A Tasty Pixel » Geekspeak

Fixing Xcode 4’s symbolicate utility to get comprehensible crash logs

‘symbolicatecrash’ is the Developer Tools utility which replaces all those meaningless addresses from crash logs with actual symbol names and source code references. It lives at some obscure folder within /Developer – use find to dig it up and symlink it into /usr/local/bin if you wanna use it conveniently from the command line.

Anyway, after plenty of frustration, I noticed some chatter about the damn thing being busted in Xcode 4. Figures!

There’s an alternate third party version on GitHub, but this didn’t really help me – I still got inscrutable errors, so I took a look at the original.

The version that comes with Xcode 4 appears to have some problems distinguishing, say, an iPhone Simulator build of the app from a native build sitting in the Archives folder. I’d just see an error about otool and some binary living in the iPhone Simulator folder.

Digging into the errant symbolicatecrash source, I noticed that the code that finds the executable path tests each candidate using otool, but doesn’t seem to be able to comprehend the output from otool caused by running it on the wrong architecture.

So, replacing the rather unhelpful ‘die’ statement on line 323:

die "Can't understand the output from otool ($TEST_uuid -> '$otool -arch $arch -l $path')";

With a “No, it ain’t this executable” response:

return 0;

…solves the problem immediately. Now I can drag crash logs straight into the Organizer in Xcode, and it’ll symbolicate correctly.

Quick tip: Manipulating the OS X clipboard

Here’s a shortcut that comes in handy sometimes. There are two command-line utilities, pbcopy and pbpaste that provide direct access to the OS X clipboard.

They’re quite useful for doing various quick things with clipboard contents, like, say, writing it to a file:

pbpaste > Desktop/output.txt

Or altering them:

pbpaste | sed s/bacon/bea-con/g | pbcopy

Fun!

Post Grabber sniffs out POST data, generates curl scripts

Every now and then I find myself needing to automate some web requests, either to download using something a little more robust than a web browser, scrape some web content, or to maintain a session. That automation can be a bit of a pain if there’s a form submission involved, because it means opening up the page source, finding the form and any connected javascript code, and figuring out what fields are submitted.

A little utility I just put together does that for you: Post Grabber detects POST data and generates an equivalent “curl” command that can be used in shell or Automator scripts.

Post Grabber works with its own internal browser, so it can intercept POST submissions directly. That means it works with HTTPS, unlike the traditional web sniffer approach.

Download the app, or see the source on GitHub.

A drop-in universal solution for moving text fields out of the way of the keyboard

There are a hundred and one proposed solutions out there for how to move UITextField and UITextView out of the way of the keyboard during editing — usually, it comes down to observing UIKeyboardWillShowNotification and UIKeyboardWillHideNotification, or implementing UITextFieldDelegate delegate methods, and adjusting the frame of the superview, or using UITableView‘s scrollToRowAtIndexPath:atScrollPosition:animated:, but all the proposed solutions I’ve found tend to be quite DIY, and have to be implemented for each view controller that needs it.

I thought I’d put together a relatively universal, drop-in solution: UIScrollView and UITableView subclasses that handle everything.

When the keyboard is about to appear, the subclass will find the subview that’s about to be edited, and adjust its frame and content offset to make sure that view is visible, with an animation to match the keyboard pop-up. When the keyboard disappears, it restores its prior size.

It should work with basically any setup, either a UITableView-based interface, or one consisting of views placed manually.

Easy AAC compressed audio conversion on iOS

From the iPhone 3Gs up, it’s possible to encode compressed AAC audio from PCM audio data. That means great things for apps that deal with audio sharing and transmission, as the audio can be sent in compressed form, rather than sending huge PCM audio files over the network.

Apple’s produced some sample code (iPhoneExtAudioFileConvertTest), which demonstrates how it’s done, but their implementation isn’t particularly easy to use in existing projects, as it requires some wrapping to make it play nice.

For my upcoming looper app Loopy, I’ve put together a simple Objective-C class that performs the conversion of any audio file to an AAC-encoded m4a, asynchronously with a delegate, or converts any audio provided by a data source class (which provides for recording straight to AAC) and I thought I’d share it.

A simple, fast circular buffer implementation for audio processing

Circular buffers are pretty much what they sound like – arrays that wrap around. They’re fantastically useful as scratch space for audio processing, and generally passing audio around efficiently.

They’re designed for FIFO (first-in-first-out) use, like storing audio coming in the microphone for later playback or processing.

Consider a naive alternative: You copy the incoming audio into an NSData you allocate, and then pass that NSData off. This means you’re allocating memory each time, and deallocating the memory later once you’re done processing. That allocation incurs a penalty, which can be a show-stopper when part of an audio pipeline – The Core Audio documentation advises against any allocations when within a render callback, for example.

Alternatively, you can allocate space in advance, and write to that, but that has problems too: Either you have a synchronisation nightmare, or you spend lots of time moving bytes around so that the unprocessed audio is always at the beginning of the array.

A better solution is to use a circular buffer, where data goes in at the head, and is read from the tail. When you produce data at the head, the head moves up the array, and wraps around at the end. When you consume at the tail, the tail moves up too, so the tail chases the head around the circle.

Here’s a simple C implementation I recently put together for my app Loopy: TPCircularBuffer

Internet Timer keeps track of your timed Internet usage

I threw this utility app together last year, in order to keep track of our Internet usage on a time-limited account. This is a piece of software that lives quietly in your menubar, until an Internet connection is detected. Then, it will count how long you’ve been online, showing a timer in the menubar.

Features:

Detects your Internet connection automatically, or you can start and stop the timer manually.
Keep a log of your usage, including weekly, monthly, and all-time totals, and daily average, with the ability to reset these.
Time in configurable blocks of time, if your carrier charges in blocks (e.g., 15 minutes)

“Delicious Pixel artisan” – Totally time for a name change

Google Alerts just turned up this magnificent piece of mangling, from a content farm:

Melbourne, Australia – An iPhone application Delicious Pixel artisan “The Cartographer” was presented by Apple on the iPhone Application Shop for 9 consecutive weeks and was lately voted 3rd supreme in the supreme journey Application Application Ever contest….

Delicious Pixel focuses on Mac and iPhone applications with attractive and working individual interfaces – software that works like an extension of self, with the magnetism and elegance that make it a joy to use. A Pixel Delicious is the productive expression of a single creator and its obligation to uncover order in the planet – not to put things in boxes, though to shape the regions around things.

It’s nice to hear the folks at the supreme journey Application Application Ever contest like our working and magnetic interfaces.