// Copyright 2006-2008 the V8 project authors. All rights reserved.

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//

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// 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;