richards.js.svn-base

Google浏览器V8内核代码

}

/**
 * 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";
};