Working with binary data, S-records (long)

[Greg Ewing (using news.cis.dfn.de)]

Hans-Joachim Widmaier wrote:
> Whenever I play with binary data in Python, a dream of a mutable string
> data type crops up. Doing byte fiddling with strings is quite ok as long

The array module can be useful for things like this.
array.array('c') gives you an efficient mutable sequence
of chars.

>         data = [int(line[i:i + 2], 16) for i in range(2, len(line), 2)]

You could replace this with something like

    import struct, binascii

    format = "B"*((len(line)-2)/2)
    data = struct.unpack(format, binascii.unhexlify(line[2:]))

>             adr = (long(data[0]) << 24) + (data[2] << 16) + (data[3] << 8) + data[4]

You could try

    addr = struct.unpack(">L",
      "%s%s%s%s" % (data[0], data[2], data[3], data[4]))[0]

although it's not clear whether it would be any faster.

-- 
Greg Ewing, Computer Science Dept,
University of Canterbury,	
Christchurch, New Zealand
http://www.cosc.canterbury.ac.nz/~greg