Friday, March 28, 2008

Announcing the iPhone eBook Repository

Installing eBooks onto the iPhone for reading was nearly impossible. You needed to download third party tools, use scp, rename files, the works. To help, I decided to package existing eBooks for viewing on the iPhone.

Since this is an AppTapp repository, the books can be installed onto the iPhone from any location that the device has a valid network connection, GPRS, EDGE or WiFi.

The current repository provides installation instructions for 117 SciFi novels from the Baen Free Library, with plans to add additional sources. I am currently working on Project Gutenberg.

To make use of the repository:

  1. Obtain an iPhone.
  2. Jailbreak the iPhone, I recommend ziphone for this task.
  3. Install Books, the iPhone ebook reader using the Installer application ( (1.37 only!))
  4. Add the repository to Installer:
    1. Start Installer
    2. Click "Sources"
    3. Click "Edit"
    4. Click "Add"
    5. Enter ""
    6. Click "OK"
    7. Click "Done"
    8. Click "Refresh"
  5. Select "Install" at the bottom of the screen. You will see "Baen Free Library" is now available as an application category!

Just to clarify a couple of things. I am not providing copies of the .zip archives, they are provided to the iPhone by Webscription and Baen. The content of the files themselves are unchanged, although I have had to rename the html files to better fit in with the reader (I changed the SKU in the filename to Chapter).

To make it easy to spread these repositories around, I have uploaded the scripts I used to generate the repository to google code (iphoneebookrepo). If you would like to help, either with code, by reporting faults (thanks Ross!), or just general comments, I would appreciate it!

Take that Kindle!

Wednesday, March 26, 2008

AppTapp Exec bug

I released my project to a couple of friendly users. After giving it a try, one of the testers came back and told me the installer was leaving crufty directories lying around in the root directory.

I eventually tracked it down to this:

   <string>/bin/mkdir -p "/var/root/Media/EBooks/Beyond World's End"</string>

Now, if this was in a shell, or passed to the OS using "system" or a similar call, it would work. However, it seems that they are using direct calls to exec. I can't really tell, because AppTapp is oddly closed source.

The directories it was creating were:

  • "/var/root/Media/EBooks/Beyond
  • /World's
  • /End"


Next up, I tried escaping the spaces, again with no luck. It looks like the code is splitting the parameters out through the use of spaces and ignores any attempt at grouping the packager might make.

Luckily CopyPath does the right thing, properly handling the spaces. It even creates parent directories, which is why I was using mkdir in the first place.

Now to figure out how to host it on Amazon S3. I really don't want a 2.5meg file being slurped across my cable modem every day!

Tuesday, March 25, 2008

Debugging an iPhone repository

The AppTapp Installer doesn't provide any feedback during a failed install or source update. This makes it very difficult to create packages. At first, it really feels like you are stumbling around in the dark.

Here is what I learned from my project. ignores bad XML documents. If you have one good version of your repository, and then make a change that results in a "bad" one, you will still see the good copy that has been cached on the phone. This confused me for a long time.

Always test the document for correctness first. Firefox is a quick, easy test tool. Point it at the URL, and if it displays the XML in tree format, you at least know that your XML is balanced, and that your web server is configured correctly.

Next, run manually on the iPhone. This should let you know what is going wrong with the package. (original source)

  1. make sure you are not running
  2. ssh into your iPhone (root password is "alpine")
  3. for 1.1.3 firmware and higher: su - mobile
  4. maximize your ssh window
  5. cd /Applications/
  6. ./Installer
  7. you will see pop up on the iPhone's screen
  8. reproduce the error
  9. observe the debugging output from in the ssh window

Finally, never, ever change the root password on your iPhone. You may think that because you are running an SSH server that is open to the world that it would be a good idea to change it. After all, there is a "passwd" command sitting right there in the terminal window. RESIST!

There is a problem with the 1.1.3 and later firmwares, and the version of passwd shipped with the BSD subsystem results in Springboard (the desktop shell) crashing continuously. I made this mistake and had to completely wipe the phone and restore it.

For security, install the services application, and disable the SSH server between uses. This will also help with the battery life of the phone!

Creating an iPhone AppTapp Repository.

I had a project where I needed to create a repository for AppTapp (, the application used for over the air software installation on jailbroken iphones.

It's near impossible to find instructions on how to do this. If you google for them, all you get are "how to jailbreak your phone" and "how do I install applications" questions. Nothing about how to actually create a repository!

Thankfully, I eventually found the a wiki on ipodtouchfans with a detailed description.

The repository file is an XML document using Apple's plist format. Since it's XML it is both easy to pick up and nasty to use at the same time. The header portion of the plist file is self-explanatory, check out the wiki link. Here's the header from my test repository.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "">
<plist version="1.0">
  <string>Jason Pollock</string>

The individual package instructions go in the final array. However, this is a fully specified (if empty) repository. If you place it on a publicly accessible URL, people will be able to add it to and track updates!

Next are the individual packages and installation scripts. The package themselves are separated into scripts and .zip archives. There is no provision to deliver software in any other format.

The install/uninstall scripts are part of the repository XML, not the .zip archive. This means that you can host the .zip files on a cheap, low cost volume server, while the xml document (since it is generally smaller) can be hosted closer to you. Web servers are more able to cache the repository document. Hopefully, with a single http request, the application is able to tell from the header response if the repository has changed, keeping transfers to a minimum. To keep from having someone change the .zip file on you, both a size and an md5 hash are provided in the plist file. Finally, the separation between script and installed files allows other people to provide fixed installers for your application!

The install/uninstall scripts are also XML, complete with if/then/else syntax. This is near impossible to either understand or get right due to all of the tag nesting, and chaining of siblings without explicit keyword enclosures. For example, let's look at an extremely simple "if" block to check the firmware version.

First, the logic in C, just to let you see what it should be doing:

   if (! FirmwareVersionIs("1.1.2")) {
       AbortOperation("Firmware 1.1.2 is required to update to 1.1.3.");

Now for the insanely verbose XML code.

                 <string>Firmware 1.1.2 is required to update to 1.1.3.</string>

Completely impenetrable. works best when the .zip is already in the destination layout. Then the installation process is relatively simple. However, if not, each file must be individually copied into its target location, using the <CopyPath> command.


There are several gotchas.

First, if you create directories, creates them with no permissions what so ever, you will need to perform a chmod!

Second, the location of the Media tree was moved between 1.1.2 and 1.1.3. In current releases of the iPhone firmware, applications run as the user mobile. This means that the Media tree (where the music/etc is stored), is now in /var/mobile/Media instead of /var/root/Media. Since applications are installed on both 1.1.2 and later versions of the firmware, they need to work on both. To help with this, has added support for "~", to refer to the home directory for the user. Again, however, this depends on a specific version of being present. Personally, I chose to ignore all of this, since the application I was using didn't know about /var/mobile/Media anyways. Still, it is something that developers will need to figure out.

Third the syntax in the scripts is nasty. If you find yourself writing a fair bit of it, write a tool to do it for you. I'm sure it is possible to come up with a more human readable syntax that will generate the XML for you.

Finally, debugging your packages is painful and slow. However, that's for the next post.

Other than that, there's nothing too difficult about the whole thing. If the zip file you are trying to install is already in the target layout, it's dead simple.


Thursday, March 20, 2008

No, you are not a valued "Contact"

A curious thing happened to me today. I got a connection request on LinkedIn. Obviously it isn't the request itself that was interesting. It was the combination of the request and who it came from.

I haven't had a single positive experience with this individual. I have found them to be extremely rude and unprofessional.

So, why would they ask to connect to my network? Obviously they've just joined LinkedIn and have selected everyone that listed the same employer.

Tip: When you join a social networking site, don't do that.

However, it leaves me with a dilemma. This individual is pretty senior in the company.

Do I click "Accept" and hope to gain more value from their connections than I lose by having their stench rub off on me?

Do I click "Reject" and let them know that what I really think of them?

I think I'll go with the third option, and click "Archive", stashing them with all the other people I don't like. Someone else in the company that I am connected to will click "Accept", so I'll still have access to their connections, and their stink will be at least one level removed.

Ah, social networking.

Wednesday, March 19, 2008

iCal, how can you do this to me?

After talking to Bruce, it seems that he has some of the same concerns for timezones that I do.

In a post, he pointed to something called VTIMEZONE. So, I went looking to see if perhaps there was another angle to this whole timezone storage mess.

VTIMEZONE is a data element attached to local times in iCal. It seems that when a recurring event is passed in iCal, it MUST have a VTIMEZONE component. So far so good. However, that VTIMEZONE record MUST specify information for DST! Bad iCal!

Of course, since this information is instantly incorrect, we end up with the problem we have had before. Even worse, because the information is fully specified in the message, developers are probably correct in assuming that they can't ignore the data and substitute their own information!

Personally, I feel this is a bug in iCal. I can see why it exists, to hand-wave around the timezone differences between Windows and OSX/Unix. At least they make a reference to the Olson (on which zoneinfo is based) database.

Developers, when implementing an iCal parser, use the VTIMEZONE value you receive as a way to determine the timezone, not as an actual descriptor. Based on the information in the VTIMEZONE component, find the timezone in your own TZ database and use that name when referring to the event. Never, ever, cache the definition.

Tuesday, March 18, 2008

Timezones and the FUTURE!

After reading Novell's report of the DST problem in GroupWise, I understand that a lot of these are software faults, and not problems with the OS or the timezone settings themselves.

When dealing with multiple timezones, what will a developer do? They’ll convert it to UTC for storage and comparison and then convert it back for display. This solution appears to completely remove the timezone from the problem and gives the developer a nice, sortable value to store.

Everything works fine until someone changes the start or end of DST. Immediately, all of the timestamps that were previously created for that period between the old and new start (and end) dates will be out by an hour.

If you’ve got a monthly/weekly recurring meeting it will be out by an hour into perpetuity for that 1 week every year.

The real fix is to store dates/times in the originator’s timezone and then convert them on the fly. It makes sorting a pain in the ass (time is no longer a single int!), but we’ve got CPU to burn so why not?

One final gotcha with that. You CANNOT store the originator's timezone as an offset! It needs to be a name used to retrieve the TZ information. If it is stored as an offset (I'm looking at you Oracle), you have the exact same problem. Using a name means that it becomes difficult to create an index across timestamps with mixed timezones, but the values will be correct!

The lesson to take away? You cannot convert a timestamp to UTC for storage if that timestamp is in the future.