How to convert 4 hex bytes into a single integer
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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.
1 Comment
James Tursa
on 31 Jan 2013
Edited: James Tursa
on 31 Jan 2013
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.
Accepted Answer
James Tursa
on 31 Jan 2013
Edited: James Tursa
on 31 Jan 2013
Depending on the machine you are on, you may need to use the swapbytes function as well. E.g., try:
swapbytes(typecast(uint8(A),'uint32'))
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