Fast File Finder

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Your task is to write a platform independent Fast File Find. I suggest you tackle it like this:

1. Create a SQL database of all the filenames in the system.
2. Ask SQL to build three indexes, by directory name, by filename, and by extension.
3. When you get a request, analyse the wild card and convert it into a SQL query on those three fields. SQL will be clever and use its indexes or brute force if necessary. In any case it will always be faster than the Windows File Find since its database is contiguous. The directory that Windows searches can be scattered higgledy piggledy all over the disk.
4. If you don’t want to use SQL, you will need some sort of treemap/btree indexed file manager. Btrieve will let you package their product free with your apps, but that only covers Windows.
5. Allow copy to the clipboard of any result with a single click, as well as the traditional ways.
6. Allow launch of any of the result files with a double click, ideally support everything in the Windows right click menu for that file type.
7. Now for the hard part. How do you keep your SQL database up to date?
   • You could do it by brute force, just slowly and continuously scan through all the files on the disk looking for new, renamed or deleted ones. You don’t want to create so much I/O you become a pest. Then again you don’t want to dawdle so that you are too far out of date.
   • If you can persuade the OS to notify you of new, renamed or updated files, you can save considerable work. That hook would almost certainly require some JNI code, or an independent auxiliary C program that sent you updates via TCP/IP. You might check Filemon . They provide source for a VXD.

     There is a change-tracking facility built into Win2K, and Win2K also implements a find utility that’s based on an index (database) of the disk, using Microsoft Index Server (which comes bundled with Win2K). Windows 2000 now has a “fast find” built in. It is hopelessly slow the way it grinds away for hours building indexes of file content that are always out of date.

     If you do hook into the OS for change notification, make sure you do your processing asynchronously. You don’t want to tie up the universe while you update your database. Just enqueue the work to be done later, so you don’t overload the system. Later when things aren’t so frantic you will eventually catch up.

8. Now you can get a little clever. You can do lazy updates of deleted files, procrastinating discovering and telling your SQL database about them. Don’t bother checking if the files exist until they show up in a result list of someone’s SQL query. Then at the last second check if the files still exist, and update the SQL database accordingly. You can also discover them with a low priority background process.
9. Of course you want something that at 3 AM refreshes the database and ensures it is not corrupt in any way and is 100% up-to-date.
10. For bonus points, in your displays, mark files that are in-use, or open-for-write. You can use File.canWrite or some platform specific code to find files that are being read too.
11. Consider a more elaborate user interface that looks something like this:

    If, ff, the above FileFinder Java Applet does not work…

    1. This Java Applet needs Java 1.1 or later, version 1.6.0_11 recommended and a recent browser.
    2. You should see the Applet above looking much like the screenshot. If you don’t, the following should help you get it working:
    3. If you are using Microsoft Internet Explorer, try another browser. Seriously. Microsoft has taken great pains, over and over, to screw up Java and every other multi-platform standardisation.
    4. If you are using Internet Explorer 7 or 8, you must allow blocked content permission for Active X to run. This also gives permission to Java to run. Click the Information bar, and then click Allow blocked content. Unfortunately, this also allows dangerous ActiveX code to run. However, you must do this in order to get access to perfectly-safe Java Applets running in a sandbox. This is part of Microsoft’s war on Java. Don’t put up with it! Use a different browser.
    5. Especially if this Applet has worked before, try clearing the browser cache and rebooting.
    6. To ensure your Java is up to date, check with Wassup. First, download it and run it as an application independent of your browser, then run it online as an Applet to add the complication of your browser.
    7. If the above Applet does not work, check the Java console for error messages.
    8. If the above Applet does not work, you might have better luck with the downloadable version.
    9. If you still can’t get the program working click HELP for more detail.
    10. If you can’t get the above Applet working after trying the advice above and from the HELP button below, have bugs to report or ideas to improve the program or its documentation, please send me an email at.

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Why JNI?

The reasons I originally wanted to write a file find to replace Microsoft’s are:

1. I wanted it much faster.
2. I wanted it low overhead.
3. I wanted it up-to-date. I most often search for a file that I recently saved under the wrong name.

One nice thing about native classes is you can add more implementations later without disturbing existing code. JWS selects the right library for you.

FindCat

Desktop Google has provided a fast search, but by content, not by name.

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