gCommand.py

#!/usr/local/bin/python
#
#                               Copyright 2004
#                                     by
#                        The Board of Trustees of the
#                     Leland Stanford Junior University.
#                            All rights reserved.
#


__facility__ = "Online"
__abstract__ = "Commanding"
__author__   = "Amedeo Perazzo <perazzo@slac.stanford.edu> SLAC - GLAST I&T/Online"
__date__     = ("$Date: 2004/09/11 00:52:01 $").split(' ')[1]
__version__  = "$Revision: 2.3 $"
__release__  = "$Name: R04-12-00 $"
__credits__  = "SLAC"

import LATTE.copyright_SLAC

import struct

def packstring(arg, type):
  strlen = len(arg)
  strpad = 4-(strlen&0x3)
  fmt = '!HH%ds%dx' %(strlen, strpad)
  return struct.pack(fmt, strlen+strpad, type, arg)

class Command:
  __Function = 0
  __Handler  = 1
  __Payload  = 2
  __Value    = 3
  __Input    = 4

  def __init__(self, functionname, *arguments):
    self.__packet = None
    self.__payloadfmts = []

    cmd = packstring(functionname, Command.__Function)
    for arg in arguments:
      if isinstance(arg, str):
        if arg[0] == '!':
          cmd += packstring(arg[1:], Command.__Payload)
          self.__payloadfmts.append(arg[1:])
        elif arg[0] == '>':
          cmd += packstring(arg[1:], Command.__Input)
        else:
          cmd += packstring(arg, Command.__Handler)
      elif isinstance(arg, int) or isinstance(arg, long):
        cmd += struct.pack('!HHI', 4, Command.__Value, arg)
      else:
        raise Exception, "*** gCommand: cannot handle type %s" \
                        %(arg.__class__.__name__)
    self.__packet = struct.pack('!I', len(cmd)) + cmd

  def packet(self):
    return self.__packet

  def payloadfmts(self):
    return self.__payloadfmts

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