You need two variables anyway to make any sense into the code.
Where would you get the value of 'i' if you didn't have 'data' and what would you do with the value read from 'data' if you didn't have 'i' or some equivalent?
I don't need a 'data' variables when I read directly from file. For example: "fread( (void *)&i, sizeof(i), 1, file);". Works also with (packed) structs. For the solution as given in the article I need now a second variable 'data' first to buffer the information I read from file.
edit: I mention this case as it covers around 90% of the cases I've seen on a quick check over a codebase I'm working with (Irrlicht). Swapping endian is nearly always done after reading in the data from a file-stream.
Where would you get the value of 'i' if you didn't have 'data' and what would you do with the value read from 'data' if you didn't have 'i' or some equivalent?