cpython/Modules/cgen.py

# Python script to parse cstubs file for gl and generate C stubs.
# usage: python cgen.py <cstubs >glmodule.c
#
# NOTE: You  must first make a python binary without the "GL" option
#	before you can run this, when building Python for the first time.
#	See comments in the Makefile.
#
# XXX BUG return arrays generate wrong code
# XXX need to change error returns into gotos to free mallocked arrays


import string
import sys


# Function to print to stderr
#
def err(args):
	savestdout = sys.stdout
	try:
		sys.stdout = sys.stderr
		for i in args:
			print i,
		print
	finally:
		sys.stdout = savestdout


# The set of digits that form a number
#
digits = '0123456789'


# Function to extract a string of digits from the front of the string.
# Returns the leading string of digits and the remaining string.
# If no number is found, returns '' and the original string.
#
def getnum(s):
	n = ''
	while s and s[0] in digits:
		n = n + s[0]
		s = s[1:]
	return n, s


# Function to check if a string is a number
#
def isnum(s):
	if not s: return 0
	for c in s:
		if not c in digits: return 0
	return 1


# Allowed function return types
#
return_types = ['void', 'short', 'long']


# Allowed function argument types
#
arg_types = ['char', 'string', 'short', 'float', 'long', 'double']


# Need to classify arguments as follows
#	simple input variable
#	simple output variable
#	input array
#	output array
#	input giving size of some array
#
# Array dimensions can be specified as follows
#	constant
#	argN
#	constant * argN
#	retval
#	constant * retval
#
# The dimensions given as constants * something are really
# arrays of points where points are 2- 3- or 4-tuples
#
# We have to consider three lists:
#	python input arguments
#	C stub arguments (in & out)
#	python output arguments (really return values)
#
# There is a mapping from python input arguments to the input arguments
# of the C stub, and a further mapping from C stub arguments to the
# python return values


# Exception raised by checkarg() and generate()
#
arg_error = 'bad arg'


# Function to check one argument.
# Arguments: the type and the arg "name" (really mode plus subscript).
# Raises arg_error if something's wrong.
# Return type, mode, factor, rest of subscript; factor and rest may be empty.
#
def checkarg(type, arg):
	#
	# Turn "char *x" into "string x".
	#
	if type == 'char' and arg[0] == '*':
		type = 'string'
		arg = arg[1:]
	#
	# Check that the type is supported.
	#
	if type not in arg_types:
		raise arg_error, ('bad type', type)
	#
	# Split it in the mode (first character) and the rest.
	#
	mode, rest = arg[:1], arg[1:]
	#
	# The mode must be 's' for send (= input) or 'r' for return argument.
	#
	if mode not in ('r', 's'):
		raise arg_error, ('bad arg mode', mode)
	#
	# Is it a simple argument: if so, we are done.
	#
	if not rest:
		return type, mode, '', ''
	#	
	# Not a simple argument; must be an array.
	# The 'rest' must be a subscript enclosed in [ and ].
	# The subscript must be one of the following forms,
	# otherwise we don't handle it (where N is a number):
	#	N
	#	argN
	#	retval
	#	N*argN
	#	N*retval
	#
	if rest[:1] <> '[' or rest[-1:] <> ']':
		raise arg_error, ('subscript expected', rest)
	sub = rest[1:-1]
	#
	# Is there a leading number?
	#
	num, sub = getnum(sub)
	if num:
		# There is a leading number
		if not sub:
			# The subscript is just a number
			return type, mode, num, ''
		if sub[:1] == '*':
			# There is a factor prefix
			sub = sub[1:]
		else:
			raise arg_error, ('\'*\' expected', sub)
	if sub == 'retval':
		# size is retval -- must be a reply argument
		if mode <> 'r':
			raise arg_error, ('non-r mode with [retval]', mode)
	elif sub[:3] <> 'arg' or not isnum(sub[3:]):
		raise arg_error, ('bad subscript', sub)
	#
	return type, mode, num, sub


# List of functions for which we have generated stubs
#
functions = []


# Generate the stub for the given function, using the database of argument
# information build by successive calls to checkarg()
#
def generate(type, func, database):
	#
	# Check that we can handle this case:
	# no variable size reply arrays yet
	#
	n_in_args = 0
	n_out_args = 0
	#
	for a_type, a_mode, a_factor, a_sub in database:
		if a_mode == 's':
			n_in_args = n_in_args + 1
		elif a_mode == 'r':
			n_out_args = n_out_args + 1
		else:
			# Can't happen
			raise arg_error, ('bad a_mode', a_mode)
		if (a_mode == 'r' and a_sub) or a_sub == 'retval':
			e = 'Function', func, 'too complicated:'
			err(e + (a_type, a_mode, a_factor, a_sub))
			print '/* XXX Too complicated to generate code for */'
			return
	#
	functions.append(func)
	#
	# Stub header
	#
	print
	print 'static object *'
	print 'gl_' + func + '(self, args)'
	print '\tobject *self;'
	print '\tobject *args;'
	print '{'
	#
	# Declare return value if any
	#
	if type <> 'void':
		print '\t' + type, 'retval;'
	#
	# Declare arguments
	#
	for i in range(len(database)):
		a_type, a_mode, a_factor, a_sub = database[i]
		print '\t' + a_type,
		if a_sub:
			print '*',
		print 'arg' + `i+1`,
		if a_factor and not a_sub:
			print '[', a_factor, ']',
		print ';'
	#
	# Find input arguments derived from array sizes
	#
	for i in range(len(database)):
		a_type, a_mode, a_factor, a_sub = database[i]
		if a_mode == 's' and a_sub[:3] == 'arg' and isnum(a_sub[3:]):
			# Sending a variable-length array
			n = eval(a_sub[3:])
			if 1 <= n <= len(database):
			    b_type, b_mode, b_factor, b_sub = database[n-1]
			    if b_mode == 's':
			        database[n-1] = b_type, 'i', a_factor, `i`
			        n_in_args = n_in_args - 1
	#
	# Assign argument positions in the Python argument list
	#
	in_pos = []
	i_in = 0
	for i in range(len(database)):
		a_type, a_mode, a_factor, a_sub = database[i]
		if a_mode == 's':
			in_pos.append(i_in)
			i_in = i_in + 1
		else:
			in_pos.append(-1)
	#
	# Get input arguments
	#
	for i in range(len(database)):
		a_type, a_mode, a_factor, a_sub = database[i]
		if a_mode == 'i':
			#
			# Implicit argument;
			# a_factor is divisor if present,
			# a_sub indicates which arg (`database index`)
			#
			j = eval(a_sub)
			print '\tif',
			print '(!geti' + a_type + 'arraysize(args,',
			print `n_in_args` + ',',
			print `in_pos[j]` + ',',
			print '&arg' + `i+1` + '))'
			print '\t\treturn NULL;'
			if a_factor:
				print '\targ' + `i+1`,
				print '= arg' + `i+1`,
				print '/', a_factor + ';'
		elif a_mode == 's':
			if a_sub: # Allocate memory for varsize array
				print '\tif ((arg' + `i+1`, '=',
				print 'NEW(' + a_type + ',',
				if a_factor: print a_factor, '*',
				print a_sub, ')) == NULL)'
				print '\t\treturn err_nomem();'
			print '\tif',
			if a_factor or a_sub: # Get a fixed-size array array
				print '(!geti' + a_type + 'array(args,',
				print `n_in_args` + ',',
				print `in_pos[i]` + ',',
				if a_factor: print a_factor,
				if a_factor and a_sub: print '*',
				if a_sub: print a_sub,
				print ', arg' + `i+1` + '))'
			else: # Get a simple variable
				print '(!geti' + a_type + 'arg(args,',
				print `n_in_args` + ',',
				print `in_pos[i]` + ',',
				print '&arg' + `i+1` + '))'
			print '\t\treturn NULL;'
	#
	# Begin of function call
	#
	if type <> 'void':
		print '\tretval =', func + '(',
	else:
		print '\t' + func + '(',
	#
	# Argument list
	#
	for i in range(len(database)):
		if i > 0: print ',',
		a_type, a_mode, a_factor, a_sub = database[i]
		if a_mode == 'r' and not a_factor:
			print '&',
		print 'arg' + `i+1`,
	#
	# End of function call
	#
	print ');'
	#
	# Free varsize arrays
	#
	for i in range(len(database)):
		a_type, a_mode, a_factor, a_sub = database[i]
		if a_mode == 's' and a_sub:
			print '\tDEL(arg' + `i+1` + ');'
	#
	# Return
	#
	if n_out_args:
		#
		# Multiple return values -- construct a tuple
		#
		if type <> 'void':
			n_out_args = n_out_args + 1
		if n_out_args == 1:
			for i in range(len(database)):
				a_type, a_mode, a_factor, a_sub = database[i]
				if a_mode == 'r':
					break
			else:
				raise arg_error, 'expected r arg not found'
			print '\treturn',
			print mkobject(a_type, 'arg' + `i+1`) + ';'
		else:
			print '\t{ object *v = newtupleobject(',
			print n_out_args, ');'
			print '\t  if (v == NULL) return NULL;'
			i_out = 0
			if type <> 'void':
				print '\t  settupleitem(v,',
				print `i_out` + ',',
				print mkobject(type, 'retval') + ');'
				i_out = i_out + 1
			for i in range(len(database)):
				a_type, a_mode, a_factor, a_sub = database[i]
				if a_mode == 'r':
					print '\t  settupleitem(v,',
					print `i_out` + ',',
					s = mkobject(a_type, 'arg' + `i+1`)
					print s + ');'
					i_out = i_out + 1
			print '\t  return v;'
			print '\t}'
	else:
		#
		# Simple function return
		# Return None or return value
		#
		if type == 'void':
			print '\tINCREF(None);'
			print '\treturn None;'
		else:
			print '\treturn', mkobject(type, 'retval') + ';'
	#
	# Stub body closing brace
	#
	print '}'


# Subroutine to return a function call to mknew<type>object(<arg>)
#
def mkobject(type, arg):
	return 'mknew' + type + 'object(' + arg + ')'


# Open optional file argument
if sys.argv[1:]:
	sys.stdin = open(sys.argv[1], 'r')


# Input line number
lno = 0


# Input is divided in two parts, separated by a line containing '%%'.
#	<part1>		-- literally copied to stdout
#	<part2>		-- stub definitions

# Variable indicating the current input part.
#
part = 1

# Main loop over the input
#
while 1:
	try:
		line = raw_input()
	except EOFError:
		break
	#
	lno = lno+1
	words = string.split(line)
	#
	if part == 1:
		#
		# In part 1, copy everything literally
		# except look for a line of just '%%'
		#
		if words == ['%%']:
			part = part + 1
		else:
			#
			# Look for names of manually written
			# stubs: a single percent followed by the name
			# of the function in Python.
			# The stub name is derived by prefixing 'gl_'.
			#
			if words and words[0][0] == '%':
				func = words[0][1:]
				if (not func) and words[1:]:
					func = words[1]
				if func:
					functions.append(func)
			else:
				print line
	elif not words:
		pass			# skip empty line
	elif words[0] == '#include':
		print line
	elif words[0][:1] == '#':
		pass			# ignore comment
	elif words[0] not in return_types:
		err('Line', lno, ': bad return type :', words[0])
	elif len(words) < 2:
		err('Line', lno, ': no funcname :', line)
	else:
		if len(words) % 2 <> 0:
			err('Line', lno, ': odd argument list :', words[2:])
		else:
			database = []
			try:
				for i in range(2, len(words), 2):
					x = checkarg(words[i], words[i+1])
					database.append(x)
				print
				print '/*',
				for w in words: print w,
				print '*/'
				generate(words[0], words[1], database)
			except arg_error, msg:
				err('Line', lno, ':', msg)


print
print 'static struct methodlist gl_methods[] = {'
for func in functions:
	print '\t{"' + func + '", gl_' + func + '},'
print '\t{NULL, NULL} /* Sentinel */'
print '};'
print
print 'initgl()'
print '{'
print '\tinitmodule("gl", gl_methods);'
print '}'