def _read_resource_dt_header()

in pci_vpd_lib/pci_vpd_lib.py [0:0]

• 17 lines of code
• 6 McCabe index (conditional complexity)

    def _read_resource_dt_header(self, f):
        checksum = 0
        buf = bytearray(f.read(1))
        # not enough data, return END tag
        if len(buf) < 1:
            return (0xF, 0, 0)
        checksum = self._combine_checksum(checksum, buf)
        # handle small resource data type
        if (buf[0] & 0x80) == 0:
            # small resource data type header just one byte with mask
            # 0b0XXXXYYY, where XXXX is a tag id and YYY is length
            tag = (buf[0] & 0b1111000) >> 3
            length = buf[0] & 0b111
            return (tag, length, checksum)
        else:
            # large resource data type header consists of three bytes
            # first one is 0b1XXXXXXX, where XXXXXXX is a tag id and
            # next two bytes are length with first of the two being least
            # significant
            tag = buf[0] & 0x7F
            # read the length
            buf = bytearray(f.read(2))
            # handle not enough data
            if len(buf) < 2:
                return (0xF, 0, 0)
            checksum = self._combine_checksum(checksum, buf)
            return (tag, buf[0] + buf[1] * 256, checksum)