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