Changing yyin (2)

[Mhaxx]

Maybe I've found the solution:

(1)
tmp = yyin;
yy_switch_to_buffer(yy_create_buffer("file_B", YY_BUF_SIZE));

This is ok because it permits to continue scanning/parsing but the problem
is the second time I use it (to return to process file A):

(2)
yy_switch_to_buffer(yy_create_buffer(tmp, YY_BUF_SIZE));

This is not ok, I don't know why!
Maybe I have to save YY_CURRENT_BUFFER in (1) and to use it in (2) in
substitution of tmp... but I don't know how to save it! :-(

Mhaxx