def unpack(self, buf, offset):
"""Unpack an element header from an FFFF header buffer
Unpacks an element header from an FFFF header buffer at the specified
offset. Returns a flag indicating if the unpacked element is an
end-of-table marker
"""
element_hdr = unpack_from("<LLLLL", buf, offset)
type_class = element_hdr[0]
self.element_type = type_class & 0x000000ff
self.element_class = (type_class >> 8) & 0x00ffffff
self.element_id = element_hdr[1]
self.element_length = element_hdr[2]
self.element_location = element_hdr[3]
self.element_generation = element_hdr[4]
# Get the element data into our tftf_blob
if self.element_type != FFFF_ELEMENT_END_OF_ELEMENT_TABLE:
# Create a TFTF blob and load the contents from the specified
# TFTF file
span_start = self.element_location
span_end = span_start + self.element_length
self.tftf_blob = Tftf(0, None)
span_start = self.element_location
span_end = span_start + self.element_length
self.tftf_blob.load_tftf_from_buffer(buf[span_start:span_end])
return False
else:
# EOT is always valid
self.in_range = True
self.aligned = True
self.valid_type = True
return True
def init(self):
"""FFFF Element post-constructor initializer
Loads the element from TFTF file, setting the element length to
that of the file. Returns a success flag if the file was loaded
(no file is treated as success).
"""
success = True
# Try to size it from the TFTF file
if self.filename and not self.tftf_blob:
# Create a TFTF blob and load the contents from the specified
# TFTF file
self.tftf_blob = Tftf(0, self.filename)
success = self.tftf_blob.load_tftf_file(self.filename)
if success and self.tftf_blob.is_good():
# element_length must be that of the entire TFTF blob,
# not just the TFTF's "load_length" or "expanded_length".
self.element_length = self.tftf_blob.tftf_length
else:
raise ValueError("Bad TFTF file: {0:x}".format(self.filename))
return True
