Anyone recognize this numeric storage format - similar to "float", but not quite

[Terry Reedy]

This appears to be a repost, perhaps not by the op but due to a glitch 
somewhere, of a question posted about a month ago and answered.

<geskerrett at hotmail.com> wrote in message 
news:1124849085.656718.97720 at g43g2000cwa.googlegroups.com...
> 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.
>
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>