At 08:00 AM 1/6/2006, Thomas Heller wrote: >RayS <[EMAIL PROTECTED]> writes: > >> I'm trying to find an efficient way to convert from DSP32C binary files >> smmmmmmm mmmmmmmm mmmmmmmm eeeeeeee >> to IEEE float >> seeeeeee emmmmmmm mmmmmmmm mmmmmmmm >> >> I tried struct and bit-shifting from a C manual example, but it >> failed. Has someone else coded this in Python? I'll post the early >> attempt when I get into the office later, if not. >> >> I re-coded from scratch, converting each 32 bit ATT value to a binary >> string, slice-rearranging bits, then re-packing to IEEE. A bit >> slowwwww. At least they're small files. > >You could try ctypes bitfield structures, maybe, to access the fields?
Sounds interesting, but I have not used them; and on http://starship.python.net/crew/theller/ctypes/tutorial.html you wrote "Bugs, ToDo and non-implemented things Bitfields are not implemented." Are they available? Documented? I have __version__ = "0.9.6" I also just read http://publications.gbdirect.co.uk/c_book/chapter6/bitfields.html which warned "Be careful using them. It can require a surprising amount of run-time code to manipulate these things and you can end up using more space than they save. Bit fields do not have addressesÂyou can't have pointers to them or arrays of them." My previous code from a C example, fast, but which does NOT return correct values!: def DSP32ToIEEE(fh, address): """ bytes == 4 """ res = '' fh.seek(address) b1 = struct.unpack("B",fh.read(1))[0] fh.seek(address+1) b2 = struct.unpack("B",fh.read(1))[0] fh.seek(address+2) b3 = struct.unpack("B",fh.read(1))[0] fh.seek(address+3) b4 = struct.unpack("B",fh.read(1))[0] if b4 & 0x80: ## check the sign bit b4 = b4 & 0x7f b2 = ~b2 b3 = ~b3 b4 = ~b4 sign = -1 else: b4 = b4 | 0x80 sign = 1 l4 = long(b4) << 16 l3 = long(b3) << 8 mantissa = (l4+l3+b2) / pow(2., 23) exp = pow(2., b1-127) VrmsSqd = sign*(mantissa*exp)/2. fh.seek(address) return VrmsSqd Thanks, Ray _______________________________________________ Python-win32 mailing list Python-win32@python.org http://mail.python.org/mailman/listinfo/python-win32
