POX控制器源码阅读(一) 组件如何注册

以l3_learning为例

def launch (fakeways="", arp_for_unknowns=None):
    fakeways = fakeways.replace(","," ").split()
    fakeways = [IPAddr(x) for x in fakeways]
    if arp_for_unknowns is None:
      arp_for_unknowns = len(fakeways) > 0
    else:
      arp_for_unknowns = str_to_bool(arp_for_unknowns)
    core.registerNew(l3_switch, fakeways, arp_for_unknowns)

launch函数最后一行registerNew进行注册，在core中POXCore类下找到该函数

def registerNew (self, __componentClass, *args, **kw):
    """
    Give it a class (and optional __init__ arguments), and it will
    create an instance and register it using the class name.  If the
    instance has a _core_name property, it will use that instead.
    It returns the new instance.
    core.registerNew(FooClass, arg) is roughly equivalent to
    core.register("FooClass", FooClass(arg)).
    """
    name = __componentClass.__name__
    obj = __componentClass(*args, **kw)
    if hasattr(obj, '_core_name'):
      # Default overridden
      name = obj._core_name
    self.register(name, obj)
    return obj

注释里基本解释了。参数为类名，该方法将在core中为该类创建一个实例，并且使用类名注册这个实例，注册名名可被类中的_core_name替换

该注册方法core.registerNew(FooClass, arg)与core.register("FooClass", FooClass(arg))基本相同

register函数：

def register (self, name, component=None):
    """
    Makes the object "component" available as pox.core.core.name.

    If only one argument is specified, the given argument is registered
    using its class name as the name.
    """
    #TODO: weak references?
    if component is None:
      component = name
      name = component.__class__.__name__
      if hasattr(component, '_core_name'):
        # Default overridden
        name = component._core_name

    if name in self.components:
      log.warn("Warning: Registered '%s' multipled times" % (name,))
    self.components[name] = component
    self.raiseEventNoErrors(ComponentRegistered, name, component)
    self._try_waiters()

通过register()实现了在初始化的时候，将组件加入到pox.core.core中，同时

self.raiseEventNoErrors(ComponentRegistered, name, component)

说明core引发一个事件"ComponentRegistered"。注意这个事件的参数是组件和组件的名字，即该组件的注册事件。

此即注册事件的第一步，在core中注册组件，之后学习如何将组件中的event_handler与相关的具体事件绑定在一起。