kc3-lang/libevent/make_epoll_table.py

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• Hash : 8c83eb69
  Author :
  Date : 2010-10-24T12:53:52
  

  Replace big chain of if/thens in epoll.c with a table lookup
  
  This should save a bunch of branches by doing instead a lookup in a
  nice static table.
  
  To ensure correctness, the table is generated from a Python script,
  included with this commit.
  

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• make_epoll_table.py

• #!/usr/bin/python
  
  def get(old,wc,rc):
      if ('xxx' in (rc, wc)):
          return "0",-1
  
      if ('add' in (rc, wc)):
          events = []
          if rc == 'add' or (rc != 'del' and 'r' in old):
              events.append("EPOLLIN")
          if wc == 'add' or (wc != 'del' and 'w' in old):
              events.append("EPOLLOUT")
  
          if old == "0":
              op = "EPOLL_CTL_ADD"
          else:
              op = "EPOLL_CTL_MOD"
          return "|".join(events), op
  
      if ('del' in (rc, wc)):
          op = "EPOLL_CTL_DEL"
          if rc == 'del':
              if wc == 'del':
                  events = "EPOLLIN|EPOLLOUT"
              elif 'w' in old:
                  events = "EPOLLOUT"
                  op = "EPOLL_CTL_MOD"
              else:
                  events = "EPOLLIN"
          else:
              assert wc == 'del'
              if 'r' in old:
                  events = "EPOLLIN"
                  op = "EPOLL_CTL_MOD"
              else:
                  events = "EPOLLOUT"
          return events, op
  
      return 0, 0
  
  
  def fmt(op, ev, old, wc, rc):
      entry = "{ %s, %s },"%(op, ev)
      assert len(entry)<=36
      sp = " "*(36-len(entry))
      print "\t%s%s/* old=%2s, write:%3s, read:%3s */" % (
          entry, sp, old, wc, rc)
  
  
  for old in ('0','r','w','rw'):
      for wc in ('0', 'add', 'del', 'xxx'):
          for rc in ('0', 'add', 'del', 'xxx'):
  
              op,ev = get(old,wc,rc)
  
              fmt(op, ev, old, wc, rc)
  
  

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