Whoever wrote the tsearch/tfind/tdelete/twalk functions for libc clearly stopped thinking about how it would be used. The only way I can see to iterate the tree is to use twalk, which doesn't let you pass any extra arguments to your provided action method.

This sucks if, for example, you wanted to get a list of all entries in the tree in a threadsafe or multiplicity-safe way.

Some workarounds include:

• Every time you insert, add the same structure to an array.
• Use something that supports sane iteration (bdb, for example).

I looked into using bdb for some things, but the tree I wanted to iterate over most was a structure that held, among other things, a function pointer. Function pointers are magical and special and are held in a place in memory you can't simply make a copy of. If you try to store a function pointer in an in-memory BDB database, the value that comes out of your query will be different than the function pointer.

This bdb code sample attempts to store a function pointer in bdb. The output is:

stored: 607a70
actual: 4005e8

The value changed because copying a function pointer doesn't work.

There's a workaround here that might be useful - dlopen(). Any functions I want to store in bdb, I would store by string name and fetch the function pointer with dlsym().

This dlopen example shows how to dlopen yourself and fetch a function by string name.

Fun with pointers.

I spent some time putting love into cgrok (uses libpcre) tonight.

• Logging facility to help in debugging. Lets you choose what features you want logging (instead of lame warn/info/number log levels)
• Added string and number comparison predicates
• Wrote a few more tests which uncovered some bugs

I also broke 2000 revisions in subversion. Yay.

Sending        test/Makefile
Transmitting file data .
Committed revision 2001.

I was happily moving along doing windows automation tonight, when suddenly sysprep broke. I'm sure I killed it by accident, or something. Googling around for the error found this knowledgebase article explaining that there is no way to recover and, quote, "When you experience this error, you must re-create the image. You cannot correct the problem with the image."

Fuck that.

If you read the docs on using sysprep/wsim/windows aik/whatever, they all point you at building a 'reference computer' which entails lots of manual work modifying settings and installing things. Sysprep can make useless all of your precious work? Sweet!

I'm just glad most of the things I've done to this system were automated so I can just reinstall and rerun the scripts.

jls(~) % sudo yum install subversion
Loaded plugins: refresh-packagekit
Setting up Install Process
Parsing package install arguments
Package subversion-1.4.6-7.x86_64 already installed and latest version

I had hoped (hope is not a strategy) Fedora would have given me svn 1.5 by now. Nope.

To get svn 1.5, rather than ask fedora or google, I just built it myself. I needed to 'yum install neon-devel' and used './configure --with-neon=/usr --with-ssl --with-zlib=/usr/lib' to configure subversion. Otherwise the build/install went fine.

Huzzah!

I have a confession: I actually like Vista. It has some nice new features.

Vista beats the pants off of XP. Both my work laptop and a recently-purchased workstation at home run Vista (business and home premium, respectively) and I've never looked back. I can't tell you if it's slower, or if it eats more memory, because I haven't thought about it (because it's not a problem).

I didn't like it at first. They moved everything. Normal control panel operations were totally moved around, icons changed, start->run went away. It took me atleast a week to stop looking for folders like "My Computer" or "My Documents" which had been renamed simply "Computer" and "Documents".

The two best things so far are search related: the start menu search box and the search box in the control panel are both awesome. Forget futzing around with %PATH%, the start menu search box will just search for things in the start menu as you type (and perhaps other areas); certainly a nice touch.

The control panel search is awesome, and actually helped me stop asking "Where the F is network configuration?"-type questions. I type 'disable uac' and get this result - so useful.

Aero is meh, but it's not displeasing. The task switcher showing a thumbnail of the actual window is kind of neat and slightly helpful, too. I installed virtuawin to give me multiple desktops and everything's been peachy.

Woot. Another Yahoo! Hackday :)

Same basic structure as the one held 2 years ago at the same location (Y!'s Sunnyvale campus): free concert, free api tutorial sessions, and a 24-hour idea-to-implementation challenge.

The only bad part, which was the only bad part about the last hackday, was the presence of startup companies presenting their product as their 'hack'. This year's overall winner was Xoopit which won simply on not a hack but on Xoopit's product, which has been around for a while. Maybe I was already annoyed at Xoopit for plastering their stickers all over Yahoo's cafeteria.

Big frownyface to all the companies who used hackday submissions as an advertising feature.

Ignoring those silly people, the rest of the hackday festivities were quite good. The concert was a bit strange but still very entertaining - Girl Talk puts on quite a show. My favorite hacks, mostly because of the entertainment value of the presentation and the hacks, were iHeater and Moshpit.

My hack, as listed on hackday.org:

    * hack: SnackUpon
    * url: http://pipes.yahoo.com/jordansissel/snackupon
    * people: Jordan Sissel
    * comments: Get StumbleUpon-like behavior trained automatically from your
      own tags in delicious. Sources are BOSS news and web search, your
      Delicious network, recent Delicious posts, and your own recent posts.

Slides are here Super huge thanks to Yahoo! for hosting another hackday near me; it was fantastic.

Last year had some strange badges at Defcon, but they were fun. This year, they're even more full of technology (mini sd card reader, infrared stuff, and what looks like a usb mount point) and much less fun.

Although it is foolish for me to think another conference badge could be as awesome as the Shmoocon 2007 badge, I think it's safe to conclude that Defcon's badges have jumped the shark, because this year's badges are kind of stupid.

Another year, another Defcon.

I'm heading up a day early for my bachelor party (woo!) and then it'll be the Con all weekend. If you're going, email me and let me know where you are.

I'm eager to watch Kaminsky talk about how awesome he is for [insert reason]. He's deliciously full of himself (not that he doesn't release interesting things). Lots of other talks look interesting, so it should be a good weekend full of booze and geeking.

I have a host (let's call it filer) that is only accessible through a bastion server. Here's how to rsync directly do that host:

rsync -e 'ssh bastion ssh' somefile.tar.gz filer:

I haven't posted much recently due to my wedding coming soon and being extremely busy with work. I've been learning a great deal of new tools recently, so expect some brain dumps about some of the following:

• lvm
• qemu
• windows hackery

When you create a loop device from a disk image with losetup, it doesn't bother reading the partition table from the disk image so you don't get the nice and easy access to, for example, /dev/loop0p1 for partition 1.

FreeBSD seems to get this right, as I recall, but Linux does not.

fdisk outputs these devices, but they don't exist:

% sudo fdisk -l /dev/loop0 | grep '^/'
/dev/loop0p1   *           1        1043     8377866    7  HPFS/NTFS
/dev/loop0p2            1044        2088     8393962+   7  HPFS/NTFS

Linux's mount(8) command gives you the '-o offset=XXX' option. The offset is a byte offset, and lets you decide how far into your disk image you want to start. However, fdisk doesn't output in bytes, it outputs in cylinders or sectors.

Not to worry, it helpfully outputs the conversion between the units and bytes:

% sudo fdisk -l /dev/loop0 | grep Units
Units = cylinders of 16065 * 512 = 8225280 bytes

Knowing this, let's use awk to generate the offsets for us:

% sudo fdisk -l /dev/loop0 
  | awk '/^Units/ { bytes=$(NF-1) } /^\// { print $1 "[" $NF "]: mount -o offset=" $3 * bytes }'
/dev/loop0p1[HPFS/NTFS]: mount -o offset=8225280
/dev/loop0p2[HPFS/NTFS]: mount -o offset=17174384640

Now simply mount them with 'mount -t ntfs -o loop,offset=XXXX mydiskimage /mnt' or whatever you want :)