4byte uint8 array to single uint32 value

I have an uint8 array containing 4 elements each representing 1byte.

myArray = [0x32 0x45 0x56 0x81] % just an example
% looks like this: myArray(1)=8bit, myArray(2)=8bit, myArray(3)=8bit, myArray(4)=8bit]

I mainly need to extract all the 32 bits and combine them to one uint32 value:

myValue = 0x32455681
%should look like this 32bit: myArray(1)myArray(2)myArray(3)myArray(4)

The goal is basically to remove the array structure and chain all the 32bits together

I once came from such an uint32 number and used the rearrange and bitget function to crate this array structure, but I somehow don't see how to come back.

As an important requirement, all the used functions must be able to be generate to C code

Any ideas?

Answer 1

[Ameer Hamza]

You can use typecast()

myArray = [0x32 0x45 0x56 0x81];
out = swapbytes(typecast(myArray, 'uint32')); % swapbytes is needed on little-endian systems

Result

>> out
out =
  uint32
   843404929
>> dec2hex(out)
ans =
    '32455681'

[Maximilian Becker]

Thanks alot! I've been trying the exact same thing, but I somehow discarded the solution for no reason.

Way simpler than my latest work around!

[Ameer Hamza]

I am glad to be of help! :)

[Daryl Lee]

I not ewith interest the comment about swapbyes andendian-ness. Is there a portable way to do this, so the same code will run correctly whatever the endian-ness of the host? Kind of like htonl() and ntohl()?

[Walter Roberson]

@Daryl Otis Lee

No portable function is provided. You can use computer() to probe the host endian.

[C, arch, endian] = computer()

C = 'GLNXA64'

arch = 2.8147e+14

endian = 'L'

MATLAB has only been supported on little-endian hosts for quite a number of years; I believe SGI was the last supported big-endian host.

[Daryl Lee]

Thanks

[Nur Fatin Atirah Mohd Rawi]

Do you know how to convert single uint 32 into uint 8?

[Steven Lord]

format longg
x = randi([intmin('uint32') intmax('uint32')], 1)

x = 
                3159077208

y = typecast(x, 'uint8')

y = 1×8

0 0 0 43 118 137 231 65

format hex
x

x = 
   41e789762b000000

y

y = 1×8

00 00 00 2b 76 89 e7 41

swapbytes(x)

ans = 
   0000002b7689e741