How can I apply circular shift on bits in MATLAB?

I want to apply shift right operation on aset of bits

Answer 1

[Youssef Khmou]

hi,

suppose you have a vector a=011000011, then shift circularly the vector :

 b=circshift(a,[1 1]), % if 1 is >0 then the vector is shifted the right

 b=circshift(a,[1 -1])

 b=circshift(a,[1 2]),

...

[Sana Shaikh]

Thank you!

Answer 2

[Walter Roberson]

MATLAB does not offer that operation directly.

You can extract the bits that would be shifted "off the bottom", do the shift, and then put the bits back on top. Or you can proceed numerically, such as

mod(x,2)*2^7 + floor(x/2)

[Sana Shaikh]

okie if in binary a=011000011 then how can I perform the first method??

[Sana Shaikh]

Thank you!

[sushmitha kemisetti]

what is the numerical function for circular left shift?

[Walter Roberson]

Supposing your array is named YourMatrix, and each of the values is to individually be left-shifted by K bits, then:

vc = class(YourMatrix);
switch vc
   case 'int8'; uc = 'uint8'; wl = 8;
   case 'uint8'; uc = 'uint8'; wl = 8;
   case 'int16'; uc = 'uint16'; wl = 16;
   case 'uint16'; uc = 'uint16'; wl = 16;
   case 'int32'; uc = 'uint32'; wl = 32;
   case 'uint32'; uc = 'uint32'; wl = 32;
   case 'int64'; uc = 'uint64'; wl = 64;
   case 'single'; uc = 'uint32'; wl = 32;
   case 'double'; uc = 'uint64'; wl = 64;
   otherwise; error('YourMatrix is not numeric, is class %s', vc);
end

uMatrix = typecast(YourMatrix, uc);
shifted_uMatrix = bitshift(uMatrix, K, uc) + bitshift( uMatrix, K-wl, uc);
shifted_YourMatrix = typecast(shifted_uMatrix, vc);

... As you can probably see, the process would be much simpler if you were to ask about one particular data type.

[sushmitha kemisetti]

If I give a matrix, then how should I get a matrix, where all elements should be circularly left shifted? Is there any numerical function "mod(x,2)*2^7 + floor(x/2)" like this?

[Walter Roberson]

Do you want the individual bits to be left shifted, or do you want the elements to be left shifted relative to the other elements? For example if you had A = uint8([1 2 3 129]) to be circular left shifted by 2, then do you want the result B = uint8([3 129 1 2]) or do you want the result B = uint8([4, 8, 12, 6]) ?

If you want the elements to be left shifted relative to each other, then

B = circshift(A, -K, 2);

If you want the bits to be circular shifted, then use the code I posted above (which I made a couple of corrections to a moment ago.)

If you want the bits to be circular shifted and you want the operation to be expressed mathematically, it is possible. In the above code, replace

shifted_uMatrix = bitshift(uMatrix, K, uc) + bitshift( uMatrix, K-wl, uc);

with

shifted_uMatrix = mod(uMatrix, 2^(wl-K)) * 2^K + uMatrix ./ 2^(wl-K);

[sushmitha kemisetti]

Thank You!