On 23 Aug 2005 19:04:45 -0700, [EMAIL PROTECTED] wrote: >We are working on a project to decipher a record structure of an old >accounting system that originates from the late80's mid-90's. >We have come across a number format that appears to be a "float" but >doesn't match any of the more standard implementations. >so we are hoping this is a recognizable number storage format with an >identifiable name AND pre-built conversion method >similiar to the "struct" modules available in python. > >Here is what we have determined so far. > >Example Number: 1234567890 > >This get stored on disk as 8 bytes, resulting in the following HEX >characters; >00 00 00 A4 05 2c 13 9f > >If we changed the order so that it is "little Endian" we get; >9F 13 2c 05 A4 00 00 00 > >If the HEX is converted to binary it looks like; >10011111 00010011 00101100 00000101 10100100 00000000 000000000 >00000000 > >If the example number 1234567890 is converted to binary it looks like; > >10010011 00101100 00000101 1010010 > >To extract the example number, you need to do the following; >1) take the decimal value of the first byte and subtract 128 >2) This tells you how many of the following bits to are significant and >must be read >3) Once the remaining bits are read, reverse the first bit of that >group (ie if it is a 0 make it a 1) >4) convert the result to decimal >... and presto, the example number ! > >Using a fixed width font it is easy to see the match at the bit level; > >10011111 00010011001011000000010110100100000000000000000000000000 >-------- 1001001100101100000001011010010 > > >If you are interested, the following are three other examples; > > Orig Hex: 00 00 00 60 92 96 72 A0 >Actual Value: 4069954144 > > Orig Hex: 00 00 80 22 A3 26 3C A1 >Actual Value: 6313297477 > > >So ... does anyone recognize this ?? >Is there a "built-in" conversion method in Python ?? > >Thanks in advance. > Not looking too closely, but I recall something similar (although I suspect that the bit you are "reversing" is a sign bit that shadows a known constant MSB 1 for non-zero numbers, and shouldn't just be reversed):
http://groups.google.com/group/comp.lang.python/browse_thread/thread/42150ccc20a1d8d5/4aadc71be8aeddbe#4aadc71be8aeddbe Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
