modules/coroutine.js

   1 /**
   2  * (C) Copyright 2008 Jeremy Maitin-Shepard
   3  *
   4  * Use, modification, and distribution are subject to the terms specified in the
   5  * COPYING file.
   6 **/
   7
   8 function _return_value(x) {
   9     this.value = x;
  10 }
  11
  12 function co_return(x) {
  13     return new _return_value(x);
  14 }
  15
  16 const CONTINUATION = { toString: function () "[object CONTINUATION]" };
  17 const SUSPEND = { toString: function () "[object SUSPEND]" };
  18
  19 function is_coroutine(obj) {
  20     return obj != null &&
  21         typeof(obj) == "object" &&
  22         typeof(obj.next) == "function" &&
  23         typeof(obj.send) == "function";
  24 }
  25
  26 function _do_call(f) {
  27     var cc = yield;
  28
  29     var stack = [];
  30     var y = undefined;
  31     var throw_value = false;
  32     while (true) {
  33         try {
  34             let x;
  35             if (throw_value) {
  36                 throw_value = false;
  37                 x = f.throw(y);
  38             }
  39             else
  40                 x = f.send(y);
  41
  42             if (x == CONTINUATION) {
  43                 y = cc;
  44                 continue;
  45             }
  46
  47             if (x === SUSPEND) {
  48                 try {
  49                     x = yield;
  50                     y = x;
  51                 } catch (e) {
  52                     throw_value = true;
  53                     y = e;
  54                 }
  55                 continue;
  56             }
  57
  58             if (is_coroutine(x))
  59             {
  60                 stack[stack.length] = f;
  61                 f = x;
  62                 y = undefined;
  63                 continue;
  64             }
  65
  66             if (x instanceof _return_value) {
  67                 if (stack.length == 0)
  68                     return;
  69                 f.close();
  70                 f = stack[stack.length - 1];
  71                 stack.length--;
  72                 y = x.value;
  73                 continue;
  74             }
  75
  76             // Just return the value back to the function
  77             y = x;
  78         } catch (e) {
  79             if (stack.length == 0)
  80                 return;
  81             f = stack[stack.length - 1];
  82             stack.length--;
  83             if (e instanceof StopIteration)
  84                 y = undefined;
  85             else {
  86                 y = e;
  87                 throw_value = true;
  88             }
  89         }
  90     }
  91 }
  92
  93 function co_call(f) {
  94     if (!is_coroutine(f))
  95         return;
  96     var g = _do_call(f);
  97     g.next();
  98     var cc = function (x) {
  99         try {
 100             g.send(x);
 101         } catch (e if e instanceof StopIteration) {}
 102         catch (e) {
 103             // Dump this error, because it indicates a programming error
 104             dump_error(e);
 105         }
 106     };
 107     cc.throw = function (x) {
 108         try {
 109             g.throw(x);
 110         } catch (e if e instanceof StopIteration) {}
 111         catch (e) {
 112             // Dump this error, because it indicates a programming error
 113             dump_error(e);
 114         }
 115     };
 116     try {
 117         g.send(cc);
 118     } catch (e if e instanceof StopIteration) {}
 119     catch (e) {
 120         // Dump this error, because it indicates a programming error
 121         dump_error(e);
 122     }
 123     return cc;
 124 }