bgentype.py

reduced python source for embedded apps

"""Type classes and a modest collection of standard types."""


from bgenOutput import *


class Type:

	"""Define the various things you can do with a C type.

	Most methods are intended to be extended or overridden.
	"""

	def __init__(self, typeName, fmt):
		"""Call with the C name and getargs format for the type.

		Example: int = Type("int", "i")
		"""
		self.typeName = typeName
		self.fmt = fmt

	def declare(self, name):
		"""Declare a variable of the type with a given name.

		Example: int.declare('spam') prints "int spam;"
		"""
		Output("%s %s;", self.typeName, name)

	def getargs(self):
		return self.getargsFormat(), self.getargsArgs()

	def getargsFormat(self):
		"""Return the format for this type for use with [new]getargs().

		Example: int.getargsFormat() returns the string "i".
		"""
		return self.fmt

	def getargsArgs(self, name):
		"""Return an argument for use with [new]getargs().

		Example: int.getargsArgs("spam") returns the string "&spam".
		"""
		return "&" + name

	def getargsCheck(self, name):
		"""Perform any needed post-[new]getargs() checks.

		This is type-dependent; the default does not check for errors.
		An example would be a check for a maximum string length."""

	def passInput(self, name):
		"""Return an argument for passing a variable into a call.

		Example: int.passInput("spam") returns the string "spam".
		"""
		return name

	def passOutput(self, name):
		"""Return an argument for returning a variable out of a call.

		Example: int.passOutput("spam") returns the string "&spam".
		"""
		return "&" + name

	def errorCheck(self, name):
		"""Check for an error returned in the variable.

		This is type-dependent; the default does not check for errors.
		An example would be a check for a NULL pointer.
		If an error is found, the generated routine should
		raise an exception and return NULL.

		XXX There should be a way to add error clean-up code.
		"""
		Output("/* XXX no err check for %s %s */", self.typeName, name)

	def mkvalue(self):
		return self.mkvalueFormat(), self.mkvalueArgs()

	def mkvalueFormat(self):
		"""Return the format for this type for use with mkvalue().

		This is normally the same as getargsFormat() but it is
		a separate function to allow future divergence.
		"""
		return self.getargsFormat()

	def mkvalueArgs(self, name):
		"""Return an argument for use with mkvalue().

		Example: int.mkvalueArgs("spam") returns the string "spam".
		"""
		return name

	def cleanup(self, name):
		"""Clean up if necessary.

		This is normally empty; it may deallocate buffers etc.
		"""
		pass

class ByAddressType(Type):
	"Simple type that is also passed by address for input"

	def passInput(self, name):
		return "&%s" % name



# Sometimes it's useful to define a type that's only usable as input or output parameter

class InputOnlyMixIn:

	"Mix-in class to boobytrap passOutput"

	def passOutput(self, name):
		raise RuntimeError, "this type can only be used for input parameters"

class InputOnlyType(InputOnlyMixIn, Type):

	"Same as Type, but only usable for input parameters -- passOutput is boobytrapped"

class OutputOnlyMixIn:

	"Mix-in class to boobytrap passInput"

	def passInput(self, name):
		raise RuntimeError, "this type can only be used for output parameters"

class OutputOnlyType(OutputOnlyMixIn, Type):

	"Same as Type, but only usable for output parameters -- passInput is boobytrapped"


# A modest collection of standard C types.
void = None
char = Type("char", "c")
short = Type("short", "h")
int = Type("int", "i")
long = Type("long", "l")
unsigned_long = Type("unsigned long", "l")
float = Type("float", "f")
double = Type("double", "d")


# The most common use of character pointers is a null-terminated string.
# For input, this is easy.  For output, and for other uses of char *,
# see the module bgenBuffer.
stringptr = InputOnlyType("char*", "s")


# Some Python related types.
objectptr = Type("PyObject*", "O")
stringobjectptr = Type("PyStringObject*", "S")
# Etc.


class FakeType(InputOnlyType):

	"""A type that is not represented in the Python version of the interface.

	Instantiate with a value to pass in the call.
	"""

	def __init__(self, substitute):
		self.substitute = substitute
		self.typeName = None	# Don't show this argument in __doc__ string

	def declare(self, name):
		pass

	def getargsFormat(self):
		return ""

	def getargsArgs(self, name):
		return None

	def passInput(self, name):
		return self.substitute


class OpaqueType(Type):

	"""A type represented by an opaque object type, always passed by address.

	Instantiate with the type name and the names of the new and convert procs.
	If fewer than three arguments are passed, the second argument is used
	to derive the new and convert procs by appending _New and _Convert; it
	defaults to the first argument.
	"""

	def __init__(self, name, arg = None, extra = None):
		self.typeName = name
		if extra is None:
			 # Two arguments (name, usetype) or one (name)
			arg = arg or name
			self.new = arg + '_New'
			self.convert = arg + '_Convert'
		else:
			# Three arguments (name, new, convert)
			self.new = arg 
			self.convert = extra 

	def getargsFormat(self):
		return "O&"

	def getargsArgs(self, name):
		return "%s, &%s" % (self.convert, name)

	def passInput(self, name):
		return "&%s" % name

	def mkvalueFormat(self):
		return "O&"

	def mkvalueArgs(self, name):
		return "%s, &%s" % (self.new, name)


class OpaqueByValueType(OpaqueType):

	"""A type represented by an opaque object type, on input passed BY VALUE.

	Instantiate with the type name, and optionally an object type name whose
	New/Convert functions will be used.
	"""

	def passInput(self, name):
		return name

	def mkvalueArgs(self, name):
		return "%s, %s" % (self.new, name)


class OpaqueArrayType(OpaqueByValueType):

	"""A type represented by an opaque object type, with ARRAY passing semantics.

	Instantiate with the type name, and optional an object type name whose
	New/Convert functions will be used.
	"""

	def getargsArgs(self, name):
		return "%s, %s" % (self.convert, name)

	def passOutput(self, name):
		return name