## Copyright (C) 2000 Paul Kienzle
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


## -*- texinfo -*-
## @deftypefn {Function File} {} strjust (@var{s}, ['left'|'right'|'center'])
## Shift the non-blank text of @var{s} to the left, right or center of
## the string. If @var{s} is a string array, justify each string in the array.
## Null characters are replaced by blanks. If no justification is specified,
## then all rows are right-justified.
## @end deftypefn

function x = strjust (x, just)

  if nargin < 1 || nargin > 2
    usage ("strjust (s, ['left'|'right'|'center'])");
  endif
  if nargin == 1
    just = "right";
  endif
  just = tolower (just);

  dfi = do_fortran_indexing;
  unwind_protect
    do_fortran_indexing = 1;

    ## convert nulls to blanks
    idx = find(toascii(x) == 0);
    if !isempty(idx), x(idx) = " "; endif

    ## For all cases, left, right and center, the algorithm is the same.
    ## Find the number of blanks at the left/right end to determine the
    ## shift, rotate the row index by using mod with that shift, then
    ## translate the shifted row index into an array index.
    [nr, nc] = size(x);
    idx = ( x' != " " );
    if strcmp (just, "right")
      [N, hi] = max ( cumsum ( idx ) );
      shift = hi;
    elseif strcmp (just, "left")
      [N, lo] = max ( cumsum ( flipud ( idx ) ) );
      shift = (nc - lo);
    else
      [N, hi] = max ( cumsum ( idx ) );
      [N, lo] = max ( cumsum ( flipud ( idx ) ) );
      shift = ceil ( nc - (lo-hi)/2 );
    endif
    idx = rem ( ones(nr,1)*[0:nc-1] + shift'*ones(1,nc), nc);
    x = x ( idx*nr + [1:nr]'*ones(1,nc) );

  unwind_protect_cleanup
    do_fortran_indexing = dfi;
  end_unwind_protect

endfunction