How to convert 4 hex bytes into a single integer

Question

Elliot 2013-1-31

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/60720-how-to-convert-4-hex-bytes-into-a-single-integer

I'm trying to convert the 4 byte sequence:

in hex:
[3E 29 C3 39]
in dec:
62    41   195    57

Manually converting this into an unsigned long (4-byte) integer (uint32):

A(1)*(256^3) + A(2)*(256^2) + A(3)*256 + A(4)
ans =
                  1042924345

Which is the proper value. However, when I use typecast, I get the wrong value:

>>typecast(A,'int32')
ans =
             0  1078919168           0  1078231040           0  1080582144           0  1078755328
>>typecast(int8(A),'int32')
ans =
     964634942

Am I doing something wrong here? I've using all variations of signed vs. unsigned integer types (both uint8/int8 and uint32/int32) and none of them give the right answer.

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James Tursa 2013-1-31

编辑：James Tursa 2013-1-31

FYI, turning a value of 195 into an int8 will clip it at the upper end and produce a 127 value (different bit pattern than what you were expecting). You should in general be using unsigned integer classes for this, since MATLAB does not do modulo style conversions ... it clips instead.

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