Monday, November 08, 2010 at 12:02 AM.

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system.verbs.builtins.Frontier.openDataFile

on openDataFile (fname, flCheckWindowOpen=true) { //returns an address
	<<Changes
		<<6/8/10; 5:21:49 AM by DW
			<<Add optional parameter, flCheckWindowOpen. If false we don't check to see if the window is open. This is where most of the time is spent, the tickcount for 1000 calls went from 764 to 30 when I turned this check off. 
		<<3/13/02; 7:54:42 AM by DW
			<<We used to initialize user.prefs.maxDataFiles to 5. This number is too low, and could result in thrashing on a user's machine if they have more than five data files. So we do something unusual, if the number is 5, we increase it to 25. 
		<<1/4/02; 2:40:13 PM by DW
			<<If the table for the file exists and has a flCompacting item, make the caller wait.
		<<1/2/02; 6:11:00 PM by DW
			<<Corner-turn for the Guest Databases folder in Radio
				<<If running in Frontier, no change in behavior, files still live in the Guest Databases folder.
				<<If running in Radio
					<<1. Look for the file in the Data Files sub-folder of the Radio folder, if it's there, you're done.
					<<2. Look for the file in the Guest Databases/ops/datafiles folder. If it's there, move it to the Data Files folder, and open that file.
					<<3. If the file doesn't exist, create it in the Data Files folder.
		<<5/16/01; 11:42:11 AM by DW
			<<Created.
			<<When an application wants to open its data file, it calls this routine. If the file is already open it's fast. If it's not, we close an existing file if we're at the maximum number, then open or create the file, and return the address of a top-level table where you can store your data. This centralizes an important function.
			<<This is a higher level routine than fileMenu.openGuestDatabase, which only opens the database, it doesn't manage a pool of databases, and it doesn't do folder management.
		<<5/18/01; 4:07:01 PM by DW
			<<When opening a file, open it hidden.
		<<5/19/01; 9:30:12 AM by DW
			<<Added ctAccesses to the sub-tables of datafiles.
	local (adrfilestable = @system.temp.frontier.datafiles);
	bundle { //initialization
		if not defined (adrfilestable^) {
			new (tabletype, adrfilestable)};
		if not defined (user.prefs.maxDataFiles) {
			user.prefs.maxDataFiles = 25};
		if user.prefs.maxDataFiles == 5 { //see comment in changes section for 3/13/02
			user.prefs.maxDataFiles = 25}};
	local (adrfile = @adrfilestable^.[fname]);
	if defined (adrfile^) {
		while defined (adrfile^.flCompacting) { //1/4/02; 2:42:20 PM by DW
			thread.sleepTicks (30)};
		if flCheckWindowOpen { //6/8/10 by DW
			if not window.isopen (adrfile^.f) {
				filemenu.open (adrfile^.f, true)}};
		adrfile^.whenLastUsed = clock.now ();
		adrfile^.ctAccesses++;
		return (adrfile^.adrData)};
	
	local (now = clock.now ());
	if sizeof (adrfilestable^) == user.prefs.maxDataFiles { //swap out least recently used
		<<scratchpad.ctswaps++
		semaphore.lock (this, 3600);
		local (adr, adrlru = nil, datelru = clock.now () + 1);
		for adr in adrfilestable {
			if adr^.whenLastUsed < datelru {
				adrlru = adr;
				datelru = adr^.whenLastUsed}};
		filemenu.save (adrlru^.f);
		filemenu.close (adrlru^.f);
		delete (adrlru);
		semaphore.unlock (this)};
	
	local (f, folder);
	bundle { //set f, folder
		if system.environment.isRadio {
			folder = frontier.pathstring + "Data Files" + file.getpathchar ()}
		else {
			folder = frontier.getsubfolder ("ops/datafiles")};
		f = folder + fname + ".root"};
	file.sureFilePath (f);
	if file.exists (f) {
		if not window.isopen (f) {
			filemenu.open (f, true)}}
	else { //file doesn't exist
		local (flnewfile = true);
		bundle { //if Radio, look for file in Guest Databases folder
			if system.environment.isRadio {
				local (oldfolder = frontier.getsubfolder ("ops/datafiles"));
				local (oldfile = oldfolder + fname + ".root");
				if file.exists (oldfile) {
					if window.isopen (oldfile) {
						filemenu.save (oldfile);
						filemenu.close (oldfile)};
					file.move (oldfile, folder);
					filemenu.open (f, true);
					flnewfile = false}}};
		if flnewfile {
			fileMenu.new (f, hidden:true);
			window.setPosition (f, 30, 40);
			window.setSize (f, 350, 525)}};
	local (adrdata = @[f].[fname]);
	if not defined (adrdata^) {
		new (tabletype, adrdata)};
	
	new (tabletype, adrfile);
	adrfile^.f = f;
	adrfile^.whenLastUsed = now;
	adrfile^.adrData = adrdata;
	adrfile^.ctAccesses = 1;
	return (adrdata)};
bundle { //test code
	local (tc = clock.ticks ());
	for i = 1 to 1000 {
		openDataFile ("scripting2", flCheckWindowOpen:false)};
	dialog.alert (clock.ticks () - tc)}

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This listing is for code that runs in the OPML Editor environment. I created these listings because I wanted the search engines to index it, so that when I want to look up something in my codebase I don't have to use the much slower search functionality in my object database. Dave Winer.