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5.11 Blocking multiple provides

The blocking keyword can (since 2.15) also be used in combination with multiple provides ports. In our explanation we will introduce a component that does two things. First it multiplexes the provides ports events over a single requires port. Secondly it maps the synchronous behavior of the provides ihello interfaces onto the asynchronous behavior of the requires iworld interface (see the interface declarations at the end of this section).

import ihello.dzn;
import iworld.dzn;

component blocking_multiple_provides
  provides blocking ihello left;
  provides blocking ihello right;
  requires iworld r;

    enum Side {None, Left, Right};
    Side side = Side.None;
    Side pending = Side.None;

      blocking on left.hello(): {r.hello(); side = Side.Left;}
      blocking on right.hello(): {r.hello(); side = Side.Right;}

    [side.Left] blocking on right.hello(): pending = Side.Right;
    [side.Right] blocking on left.hello(): pending = Side.Left;

      if(side.Left) left.reply();
      if(side.Right) right.reply();
      if(!pending.None) r.hello();
      side = pending;
      pending = Side.None;

In the event sequence trace below we can see that for each provides port that asynchronous hello world transaction is encapsulated.