Does any one recognize this binary data storage format

[Grant Edwards]

On 2005-08-10, Bengt Richter <bokr at oz.net> wrote:
> On Tue, 09 Aug 2005 21:50:06 -0000, Grant Edwards <grante at visi.com> wrote:
>
>>On 2005-08-09, Scott David Daniels <Scott.Daniels at Acm.Org> wrote:
>>> Grant Edwards wrote:
>>>>>Ex #1)   333-3333
>>>>>Hex On disk: 00 00 00 80 6a 6e 49 41
>>>>>
>>>>>Ex #2) 666-6666
>>>>>Hex On disk: 00 00 00 80 6a 6e 59 41
>>>> 
>>>> So there's only a 1-bit different between the on-disk
>>>> representation of 333-3333 and 666-6666.
>>>> 
>>>> That sounds pretty unlikely.  Are you 100% sure you're looking
>>>> at the correct bytes?
>>>
>>> Perhaps the one bit is an exponent -- some kind of floating point
>>> based format?  That matches the doubling of all digits.
>>
>>That would just be sick.  I can't imagine anybody on an 8-bit
>>CPU using FP for a phone number.

> >>> def double_binary_lehex_to_double(dhex):
>  ...     "convert little-endian hex of ieee double binary to double"
>  ...     assert len(dhex)==16, (
>  ...         "hex of double in binary must be 8 bytes (hex pairs in little-endian order")
>  ...     dhex = ''.join(reversed([dhex[i:i+2] for i in xrange(0,16,2)]))
>  ...     m = int(dhex, 16)
>  ...     x = ((m>>52)&0x7ff) - 0x3ff - 52
>  ...     s = (m>>63)&0x1
>  ...     f = (m & ((1<<52)-1))|((m and 1 or 0)<<52)
>  ...     return (1.0,-1.0)[s]*f*2.0**x
>  ...
> >>> double_binary_lehex_to_double('000000806a6e4941')
>  3333333.0
> >>> double_binary_lehex_to_double('000000806a6e5941')
>  6666666.0
> >>> double_binary_lehex_to_double('0000108777F9Fc41')
>  7777777777.0
>
> ;-)

Damn.

I still say that's just plain sick.

-- 
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