b64_encode_I2_a Subroutine

   pure subroutine b64_encode_I2_a(n, code)
   !< Encode array numbers to base64 (I2P).
   !<
   !<```fortran
   !< use befor64
   !< use penf
   !< character(len=:), allocatable :: code64
   !< call b64_encode(n=[-203_I2P,-10_I2P], code=code64)
   !< print "(A)", code64
   !<```
   !=> Nf/2/w== <<<
   integer(I2P),                  intent(in)  :: n(1:)   !< Array of numbers to be encoded.
   character(len=:), allocatable, intent(out) :: code    !< Encoded array.
   integer(I1P),     allocatable              :: nI1P(:) !< One byte integer array containing n.
   integer(I4P)                               :: padd    !< Number of padding characters ('=').
   integer(I8P)                               :: ns      !< Size of n.

   ns = size(n,dim=1)
   allocate(nI1P(1:((ns*BYI2P+2)/3)*3)) ; nI1P = 0_I1P
   code = repeat(' ',((ns*BYI2P+2)/3)*4)
   nI1P = transfer(n,nI1P)
   padd = mod((ns*BYI2P),3_I8P) ; if (padd>0_I4P) padd = 3_I4P - padd
   call encode_bits(bits=nI1P,padd=padd,code=code)
   endsubroutine b64_encode_I2_a