html/115write-byte.subx.html

   1 <!DOCTYPE html>
   2 <html>
   3 <head>
   4 <meta charset="UTF-8">
   5 <title>Mu - 115write-byte.subx</title>
   6 <meta name="Generator" content="Vim/8.2">
   7 <meta name="plugin-version" content="vim8.1_v2">
   8 <meta name="syntax" content="none">
   9 <meta name="settings" content="number_lines,use_css,no_foldcolumn,expand_tabs,line_ids,prevent_copy=,use_input_for_pc=fallback">
  10 <meta name="colorscheme" content="minimal-light">
  11 <style>
  12 <!--
  13 pre { font-family: monospace; color: #000000; background-color: #ffffd7; }
  14 body { font-size:12pt; font-family: monospace; color: #000000; background-color: #ffffd7; }
  15 a { color:inherit; }
  16 * { font-size:12pt; font-size: 1em; }
  17 .subxH1Comment { color: #005faf; text-decoration: underline; }
  18 .subxComment { color: #005faf; }
  19 .subxS1Comment { color: #0000af; }
  20 .subxS2Comment { color: #8a8a8a; }
  21 .LineNr { }
  22 .Constant { color: #008787; }
  23 .subxTest { color: #5f8700; }
  24 .subxFunction { color: #af5f00; text-decoration: underline; }
  25 .Normal { color: #000000; background-color: #ffffd7; padding-bottom: 1px; }
  26 -->
  27 </style>
  28
  29 <script>
  30 <!--
  31
  32 /* function to open any folds containing a jumped-to line before jumping to it */
  33 function JumpToLine()
  34 {
  35   var lineNum;
  36   lineNum = window.location.hash;
  37   lineNum = lineNum.substr(1); /* strip off '#' */
  38
  39   if (lineNum.indexOf('L') == -1) {
  40     lineNum = 'L'+lineNum;
  41   }
  42   var lineElem = document.getElementById(lineNum);
  43   /* Always jump to new location even if the line was hidden inside a fold, or
  44    * we corrected the raw number to a line ID.
  45    */
  46   if (lineElem) {
  47     lineElem.scrollIntoView(true);
  48   }
  49   return true;
  50 }
  51 if ('onhashchange' in window) {
  52   window.onhashchange = JumpToLine;
  53 }
  54
  55 -->
  56 </script>
  57 </head>
  58 <body onload='JumpToLine();'>
  59 <a href='https://github.com/akkartik/mu/blob/main/115write-byte.subx'>https://github.com/akkartik/mu/blob/main/115write-byte.subx</a>
  60 <pre id='vimCodeElement'>
  61 <span id="L1" class="LineNr">  1 </span><span class="subxComment"># Write a single byte to a stream.</span>
  62 <span id="L2" class="LineNr">  2 </span><span class="subxComment">#</span>
  63 <span id="L3" class="LineNr">  3 </span><span class="subxComment"># We need to do this in machine code because streams need to be opaque types,</span>
  64 <span id="L4" class="LineNr">  4 </span><span class="subxComment"># and we don't yet support opaque types in Mu.</span>
  65 <span id="L5" class="LineNr">  5 </span>
  66 <span id="L6" class="LineNr">  6 </span>== code
  67 <span id="L7" class="LineNr">  7 </span><span class="subxComment">#   instruction                     effective address                                                   register    displacement    immediate</span>
  68 <span id="L8" class="LineNr">  8 </span><span class="subxS1Comment"># . op          subop               mod             rm32          base        index         scale       r32</span>
  69 <span id="L9" class="LineNr">  9 </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>
  70 <span id="L10" class="LineNr"> 10 </span>
  71 <span id="L11" class="LineNr"> 11 </span><span class="subxComment"># Write lower byte of 'n' to 'f'.</span>
  72 <span id="L12" class="LineNr"> 12 </span><span class="subxFunction">append-byte</span>:  <span class="subxComment"># f: (addr stream byte), n: int</span>
  73 <span id="L13" class="LineNr"> 13 </span>    <span class="subxS1Comment"># . prologue</span>
  74 <span id="L14" class="LineNr"> 14 </span>    55/push-ebp
  75 <span id="L15" class="LineNr"> 15 </span>    89/copy                         3/mod/direct    5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy esp to ebp</span>
  76 <span id="L16" class="LineNr"> 16 </span>    <span class="subxS1Comment"># . save registers</span>
  77 <span id="L17" class="LineNr"> 17 </span>    50/push-eax
  78 <span id="L18" class="LineNr"> 18 </span>    51/push-ecx
  79 <span id="L19" class="LineNr"> 19 </span>    57/push-edi
  80 <span id="L20" class="LineNr"> 20 </span>    <span class="subxComment"># edi = f</span>
  81 <span id="L21" class="LineNr"> 21 </span>    8b/copy                         1/mod/*+disp8   5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          7/r32/edi   8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy *(ebp+8) to edi</span>
  82 <span id="L22" class="LineNr"> 22 </span>    <span class="subxComment"># ecx = f-&gt;write</span>
  83 <span id="L23" class="LineNr"> 23 </span>    8b/copy                         0/mod/indirect  7/rm32/edi   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          1/r32/ecx  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy *edi to ecx</span>
  84 <span id="L24" class="LineNr"> 24 </span>    <span class="subxComment"># if (f-&gt;write &gt;= f-&gt;size) abort</span>
  85 <span id="L25" class="LineNr"> 25 </span>    3b/compare                      1/mod/*+disp8   7/rm32/edi   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          1/r32/ecx   8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># compare ecx with *(edi+8)</span>
  86 <span id="L26" class="LineNr"> 26 </span>    7d/jump-if-&gt;=  $append-byte:<a href='317abort.subx.html#L5'>abort</a>/disp8
  87 <span id="L27" class="LineNr"> 27 </span><span class="Constant">$append-byte:to-stream</span>:
  88 <span id="L28" class="LineNr"> 28 </span>    <span class="subxComment"># write to stream</span>
  89 <span id="L29" class="LineNr"> 29 </span>    <span class="subxComment"># f-&gt;data[f-&gt;write] = LSB(n)</span>
  90 <span id="L30" class="LineNr"> 30 </span>    31/xor                          3/mod/direct    0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          0/r32/eax  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># clear eax</span>
  91 <span id="L31" class="LineNr"> 31 </span>    8a/copy-byte                    1/mod/*+disp8   5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          0/r32/AL    0xc/disp8      <span class="Normal"> . </span>                <span class="subxComment"># copy byte at *(ebp+12) to AL</span>
  92 <span id="L32" class="LineNr"> 32 </span>    88/copy-byte                    1/mod/*+disp8   4/rm32/sib    7/base/edi  1/index/ecx  <span class="Normal"> . </span>          0/r32/AL    0xc/disp8      <span class="Normal"> . </span>                <span class="subxComment"># copy AL to *(edi+ecx+12)</span>
  93 <span id="L33" class="LineNr"> 33 </span>    <span class="subxComment"># ++f-&gt;write</span>
  94 <span id="L34" class="LineNr"> 34 </span>    ff          0/subop/increment   0/mod/indirect  7/rm32/edi   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># increment *edi</span>
  95 <span id="L35" class="LineNr"> 35 </span><span class="Constant">$append-byte:end</span>:
  96 <span id="L36" class="LineNr"> 36 </span>    <span class="subxS1Comment"># . restore registers</span>
  97 <span id="L37" class="LineNr"> 37 </span>    5f/pop-to-edi
  98 <span id="L38" class="LineNr"> 38 </span>    59/pop-to-ecx
  99 <span id="L39" class="LineNr"> 39 </span>    58/pop-to-eax
 100 <span id="L40" class="LineNr"> 40 </span>    <span class="subxS1Comment"># . epilogue</span>
 101 <span id="L41" class="LineNr"> 41 </span>    89/copy                         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          5/r32/ebp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy ebp to esp</span>
 102 <span id="L42" class="LineNr"> 42 </span>    5d/pop-to-ebp
 103 <span id="L43" class="LineNr"> 43 </span>    c3/return
 104 <span id="L44" class="LineNr"> 44 </span>
 105 <span id="L45" class="LineNr"> 45 </span><span class="Constant">$append-byte:<a href='317abort.subx.html#L5'>abort</a></span>:
 106 <span id="L46" class="LineNr"> 46 </span>    (<a href='317abort.subx.html#L5'>abort</a> <span class="Constant">&quot;append-byte: out of space&quot;</span>)
 107 <span id="L47" class="LineNr"> 47 </span>    <span class="subxComment"># never gets here</span>
 108 <span id="L48" class="LineNr"> 48 </span>
 109 <span id="L49" class="LineNr"> 49 </span><span class="subxTest">test-append-byte-single</span>:
 110 <span id="L50" class="LineNr"> 50 </span>    <span class="subxH1Comment"># - check that append-byte writes to first byte of 'file'</span>
 111 <span id="L51" class="LineNr"> 51 </span>    <span class="subxComment"># setup</span>
 112 <span id="L52" class="LineNr"> 52 </span>    <span class="subxS1Comment"># . clear-stream(_test-stream)</span>
 113 <span id="L53" class="LineNr"> 53 </span>    <span class="subxS2Comment"># . . push args</span>
 114 <span id="L54" class="LineNr"> 54 </span>    68/push  <a href='108write.subx.html#L125'>_test-stream</a>/imm32
 115 <span id="L55" class="LineNr"> 55 </span>    <span class="subxS2Comment"># . . call</span>
 116 <span id="L56" class="LineNr"> 56 </span>    e8/call  <a href='106stream.subx.html#L20'>clear-stream</a>/disp32
 117 <span id="L57" class="LineNr"> 57 </span>    <span class="subxS2Comment"># . . discard args</span>
 118 <span id="L58" class="LineNr"> 58 </span>    81          0/subop/add         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>              4/imm32           <span class="subxComment"># add to esp</span>
 119 <span id="L59" class="LineNr"> 59 </span>    <span class="subxComment"># append-byte(_test-stream, 'A')</span>
 120 <span id="L60" class="LineNr"> 60 </span>    <span class="subxS2Comment"># . . push args</span>
 121 <span id="L61" class="LineNr"> 61 </span>    68/push  0x41/imm32
 122 <span id="L62" class="LineNr"> 62 </span>    68/push  <a href='108write.subx.html#L125'>_test-stream</a>/imm32
 123 <span id="L63" class="LineNr"> 63 </span>    <span class="subxS2Comment"># . . call</span>
 124 <span id="L64" class="LineNr"> 64 </span>    e8/call  <a href='115write-byte.subx.html#L12'>append-byte</a>/disp32
 125 <span id="L65" class="LineNr"> 65 </span>    <span class="subxS2Comment"># . . discard args</span>
 126 <span id="L66" class="LineNr"> 66 </span>    81          0/subop/add         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>              8/imm32           <span class="subxComment"># add to esp</span>
 127 <span id="L67" class="LineNr"> 67 </span>    <span class="subxComment"># check-stream-equal(_test-stream, &quot;A&quot;, msg)</span>
 128 <span id="L68" class="LineNr"> 68 </span>    <span class="subxS2Comment"># . . push args</span>
 129 <span id="L69" class="LineNr"> 69 </span>    68/push  <span class="Constant">&quot;F - test-append-byte-single&quot;</span>/imm32
 130 <span id="L70" class="LineNr"> 70 </span>    68/push  <span class="Constant">&quot;A&quot;</span>/imm32
 131 <span id="L71" class="LineNr"> 71 </span>    68/push  <a href='108write.subx.html#L125'>_test-stream</a>/imm32
 132 <span id="L72" class="LineNr"> 72 </span>    <span class="subxS2Comment"># . . call</span>
 133 <span id="L73" class="LineNr"> 73 </span>    e8/call  <a href='109stream-equal.subx.html#L194'>check-stream-equal</a>/disp32
 134 <span id="L74" class="LineNr"> 74 </span>    <span class="subxS2Comment"># . . discard args</span>
 135 <span id="L75" class="LineNr"> 75 </span>    81          0/subop/add         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>              0xc/imm32         <span class="subxComment"># add to esp</span>
 136 <span id="L76" class="LineNr"> 76 </span>    <span class="subxS1Comment"># . end</span>
 137 <span id="L77" class="LineNr"> 77 </span>    c3/return
 138 <span id="L78" class="LineNr"> 78 </span>
 139 <span id="L79" class="LineNr"> 79 </span><span class="subxFunction">undo-append-byte</span>:  <span class="subxComment"># f: (addr stream byte)</span>
 140 <span id="L80" class="LineNr"> 80 </span>    <span class="subxS1Comment"># . prologue</span>
 141 <span id="L81" class="LineNr"> 81 </span>    55/push-ebp
 142 <span id="L82" class="LineNr"> 82 </span>    89/copy                         3/mod/direct    5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy esp to ebp</span>
 143 <span id="L83" class="LineNr"> 83 </span>    <span class="subxS1Comment"># . save registers</span>
 144 <span id="L84" class="LineNr"> 84 </span>    50/push-eax
 145 <span id="L85" class="LineNr"> 85 </span>    <span class="subxComment"># eax = f</span>
 146 <span id="L86" class="LineNr"> 86 </span>    8b/copy                         1/mod/*+disp8   5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          0/r32/eax   8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy *(ebp+8) to eax</span>
 147 <span id="L87" class="LineNr"> 87 </span>    <span class="subxComment"># if (f-&gt;write &lt;= 0) abort</span>
 148 <span id="L88" class="LineNr"> 88 </span>    81          7/subop/compare     0/mod/indirect  0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>              0/imm32           <span class="subxComment"># compare *eax</span>
 149 <span id="L89" class="LineNr"> 89 </span>    7e/jump-if-&lt;=  $undo-append-byte:<a href='317abort.subx.html#L5'>abort</a>/disp8
 150 <span id="L90" class="LineNr"> 90 </span>    <span class="subxComment"># --f-&gt;write</span>
 151 <span id="L91" class="LineNr"> 91 </span>    ff          1/subop/decrement   0/mod/indirect  0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># decrement *eax</span>
 152 <span id="L92" class="LineNr"> 92 </span><span class="Constant">$undo-append-byte:end</span>:
 153 <span id="L93" class="LineNr"> 93 </span>    <span class="subxS1Comment"># . restore registers</span>
 154 <span id="L94" class="LineNr"> 94 </span>    58/pop-to-eax
 155 <span id="L95" class="LineNr"> 95 </span>    <span class="subxS1Comment"># . epilogue</span>
 156 <span id="L96" class="LineNr"> 96 </span>    89/copy                         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          5/r32/ebp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy ebp to esp</span>
 157 <span id="L97" class="LineNr"> 97 </span>    5d/pop-to-ebp
 158 <span id="L98" class="LineNr"> 98 </span>    c3/return
 159 <span id="L99" class="LineNr"> 99 </span>
 160 <span id="L100" class="LineNr">100 </span><span class="Constant">$undo-append-byte:<a href='317abort.subx.html#L5'>abort</a></span>:
 161 <span id="L101" class="LineNr">101 </span>    (<a href='317abort.subx.html#L5'>abort</a> <span class="Constant">&quot;undo-append-byte: empty stream&quot;</span>)
 162 <span id="L102" class="LineNr">102 </span>    <span class="subxComment"># never gets here</span>
 163 <span id="L103" class="LineNr">103 </span>
 164 <span id="L104" class="LineNr">104 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
 165 </pre>
 166 </body>
 167 </html>
 168 <!-- vim: set foldmethod=manual : -->