## Copyright (C) 2004 David BAteman
##
## 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., 51 Franklin Street, Fifth Floor, Boston, MA
## 02110-1301  USA

## -*- texinfo -*-
## @deftypefn {Function File} {@var{x} =} bitset (@var{a}, @var{n})
## @deftypefnx {Function File} {@var{x} =} bitset (@var{a}, @var{n}, @var{v})
## Set or reset bit(s) @var{n} of unsigned integers in @var{a}.
## @var{v} = 0 resets and @var{v} = 1 sets the bits.
## The lowest significant bit is: @var{n} = 1
##
## @example
## dec2bin (bitset (10, 1))
## @result{} 1011
## @end example
## @seealso{bitand, bitor, bitxor, bitget, bitcmp, bitshift, bitmax}
## @end deftypefn

## Liberally based of the version by Kai Habel from octave-forge

function X = bitset (A, n, value)

  if (nargin < 2 || nargin > 3)
    usage ("bitset (A, n, v)");
  endif

  if (nargin == 2)
    value = 1;
  endif
  
  if (isa (A, "double"))
    Bmax = bitmax;
    Amax = log2 (Bmax) + 1;
    _conv = @double;
  else
    if (isa (A, "uint8"))
      Amax = 8;
      _conv = @uint8;
    elseif (isa (A, "uint16"))
      Amax = 16;
      _conv = @uint16;
    elseif (isa (A, "uint32"))
      Amax = 32;
      _conv = @uint32;
    elseif (isa (A, "uint64"))
      Amax = 64;
      _conv = @uint64;
    elseif (isa (A, "int8"))
      Amax = 8;
      _conv = @int8;
    elseif (isa (A, "int16"))
      Amax = 16;
      _conv = @int16;
    elseif (isa (A, "int32"))
      Amax = 32;
      _conv = @int32;
    elseif (isa (A, "int64"))
      Amax = 64;
      _conv = @int64;
    else
      error ("invalid class %s", class (A));
    endif
    Bmax = intmax (class (A));
  endif

  m = double (n(:));
  if (any (m < 1) || any (m > Amax))
    error ("n must be in the range [1,%d]", Amax);
  endif

  mask = bitshift (_conv (1), uint8 (n) - uint8 (1));
  X = bitxor (A, bitand (A, mask));

  if (value)
    X = bitor (A, mask);
  endif

endfunction
