function save4(varargin)

% save4 -- Versatile "save", using Matlab v4 Mat-file.
%  save4('demo') exercizes itself with "save4(10)".
%  save4(N) exercizes itself with N-by-N random data.
%  save4('filename') saves all compatible variables
%   to "filename".  Default filename = 'matlab.mat';
%   default extension = '.mat'.
%  save4('filename', 'var1', 'var2', ..., '-precision', ...
%   '-asis', '-append') saves the given variables
%   (double, char, and sparse arrays) in a Matlab v4
%   Mat-file, using the specified precision, plus
%   other options:
%
%       '-double'     Default for numbers.
%       '-single'
%       '-long'
%       '-short'
%       '-ushort'     Default for strings.
%       '-uchar'
%
%       '-asis'       Store integers without packing.
%       '-append'     Append variables to existing file.
%
%   Note: Multi-dimensional arrays are cast to two-dimensions.
%   Note: Experience with NaN and Inf as integers may vary.
%
% Also see: SAVE, LOAD.

% Copyright (C) 2002 Dr. Charles R. Denham, ZYDECO.
%  All Rights Reserved.
%   Disclosure without explicit written consent from the
%    copyright owner does not constitute publication.
 
% Version of 17-Jan-2002 09:49:50.
% Updated    18-Jan-2002 11:45:34.

% Demonstration.

if length(varargin) == 1 & isequal(varargin{1}, 'demo')
	help(mfilename)
	varargin{1} = 10;
end

if length(varargin) == 1 & any(varargin{1}(1) == '01234567890+-.')
	varargin{1} = eval(varargin{1});
end

if length(varargin) == 1 & isequal(class(varargin{1}), 'double')
	n = max(round(varargin{1}), 1);
	x = rand(n, n);
	y = x;
	y(y < 0.5) = 0;
	y = sparse(y);
	z = fix(x * 100);
	c = char(z);
	xx = x;
	yy = y;
	zz = z;
	cc = c;
	filename = [mfilename '_demo.mat'];
	disp([' ## Using Mat-file "' filename '".'])
	feval(mfilename, filename, 'x', 'y')
	feval(mfilename, filename, 'z', 'c', '-append')
	clear x y z c
	load(filename)
	s = [' ## ' mfilename '(' int2str(n) '): Round-trip'];
	if isequal(x, xx) & isequal(y, yy) & ...
		isequal(z, zz) & isequal(c, cc)
		disp([s ' succeeded.'])
	else
		disp([s ' failed.'])
	end
	return
end

% Adjust calling arguments.

if nargin < 1
	varargin = {'matlab.mat'};
end

count = length(varargin);
for i = 1:length(varargin)
	var = varargin{i};
	if var(1) == '-'
		count = count - 1;
	end
end

if count < 2
	w = evalin('caller', 'whos');
	w = {w.name};
	w = w(:).';
	varargin = [varargin w];
end

% Default settings.

doAppend = 0;
doAsis = 0;
thePrecision = 'float64';

% Default M O P T code.

M = 1;   % Machine: IEEE Big-endian.
O = 0;   % Always zero.
P = 0;   % Precision: see below.
T = 0;   % Type of data: matrix (0), string (1), or sparse (2)

% Interpret the precision and other options.

for i = 2:length(varargin)
	var = varargin{i};
	if var(1) == '-'
		switch lower(var)
		case {'-double', '-float64'}
			thePrecision = 'float64';
			P = 0;
		case {'-single', '-float', '-float32'}
			thePrecision = 'float32';
			P = 1;
		case {'-long', '-slong', '-int32'}
			thePrecision = 'int32';
			P = 2;
		case {'-short', '-sshort', '-int16'}
			thePrecision = 'int16';
			P = 3;
		case {'-ushort', '-uint16'}
			thePrecision = 'uint16';
			P = 4;
		case {'-uchar', '-ubyte', '-uint8'}
			thePrecision = 'uint8';
			P = 5;
		case '-append'
			doAppend = 1;
		case '-asis'
			doAsis = 1;
		otherwise
			disp([' ## Unknown thePrecision: ' var])
			return
		end
	end
end

% Default to ".mat" extension if none given.

theFilename = varargin{1};
if ~any(theFilename == '.')
	theFilename = [theFilename '.mat'];
end

% Open the file in native format.

if doAppend
	fid = fopen(theFilename, 'a', 'native');
else
	fid = fopen(theFilename, 'w', 'native');
end

if fid < 0
	disp([' ## ' mfilename ': Unable to open file: ' theFilename])
	return
end

% Code for machine-format.

[filename, permission, machineformat] = fopen(fid);
switch machineformat
case 'ieee-le'
	M = 0;
case 'ieee-be'
	M = 1;
case 'vaxd'
	M = 2;
case 'vaxg'
	M = 3;
case 'cray'
	M = 4;
otherwise
	disp([' ## Incompatible machine-format.  Nothing saved.'])
	fclose(fid)
	return
end

% Save compatible variables.

for i = 2:length(varargin)
	var = varargin{i};
	if var(1) ~= '-'
		try
			w = evalin('caller', ['which(''' var ''')']);
			c = evalin('caller', ['class(' var ')']);
			if ~(isequal(w, 'variable') & ...
					(isequal(c, 'char') | ...
					isequal(c, 'double') | ...
					isequal(c, 'sparse')))
				disp(' ')
				disp([' ## ' mfilename ': Not a compatible type.'])
				disp([' ## Unable to save "' var '".'])
			else
				x = evalin('caller', var);
				sz = size(x);
				if length(sz) > 2   % Force to 2-d.
					sz = [sz(1) prod(sz(2:end))];
					x = reshape(x, sz);
				end
				switch class(x)
				case 'double'
					T = 0;   % Type = full-matrix.
					prec = thePrecision;
				case 'char'   % Might be 16-bit Unicode.
					T = 1;   % Type = string.
					P = 4;   % Unsigned short integer.
					prec = 'uint16';   % As in Matlab v5+.
				case 'sparse'
					T = 2;   % Type = sparse.
					prec = thePrecision;
					[row, col, val] = find(x);
					row = [row(:); sz(1)];
					col = [col(:); sz(2)];
					val = [val(:); 0];
					x = [row col val];
					sz = size(x);
				end
				if ~doAsis   % Pack if all integer.
					y = x(:);
					if all(isfinite(y))
						if ~isreal(y)
							y = [real(y); imag(y)];
						end
						if ~any(rem(y, 1))
							mn = min(y);
							mx = max(y);
							if mn >= 0 & mx < 2^8   % Unsigned byte.
								P = 5;
								prec = 'uint8';
							elseif mn >= 0 & mx < 2^16   % Unsigned short.
								P = 4;
								prec = 'uint16';
							elseif mn >= -2^15 & mx < 2^15   % Signed short.
								P = 3;
								prec = 'int16';
							elseif mn >= -2^31 & mx < 2^31   % Signed long.
								P = 2;
								prec = 'int32';
							end
						end
					end
				end
				MOPT = 1000*M + 100*O + 10*P + T;
				mrows = sz(1);
				ncols = sz(2);
				imagflag = abs(~isreal(x));
				namelen = length(var) + 1;   % Includes null-byte.
				name = var;
				null = 0;
				fwrite(fid, [MOPT mrows ncols imagflag namelen], 'uint32');
				fwrite(fid, name, 'uint8');
				fwrite(fid, 0, 'uint8');   % Null-byte.
				if imagflag
					fwrite(fid, real(x), prec);
					fwrite(fid, imag(x), prec);
				else
					fwrite(fid, x, prec);
				end
			end
		catch
			disp(' ')
			disp([' ## ' mfilename ': Error = "' lasterr '"'])
			disp([' ## Unable to save "' varargin{i} '".'])
		end
	end
end

% Close and return.

fclose(fid);