Does Matlab have a function which is similar with sizeof in C?

For example, if I type sizeof('double'), the function can give me 8. Let me know whether Matlab has a function working similarly with sizeof in C language.

[Steven Lord]

How would you use such a function if it existed? You don't need to allocate memory yourself like you do in C, instead you should use functions like zeros, ones, etc. to preallocate your arrays.

[mysiak]

For example when reading custom binary files.

I created simple binary file where all elements are of say 64bit long int64. Now I want to read such binary file in matlab with fread. I want to use fseek in order to navigate through the file, but I need to move in chunks of data which correspond to meaningful frame in my applicatio, say 5 numbers of int64.

So the fseek looks like fseek(fileid, 5*8, 'cof');

Then I use fread like fread(fileID,5,'int64')

Now it would be good if the 5*8 in fseek could be replaced by 5 *sizeof('int64') since matlab is aware of the int64 type. So the number 8 should be tied to int64 type.

Answer 1

[Birdman]

Use the sizeof.m file from the following link:

https://www.mathworks.com/matlabcentral/fileexchange/16595-sizeof

Type:

 sizeof('double')

Answer 2

[Jan]

A cheap method would be:

function S = sizeof(V)
switch lower(V)
  case {'double', 'int64', 'uint64'}
    S = 8;
  case {'single', 'int32', 'uint32'}
    S = 4;
  case {'char', 'int16', 'uint16'}
    S = 2;
  case {'logical', 'int8', 'uint8'}
    S = 1;
  otherwise
    warning('Jan:sizeof:BadClass', 'Class "%s" is not supported.', V);
    S = NaN;
end
end

Answer 3

[Horshack Horshack]

Edit: Oops, this doesn't work in Matlab, only Octave.

I simply cast an arbitrary constant value (zero) to the type and then take the size of the lvalue result. Examples:

sizeof(uint8(0))
sizeof(uint16(0))
sizeof(uint32(0))
sizeof(double(0))

Output:

1
2
4
8