3

I'm reading data from a binary file. I have a document that lets me know how the information is stored. To be sure of this I use XVI32.

I was extracting information string and int data correctly, until I bumped with float data type.

According to this file:

00800000 = 0.0
7AFBDD35 = 0.061087
9BF7783C = -0.003491
00FBFCAD = 0.031416

I tried to solve this with:

struct.unpack('!f', my_float.decode('hex'))[0]

And other different ways....

I tested this information with some online tools like: http://babbage.cs.qc.cuny.edu/IEEE-754/index.xhtml and http://www.binaryconvert.com/result_float.html?decimal=048046048054049048056055, but all of these ways throws me a different value according the original results.

I'm starting to suspect that float information is encrypted or something like that but why string and int weren't encrypted?

4

2 に答える 2

2

面白いパズル。私が思いついたドキュメントを使って作業します：

def byteswap(x):
    return ((x & 0x00ff00ff) << 8) | ((x & 0xff00ff00) >> 8)


def tms320_float(raw):
    s = (raw >> 23) & 1
    mantissa = (raw & 0x007fffff)
    exponent = raw >> 24
    if exponent >= 128:
        exponent -= 256
    if exponent == -128:
        return 0.0
    return (((-2) ** s) + float(mantissa) / float(1 << 23)) * (2.0 ** exponent)

>>> tms320_float(byteswap(0x00800000))
0.0
>>> tms320_float(byteswap(0x7AFBDD35))
0.06108652427792549
>>> tms320_float(byteswap(0x9BF7783C))
-0.003490658476948738
>>> tms320_float(byteswap(0x00FBFCAD))
0.031415924429893494
于 2012-05-23T18:35:33.480 に答える
1

上司から「浮動小数点データが IEEE 形式ではありません」という回答がありました。

データ型は TMS320 浮動小数点です

何らかの理由で、16 進数データの実際の値が 2 バイトごとに混在しています。

80000000 = 0.0
FB7A35DD = 0.061087
F79B3C78 = -0.003491
FB00ADFC = 0.031416

私をサポートしてくれてありがとう

于 2012-05-22T16:04:22.733 に答える