text: "use strict";
  
  // Copyright 2006-2008 the V8 project authors. All rights reserved.
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  //       notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  //       copyright notice, this list of conditions and the following
  //       disclaimer in the documentation and/or other materials provided
  //       with the distribution.
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  //       contributors may be used to endorse or promote products derived
  //       from this software without specific prior written permission.
  //
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  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  
  // This is a JavaScript implementation of the Richards
  // benchmark from:
  //
  //    http://www.cl.cam.ac.uk/~mr10/Bench.html
  //
  // The benchmark was originally implemented in BCPL by
  // Martin Richards.
  
  
  /**
   * The Richards benchmark simulates the task dispatcher of an
   * operating system.
   **/
  function runRichards() {
    var scheduler = new Scheduler();
    scheduler.addIdleTask(ID_IDLE, 0, null, COUNT);
  
    var queue = new Packet(null, ID_WORKER, KIND_WORK);
    queue = new Packet(queue,  ID_WORKER, KIND_WORK);
    scheduler.addWorkerTask(ID_WORKER, 1000, queue);
  
    queue = new Packet(null, ID_DEVICE_A, KIND_DEVICE);
    queue = new Packet(queue,  ID_DEVICE_A, KIND_DEVICE);
    queue = new Packet(queue,  ID_DEVICE_A, KIND_DEVICE);
    scheduler.addHandlerTask(ID_HANDLER_A, 2000, queue);
  
    queue = new Packet(null, ID_DEVICE_B, KIND_DEVICE);
    queue = new Packet(queue,  ID_DEVICE_B, KIND_DEVICE);
    queue = new Packet(queue,  ID_DEVICE_B, KIND_DEVICE);
    scheduler.addHandlerTask(ID_HANDLER_B, 3000, queue);
  
    scheduler.addDeviceTask(ID_DEVICE_A, 4000, null);
  
    scheduler.addDeviceTask(ID_DEVICE_B, 5000, null);
  
    scheduler.schedule();
  
    if (scheduler.queueCount != EXPECTED_QUEUE_COUNT ||
        scheduler.holdCount != EXPECTED_HOLD_COUNT) {
      var msg =
          "Error during execution: queueCount = " + scheduler.queueCount +
          ", holdCount = " + scheduler.holdCount + ".";
      throw new Error(msg);
    }
  }
  
  var COUNT = 1000;
  
  /**
   * These two constants specify how many times a packet is queued and
   * how many times a task is put on hold in a correct run of richards.
   * They don't have any meaning a such but are characteristic of a
   * correct run so if the actual queue or hold count is different from
   * the expected there must be a bug in the implementation.
   **/
  var EXPECTED_QUEUE_COUNT = 2322;
  var EXPECTED_HOLD_COUNT = 928;
  
  
  /**
   * A scheduler can be used to schedule a set of tasks based on their relative
   * priorities.  Scheduling is done by maintaining a list of task control blocks
   * which holds tasks and the data queue they are processing.
   * @constructor
   */
  function Scheduler() {
    this.queueCount = 0;
    this.holdCount = 0;
    this.blocks = new Array(NUMBER_OF_IDS);
    this.list = null;
    this.currentTcb = null;
    this.currentId = null;
  }
  
  var ID_IDLE       = 0;
  var ID_WORKER     = 1;
  var ID_HANDLER_A  = 2;
  var ID_HANDLER_B  = 3;
  var ID_DEVICE_A   = 4;
  var ID_DEVICE_B   = 5;
  var NUMBER_OF_IDS = 6;
  
  var KIND_DEVICE   = 0;
  var KIND_WORK     = 1;
  
  /**
   * Add an idle task to this scheduler.
   * @param {int} id the identity of the task
   * @param {int} priority the task's priority
   * @param {Packet} queue the queue of work to be processed by the task
   * @param {int} count the number of times to schedule the task
   */
  Scheduler.prototype.addIdleTask = function (id, priority, queue, count) {
    this.addRunningTask(id, priority, queue, new IdleTask(this, 1, count));
  };
  
  /**
   * Add a work task to this scheduler.
   * @param {int} id the identity of the task
   * @param {int} priority the task's priority
   * @param {Packet} queue the queue of work to be processed by the task
   */
  Scheduler.prototype.addWorkerTask = function (id, priority, queue) {
    this.addTask(id, priority, queue, new WorkerTask(this, ID_HANDLER_A, 0));
  };
  
  /**
   * Add a handler task to this scheduler.
   * @param {int} id the identity of the task
   * @param {int} priority the task's priority
   * @param {Packet} queue the queue of work to be processed by the task
   */
  Scheduler.prototype.addHandlerTask = function (id, priority, queue) {
    this.addTask(id, priority, queue, new HandlerTask(this));
  };
  
  /**
   * Add a handler task to this scheduler.
   * @param {int} id the identity of the task
   * @param {int} priority the task's priority
   * @param {Packet} queue the queue of work to be processed by the task
   */
  Scheduler.prototype.addDeviceTask = function (id, priority, queue) {
    this.addTask(id, priority, queue, new DeviceTask(this))
  };
  
  /**
   * Add the specified task and mark it as running.
   * @param {int} id the identity of the task
   * @param {int} priority the task's priority
   * @param {Packet} queue the queue of work to be processed by the task
   * @param {Task} task the task to add
   */
  Scheduler.prototype.addRunningTask = function (id, priority, queue, task) {
    this.addTask(id, priority, queue, task);
    this.currentTcb.setRunning();
  };
  
  /**
   * Add the specified task to this scheduler.
   * @param {int} id the identity of the task
   * @param {int} priority the task's priority
   * @param {Packet} queue the queue of work to be processed by the task
   * @param {Task} task the task to add
   */
  Scheduler.prototype.addTask = function (id, priority, queue, task) {
    this.currentTcb = new TaskControlBlock(this.list, id, priority, queue, task);
    this.list = this.currentTcb;
    this.blocks[id] = this.currentTcb;
  };
  
  /**
   * Execute the tasks managed by this scheduler.
   */
  Scheduler.prototype.schedule = function () {
    this.currentTcb = this.list;
    while (this.currentTcb != null) {
      if (this.currentTcb.isHeldOrSuspended()) {
        this.currentTcb = this.currentTcb.link;
      } else {
        this.currentId = this.currentTcb.id;
        this.currentTcb = this.currentTcb.run();
      }
    }
  };
  
  /**
   * Release a task that is currently blocked and return the next block to run.
   * @param {int} id the id of the task to suspend
   */
  Scheduler.prototype.release = function (id) {
    var tcb = this.blocks[id];
    if (tcb == null) return tcb;
    tcb.markAsNotHeld();
    if (tcb.priority > this.currentTcb.priority) {
      return tcb;
    } else {
      return this.currentTcb;
    }
  };
  
  /**
   * Block the currently executing task and return the next task control block
   * to run.  The blocked task will not be made runnable until it is explicitly
   * released, even if new work is added to it.
   */
  Scheduler.prototype.holdCurrent = function () {
    this.holdCount++;
    this.currentTcb.markAsHeld();
    return this.currentTcb.link;
  };
  
  /**
   * Suspend the currently executing task and return the next task control block
   * to run.  If new work is added to the suspended task it will be made runnable.
   */
  Scheduler.prototype.suspendCurrent = function () {
    this.currentTcb.markAsSuspended();
    return this.currentTcb;
  };
  
  /**
   * Add the specified packet to the end of the worklist used by the task
   * associated with the packet and make the task runnable if it is currently
   * suspended.
   * @param {Packet} packet the packet to add
   */
  Scheduler.prototype.queue = function (packet) {
    var t = this.blocks[packet.id];
    if (t == null) return t;
    this.queueCount++;
    packet.link = null;
    packet.id = this.currentId;
    return t.checkPriorityAdd(this.currentTcb, packet);
  };
  
  /**
   * A task control block manages a task and the queue of work packages associated
   * with it.
   * @param {TaskControlBlock} link the preceding block in the linked block list
   * @param {int} id the id of this block
   * @param {int} priority the priority of this block
   * @param {Packet} queue the queue of packages to be processed by the task
   * @param {Task} task the task
   * @constructor
   */
  function TaskControlBlock(link, id, priority, queue, task) {
    this.link = link;
    this.id = id;
    this.priority = priority;
    this.queue = queue;
    this.task = task;
    if (queue == null) {
      this.state = STATE_SUSPENDED;
    } else {
      this.state = STATE_SUSPENDED_RUNNABLE;
    }
  }
  
  /**
   * The task is running and is currently scheduled.
   */
  var STATE_RUNNING = 0;
  
  /**
   * The task has packets left to process.
   */
  var STATE_RUNNABLE = 1;
  
  /**
   * The task is not currently running.  The task is not blocked as such and may
  * be started by the scheduler.
   */
  var STATE_SUSPENDED = 2;
  
  /**
   * The task is blocked and cannot be run until it is explicitly released.
   */
  var STATE_HELD = 4;
  
  var STATE_SUSPENDED_RUNNABLE = STATE_SUSPENDED | STATE_RUNNABLE;
  var STATE_NOT_HELD = ~STATE_HELD;
  
  TaskControlBlock.prototype.setRunning = function () {
    this.state = STATE_RUNNING;
  };
  
  TaskControlBlock.prototype.markAsNotHeld = function () {
    this.state = this.state & STATE_NOT_HELD;
  };
  
  TaskControlBlock.prototype.markAsHeld = function () {
    this.state = this.state | STATE_HELD;
  };
  
  TaskControlBlock.prototype.isHeldOrSuspended = function () {
    return (this.state & STATE_HELD) != 0 || (this.state == STATE_SUSPENDED);
  };
  
  TaskControlBlock.prototype.markAsSuspended = function () {
    this.state = this.state | STATE_SUSPENDED;
  };
  
  TaskControlBlock.prototype.markAsRunnable = function () {
    this.state = this.state | STATE_RUNNABLE;
  };
  
  /**
   * Runs this task, if it is ready to be run, and returns the next task to run.
   */
  TaskControlBlock.prototype.run = function () {
    var packet;
    if (this.state == STATE_SUSPENDED_RUNNABLE) {
      packet = this.queue;
      this.queue = packet.link;
      if (this.queue == null) {
        this.state = STATE_RUNNING;
      } else {
        this.state = STATE_RUNNABLE;
      }
    } else {
      packet = null;
    }
    return this.task.run(packet);
  };
  
  /**
   * Adds a packet to the worklist of this block's task, marks this as runnable if
   * necessary, and returns the next runnable object to run (the one
   * with the highest priority).
   */
  TaskControlBlock.prototype.checkPriorityAdd = function (task, packet) {
    if (this.queue == null) {
      this.queue = packet;
      this.markAsRunnable();
      if (this.priority > task.priority) return this;
    } else {
      this.queue = packet.addTo(this.queue);
    }
    return task;
  };
  
  TaskControlBlock.prototype.toString = function () {
    return "tcb { " + this.task + "@" + this.state + " }";
  };
  
  /**
   * An idle task doesn't do any work itself but cycles control between the two
   * device tasks.
   * @param {Scheduler} scheduler the scheduler that manages this task
   * @param {int} v1 a seed value that controls how the device tasks are scheduled
   * @param {int} count the number of times this task should be scheduled
   * @constructor
   */
  function IdleTask(scheduler, v1, count) {
    this.scheduler = scheduler;
    this.v1 = v1;
    this.count = count;
  }
  
  IdleTask.prototype.run = function (packet) {
    this.count--;
    if (this.count == 0) return this.scheduler.holdCurrent();
    if ((this.v1 & 1) == 0) {
      this.v1 = this.v1 >> 1;
      return this.scheduler.release(ID_DEVICE_A);
    } else {
      this.v1 = (this.v1 >> 1) ^ 0xD008;
      return this.scheduler.release(ID_DEVICE_B);
    }
  };
  
  IdleTask.prototype.toString = function () {
    return "IdleTask"
  };
  
  /**
   * A task that suspends itself after each time it has been run to simulate
   * waiting for data from an external device.
   * @param {Scheduler} scheduler the scheduler that manages this task
   * @constructor
   */
  function DeviceTask(scheduler) {
    this.scheduler = scheduler;
    this.v1 = null;
  }
  
  DeviceTask.prototype.run = function (packet) {
    if (packet == null) {
      if (this.v1 == null) return this.scheduler.suspendCurrent();
      var v = this.v1;
      this.v1 = null;
      return this.scheduler.queue(v);
    } else {
      this.v1 = packet;
      return this.scheduler.holdCurrent();
    }
  };
  
  DeviceTask.prototype.toString = function () {
    return "DeviceTask";
  };
  
  /**
   * A task that manipulates work packets.
   * @param {Scheduler} scheduler the scheduler that manages this task
   * @param {int} v1 a seed used to specify how work packets are manipulated
   * @param {int} v2 another seed used to specify how work packets are manipulated
   * @constructor
   */
  function WorkerTask(scheduler, v1, v2) {
    this.scheduler = scheduler;
    this.v1 = v1;
    this.v2 = v2;
  }
  
  WorkerTask.prototype.run = function (packet) {
    if (packet == null) {
      return this.scheduler.suspendCurrent();
    } else {
      if (this.v1 == ID_HANDLER_A) {
        this.v1 = ID_HANDLER_B;
      } else {
        this.v1 = ID_HANDLER_A;
      }
      packet.id = this.v1;
      packet.a1 = 0;
      for (var i = 0; i < DATA_SIZE; i++) {
        this.v2++;
        if (this.v2 > 26) this.v2 = 1;
        packet.a2[i] = this.v2;
      }
      return this.scheduler.queue(packet);
    }
  };
  
  WorkerTask.prototype.toString = function () {
    return "WorkerTask";
  };
  
  /**
   * A task that manipulates work packets and then suspends itself.
   * @param {Scheduler} scheduler the scheduler that manages this task
   * @constructor
   */
  function HandlerTask(scheduler) {
    this.scheduler = scheduler;
    this.v1 = null;
    this.v2 = null;
  }
  
  HandlerTask.prototype.run = function (packet) {
    if (packet != null) {
      if (packet.kind == KIND_WORK) {
        this.v1 = packet.addTo(this.v1);
      } else {
        this.v2 = packet.addTo(this.v2);
      }
    }
    if (this.v1 != null) {
      var count = this.v1.a1;
      var v;
      if (count < DATA_SIZE) {
        if (this.v2 != null) {
          v = this.v2;
          this.v2 = this.v2.link;
          v.a1 = this.v1.a2[count];
          this.v1.a1 = count + 1;
          return this.scheduler.queue(v);
        }
      } else {
        v = this.v1;
        this.v1 = this.v1.link;
        return this.scheduler.queue(v);
      }
    }
    return this.scheduler.suspendCurrent();
  };
  
  HandlerTask.prototype.toString = function () {
    return "HandlerTask";
  };
  
  /* --- *
   * P a c k e t
   * --- */
  
  var DATA_SIZE = 4;
  
  /**
   * A simple package of data that is manipulated by the tasks.  The exact layout
   * of the payload data carried by a packet is not importaint, and neither is the
   * nature of the work performed on packets by the tasks.
   *
   * Besides carrying data, packets form linked lists and are hence used both as
   * data and worklists.
   * @param {Packet} link the tail of the linked list of packets
   * @param {int} id an ID for this packet
   * @param {int} kind the type of this packet
   * @constructor
   */
  function Packet(link, id, kind) {
    this.link = link;
    this.id = id;
    this.kind = kind;
    this.a1 = 0;
    this.a2 = new Array(DATA_SIZE);
  }
  
  /**
   * Add this packet to the end of a worklist, and return the worklist.
   * @param {Packet} queue the worklist to add this packet to
   */
  Packet.prototype.addTo = function (queue) {
    this.link = null;
    if (queue == null) return this;
    var peek, next = queue;
    while ((peek = next.link) != null)
      next = peek;
    next.link = this;
    return queue;
  };
  
  Packet.prototype.toString = function () {
    return "Packet";
  };
  
  for (var i = 0; i < 350; ++i)
    runRichards();
  