%N uvread %F $MIR/src/subs/uvio.c
%D Read in some uv correlation data.
%P rjs
%: uv-i/o
%B
FORTRAN call sequence:
        subroutine uvread(tno,preamble,data,flags,n,nread)
        integer tno,n,nread
        double precision preamble(*)
        complex data(n)
        logical flags(n)

  This reads a single visibility from the data file. This starts by scanning
  the uv data stream until a correlation record is found. The correlations
  are then converted to complex numbers if necessary, and returned to the
  caller. Uvread also performs some massaging (see uvset) and selection
  (see uvselect) steps.

  Input:
    tno         Handle of the uv data set.
    n           Max number of channels that can be read.
  Output:
    preamble    A double array of elements giving things such as
                u,v, time and baseline number. Setable using uvset.
    data        A real array of at least n complex elements (or 2n real
                elements). This returns the correlation data.
    flags       Logical array of at least n elements. A true value for
                a channel indicates good data.
    nread       Number of correlations returned. On end-of-file, zero
                is returned.                                            
