function file_mask = mktemp( file_mask )
% function file_mask = mktemp( file_mask )
%
% Creates an almost guaranteed unique file name, given some template with one
% or more contiguous 'X' characters.  Once a unique name is found, a blank file
% is created with that name.  This is done to minimize potential race
% conditions (but they definitely do still exist!)
%
% See also: the mktemp manpage, from which this function was inspired
%
% Joshua V. Dillon; Feb. 20, 2007; jvdillon AAT purdue DDOT edu

tries = 100;

% ensure the supplied path is valid
pos = strfind(file_mask,'/');
if length(pos)~=0 & ~exist(file_mask(1:pos(end)),'dir')
	error(['directory "' file_mask(1:pos(end)) '" doesn''t exist']);
end
	
% find the start and end of the longest chain of X's
mend   = regexp(file_mask,'X+','end');
if numel(mend)==0
	error('invalid filename mask: must contain one or more ''X''');
end
mstart = regexp(file_mask,'X+','start');
[digs pos]=max(1+mend-mstart);

% replace the X's and see if the file exists
for ii=1:tries
	num = num2str(ceil(rand*10^digs));
	file_mask(mstart(pos):mend(pos)) = [repmat('0',1,digs-length(num)) num];
	if ~exist(file_mask,'file')
		% NB: Although race conditions are still possible, this should help.
		%     This also has the advantage of verifying one can actually write
		%     to this file.
		fclose(fopen(file_mask,'w'));
		return;
	end
end

file_mask = '';
error(['couldn''t create a unique file name after ' ...
			num2str(tries) ' tries--giving up!']);