modules/coroutine.js

   1
   2 function _return_value(x) {
   3     this.value = x;
   4 }
   5
   6 function co_return(x) {
   7     return new _return_value(x);
   8 }
   9
  10 const CONTINUATION = { toString: function () "[object CONTINUATION]" };
  11 const SUSPEND = { toString: function () "[object SUSPEND]" };
  12
  13 function is_coroutine(obj) {
  14     return obj != null &&
  15         typeof(obj) == "object" &&
  16         typeof(obj.next) == "function" &&
  17         typeof(obj.send) == "function";
  18 }
  19
  20 function _do_call(f) {
  21     var cc = yield;
  22
  23     var stack = [];
  24     var y = undefined;
  25     var throw_value = false;
  26     while (true) {
  27         try {
  28             let x;
  29             if (throw_value) {
  30                 throw_value = false;
  31                 x = f.throw(y);
  32             }
  33             else
  34                 x = f.send(y);
  35
  36             if (x == CONTINUATION) {
  37                 y = cc;
  38                 continue;
  39             }
  40
  41             if (x === SUSPEND) {
  42                 try {
  43                     x = yield;
  44                     y = x;
  45                 } catch (e) {
  46                     throw_value = true;
  47                     y = e;
  48                 }
  49                 continue;
  50             }
  51
  52             if (is_coroutine(x))
  53             {
  54                 stack[stack.length] = f;
  55                 f = x;
  56                 y = undefined;
  57                 continue;
  58             }
  59
  60             if (x instanceof _return_value) {
  61                 if (stack.length == 0)
  62                     return;
  63                 f.close();
  64                 f = stack[stack.length - 1];
  65                 stack.length--;
  66                 y = x.value;
  67                 continue;
  68             }
  69
  70             // Just return the value back to the function
  71             y = x;
  72         } catch (e) {
  73             if (stack.length == 0)
  74                 return;
  75             f = stack[stack.length - 1];
  76             stack.length--;
  77             if (e instanceof StopIteration)
  78                 y = undefined;
  79             else {
  80                 y = e;
  81                 throw_value = true;
  82             }
  83         }
  84     }
  85 }
  86
  87 function co_call(f) {
  88     if (!is_coroutine(f))
  89         return;
  90     var g = _do_call(f);
  91     g.next();
  92     var cc = function (x) {
  93         try {
  94             g.send(x);
  95         } catch (e if e instanceof StopIteration) {}
  96     };
  97     cc.throw = function (x) {
  98         try {
  99             g.throw(x);
 100         } catch (e if e instanceof StopIteration) {}
 101     };
 102     try {
 103         g.send(cc);
 104     } catch (e if e instanceof StopIteration) {}
 105     return cc;
 106 }