bgenvariable.py

reduced python source for embedded apps

"""Variables, arguments and argument transfer modes etc."""


# Values to represent argument transfer modes
InMode    = 1 # input-only argument
OutMode   = 2 # output-only argument
InOutMode = 3 # input-output argument
ModeMask  = 3 # bits to keep for mode


# Special cases for mode/flags argument
# XXX This is still a mess!
SelfMode   =  4+InMode  # this is 'self' -- don't declare it
ReturnMode =  8+OutMode # this is the function return value
ErrorMode  = 16+OutMode # this is an error status -- turn it into an exception


class Variable:

	"""A Variable holds a type, a name, a transfer mode and flags.

	Most of its methods call the correponding type method with the
	variable name.
	"""

	def __init__(self, type, name = None, flags = InMode):
		"""Call with a type, a name and flags.

		If name is None, it muse be set later.
		flags defaults to InMode.
		"""
		self.type = type
		self.name = name
		self.flags = flags
		self.mode = flags & ModeMask

	def declare(self):
		"""Declare the variable if necessary.

		If it is "self", it is not declared.
		"""
		if self.flags != SelfMode:
			self.type.declare(self.name)

	def getargsFormat(self):
		"""Call the type's getargsFormatmethod."""
		return self.type.getargsFormat()

	def getargsArgs(self):
		"""Call the type's getargsArgsmethod."""
		return self.type.getargsArgs(self.name)

	def getargsCheck(self):
		return self.type.getargsCheck(self.name)

	def passArgument(self):
		"""Return the string required to pass the variable as argument.

		For "in" arguments, return the variable name.
		For "out" and "in out" arguments,
		return its name prefixed with "&".
		"""
		if self.mode == InMode:
			return self.type.passInput(self.name)
		if self.mode in (OutMode, InOutMode):
			return self.type.passOutput(self.name)
		# XXX Shouldn't get here
		return "/*mode?*/" + self.type.passInput(self.name)

	def errorCheck(self):
		"""Check for an error if necessary.

		This only generates code if the variable's mode is ErrorMode.
		"""
		if self.flags == ErrorMode:
			self.type.errorCheck(self.name)

	def mkvalueFormat (self):
		"""Call the type's mkvalueFormat method."""
		return self.type.mkvalueFormat()

	def mkvalueArgs(self):
		"""Call the type's mkvalueArgs method."""
		return self.type.mkvalueArgs(self.name)

	def cleanup(self):
		"""Call the type's cleanup method."""
		return self.type.cleanup(self.name)