+<span id="L240" class="LineNr">240 </span>    _test-stream/imm32
+<span id="L241" class="LineNr">241 </span>    <span class="subxComment"># current write index</span>
+<span id="L242" class="LineNr">242 </span>    00 00 00 00
+<span id="L243" class="LineNr">243 </span>    <span class="subxComment"># current read index</span>
+<span id="L244" class="LineNr">244 </span>    00 00 00 00
+<span id="L245" class="LineNr">245 </span>    <span class="subxComment"># length (6)</span>
+<span id="L246" class="LineNr">246 </span>    06 00 00 00
+<span id="L247" class="LineNr">247 </span>    <span class="subxComment"># data</span>
+<span id="L248" class="LineNr">248 </span>    00 00 00 00 00 00  <span class="subxComment"># 6 bytes</span>
+<span id="L249" class="LineNr">249 </span>
+<span id="L250" class="LineNr">250 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
 </pre>
 </body>
 </html>
diff --git a/html/subx/064write-buffered.subx.html b/html/subx/064write-buffered.subx.html
new file mode 100644
index 00000000..c87ecb79
--- /dev/null
+++ b/html/subx/064write-buffered.subx.html
@@ -0,0 +1,289 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<title>Mu - subx/064write-buffered.subx</title>
+<meta name="Generator" content="Vim/8.0">
+<meta name="plugin-version" content="vim7.4_v2">
+<meta name="syntax" content="none">
+<meta name="settings" content="number_lines,use_css,no_foldcolumn,expand_tabs,line_ids,prevent_copy=">
+<meta name="colorscheme" content="minimal">
+<style type="text/css">
+<!--
+pre { font-family: monospace; color: #aaaaaa; background-color: #080808; }
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+.subxH1Comment { color:#00ffff; }
+-->
+</style>
+
+<script type='text/javascript'>
+<!--
+
+/* function to open any folds containing a jumped-to line before jumping to it */
+function JumpToLine()
+{
+  var lineNum;
+  lineNum = window.location.hash;
+  lineNum = lineNum.substr(1); /* strip off '#' */
+
+  if (lineNum.indexOf('L') == -1) {
+    lineNum = 'L'+lineNum;
+  }
+  lineElem = document.getElementById(lineNum);
+  /* Always jump to new location even if the line was hidden inside a fold, or
+   * we corrected the raw number to a line ID.
+   */
+  if (lineElem) {
+    lineElem.scrollIntoView(true);
+  }
+  return true;
+}
+if ('onhashchange' in window) {
+  window.onhashchange = JumpToLine;
+}
+
+-->
+</script>
+</head>
+<body onload='JumpToLine();'>
+<a href='https://github.com/akkartik/mu/blob/master/subx/064write-buffered.subx'>https://github.com/akkartik/mu/blob/master/subx/064write-buffered.subx</a>
+<pre id='vimCodeElement'>
+<span id="L1" class="LineNr">  1 </span><span class="subxComment"># write-buffered: like 'write', but for a buffered-file</span>
+<span id="L2" class="LineNr">  2 </span>
+<span id="L3" class="LineNr">  3 </span>== code
+<span id="L4" class="LineNr">  4 </span><span class="subxComment">#   instruction                     effective address                                                   register    displacement    immediate</span>
+<span id="L5" class="LineNr">  5 </span><span class="subxS1Comment"># . op          subop               mod             rm32          base        index         scale       r32</span>
+<span id="L6" class="LineNr">  6 </span><span class="subxS1Comment"># . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes</span>
+<span id="L7" class="LineNr">  7 </span>
+<span id="L8" class="LineNr">  8 </span><span class="subxComment"># main:</span>
+<span id="L9" class="LineNr">  9 </span><span class="CommentedCode">#?     e8/call test-write-buffered/disp32</span>
+<span id="L10" class="LineNr"> 10 </span><span class="CommentedCode">#?     e8/call test-write-buffered-with-intermediate-flush/disp32</span>
+<span id="L11" class="LineNr"> 11 </span>    e8/call  run-tests/disp32  <span class="subxComment"># 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.</span>
+<span id="L12" class="LineNr"> 12 </span>    <span class="subxComment"># syscall(exit, Num-test-failures)</span>
+<span id="L13" class="LineNr"> 13 </span>    8b/copy                         0/mod/indirect  5/rm32/.disp32           <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          3/r32/EBX   <span class="SpecialChar">Num-test-failures</span>/disp32          <span class="subxComment"># copy *Num-test-failures to EBX</span>
+<span id="L14" class="LineNr"> 14 </span>    b8/copy-to-EAX  1/imm32
+<span id="L15" class="LineNr"> 15 </span>    cd/syscall  0x80/imm8
+<span id="L16" class="LineNr"> 16 </span>
+<span id="L17" class="LineNr"> 17 </span><span class="subxFunction">write-buffered</span>:  <span class="subxComment"># f : (address buffered-file), msg : (address array byte) -&gt; &lt;void&gt;</span>
+<span id="L18" class="LineNr"> 18 </span>    <span class="subxComment"># pseudocode:</span>
+<span id="L19" class="LineNr"> 19 </span>    <span class="subxComment">#   in = msg-&gt;data</span>
+<span id="L20" class="LineNr"> 20 </span>    <span class="subxComment">#   inend = &amp;msg-&gt;data[msg-&gt;length]</span>
+<span id="L21" class="LineNr"> 21 </span>    <span class="subxComment">#   while in &lt; inend</span>
+<span id="L22" class="LineNr"> 22 </span>    <span class="subxComment">#     if f-&gt;write &gt;= f-&gt;length</span>
+<span id="L23" class="LineNr"> 23 </span>    <span class="subxComment">#       flush(f)</span>
+<span id="L24" class="LineNr"> 24 </span>    <span class="subxComment">#       clear-stream(f)</span>
+<span id="L25" class="LineNr"> 25 </span>    <span class="subxComment">#     f-&gt;data[f-&gt;write] = *in</span>
+<span id="L26" class="LineNr"> 26 </span>    <span class="subxComment">#     ++f-&gt;write</span>
+<span id="L27" class="LineNr"> 27 </span>    <span class="subxComment">#     ++in</span>
+<span id="L28" class="LineNr"> 28 </span>    <span class="subxComment">#</span>
+<span id="L29" class="LineNr"> 29 </span>    <span class="subxComment"># registers:</span>
+<span id="L30" class="LineNr"> 30 </span>    <span class="subxComment">#   ESI : in</span>
+<span id="L31" class="LineNr"> 31 </span>    <span class="subxComment">#   ECX : inend</span>
+<span id="L32" class="LineNr"> 32 </span>    <span class="subxComment">#   EDI : f</span>
+<span id="L33" class="LineNr"> 33 </span>    <span class="subxComment">#   EDX : f-&gt;length</span>
+<span id="L34" class="LineNr"> 34 </span>    <span class="subxComment">#   EBX : f-&gt;write (cached copy, need to keep in sync)</span>
+<span id="L35" class="LineNr"> 35 </span>    <span class="subxComment">#   EAX : temp</span>
+<span id="L36" class="LineNr"> 36 </span>    <span class="subxComment">#</span>
+<span id="L37" class="LineNr"> 37 </span>    <span class="subxS1Comment"># . prolog</span>
+<span id="L38" class="LineNr"> 38 </span>    55/push-EBP
+<span id="L39" class="LineNr"> 39 </span>    89/copy                         3/mod/direct    5/rm32/EBP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          4/r32/ESP  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># copy ESP to EBP</span>
+<span id="L40" class="LineNr"> 40 </span>    <span class="subxS1Comment"># . save registers</span>
+<span id="L41" class="LineNr"> 41 </span>    50/push-EAX
+<span id="L42" class="LineNr"> 42 </span>    51/push-ECX
+<span id="L43" class="LineNr"> 43 </span>    52/push-EDX
+<span id="L44" class="LineNr"> 44 </span>    53/push-EBX
+<span id="L45" class="LineNr"> 45 </span>    56/push-ESI
+<span id="L46" class="LineNr"> 46 </span>    57/push-EDI
+<span id="L47" class="LineNr"> 47 </span>    <span class="subxComment"># EAX = msg</span>
+<span id="L48" class="LineNr"> 48 </span>    8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none              0/r32/EAX   0xc/disp8      <span class="CommentedCode"> . </span>                <span class="subxComment"># copy *(EBP+12) to EAX</span>
+<span id="L49" class="LineNr"> 49 </span>    <span class="subxComment"># in/ESI = msg-&gt;data</span>
+<span id="L50" class="LineNr"> 50 </span>    8d/copy-address                 1/mod/*+disp8   0/rm32/EAX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          6/r32/ESI   4/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># copy EAX+4 to ESI</span>
+<span id="L51" class="LineNr"> 51 </span>    <span class="subxComment"># inend/ECX = &amp;msg-&gt;data[msg-&gt;length]</span>
+<span id="L52" class="LineNr"> 52 </span>    8b/copy                         0/mod/indirect  0/rm32/EAX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          1/r32/ECX  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># copy *EAX to ECX</span>
+<span id="L53" class="LineNr"> 53 </span>    8d/copy-address                 0/mod/indirect  4/rm32/sib    6/base/ESI  1/index/ECX  <span class="CommentedCode"> . </span>          1/r32/ECX  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># copy ESI+ECX to ECX</span>
+<span id="L54" class="LineNr"> 54 </span>    <span class="subxComment"># EDI = f</span>
+<span id="L55" class="LineNr"> 55 </span>    8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none              7/r32/EDI   8/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># copy *(EBP+8) to EDI</span>
+<span id="L56" class="LineNr"> 56 </span>    <span class="subxComment"># EDX = f-&gt;length</span>
+<span id="L57" class="LineNr"> 57 </span>    8b/copy                         1/mod/*+disp8   7/rm32/EDI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          2/r32/EDX   0xc/disp8      <span class="CommentedCode"> . </span>                <span class="subxComment"># copy *(EDI+12) to EDX</span>
+<span id="L58" class="LineNr"> 58 </span>    <span class="subxComment"># EBX = f-&gt;write</span>
+<span id="L59" class="LineNr"> 59 </span>    8b/copy                         1/mod/*+disp8   7/rm32/EDI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          3/r32/EBX   4/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># copy *(EDI+4) to EBX</span>
+<span id="L60" class="LineNr"> 60 </span><span class="Constant">$write-buffered:loop</span>:
+<span id="L61" class="LineNr"> 61 </span>    <span class="subxComment"># if (in &gt;= inend) break</span>
+<span id="L62" class="LineNr"> 62 </span>    39/compare                      3/mod/direct    6/rm32/ESI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          1/r32/ECX  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># compare ESI with ECX</span>
+<span id="L63" class="LineNr"> 63 </span>    7d/jump-if-greater-or-equal  $write-buffered:loop-end/disp8
+<span id="L64" class="LineNr"> 64 </span>    <span class="subxComment"># if (f-&gt;write &gt;= f-&gt;length) flush and clear f's stream</span>
+<span id="L65" class="LineNr"> 65 </span>    39/compare                      3/mod/direct    3/rm32/EBX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          2/r32/EDX  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># compare EBX with EDX</span>
+<span id="L66" class="LineNr"> 66 </span>    7c/jump-if-lesser  $write-buffered:to-stream/disp8
+<span id="L67" class="LineNr"> 67 </span>    <span class="subxS1Comment"># . persist f-&gt;write</span>
+<span id="L68" class="LineNr"> 68 </span>    89/copy                         1/mod/*+disp8   7/rm32/EDI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          3/r32/EBX   4/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># copy EBX to *(EDI+4)</span>
+<span id="L69" class="LineNr"> 69 </span>    <span class="subxS1Comment"># . flush(f)</span>
+<span id="L70" class="LineNr"> 70 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L71" class="LineNr"> 71 </span>    57/push-EDI
+<span id="L72" class="LineNr"> 72 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L73" class="LineNr"> 73 </span>    e8/call  flush/disp32
+<span id="L74" class="LineNr"> 74 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L75" class="LineNr"> 75 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              4/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L76" class="LineNr"> 76 </span>    <span class="subxS1Comment"># . clear-stream(stream = f+4)</span>
+<span id="L77" class="LineNr"> 77 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L78" class="LineNr"> 78 </span>    8d/copy-address                 1/mod/*+disp8   7/rm32/EDI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          0/r32/EAX   4/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># copy EDI+4 to EAX</span>
+<span id="L79" class="LineNr"> 79 </span>    50/push-EAX
+<span id="L80" class="LineNr"> 80 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L81" class="LineNr"> 81 </span>    e8/call  clear-stream/disp32
+<span id="L82" class="LineNr"> 82 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L83" class="LineNr"> 83 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              4/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L84" class="LineNr"> 84 </span>    <span class="subxS1Comment"># . clear EBX (cached f-&gt;write)</span>
+<span id="L85" class="LineNr"> 85 </span>    31/xor                          3/mod/direct    3/rm32/EBX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          3/r32/EBX  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># clear EBX</span>
+<span id="L86" class="LineNr"> 86 </span><span class="Constant">$write-buffered:to-stream</span>:
+<span id="L87" class="LineNr"> 87 </span>    <span class="subxComment"># write to stream</span>
+<span id="L88" class="LineNr"> 88 </span>    <span class="subxComment"># f-&gt;data[f-&gt;write] = *in</span>
+<span id="L89" class="LineNr"> 89 </span>    <span class="subxS1Comment"># . AL = *in</span>
+<span id="L90" class="LineNr"> 90 </span>    31/xor                          3/mod/direct    0/rm32/EAX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          0/r32/EAX  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># clear EAX</span>
+<span id="L91" class="LineNr"> 91 </span>    8a/copy-byte                    0/mod/indirect  6/rm32/ESI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          0/r32/AL   <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># copy byte at *ESI to AL</span>
+<span id="L92" class="LineNr"> 92 </span>    <span class="subxS1Comment"># . f-&gt;data[f-&gt;write] = AL</span>
+<span id="L93" class="LineNr"> 93 </span>    88/copy-byte                    1/mod/*+disp8   4/rm32/sib    7/base/EDI  3/index/EBX  <span class="CommentedCode"> . </span>          0/r32/AL    0x10/disp8     <span class="CommentedCode"> . </span>                <span class="subxComment"># copy AL to *(EDI+EBX+16)</span>
+<span id="L94" class="LineNr"> 94 </span>    <span class="subxComment"># ++f-&gt;write</span>
+<span id="L95" class="LineNr"> 95 </span>    43/increment-EBX
+<span id="L96" class="LineNr"> 96 </span>    <span class="subxComment"># ++in</span>
+<span id="L97" class="LineNr"> 97 </span>    46/increment-ESI
+<span id="L98" class="LineNr"> 98 </span>    eb/jump  $write-buffered:loop/disp8
+<span id="L99" class="LineNr"> 99 </span><span class="Constant">$write-buffered:loop-end</span>:
+<span id="L100" class="LineNr">100 </span>    <span class="subxComment"># persist necessary variables from registers</span>
+<span id="L101" class="LineNr">101 </span>    89/copy                         1/mod/*+disp8   7/rm32/EDI   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          3/r32/EBX   4/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># copy EBX to *(EDI+4)</span>
+<span id="L102" class="LineNr">102 </span><span class="Constant">$write-buffered:end</span>:
+<span id="L103" class="LineNr">103 </span>    <span class="subxS1Comment"># . restore registers</span>
+<span id="L104" class="LineNr">104 </span>    5f/pop-to-EDI
+<span id="L105" class="LineNr">105 </span>    5e/pop-to-ESI
+<span id="L106" class="LineNr">106 </span>    5b/pop-to-EBX
+<span id="L107" class="LineNr">107 </span>    5a/pop-to-EDX
+<span id="L108" class="LineNr">108 </span>    59/pop-to-ECX
+<span id="L109" class="LineNr">109 </span>    58/pop-to-EAX
+<span id="L110" class="LineNr">110 </span>    <span class="subxS1Comment"># . epilog</span>
+<span id="L111" class="LineNr">111 </span>    89/copy                         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>          5/r32/EBP  <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># copy EBP to ESP</span>
+<span id="L112" class="LineNr">112 </span>    5d/pop-to-EBP
+<span id="L113" class="LineNr">113 </span>    c3/return
+<span id="L114" class="LineNr">114 </span>
+<span id="L115" class="LineNr">115 </span><span class="subxTest">test-write-buffered</span>:
+<span id="L116" class="LineNr">116 </span>    <span class="subxH1Comment"># - check that write-buffered writes to the file</span>
+<span id="L117" class="LineNr">117 </span>    <span class="subxComment"># setup</span>
+<span id="L118" class="LineNr">118 </span>    <span class="subxS1Comment"># . clear-stream(_test-stream)</span>
+<span id="L119" class="LineNr">119 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L120" class="LineNr">120 </span>    68/push  _test-stream/imm32
+<span id="L121" class="LineNr">121 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L122" class="LineNr">122 </span>    e8/call  clear-stream/disp32
+<span id="L123" class="LineNr">123 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L124" class="LineNr">124 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              4/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L125" class="LineNr">125 </span>    <span class="subxS1Comment"># . clear-stream(_test-buffered-file+4)</span>
+<span id="L126" class="LineNr">126 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L127" class="LineNr">127 </span>    b8/copy-to-EAX  _test-buffered-file/imm32
+<span id="L128" class="LineNr">128 </span>    05/add-to-EAX  4/imm32
+<span id="L129" class="LineNr">129 </span>    50/push-EAX
+<span id="L130" class="LineNr">130 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L131" class="LineNr">131 </span>    e8/call  clear-stream/disp32
+<span id="L132" class="LineNr">132 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L133" class="LineNr">133 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              4/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L134" class="LineNr">134 </span>    <span class="subxComment"># write-buffered(_test-buffered-file, &quot;Abc&quot;)</span>
+<span id="L135" class="LineNr">135 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L136" class="LineNr">136 </span>    68/push  <span class="Constant">&quot;Abc&quot;</span>/imm32
+<span id="L137" class="LineNr">137 </span>    68/push  _test-buffered-file/imm32
+<span id="L138" class="LineNr">138 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L139" class="LineNr">139 </span>    e8/call  write-buffered/disp32
+<span id="L140" class="LineNr">140 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L141" class="LineNr">141 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              8/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L142" class="LineNr">142 </span>    <span class="subxComment"># flush(_test-buffered-file)</span>
+<span id="L143" class="LineNr">143 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L144" class="LineNr">144 </span>    68/push  _test-buffered-file/imm32
+<span id="L145" class="LineNr">145 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L146" class="LineNr">146 </span>    e8/call  flush/disp32
+<span id="L147" class="LineNr">147 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L148" class="LineNr">148 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              4/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L149" class="LineNr">149 </span>    <span class="subxComment"># check-ints-equal(*_test-stream-&gt;data, &quot;Abc&quot;, msg)</span>
+<span id="L150" class="LineNr">150 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L151" class="LineNr">151 </span>    68/push  <span class="Constant">&quot;F - test-write-buffered-single&quot;</span>/imm32
+<span id="L152" class="LineNr">152 </span>    68/push  0x636241/imm32
+<span id="L153" class="LineNr">153 </span>    <span class="subxS2Comment"># . . push *_test-stream-&gt;data</span>
+<span id="L154" class="LineNr">154 </span>    b8/copy-to-EAX  _test-stream/imm32
+<span id="L155" class="LineNr">155 </span>    ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>          0xc/disp8      <span class="CommentedCode"> . </span>                <span class="subxComment"># push *(EAX+12)</span>
+<span id="L156" class="LineNr">156 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L157" class="LineNr">157 </span>    e8/call  check-ints-equal/disp32
+<span id="L158" class="LineNr">158 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L159" class="LineNr">159 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              0xc/imm32         <span class="subxComment"># add to ESP</span>
+<span id="L160" class="LineNr">160 </span>    <span class="subxS1Comment"># . end</span>
+<span id="L161" class="LineNr">161 </span>    c3/return
+<span id="L162" class="LineNr">162 </span>
+<span id="L163" class="LineNr">163 </span><span class="subxTest">test-write-buffered-with-intermediate-flush</span>:
+<span id="L164" class="LineNr">164 </span>    <span class="subxH1Comment"># - check that write-buffered flushes in the middle if its buffer fills up</span>
+<span id="L165" class="LineNr">165 </span>    <span class="subxComment"># setup</span>
+<span id="L166" class="LineNr">166 </span>    <span class="subxS1Comment"># . clear-stream(_test-stream)</span>
+<span id="L167" class="LineNr">167 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L168" class="LineNr">168 </span>    68/push  _test-stream/imm32
+<span id="L169" class="LineNr">169 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L170" class="LineNr">170 </span>    e8/call  clear-stream/disp32
+<span id="L171" class="LineNr">171 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L172" class="LineNr">172 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              4/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L173" class="LineNr">173 </span>    <span class="subxS1Comment"># . clear-stream(_test-buffered-file+4)</span>
+<span id="L174" class="LineNr">174 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L175" class="LineNr">175 </span>    b8/copy-to-EAX  _test-buffered-file/imm32
+<span id="L176" class="LineNr">176 </span>    05/add-to-EAX  4/imm32
+<span id="L177" class="LineNr">177 </span>    50/push-EAX
+<span id="L178" class="LineNr">178 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L179" class="LineNr">179 </span>    e8/call  clear-stream/disp32
+<span id="L180" class="LineNr">180 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L181" class="LineNr">181 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              4/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L182" class="LineNr">182 </span>    <span class="subxComment"># _test-stream can hold 8 bytes, but _test-buffered-file can hold only 6.</span>
+<span id="L183" class="LineNr">183 </span>    <span class="subxComment"># Try to write 7 bytes.</span>
+<span id="L184" class="LineNr">184 </span>    <span class="subxS1Comment"># . write-buffered(_test-buffered-file, &quot;Abcdefg&quot;)</span>
+<span id="L185" class="LineNr">185 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L186" class="LineNr">186 </span>    68/push  <span class="Constant">&quot;Abcdefg&quot;</span>/imm32
+<span id="L187" class="LineNr">187 </span>    68/push  _test-buffered-file/imm32
+<span id="L188" class="LineNr">188 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L189" class="LineNr">189 </span>    e8/call  write-buffered/disp32
+<span id="L190" class="LineNr">190 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L191" class="LineNr">191 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              8/imm32           <span class="subxComment"># add to ESP</span>
+<span id="L192" class="LineNr">192 </span>    <span class="subxComment"># don't flush</span>
+<span id="L193" class="LineNr">193 </span>    <span class="subxComment"># 6 bytes should still have gotten to _test-stream</span>
+<span id="L194" class="LineNr">194 </span>    <span class="subxS1Comment"># . check-ints-equal(*_test-stream-&gt;write, 6, msg)</span>
+<span id="L195" class="LineNr">195 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L196" class="LineNr">196 </span>    68/push  <span class="Constant">&quot;F - test-write-buffered-with-intermediate-flush: flushed data&quot;</span>/imm32
+<span id="L197" class="LineNr">197 </span>    68/push  6/imm32
+<span id="L198" class="LineNr">198 </span>    <span class="subxS2Comment"># . . push *_test-stream-&gt;write</span>
+<span id="L199" class="LineNr">199 </span>    b8/copy-to-EAX  _test-stream/imm32
+<span id="L200" class="LineNr">200 </span>    ff          6/subop/push        0/mod/indirect  0/rm32/EAX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>             <span class="CommentedCode"> . </span>                <span class="subxComment"># push *EAX</span>
+<span id="L201" class="LineNr">201 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L202" class="LineNr">202 </span>    e8/call  check-ints-equal/disp32
+<span id="L203" class="LineNr">203 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L204" class="LineNr">204 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              0xc/imm32         <span class="subxComment"># add to ESP</span>
+<span id="L205" class="LineNr">205 </span>    <span class="subxComment"># and 1 byte should still be in _test-buffered-file</span>
+<span id="L206" class="LineNr">206 </span>    <span class="subxS1Comment"># . check-ints-equal(*_test-buffered-file&gt;write, 1, msg)</span>
+<span id="L207" class="LineNr">207 </span>    <span class="subxS2Comment"># . . push args</span>
+<span id="L208" class="LineNr">208 </span>    68/push  <span class="Constant">&quot;F - test-write-buffered-with-intermediate-flush: unflushed bytes&quot;</span>/imm32
+<span id="L209" class="LineNr">209 </span>    68/push  1/imm32
+<span id="L210" class="LineNr">210 </span>    <span class="subxS2Comment"># . . push *_test-buffered-file-&gt;write</span>
+<span id="L211" class="LineNr">211 </span>    b8/copy-to-EAX  _test-buffered-file/imm32
+<span id="L212" class="LineNr">212 </span>    ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>          4/disp8        <span class="CommentedCode"> . </span>                <span class="subxComment"># push *(EAX+4)</span>
+<span id="L213" class="LineNr">213 </span>    <span class="subxS2Comment"># . . call</span>
+<span id="L214" class="LineNr">214 </span>    e8/call  check-ints-equal/disp32
+<span id="L215" class="LineNr">215 </span>    <span class="subxS2Comment"># . . discard args</span>
+<span id="L216" class="LineNr">216 </span>    81          0/subop/add         3/mod/direct    4/rm32/ESP   <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>           <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>         <span class="CommentedCode"> . </span>              0xc/imm32         <span class="subxComment"># add to ESP</span>
+<span id="L217" class="LineNr">217 </span>    <span class="subxS1Comment"># . end</span>
+<span id="L218" class="LineNr">218 </span>    c3/return
+<span id="L219" class="LineNr">219 </span>
+<span id="L220" class="LineNr">220 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
+</pre>
+</body>
+</html>
+<!-- vim: set foldmethod=manual : -->
diff --git a/html/subx/apps/crenshaw2-1.subx.html b/html/subx/apps/crenshaw2-1.subx.html
index 3ebe75c1..11f2204f 100644
--- a/html/subx/apps/crenshaw2-1.subx.html
+++ b/html/subx/apps/crenshaw2-1.subx.html
@@ -277,7 +277,7 @@ if ('onhashchange' in window) {
 <span id="L211" class="LineNr">211 </span>    <span class="subxComment">#   ESI : in</span>
 <span id="L212" class="LineNr">212 </span>    <span class="subxComment">#   EDI : out</span>
 <span id="L213" class="LineNr">213 </span>    <span class="subxComment">#   EAX : temp</span>
-<span id="L214" class="LineNr">214 </span>    <span class="subxComment">#   ECX : out-&gt;write</span>
+<span id="L214" class="LineNr">214 </span>    <span class="subxComment">#   ECX : out-&gt;write (persisted back at end)</span>
 <span id="L215" class="LineNr">215 </span>    <span class="subxComment">#   EDX : out-&gt;length</span>
 <span id="L216" class="LineNr">216 </span>    <span class="subxComment">#   EBX : temp2</span>
 <span id="L217" class="LineNr">217 </span>    <span class="subxComment"># We can't allocate Look to a register because it gets written implicitly in</span>
diff --git a/html/subx/apps/crenshaw2-1b.subx.html b/html/subx/apps/crenshaw2-1b.subx.html
index 0210158b..b9678f34 100644
--- a/html/subx/apps/crenshaw2-1b.subx.html
+++ b/html/subx/apps/crenshaw2-1b.subx.html
@@ -282,7 +282,7 @@ if ('onhashchange' in window) {
 <span id="L216" class="LineNr">216 </span>    <span class="subxComment">#   ESI : in</span>
 <span id="L217" class="LineNr">217 </span>    <span class="subxComment">#   EDI : out</span>
 <span id="L218" class="LineNr">218 </span>    <span class="subxComment">#   EAX : temp</span>
-<span id="L219" class="LineNr">219 </span>    <span class="subxComment">#   ECX : out-&gt;write</span>
+<span id="L219" class="LineNr">219 </span>    <span class="subxComment">#   ECX : out-&gt;write (persisted back at end)</span>
 <span id="L220" class="LineNr">220 </span>    <span class="subxComment">#   EDX : out-&gt;length</span>
 <span id="L221" class="LineNr">221 </span>    <span class="subxComment">#   EBX : temp2</span>
 <span id="L222" class="LineNr">222 </span>    <span class="subxComment"># We can't allocate Look to a register because it gets written implicitly in</span>
diff --git a/subx/059read-byte.subx b/subx/059read-byte.subx
index e91a3532..ea16c928 100644
--- a/subx/059read-byte.subx
+++ b/subx/059read-byte.subx
@@ -81,7 +81,7 @@ $read-byte:from-stream:
     # read byte from stream
     # AL = f->data[f->read]
     31/xor                          3/mod/direct    0/rm32/EAX    .           .             .           0/r32/EAX   .               .                 # clear EAX
-    8a/copy-byte                    1/mod/*+disp8   4/rm32/sib    6/base/ESI  1/index/ECX   .           0/r32/AL    0x10/disp8      .                 # copy *(ESI+ECX+16) to AL
+    8a/copy-byte                    1/mod/*+disp8   4/rm32/sib    6/base/ESI  1/index/ECX   .           0/r32/AL    0x10/disp8      .                 # copy byte at *(ESI+ECX+16) to AL
     # ++f->read
     ff          0/subop/increment   1/mod/*+disp8   6/rm32/ESI    .           .             .           .           8/disp8         .                 # increment *(ESI+8)
 $read-byte:end:
@@ -234,6 +234,7 @@ test-read-byte-end-of-file:
 
 == data
 
+# a test buffered file for _test-stream
 _test-buffered-file:
     # file descriptor or (address stream)
     _test-stream/imm32
@@ -241,9 +242,9 @@ _test-buffered-file:
     00 00 00 00
     # current read index
     00 00 00 00
-    # length (8)
-    08 00 00 00
+    # length (6)
+    06 00 00 00
     # data
-    00 00 00 00 00 00 00 00  # 8 bytes
+    00 00 00 00 00 00  # 6 bytes
 
 # . . vim:nowrap:textwidth=0
diff --git a/subx/064write-buffered.subx b/subx/064write-buffered.subx
new file mode 100644
index 00000000..7889e255
--- /dev/null
+++ b/subx/064write-buffered.subx
@@ -0,0 +1,220 @@
+# write-buffered: like 'write', but for a buffered-file
+
+== code
+#   instruction                     effective address                                                   register    displacement    immediate
+# . op          subop               mod             rm32          base        index         scale       r32
+# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+
+# main:
+#?     e8/call test-write-buffered/disp32
+#?     e8/call test-write-buffered-with-intermediate-flush/disp32
+    e8/call  run-tests/disp32  # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
+    # syscall(exit, Num-test-failures)
+    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/EBX   Num-test-failures/disp32          # copy *Num-test-failures to EBX
+    b8/copy-to-EAX  1/imm32
+    cd/syscall  0x80/imm8
+
+write-buffered:  # f : (address buffered-file), msg : (address array byte) -> <void>
+    # pseudocode:
+    #   in = msg->data
+    #   inend = &msg->data[msg->length]
+    #   while in < inend
+    #     if f->write >= f->length
+    #       flush(f)
+    #       clear-stream(f)
+    #     f->data[f->write] = *in
+    #     ++f->write
+    #     ++in
+    #
+    # registers:
+    #   ESI : in
+    #   ECX : inend
+    #   EDI : f
+    #   EDX : f->length
+    #   EBX : f->write (cached copy, need to keep in sync)
+    #   EAX : temp
+    #
+    # . prolog
+    55/push-EBP
+    89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
+    # . save registers
+    50/push-EAX
+    51/push-ECX
+    52/push-EDX
+    53/push-EBX
+    56/push-ESI
+    57/push-EDI
+    # EAX = msg
+    8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none              0/r32/EAX   0xc/disp8       .                 # copy *(EBP+12) to EAX
+    # in/ESI = msg->data
+    8d/copy-address                 1/mod/*+disp8   0/rm32/EAX    .           .             .           6/r32/ESI   4/disp8         .                 # copy EAX+4 to ESI
+    # inend/ECX = &msg->data[msg->length]
+    8b/copy                         0/mod/indirect  0/rm32/EAX    .           .             .           1/r32/ECX   .               .                 # copy *EAX to ECX
+    8d/copy-address                 0/mod/indirect  4/rm32/sib    6/base/ESI  1/index/ECX   .           1/r32/ECX   .               .                 # copy ESI+ECX to ECX
+    # EDI = f
+    8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none              7/r32/EDI   8/disp8         .                 # copy *(EBP+8) to EDI
+    # EDX = f->length
+    8b/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           2/r32/EDX   0xc/disp8       .                 # copy *(EDI+12) to EDX
+    # EBX = f->write
+    8b/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   4/disp8         .                 # copy *(EDI+4) to EBX
+$write-buffered:loop:
+    # if (in >= inend) break
+    39/compare                      3/mod/direct    6/rm32/ESI    .           .             .           1/r32/ECX   .               .                 # compare ESI with ECX
+    7d/jump-if-greater-or-equal  $write-buffered:loop-end/disp8
+    # if (f->write >= f->length) flush and clear f's stream
+    39/compare                      3/mod/direct    3/rm32/EBX    .           .             .           2/r32/EDX   .               .                 # compare EBX with EDX
+    7c/jump-if-lesser  $write-buffered:to-stream/disp8
+    # . persist f->write
+    89/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   4/disp8         .                 # copy EBX to *(EDI+4)
+    # . flush(f)
+    # . . push args
+    57/push-EDI
+    # . . call
+    e8/call  flush/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # . clear-stream(stream = f+4)
+    # . . push args
+    8d/copy-address                 1/mod/*+disp8   7/rm32/EDI    .           .             .           0/r32/EAX   4/disp8         .                 # copy EDI+4 to EAX
+    50/push-EAX
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # . clear EBX (cached f->write)
+    31/xor                          3/mod/direct    3/rm32/EBX    .           .             .           3/r32/EBX   .               .                 # clear EBX
+$write-buffered:to-stream:
+    # write to stream
+    # f->data[f->write] = *in
+    # . AL = *in
+    31/xor                          3/mod/direct    0/rm32/EAX    .           .             .           0/r32/EAX   .               .                 # clear EAX
+    8a/copy-byte                    0/mod/indirect  6/rm32/ESI    .           .             .           0/r32/AL    .               .                 # copy byte at *ESI to AL
+    # . f->data[f->write] = AL
+    88/copy-byte                    1/mod/*+disp8   4/rm32/sib    7/base/EDI  3/index/EBX   .           0/r32/AL    0x10/disp8      .                 # copy AL to *(EDI+EBX+16)
+    # ++f->write
+    43/increment-EBX
+    # ++in
+    46/increment-ESI
+    eb/jump  $write-buffered:loop/disp8
+$write-buffered:loop-end:
+    # persist necessary variables from registers
+    89/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   4/disp8         .                 # copy EBX to *(EDI+4)
+$write-buffered:end:
+    # . restore registers
+    5f/pop-to-EDI
+    5e/pop-to-ESI
+    5b/pop-to-EBX
+    5a/pop-to-EDX
+    59/pop-to-ECX
+    58/pop-to-EAX
+    # . epilog
+    89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
+    5d/pop-to-EBP
+    c3/return
+
+test-write-buffered:
+    # - check that write-buffered writes to the file
+    # setup
+    # . clear-stream(_test-stream)
+    # . . push args
+    68/push  _test-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # . clear-stream(_test-buffered-file+4)
+    # . . push args
+    b8/copy-to-EAX  _test-buffered-file/imm32
+    05/add-to-EAX  4/imm32
+    50/push-EAX
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # write-buffered(_test-buffered-file, "Abc")
+    # . . push args
+    68/push  "Abc"/imm32
+    68/push  _test-buffered-file/imm32
+    # . . call
+    e8/call  write-buffered/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # flush(_test-buffered-file)
+    # . . push args
+    68/push  _test-buffered-file/imm32
+    # . . call
+    e8/call  flush/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # check-ints-equal(*_test-stream->data, "Abc", msg)
+    # . . push args
+    68/push  "F - test-write-buffered-single"/imm32
+    68/push  0x636241/imm32
+    # . . push *_test-stream->data
+    b8/copy-to-EAX  _test-stream/imm32
+    ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           0xc/disp8       .                 # push *(EAX+12)
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    # . end
+    c3/return
+
+test-write-buffered-with-intermediate-flush:
+    # - check that write-buffered flushes in the middle if its buffer fills up
+    # setup
+    # . clear-stream(_test-stream)
+    # . . push args
+    68/push  _test-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # . clear-stream(_test-buffered-file+4)
+    # . . push args
+    b8/copy-to-EAX  _test-buffered-file/imm32
+    05/add-to-EAX  4/imm32
+    50/push-EAX
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # _test-stream can hold 8 bytes, but _test-buffered-file can hold only 6.
+    # Try to write 7 bytes.
+    # . write-buffered(_test-buffered-file, "Abcdefg")
+    # . . push args
+    68/push  "Abcdefg"/imm32
+    68/push  _test-buffered-file/imm32
+    # . . call
+    e8/call  write-buffered/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # don't flush
+    # 6 bytes should still have gotten to _test-stream
+    # . check-ints-equal(*_test-stream->write, 6, msg)
+    # . . push args
+    68/push  "F - test-write-buffered-with-intermediate-flush: flushed data"/imm32
+    68/push  6/imm32
+    # . . push *_test-stream->write
+    b8/copy-to-EAX  _test-stream/imm32
+    ff          6/subop/push        0/mod/indirect  0/rm32/EAX    .           .             .           .           .               .                 # push *EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    # and 1 byte should still be in _test-buffered-file
+    # . check-ints-equal(*_test-buffered-file>write, 1, msg)
+    # . . push args
+    68/push  "F - test-write-buffered-with-intermediate-flush: unflushed bytes"/imm32
+    68/push  1/imm32
+    # . . push *_test-buffered-file->write
+    b8/copy-to-EAX  _test-buffered-file/imm32
+    ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           4/disp8         .                 # push *(EAX+4)
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    # . end
+    c3/return
+
+# . . vim:nowrap:textwidth=0
diff --git a/subx/apps/crenshaw2-1 b/subx/apps/crenshaw2-1
index 81739421..fbe0c10a 100755
--- a/subx/apps/crenshaw2-1
+++ b/subx/apps/crenshaw2-1
Binary files differdiff --git a/subx/apps/crenshaw2-1.subx b/subx/apps/crenshaw2-1.subx
index 25926b0e..25bc897b 100644
--- a/subx/apps/crenshaw2-1.subx
+++ b/subx/apps/crenshaw2-1.subx
@@ -211,7 +211,7 @@ get-num:  # in : (address buffered-file), out : (address stream), err : fd or (a
     #   ESI : in
     #   EDI : out
     #   EAX : temp
-    #   ECX : out->write
+    #   ECX : out->write (persisted back at end)
     #   EDX : out->length
     #   EBX : temp2
     # We can't allocate Look to a register because it gets written implicitly in
diff --git a/subx/apps/crenshaw2-1b b/subx/apps/crenshaw2-1b
index 9975fd8c..fecd6c39 100755
--- a/subx/apps/crenshaw2-1b
+++ b/subx/apps/crenshaw2-1b
Binary files differdiff --git a/subx/apps/crenshaw2-1b.subx b/subx/apps/crenshaw2-1b.subx
index d692d154..eec78f85 100644
--- a/subx/apps/crenshaw2-1b.subx
+++ b/subx/apps/crenshaw2-1b.subx
@@ -216,7 +216,7 @@ get-num:  # in : (address buffered-file), out : (address stream), err : fd or (a
     #   ESI : in
     #   EDI : out
     #   EAX : temp
-    #   ECX : out->write
+    #   ECX : out->write (persisted back at end)
     #   EDX : out->length
     #   EBX : temp2
     # We can't allocate Look to a register because it gets written implicitly in
diff --git a/subx/apps/factorial b/subx/apps/factorial
index 35405339..83dab085 100755
--- a/subx/apps/factorial
+++ b/subx/apps/factorial
Binary files differ