Code. Lather, rinse, repeat.

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[titusmagnus]

IPv6 Validator for Cocoa

I've been spending quite a bit of time trying to find a regex match that will allow me to verify IPv6 addresses. I finally found one that works very well in Cocoa:

- (BOOL)isIPv6:(NSString *)candidate { /* fe80:0000:0000:0000:0204:61ff:fe9d:f156 // full form of IPv6 fe80:0:0:0:204:61ff:fe9d:f156 // drop leading zeroes fe80::204:61ff:fe9d:f156 // collapse multiple zeroes to :: in the IPv6 address fe80:0000:0000:0000:0204:61ff:254.157.241.86 // IPv4 dotted quad at the end fe80:0:0:0:0204:61ff:254.157.241.86 // drop leading zeroes, IPv4 dotted quad at the end fe80::204:61ff:254.157.241.86 // dotted quad at the end, multiple zeroes collapsed In addition, the regular expression matches these IPv6 forms: ::1 // localhost fe80:: // link-local prefix 2001:: // global unicast prefix */ NSString *regex = @"^\\s*((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:)))\\s*$"; NSPredicate *test = [NSPredicate predicateWithFormat:@"SELF MATCHES[c] %@", regex]; return [test evaluateWithObject:candidate]; }

I've written a unit test verifying all the cases mentioned above and it works great.

[titusmagnus]

Removing subviews from an NSView

Typically, the solution involves iterating through NSView's - [NSArray subviews] and invoke the child's - (void)removeFromSuperview method. This is tedious. A much easier solution is to set an empty list of childs on the parent NSView, like so:

[self setSubviews:[NSArray array]];

It's simple, clean and better yet... won't crash while you iterate the array and destroy the objects while you're ennumerating ;-)

[titusmagnus]

Converting an NSColor to a CGColor

Here's an easy way to convert an NSColor to a CGColor:

- (CGColorRef)NSColorToCGColor:(NSColor *)color { NSInteger numberOfComponents = [color numberOfComponents]; CGFloat components[numberOfComponents]; CGColorSpaceRef colorSpace = [[color colorSpace] CGColorSpace]; [color getComponents:(CGFloat *)&components]; CGColorRef cgColor = CGColorCreate(colorSpace, components); return cgColor; }

Easy.

[titusmagnus]

Reverting a local commit (that hasn't been pushed to the remote repo)

How can I undo an accidental commit that hasn't been pushed yet? Easy:

git reset --soft HEAD^

This will revert the commit and leave the changes in your local repo.

[titusmagnus]

Copying a Raspberry OS image to the SD card in Mac OS X

These commands and actions need to be performed from an account that has administrator privileges. 1. Download the image from a mirror or torrent: http://www.raspberrypi.org/downloads 2. Verify if the the hash key is the same (optional), in the terminal run: shasum ~/Downloads/2012-12-16-wheezy-raspbian.zip 3. Double click the zip, it will extract the image automatically. 4. From the terminal run df -h 5. Connect the SD card reader with the SD card inside. Run df -h again and look for the new device that wasn't listed last time. Record the device name of the filesystem's partition, for example, /dev/disk3s1. Example: TurboMonkey:Desktop tciuro$ df -h Filesystem Size Used Avail Capacity iused ifree %iused Mounted on /dev/disk0s2 233Gi 185Gi 48Gi 80% 48594722 12474718 80% / devfs 197Ki 197Ki 0Bi 100% 682 0 100% /dev map -hosts 0Bi 0Bi 0Bi 100% 0 0 100% /net map auto_home 0Bi 0Bi 0Bi 100% 0 0 100% /home localhost:/mxqCAh80ehTrmCCc-8n_X5 233Gi 233Gi 0Bi 100% 0 0 100% /Volumes/MobileBackups /dev/disk1s1 15Gi 2.2Mi 15Gi 1% 0 0 100% /Volumes/NO NAME 6. Unmount the partition so that you will be allowed to overwrite the disk: sudo diskutil unmount /dev/disk3s1 7. Using the device name of the partition work out the raw device name for the entire disk, by omitting the final "s1" and replacing "disk" with "rdisk" (this is very important: you will lose all data on the hard drive on your computer if you get the wrong device name). Make sure the device name is the name of the whole SD card as described above, not just a partition of it (for example, rdisk3, not rdisk3s1. Similarly you might have another SD drive name/number like rdisk2 or rdisk4, etc. -- recheck by using the df -h command both before & after you insert your SD card reader into your Mac if you have any doubts!). Example: /dev/disk1s1 => /dev/rdisk1 8. In the terminal write the image to the card with this command, using the raw disk device name from above (read carefully the above step, to be sure you use the correct rdisk# here!): sudo dd bs=1m if=~/Desktop/2012-12-16-wheezy-raspbian.img of=/dev/rdisk1 If the above command report an error(dd: bs: illegal numeric value), please change bs=1M to bs=1m (note that dd will not feedback any information until there is an error or it is finished, information will show and disk will re-mount when complete. However if you are curious as to the progress - ctrl-T (SIGINFO, the status argument of your tty) will display some en-route statistics). 9. After the dd command finishes, eject the card: sudo diskutil eject /dev/rdisk1 Insert it in the Raspberry Pi, and have fun!

[titusmagnus]

Why is it easier to say there's some God that always existed, as opposed to the Universe always existed? How is it that a God could always exist, but not a Universe? Or conversely, how is it that a God could come from nothing, but not a Universe?

[titusmagnus]

How to commit selectively using Git

**Problem** Oftentimes, we're fixing a bug and as we go along we see other issues which end being fixed as well. The problem results in a different set of changes which would typically end up committed at once. **Solution** Commit selectively using **git add -p ...** **Example** Locate the Git directory and check its status: git status It will list the files with changes, such as: ipanema:MyProject tciuro$ git status '# On branch master # Changes not staged for commit: # (use "git add ..." to update what will be committed) # (use "git checkout -- ..." to discard changes in working directory) # # modified: foo.m # modified: bar.m # no changes added to commit (use "git add" and/or "git commit -a") For each of the files, issue the following command (we'll start with foo.m): git add -p foo.m It'll display each of the changes separately: @@ -113,21 +113,15 @@ typedef enum { - // Preflight - NSAssert(username.length > 0, @"the user name is required"); - self.username = username; - self.password = (password.length > 0 ? password : @""); + self.password = password; self.authType = SSH; } Stage this hunk [y,n,q,a,d,/,j,J,g,s,e,?]? y Type **y** or **no** and continue until you're done. Repeat the same step with the other modified files.

[titusmagnus]

How to enable tag search in your Tumblr blog

By default, Tumblr doesn't allow to search by tags. Assuming you have a theme with a search bar, chances are that even though you tagged your posts, nothing comes up when you search by tag. No problem. It's quite easy to fix this. Just follow these steps: 1) Open your blog and click "Customize." A configuration panel opens to the right of the window. 2) Click "Edit HTML." 3) Hit Command-F (i.e. Find...) and search for "body" (without the quotes). 4) Right after "body" paste the following script:

<!-- function handleThis(formElm) { window.location="http://yourtumblrURLhere.tumblr.com/tagged/"+formElm.number.value+""; return false; } ... ... Some users have their own custom domain (e.g. www.yourdomain.com). If this the case, replace the window.location URL above: window.location="http://yourtumblrURLhere.tumblr.com/tagged/"+formElm.number.value+""; with this: window.location="http://www.yourdomain.com/tagged/"+formElm.number.value+""; That's it really! Just save the HTML changes, reload your blog, tag something and search. Happy tagging!

[titusmagnus]

How to setup SSH keys

This brief tutorial explains how to generate SSH keys and publish them to a server. It's been tested on Mac OS X Mountain Lion (10.8). **Objective** Generate an SSH key and upload them to a server. In our example, we'll upload it to server.example.com. **Step #1** Launch Terminal.app and type: ipanema:~ jdoe$ ssh server.example.com The authenticity of host 'server.example.com (xx.xxx.xx.xxx)' can't be established. RSA key fingerprint is xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:. Type *yes* to add the host to your list of known hosts: Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'server.example.com,xx.xxx.xx.xxx' (RSA) to the list of known hosts. Enter the password. This will create an *.ssh* directory in your home directory with the proper permissions. Password: Last login: Tue Nov 6 20:33:46 2012 from xx.xxx.xx.xxx Welcome to server.example.com. This server is managed by the SEO Puppet configuration management system. Local ad-hoc changes to this system are strictly discouraged. Any files that contain an auto-generated header will be updated via puppet and local changes will be overwritten. Please contact [email protected] for more info. server:~ jdoe$ We can close the connection for now: server:~ jdoe$ exit logout Connection to server.example.com closed. **Step #2** Now we'll generate the SSH key: ipanema:~ jdoe$ ssh-keygen -t rsa This will prompt you for a secret passphrase: Generating public/private rsa key pair. Enter file in which to save the key (/Users/jdoe/.ssh/id_rsa): Created directory '/Users/jdoe/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /Users/jdoe/.ssh/id_rsa. Your public key has been saved in /Users/jdoe/.ssh/id_rsa.pub. The key fingerprint is: 15:db:96:0d:92:bc:51:4d:bf:d6:43:89:98:98:fb:c8 [email protected] The key's randomart image is: +--[ rsa 1024]----+ | .oooo. | | *=o+o..| | oo=+..o.| | .o. . o| | S. +.| | . o . .| | E . | | | | | +-----------------+ ipanema:~ jdoe$ **IMPORTANT** Always use a good passphrase and never leave it blank. If this works right you will get two files called id_rsa and id_rsa.pub in your .ssh directory. **Step #3** Now it's time to upload the credentials to server.example.com: scp ~/.ssh/id_rsa.pub server.example.com:.ssh/authorized_keys This command copies the id_rsa.pub file to the other host's *.ssh* directory with the name authorized_keys2. Now server.example.com is ready to accept your ssh key. **How to tell it which keys to use?** The ssh-add command will allow us to confirm which SSH key will be used: bash-3.2$ ssh-agent sh -c 'ssh-add < /dev/null && bash' Identity added: /Users/jdoe/.ssh/id_rsa (/Users/jdoe/.ssh/id_rsa) **The moment of truth** Everything looks good, so let's try to ssh into server.example.com once again. This time, no prompt should appear because the magic of SSH keys will take over: bash-3.2$ ssh serverexample.com Last login: Tue Nov 6 20:18:18 2012 from 17.226.33.162 Welcome to serverexample.com. This server is managed by the SEO Puppet configuration management system. Local ad-hoc changes to this system are strictly discouraged. Any files that contain an auto-generated header will be updated via puppet and local changes will be overwritten. Please contact [email protected] for more info. server:~ jdoe$ Did you gain access without a prompt? If so, congratulations! Otherwise, start over and pay attention to the instructions ;-)

[titusmagnus]

“Bacteria produce a new generation every 20 minutes. And every time they reproduce, which is they copy themselves, they make little copying errors. So when those little copying changes make the bacteria stronger as opposed to weaker then that means they are better able to defend themselves against those compounds, antibiotics.”

_CDC (Centers for Disease Control and Prevention)_ [Drug-Resistant Gonorrhea: Is The Antibiotic Era Coming To An End?](http://www.huffingtonpost.com/2012/10/11/antibiotic-resistance-gonorrhea_n_1916862.html)

[titusmagnus]

Git – setting up a remote repository and doing an initial “push”

This is more of a note to self as I keep forgetting the steps needed to set up a remote repository and doing an initial “push”. So, first setup the remote repository: ipanema:~ tciuro$ cd ~/Desktop ipanema:Desktop tciuro$ mkdir RemoteRepo.git ipanema:Desktop tciuro$ cd RemoteRepo.git ipanema:RemoteRepo.git tciuro$ git --bare init Initialized empty Git repository in /Users/tciuro/Desktop/RemoteRepo.git/ Now we have to setup the local sources directory. This directory contains your source files and must not have been initialized with Git, of course: ipanema:RemoteRepo.git tciuro$ cd ../LocalSources/ ipanema:LocalSources tciuro$ git init Initialized empty Git repository in /Users/tciuro/Desktop/LocalSources/.git/ ipanema:LocalSources tciuro$ git add * ipanema:LocalSources tciuro$ git commit -m "Initial release" [master (root-commit) 744e73a] Initial release 55 files changed, 3236 insertions(+) ... ... Let's verify that everything is in order by checking the branch: ipanema:LocalSources tciuro$ git branch * master Before we can push the contents from our local sources directory to the remote repo, we have to link the local sources directory to the remote repo: ipanema:LocalSources tciuro$ git remote add origin /Users/tciuro/Desktop/RemoteRepo.git Cool. Now we can push the changes from local to remote: ipanema:LocalSources tciuro$ git push -u origin master Counting objects: 73, done. Delta compression using up to 16 threads. Compressing objects: 100% (69/69), done. Writing objects: 100% (73/73), 790.82 KiB, done. Total 73 (delta 21), reused 0 (delta 0) Unpacking objects: 100% (73/73), done. To /Users/tciuro/Desktop/RemoteRepo.git * [new branch] master -> master Branch master set up to track remote branch master from origin. Let's start clean by making a new local repo: ipanema:LocalSources tciuro$ cd ../ ipanema:ClonedRepo tciuro$ git clone /Users/tciuro/Desktop/RemoteRepo.git ClonedRepo Cloning into 'ClonedRepo'... done. ipanema:Desktop tciuro$ cd ClonedRepo ipanema:ClonedRepo tciuro$ git status # On branch master nothing to commit (working directory clean) Excellent. Quick check to verify that we're in business: ipanema:ClonedRepo tciuro$ git log commit 8aaa16b6feed7a8b0c01526472e7e89efaab6bd3 Author: Tito Ciuro <...> Date: Fri Oct 5 10:40:06 2012 -0700 Initial release ipanema:ClonedRepo tciuro$ Woohoo! That's it! I hope this helps ;-)

[titusmagnus]

Rolling back a Git repo to a specific version

Once in a while you may want to rollback a specific Git repo, perhaps for testing, comparing, etc. For simplicity sake, we'll perform the following steps: Clone your Git repo git clone Obtain the log with the changes. git log Find the commit you want to rollback to and take note of the commit SHA hash, for example: commit 53d02f22d72544c56ef07e460bf7ec5cdd830f9c Author: Tito Ciuro Date: Wed Jun 6 21:56:54 2012 -0700 Fixed #8: Add a sticky notice view and refactor the code a bit Rollback the project: git reset --hard 53d02f22d72544c56ef07e460bf7ec5cdd830f9c Verify the repo status: git status It should display something like this: ipanema:GitTest tciuro$ git status # On branch master # Your branch is behind 'origin/master' by 7 commits, and can be fast-forwarded. # nothing to commit (working directory clean) ipanema:GitTest tciuro$ Cool! We now have a repo that's been rolled back to a specific commit. If at some point you want to rollback to the latest commit, you'd issue the following command: ipanema:GitTest tciuro$ git reset --hard origin/master HEAD is now at 3087973 Fixed #34: NSFNanoObject init issue: init shouldn't set the key to nil ipanema:GitTest tciuro$ Let's just make sure...: ipanema:GitTest tciuro$ git status # On branch master # Untracked files: # (use "git add ..." to include in what will be committed) # # .DS_Store nothing added to commit but untracked files present (use "git add" to track) ipanema:GitTest tciuro$ There you go!

[titusmagnus]

Rewind History in Git

If you f**k up a Push in Git like I just did, you'll have to undo/rewind History. These are the steps involved: 1) Locate the SHA hash of the commit you want to rewind to. Let's say it's 1349fbd97f063b360c431d2a27a6396c0a87172a. 2) Take note of the branch. Let's assume it's 'master'. 3) The format is git push -f origin [SHA hash]:[branch]. The command will therefore be: git push -f origin 1349fbd97f063b360c431d2a27a6396c0a87172a:master That should do it. For more information, check the following thread: http://stackoverflow.com/questions/1270514/undoing-a-git-push

[titusmagnus]

Five Reasons Why Synchronous Networking Is Bad

When you do networking, you have a choice of three different modes: * asynchronous -- For example, you can schedule an NSStream on a runloop and have it call you when data arrives. * synchronous, polled -- For example, you can periodically call -[NSInputStream hasBytesAvailable] to see if data is available. * synchronous, blocking -- For example, you can just call -[NSInputStream read:maxLength:] which will block if no data is available. In virtually all cases I recommend that you use asynchronous networking. That's because the other two options have fundamental pitfalls, as explained by the rest of this document. To start, it's obvious that polled mode is bad: it forces you to choose between wasting CPU time or wasting network performance. If you poll frequently then, on a slow network, you will be wasting CPU time (and thus power, which is obviously an issue on mobile and notebook hardware, but has recently become an issue on desktop and server hardware as well). If you poll infrequently then, on a fast network, you will be squandering network performance. It's less obvious why synchronous blocking networking is bad. Each of the five sections below describes a serious problem with it. 1. Resource Usage ----------------- The number one reason synchronous blocking networking is bad is that it wastes resources. You can't do synchronous blocking networking on the main thread, so you necessarily have to create a secondary thread to do the work. That thread is a waste of resources, most notably: * virtual address space (always consumed) * a /wired/ kernel stack (consumed while the thread is blocked) This is especially bad when you're handling lots of connections simultaneously, most of which are idle. You consume a bunch of wired kernel stacks to get exactly /no/ work done. 2. Threads Are Evil ------------------- Because synchronous blocking networking requires a secondary thread, you have to deal with having multiple threads in your process. This raises a host of thread-related issues, most notably the problem of sharing data between threads. It's best to avoid this if you can. 3. Cancellation --------------- Synchronous blocking networking makes it very hard to support cancellation. You either have to jump through a bunch of hoops (see my SocketCancel sample) or poll for cancellation (and did I mention that polling was bad?). 4. Timeouts ----------- Implementing a timeout is tricky with synchronous blocking networking. Some synchronous blocking APIs implement some form of timeout support, but not all. And where they do, the support tends to be less robust than you'd like. Again, you can work around this with various tricks but this serves to further undermines the illusion that synchronous blocking networking is easier. 5. Bidirectional ---------------- It's not possible to support full bidirectional communications on a single synchronous blocking connection. * * * Share and Enjoy -- Quinn "The Eskimo!" Apple Developer Relations, Developer Technical Support, Core OS/Hardware

[titusmagnus]

How to create a RAM disk

The formula to calculate the size needed is: RequestedMB * 2048. For example, to create a 4GB RAM disk (4096MB), the command would be the following: diskutil erasevolume HFS+ "ramdisk" `hdiutil attach -nomount ram://8388608`

[titusmagnus]

How to find which terminal commands you use more

Just enter the following command in Terminal: history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head

[titusmagnus]

Tagging in Git

Here's an example: $ git tag -a 1.0.0 -m "Tag release 1.0.0" $ git push --tags