def get_or_create_indexed_instance(self, index):
""" index may be a number or 'next'.
Create instance if it does not exist, IF it is the next to be created.
"""
if index != 'next' and index != 'last': index = get_integer(index)
# Create a new header_inst if index is next or else it is a value equal to
# the next index to be used in the stack.
if index == 'next' or index == len(self.stack):
if len(self.stack) == self.stack_max_size: # full - return None
print "Referenced instance",index,"of stack %s but stack is full." % self.hdr_inst_name
return None
# Create new header instance
#print "Creating hdr inst %s[%d]" % (self.hdr_inst_name, len(self.stack))
h_i = Header_Instance( self.string, self.loc,
self.hdr_type_name,
self.hdr_is_metadata,
"%s[%d]" % (self.hdr_inst_name, len(self.stack))
)
self.stack.append(h_i)
return h_i
if index == 'last':
if len(self.stack) == 0:
print "Referenced 'last' hdr_inst of stack %s but stack is empty." % self.hdr_inst_name
return None
return self.stack[-1]
# Get actual numbered entry
if index >= len(self.stack):
print "Indexed entry %d of stack %s but stack only has %d entries." % (
index, self.hdr_inst_name, len(self.stack) )
return None
return self.stack[index]
def __init__(self, string, loc, hdr_name , hdr_body ):
assert len(hdr_body)>0 and len(hdr_body)<4
super(Header_Declaration, self).__init__(string, loc, 'header_declaration')
self.name = hdr_name
self.fields = hdr_body[0] # [ Field objects ]
self.field_names = [] # ordered list of field names
self.length_expr = None # list of strings. expression to calc length.
self.max_length = 0 # Integer. max length for header
hdr_len_undefined = False # True if we see a field with bit_width '*' (0)
bit_count = 0
for f in self.fields:
if f.name in self.field_names:
print_syntax_err('Field name "%s" already defined in header "%s"' %
(f.name, self.name), string, loc)
if f.bit_width == 0:
if hdr_len_undefined:
print_syntax_err('In header "%s" two or more fields have undefined width.' %
self.name, string, loc)
hdr_len_undefined = True
bit_count += f.bit_width
self.field_names.append(f.name)
if ( bit_count % 8 ) != 0:
if not hdr_len_undefined:
print_syntax_err('In header "%s" total field bit_width not byte aligned: %d bits.' %
(self.name, bit_count), string, loc)
# Process options
if len(hdr_body)>1:
for opt in hdr_body[1:]:
# print " opt:", opt
assert len(opt)>1 # [0]=opt name, [1] = value
opt_name = opt[0]
if opt_name == 'length':
self.length_expr = opt.asList()[1:]
if opt_name == 'max_length':
self.max_length = get_integer(opt[1])
if hdr_len_undefined:
if not self.length_expr:
print_syntax_err('In header "%s" a field has width "*" so "length" must be defined.' %
self.name, string, loc)
def get_indexed_instance(self, index):
index = get_integer(index)
if len(self.stack) <= index: return None
else: return self.stack[index]
def is_legal_index(self, index):
if index == 'last': return True
if index == 'next':
return len(self.stack) < self.stack_max_size
return get_integer(index) < self.stack_max_size
