Chris' Blog.

My occasional thoughts on iOS development, developers careers, trying to make an income from the App Store, and updates on life in general.

Rust

Hi! Here is a PNG writer I wrote as a utility as part of a hobby project I’ve been working on, where I preferred to minimise dependencies and keep things simple. It hope it serves as a good way of understanding the PNG format! Note that this doesn’t compress, and it only supports RGBA; but it can be useful for tiny pixel art images.

Let’s start with the prerequisites:

RFC 1951 Deflate stream

The first thing needed is a function to convert an arbitrary buffer into a ‘deflate stream’. A deflate stream is made up of blocks of up to 64kb. The simplest possible compliant deflate block looks like this:

  • 1 byte: 1 = this is the final block; 0 = this is not the final block.
  • 2 bytes: data length, lowest-significant-byte first.
  • 2 bytes: length 1’s complement (all bits flipped).
  • N bytes: data

In Rust, this looks like:

fn to_deflate_stream(input: &[u8]) -> Vec<u8> {
    if input.is_empty() {
        return vec![1, 0, 0, 0xff, 0xff]; // 1 block with no content.
    }
    let mut output = Vec::<u8>::new();
    let chunks = input.chunks(0xffff);
    let final_index = chunks.len() - 1;
    for (index, chunk) in chunks.enumerate() {
        let is_final = index == final_index;
        output.push(if is_final { 1 } else { 0 });
        let len = chunk.len();
        let len_lsb = (len & 0xff) as u8;
        let len_msb = (len >> 8) as u8;
        output.push(len_lsb); // Max len.
        output.push(len_msb);
        output.push(!len_lsb); // 1's complement of len.
        output.push(!len_msb);
        output.extend_from_slice(chunk);
    }
    output
}

RFC 1950 Zlib stream

The next building block necessary is to convert a data buffer into a Zlib stream. This consists of adding a header and footer to a Deflate stream. The simplest possible header for the uncompressed case is 0x7801, meaning:

  • A standard window size of 7 (meaningless when not compressed).
  • A method of 8 (meaning deflate).
  • A 1 in the second byte for a checksum, no dictionary bit set, and 0 for the compression level bits.

The footer is an ADLER32 checksum.

In Rust, this looks like:

fn to_zlib_stream(input: &[u8]) -> Vec<u8> {
    // Header.
    let mut output = Vec::<u8>::new();
    output.push(0x78); // CMF byte. Bits 0-3=method, 4-7=info/window size. Method=8, Window size=7.
    output.push(1); // FLG byte. Bits 0-4=fcheck, 5=fdict which we dont want so 0, 6-7=flevel where 0 means fastest.

    // Body.
    let deflated = to_deflate_stream(input);
    output.extend(deflated);

    // Checksum.
    // See: https://en.wikipedia.org/wiki/Adler-32#Example_implementation
    let mut a: u32 = 1;
    let mut b: u32 = 0;
    for data in input {
        a = (a + (*data as u32)) % 65521;
        b = (b + a) % 65521;
    }
    output.push((b >> 8) as u8);
    output.push((b & 0xff) as u8);
    output.push((a >> 8) as u8);
    output.push((a & 0xff) as u8);

    output
}

CRC32

Another important piece of the puzzle is the ability to calculate CRCs for a buffer.

I can’t claim to understand how these work. If interested, you could read more here: http://libpng.org/pub/png/spec/1.0/PNG-CRCAppendix.html

In Rust, it looks like:

fn crc(data: &[u8]) -> u32 {
    // Make the CRC table first.
    // An optimised implementation would only do this once.
    let mut crc_table: [u32; 256] = [0; 256];
    for n in 0..256 {
        let mut c: u32 = n as u32;
        for _k in 0..8 {
            if c & 1 == 1 {
                c = 0xedb88320u32 ^ (c >> 1);
            } else {
                c = c >> 1;
            }
        }
        crc_table[n] = c;
    }

    // Calculate the CRC.
    let mut crc: u32 = 0xffffffff;
    for b in data {
        let index = ((crc ^ (*b as u32)) & 0xff) as usize;
        crc = crc_table[index] ^ (crc >> 8);
    }
    !crc
}

PNG

And now we have the prerequisites for generating the PNG. PNG files consist of a header then at least 3 blocks. The following describes the RGBA case, which has no palette:

The header looks like: 0x89 “PNG” CR LF EOF LF.

Each block looks like:

  • Data length: 4 bytes, most significant byte first.
  • Type: 4 ascii chars.
  • Data
  • 4 bytes CRC of the type and data.

The compulsory 3 blocks are: IHDR, IDAT, and IEND.

IHDR

The header block’s data consists of:

  • Width and height: 4 bytes each, MSB first.
  • Bits per pixel: 1 byte.
  • Type: 6 means RGBA.
  • Compression: always 0 which means Zlib.
  • Filter method: always 0.
  • Interlacing flag.

IDAT

The data block consists of RGBA samples, left to right, top to bottom, in a Zlib stream. At the start of each row, a 0 is prefixed which means ‘no filter applies to this row’.

IEND

The end block has empty data. I’d be willing to bet you could omit this block and no parser would care.

The PNG generator code looks like the following in Rust:

fn png(width: u32, height: u32, rgba: &[u32]) -> Vec<u8> {
    let mut output = Vec::<u8>::new();

    // Header.
    output.push(0x89);
    output.push(b'P');
    output.push(b'N');
    output.push(b'G');
    output.push(0x0d); // Cr
    output.push(0x0a); // Lf
    output.push(0x1a); // Eof
    output.push(0x0a); // Lf

    // Build IHDR.
    let mut ihdr_type_and_data = Vec::<u8>::new();
    ihdr_type_and_data.push(b'I');
    ihdr_type_and_data.push(b'H');
    ihdr_type_and_data.push(b'D');
    ihdr_type_and_data.push(b'R');
    append_msb(&mut ihdr_type_and_data, width);
    append_msb(&mut ihdr_type_and_data, height);
    ihdr_type_and_data.push(8); // 8bpp.
    ihdr_type_and_data.push(6); // RGBA.
    ihdr_type_and_data.push(0); // Compression method: zlib.
    ihdr_type_and_data.push(0); // Filter method.
    ihdr_type_and_data.push(0); // No interlace.
    let ihdr_len = ihdr_type_and_data.len() - 4; // Minus the type.
    let ihdr_crc = crc(&ihdr_type_and_data);
    // Append IHDR to output.
    append_msb(&mut output, ihdr_len as u32);
    output.extend_from_slice(&ihdr_type_and_data);
    append_msb(&mut output, ihdr_crc);

    // Build image data.
    let mut idat_data = Vec::<u8>::new();
    let mut rgba_iter = rgba.iter();
    for _y in 0..height {
        idat_data.push(0); // Each line is prepended a filter type byte (0).
        for _x in 0..width {
            let rgba = rgba_iter.next().unwrap_or(&0);
            idat_data.push((rgba >> 24) as u8);
            idat_data.push((rgba >> 16) as u8); // 'as u8' truncates upper bits for us.
            idat_data.push((rgba >> 8) as u8);
            idat_data.push((*rgba) as u8);
        }
    }
    let compressed_idat_data = to_zlib_stream(&idat_data);

    // Build IDAT.
    let mut idat_type_and_data = Vec::<u8>::new();
    idat_type_and_data.push(b'I');
    idat_type_and_data.push(b'D');
    idat_type_and_data.push(b'A');
    idat_type_and_data.push(b'T');
    idat_type_and_data.extend_from_slice(&compressed_idat_data);
    let idat_len = idat_type_and_data.len() - 4; // Minus the type.
    let idat_crc = crc(&idat_type_and_data);
    // Append IDAT to output.
    append_msb(&mut output, idat_len as u32);
    output.extend_from_slice(&idat_type_and_data);
    append_msb(&mut output, idat_crc);

    // IEND (no data).
    append_msb(&mut output, 0); // Length.
    output.push(b'I'); // Type.
    output.push(b'E');
    output.push(b'N');
    output.push(b'D');
    let iend_crc = crc(b"IEND");
    append_msb(&mut output, iend_crc);

    output
}

fn append_msb(vec: &mut Vec<u8>, value: u32) {
    vec.push((value >> 24) as u8);
    vec.push((value >> 16) as u8);
    vec.push((value >> 8) as u8);
    vec.push((*value) as u8);
}

And that’s it! That’s the basics of writing PNGs in around 150LOC.

The full code can be seen here: github.com/chrishulbert/rust_png_write_sans_dependencies.

Feel free to use it in your projects by copying the file in; I haven’t published this as crate, I think it’s too simple to justify that.

Thanks for reading, I hope this is helpful, God bless :)

Photo by Tengyart on Unsplash


Stack

In practice, I usually find that using a UITableView makes most sense for displaying scrollable content in an app, however every now and again it is handy to use a UIScrollView + UIStackView. The problem is: it occurs infrequently enough that I cannot recall how to set up the constraints! So here’s my notes for my future reference, and hopefully yours too :)

Here’s a screenshot of how to set it up in Xcode: (click to zoom)

Xcode

Theory

  • The frame layout guide and content layout guides are only to be used for child views of the scroll, and the child views are to be (usually) only constrained to these guides.
  • The frame layout guide is for setting child view’s sizes to match the scroll’s visual size.
  • The content layout guide is what defines the scroll view’s content size.

Vertical scroll setup

  • Make a UIScrollView and constrain it normally to define its size (eg not using its layout guides).
  • Put a vertical UIStackView inside the UIScrollView.
  • Constrain the stack’s leading/trailing/top/bottom to the scroll’s content layout guide.
  • Make the stack’s width equal to the scroll’s frame layout guide.
  • Put views in the stack. These views don’t need any constraints put on them at all.

Horizontal scroll setup

  • Make a UIScrollView and constrain it normally to define its size (eg not using its layout guides).
  • Put a horizontal UIStackView inside the UIScrollView.
  • Constrain the stack’s leading/trailing/top/bottom to the scroll’s content layout guide.
  • Make the stack’s height equal to the scroll’s frame layout guide.
  • Put views in the stack. These views don’t need any constraints put on them at all.

Paged scroll setup

If you want each child of the stack to be a whole ‘page’:

  • Horizontal scrolling: Constrain the stack’s childrens’ width to equal the scroll’s frame layout guide.
  • Vertical scrolling: Constrain the stack’s children’ height to equal the scroll’s frame layout guide.
  • Set ‘isPagingEnabled’ to true on the scroll.

Thanks for reading, I hope this is helpful, God bless :)

Photo by Fernando Andrade on Unsplash


RSA and EC

I recently had to perform RSA encryption/decryption in Swift for an iOS app. Unfortunately I couldn’t find any examples for how to do this without bringing in a library dependency, which I really wanted to avoid to keep the app efficient and because I can’t reasonably vet their code. And besides: Apple already provides the Security.framework which handles RSA, so it’d be a shame not to use it. It doesn’t bridge nicely to Swift however, so here’s a wrapper I wrote to help use it. I couldn’t find any good examples on the internet so I hope this helps someone:

import Security

// See: https://developer.apple.com/documentation/security/certificate_key_and_trust_services/keys
extension SecKey {
    
    enum KeyType {
        case rsa
        case ellipticCurve
        var secAttrKeyTypeValue: CFString {
            switch self {
            case .rsa:
                return kSecAttrKeyTypeRSA
            case .ellipticCurve:
                return kSecAttrKeyTypeECSECPrimeRandom
            }
        }
    }
    
    /// Creates a random key.
    /// Elliptic curve bits options are: 192, 256, 384, or 521.
    static func createRandomKey(type: KeyType, bits: Int) throws -> SecKey {
        var error: Unmanaged<CFError>?
        let keyO = SecKeyCreateRandomKey([
            kSecAttrKeyType: type.secAttrKeyTypeValue,
            kSecAttrKeySizeInBits: NSNumber(integerLiteral: bits),
        ] as CFDictionary, &error)
        // See here for apple's sample code for memory-managing returned errors
        // from the Security framework:
        // https://developer.apple.com/documentation/security/certificate_key_and_trust_services/keys/storing_keys_as_data
        if let error = error?.takeRetainedValue() { throw error }
        guard let key = keyO else { throw MyErrors.nilKey }
        return key
    }
    
    /// Gets the public key from a key pair.
    func publicKey() throws -> SecKey {
        let publicKeyO = SecKeyCopyPublicKey(self)
        guard let publicKey = publicKeyO else { throw MyErrors.nilPublicKey }
        return publicKey
    }
    
    /// Exports a key.
    /// RSA keys are returned in PKCS #1 / DER / ASN.1 format.
    /// EC keys are returned in ANSI X9.63 format.
    func externalRepresentation() throws -> Data {
        var error: Unmanaged<CFError>?
        let dataO = SecKeyCopyExternalRepresentation(self, &error)
        if let error = error?.takeRetainedValue() { throw error }
        guard let data = dataO else { throw MyErrors.nilExternalRepresentation }
        return data as Data
    }
    
    // Self must be the public key returned by publicKey().
    // Algorithm should be SecKeyAlgorithm.rsaEncryption* or .eciesEncryption*
    func encrypt(algorithm: SecKeyAlgorithm, plaintext: Data) throws -> Data {
        var error: Unmanaged<CFError>?
        let ciphertextO = SecKeyCreateEncryptedData(self, algorithm,
            plaintext as CFData, &error)
        if let error = error?.takeRetainedValue() { throw error }
        guard let ciphertext = ciphertextO else { throw MyErrors.nilCiphertext }
        return ciphertext as Data
    }
    
    // Self must be the private/public key pair returned by createRandomKey().
    // Algorithm should be SecKeyAlgorithm.rsaEncryption* or .eciesEncryption*
    func decrypt(algorithm: SecKeyAlgorithm, ciphertext: Data) throws -> Data {
        var error: Unmanaged<CFError>?
        let plaintextO = SecKeyCreateDecryptedData(self, algorithm,
            ciphertext as CFData, &error)
        if let error = error?.takeRetainedValue() { throw error }
        guard let plaintext = plaintextO else { throw MyErrors.nilPlaintext }
        return plaintext as Data
    }

    enum MyErrors: Error {
        case nilKey
        case nilPublicKey
        case nilExternalRepresentation
        case nilCiphertext
        case nilPlaintext
    }

}

How to use it

It boils down to calling:

  • createRandomKey(…) to get a key pair.
  • publicKey() to get just the public key.
  • externalRepresentation() to get the public key as data that you can send to eg your backend.
  • encrypt(…) to encrypt something with the public key.
  • decrypt(…) to decrypt something with the key pair.

Here’s some demo code for using the above:

// Elliptic curve test.
do {
    let keyPair = try SecKey.createRandomKey(
        type: .ellipticCurve,
        bits: 384)
    let publicKey = try keyPair.publicKey()
    let plain = "Chuck Norris has counted to infinity. Twice.".data(using: .utf8)!
    let ciphertext = try publicKey.encrypt(
        algorithm: .eciesEncryptionStandardVariableIVX963SHA256AESGCM,
        plaintext: plain)
    let plainAgain = try keyPair.decrypt(
        algorithm: .eciesEncryptionStandardVariableIVX963SHA256AESGCM,
        ciphertext: ciphertext)
    let string = String(data: plainAgain, encoding: .utf8)! // Don't force-unwrap in real code.
    print("EC decrypted: " + string)
} catch {
    print("Error: \(error)")
}

// RSA test.
do {
    let keyPair = try SecKey.createRandomKey(
        type: .rsa,
        bits: 2048)
    let publicKey = try keyPair.publicKey()
    let plain = "Chuck Norris can set ants on fire with a magnifying glass. At night.".data(using: .utf8)!
    let ciphertext = try publicKey.encrypt(
        algorithm: .rsaEncryptionOAEPSHA1AESGCM,
        plaintext: plain)
    let plainAgain = try keyPair.decrypt(
        algorithm: .rsaEncryptionOAEPSHA1AESGCM,
        ciphertext: ciphertext)
    let string = String(data: plainAgain, encoding: .utf8)! // Don't force-unwrap in real code.
    print("RSA decrypted: " + string)
} catch {
    print("Error: \(error)")
}

Algorithm selection

If you’re integrating with an existing system, you’ll simply have to match their key type and algorithm. But if it’s up to you, here’s some tips for how to choose:

Read Apple’s headers! In Xcode, command-click on SecKeyAlgorithm and read the comments above it. Many algorithms will be noted as legacy, so avoid if possible. And some do not support arbitrary-length data which might be a problem for you. So choose wisely.

And a reasonable option in my opinion is:

  • Key type: .ellipticCurve
  • Key size: 384 bits
  • Algorithm: .eciesEncryptionCofactorVariableIVX963SHA384AESGCM

Note

I’m not a qualified cryptographer, this information carries no warranty, you should talk to a qualified security professional about the implications of when to use this appropriately!

Thanks for reading, I hope this is helpful, God bless :)

Photo by David Clode on Unsplash


You can see older posts in the right panel, under 'archive'.

Archive

Rust PNG writer from scratch 12 Jul 2022

UIScrollView content and frame layout guides: scroll your UIStackView content purely in storyboards (iOS) 1 May 2022

Swift Security framework wrapper for RSA and Elliptic Curve encryption / decryption 21 Sep 2021

Simple, practical async await Swift examples 3 Jul 2021

Xcode pbxproj project generator in Swift 17 May 2021

UITableViewDiffableDataSource for adding and removing rows automatically to a table view in Swift 10 May 2021

Super simple iOS Combine example 23 Feb 2021

Introducing Chalkinator: Native desktop blogging app 7 Jun 2020

Flare: Open source 2-way folder sync to Backblaze B2 in Swift 28 May 2020

Making a baby monitor out of a couple of ESP32s, an I2S microphone, and a small speaker 16 Apr 2020

Chris' 2020 guide to hosting a HTTPS static site on AWS S3 + Cloudfront 15 Mar 2020

Simple Javascript debounce, no libraries needed 20 Feb 2020

Asynchronous NSOperations in Swift 5 3 Jan 2020

Deploying Golang Revel sites to AWS Elastic Beanstalk 9 Dec 2019

Golang and pure Swift Compression and Decompression 28 Jul 2019

Pure Swift simple Keychain wrapper 23 Jun 2019

Pure Swift 5 CommonCrypto AES Encryption 9 Jun 2019

Bluetooth example code for Swift/iOS 6 Jun 2019

Talking to a Bluetooth LE peripheral with Swift/iOS 18 May 2019

Obfuscating Keys using Swift 5 May 2019

State Machines in Swift using enums 10 Apr 2019

iOS timers without circular references with Pendulum 28 Mar 2019

Pragmatic Reactive Programming 11 Oct 2017

React Native first impressions 7 Apr 2017

Gondola 26 Feb 2017

Scalable Swift 22 Nov 2016

Swift 3 Migration 6 Nov 2016

Enum-Driven View Controllers 3 Jan 2016

Status bar colours: Everything there is to know 30 Dec 2015

Android server 20 Dec 2015

Generating heightmap terrain with Swift 8 Nov 2015

Swift Education Screencasts 27 Oct 2015

Swift Image Cache 24 Sep 2015

Don't be slack 13 Sep 2015

Swift KVO alternative 23 Jul 2015

Swift Keychain wrapper 21 Jun 2015

Swift NSURLSession wrapper 12 Jun 2015

iOS8 View Controller transitioning bug 17 Apr 2015

IB Designable 18 Mar 2015

iOS App Architecture 2 Mar 2015

Video Course Launch 14 Feb 2015

Video Course Pre-launch 8 Feb 2015

Blogging Platforms 13 Jan 2015

Mobile in 2014 - Year in Review 11 Jan 2015

Secret Keys talk 16 Nov 2014

Dimmi 11 Nov 2014

Project setup in Xcode6 22 Oct 2014

Uploading to an S3 bucket from iOS 15 Oct 2014

iOS8 App Testing Roundup 28 Sep 2014

Storing obfuscated secret keys in your iOS app 16 Sep 2014

Getting Core Location / CLLocationManager to work on iOS8 14 Sep 2014

Accessing the response body in failure blocks with AFNetworking 2 10 Sep 2014

How to allow your UITextFields to scroll out of the way of the keyboard 8 Sep 2014

How to subclass UIButton in iOS7 and make a UIButtonTypeSystem 4 Sep 2014

New season 1 Aug 2014

House finished 17 Jun 2014

WebP decoding on iOS 9 Feb 2014

Moving on again 22 Jan 2014

Lossy images for retina iPads - JPEG vs WebP 30 Nov 2013

Career options I wish I knew about when I was younger 20 Oct 2013

Positivity and your friends 7 Oct 2013

Tactility 26 Jul 2013

WWDC-induced narcolepsy 15 Jul 2013

Back on rails 31 May 2013

Full circle 6 May 2013

Programmatic UI on iOS 3 May 2013

Screencasts and positivity 8 Apr 2013

Year of positivity 14 Mar 2013

iOS Dev State of the Union 6 Feb 2013

Adventures with IAPs 3 Feb 2013

No longer a Googler 23 Dec 2012

Localising iPhone apps with Microsoft Translator 8 Dec 2012

Fight back (app biz update 13) 12 Nov 2012

Sent to the backburner (app biz update 12) 25 Oct 2012

Lisi Schappi 7 Oct 2012

Today's happy plateau (app biz update 11) 26 Aug 2012

First week's sales of Today (app biz update 10) 19 Aug 2012

Today launch! And a difficult decision made... (app biz update 9) 15 Aug 2012

Approved! (app biz update 8) 5 Aug 2012

Creating a graph in Objective-C on the iPhone 3 Aug 2012

Hurry up and wait (app biz update 7) 30 Jul 2012

Today app marketing site 27 Jul 2012

Today app submitted 25 Jul 2012

UIAlertView input wrapper 24 Jul 2012

Mentoring 23 Jul 2012

This is too hard! (app biz update 6) 20 Jul 2012

Perspectives (app biz update 5) 9 Jul 2012

4th starting-my-own-biz update 1 Jul 2012

ScrumFox landing page 28 Jun 2012

Server Scope landing page 27 Jun 2012

Telstra Calls and Data Usage 26 Jun 2012

Service History + Dropbox 26 Jun 2012

Impromptu Presenter 26 Jun 2012

Fertility Tracker 26 Jun 2012

Baby Allergy Tracker 26 Jun 2012

Starting my own business, update 3 22 Jun 2012

Starting my own business, update 2 17 Jun 2012

Starting my own business - First update 10 Jun 2012

I must be crazy 6 Jun 2012

Finding your location on an iPhone 7 May 2012

A generous career 4 May 2012

Skeleton Key Cocoaheads presentation 3 May 2012

CHBgDropboxSync - Dropbox auto-sync for your iOS apps 1 May 2012

That book about that Steve Jobs guy 30 Apr 2012

Another app marketing idea 23 Apr 2012

Sweet grouped tables on the iPhone 17 Apr 2012

Skeleton Key App 11 Apr 2012

Another app marketing idea... 5 Apr 2012

Quickly check for any missing retina graphics in your project 3 Apr 2012

Skeleton Key Password Manager with Dropbox 2 Apr 2012

RC Boat motor finally mounted 2 Apr 2012

Promoting apps presentation slides 1 Apr 2012

How i just wasted a month on my latest app, and how you don't need to 26 Mar 2012

The Finishing Line 20 Mar 2012

Using Launchd to run a script every 5 mins on a Mac 20 Feb 2012

Generating AES256 keys from a password/passphrase in ObjC 20 Feb 2012

Indie iPhone app marketing, part 2 19 Feb 2012

My App Manifesto: Syncing + Dropbox + YAML = Awesome 15 Feb 2012

Indie iPhone App Marketing part 1 7 Feb 2012

Perspectives 2 Feb 2012

Accountability and Free Will 1 Feb 2012

Badassery 31 Jan 2012

Sacrifice 30 Jan 2012

Lead Yourself First 29 Jan 2012

How to ping a server in Objective-C / iPhone 26 Jan 2012

iOS Automated Builds with Xcode4 16 Jan 2012

Xcode 4 - Command line builds of iPhone apps 15 Jan 2012

Guest post by Jason McDougall 13 Jan 2012

Scouts, Games and Motivation 10 Jan 2012

2011 Re-cap 8 Jan 2012

Ruby script to increment a build number 4 Jan 2012

Turning 30? All ideas, no execution? 18 Dec 2011

CHDropboxSync - simply sync your iOS app's documents to Dropbox 14 Dec 2011

Deep-enumerating a directory on the iphone, getting file attributes as you go 10 Dec 2011

Getting a date without the time component in objective-c 6 Dec 2011

Memory management in Objective-C 4 Dec 2011

Starting small 29 Nov 2011

Dictionary Types Helper 29 Nov 2011

Observer Pattern in Objective-C 16 Nov 2011

Why you should give presentations 13 Nov 2011

How to get a programming or design job in Sydney 9 Nov 2011

Custom nav bar / toolbar backgrounds in iOS5 8 Nov 2011

Stuck 27 Oct 2011

Dead easy singletons in Obj-C 19 Oct 2011

JSON vs OCON (Objective-C Object Notation) 18 Oct 2011

In defence of Objective-C 16 Oct 2011

Update the MessagePack objective-c library to support packing 12 Oct 2011

Icons 11 Oct 2011

How to host a site on Amazon AWS S3, step-by-step 7 Oct 2011

Drawing a textured pattern over the default UINavigationBar 6 Oct 2011

Markdown Presentations 1 Oct 2011

More MegaComet testing: Ruling out keepalives 15 Sep 2011

MegaComet test #4 - This time with more kernel 14 Sep 2011

Building People 10 Sep 2011

Half way there: Getting MegaComet to 523,000 concurrent HTTP connections 5 Sep 2011

Making a progress bar in your iPhone UINavigationBar 22 Aug 2011

Hacker News Reader 20 Aug 2011

How to programmatically resize elements for landscape vs portrait in your iphone interface 16 Aug 2011

MegaComet testing part 2 3 Aug 2011

Australian Baby Colours 28 Jul 2011

Boat prop shaft 25 Jul 2011

Megacomet with 1 million queued messages 24 Jul 2011

Installed the strut and rudder 18 Jul 2011

Painted the inside of the boat 17 Jul 2011

Fuzzy iphone graphics when using an UIImageView set to UIViewContentModeCenter 13 Jul 2011

My 3 Data and Calls Usage 11 Jul 2011

Reading a line from the console in node.js 10 Jul 2011

Trim whitespaces on all text fields in a view controller 9 Jul 2011

Final finish 9 Jul 2011

MessagePack parser for Objective-C / iPhone 30 Jun 2011

Lacquering the starboard side 25 Jun 2011

What do do with EXC_ARM_DA_ALIGN on an iPhone app 23 Jun 2011

Lacquering the hull 23 Jun 2011

Staining the boat 22 Jun 2011

NSMutableSet with weak references in objective-c 20 Jun 2011

Iphone gesture recogniser that works for baby games 20 Jun 2011

Image manipulation pixel by pixel in objective C for the iphone 19 Jun 2011

Baby Allergy Tracker 12 Jun 2011

Power sanding the deck 10 Jun 2011

Planing the edge of the deck 2 Jun 2011

Figured out the deck 2 Jun 2011

Boat bulkheads 2 Jun 2011

Simulating iOS memory warnings 31 May 2011

Putting a UIButton in a UIToolbar 29 May 2011

How to allow closing a UIActionSheet by tapping outside it 29 May 2011

Finding the currently visible view in a UITabBarController 24 May 2011

Random Chef 17 May 2011

Centered UIButton in a navigation bar on the iphone 16 May 2011

Little Orchard 13 May 2011

Boat update 13 May 2011

How to get the current time in all time zones for the iphone / obj-c 12 May 2011

Design portfolio 10 May 2011

Tricks with grand central dispatch, such as objective-c's equivalent to setTimeout 9 May 2011

How to make an iphone view controller detect left or right swipes 5 May 2011

Centered section headers on a UITableView 5 May 2011

Christmas in may 4 May 2011

Finished trimming the boat (its floatable now!) and got some parts 29 Apr 2011

How to make a multiline label with dynamic text on the iphone and get the correct height 27 Apr 2011

Forcing an image size on the image in a table view cell on an iphone 20 Apr 2011

Git on the Mac 19 Apr 2011

Build a url query string in obj-c from a dictionary of params like jquery does 12 Apr 2011

Rendering a radial gradient on the iphone / objective-c 11 Apr 2011

Skinning the port side of the boat 8 Apr 2011

Skinning the side of the boat 5 Apr 2011

Sending a UDP broadcast packet in C / Objective-C 5 Apr 2011

How to talk to a unix socket / named pipe with python 4 Apr 2011

Skinning the bottom of the boat 31 Mar 2011

Service discovery using node.js and ssdp / universal plug n play 30 Mar 2011

Extremely simple python threading 29 Mar 2011

New rescue boat 26 Mar 2011

HttpContext vs HttpContextBase vs HttpContextWrapper 5 Nov 2010

Simple C# Wiki engine 30 Sep 2010

Simple way to throttle parts of your Asp.Net web app 29 Sep 2010

How to implement DES and Triple DES from scratch 4 Aug 2010

How to use sessions with Struts 2 30 Jul 2010

How to use Cookies in Struts 2 with ServletRequest and ServletResponse 30 Jul 2010

Using Quartz Scheduler in a Java web app (servlet) 27 Jul 2010

Javascript date picker that Doesn't Suck!(tm) 27 Jul 2010

Using Oracle XE with Hibernate 20 Jul 2010

A simple implementation of AES in Ruby from scratch 29 Jun 2010

Asp.Net Forms authentication to your own database 28 May 2010

AS2805 (like ISO8583) financial message parser in C# 7 May 2010

Ruby hex dumper 4 May 2010

Using Spring to manage Hibernate sessions in Struts2 (and other web frameworks) 13 Jan 2010

Emails in C#: Delivery and Read receipts / Attachments 12 Jan 2010

Using Java libraries in a C# app with IKVM 16 Dec 2009

Learning Java tutorial 27 Nov 2009

Using generic database providers with C# 17 Nov 2009

Scheduled task executable batch babysitter 29 Oct 2009

Working with query strings in Javascript using Prototype 30 Sep 2009

Still fighting with String.Format? 9 Sep 2009

How I'd build the next Google 24 Aug 2009

Getting IIS and Tomcat to play nicely with isapi_redirect 24 Aug 2009

Using the new ODP.Net to access Oracle from C# with simple deployment 11 Aug 2009

C# Cryptography - Encrypting a bunch of bytes 14 Jul 2009

Sorting enormous files using a C# external merge sort 10 Jul 2009

Reconciling/comparing huge data sets with C# 9 Jul 2009

Some keyboard-friendly DHTML tricks 10 Jun 2009

How to figure out what/who is connected to your SQL server 18 Mar 2009

Adding a column to a massive Sql server table 16 Mar 2009

Multithreading using Delegates in C# 10 Mar 2009

Using C# locks and threads to rip through a to-do list 6 Feb 2009

Using threads and lock in C# 3 Feb 2009

Compressing using the 7Zip LZMA algorithm in C# beats GZipStream 14 Jan 2009

MS Sql Server 2005 locking 17 Dec 2008

Simple Comet demo for Ruby on Rails 19 Nov 2008

Geocoding part 2 - Plotting postcodes onto a map of Australia with C# 24 Oct 2008

Using evolutionary algorithms to make a walkthrough for the light-bot game with C# 20 Oct 2008

How to tell when memory leaks are about to kill your Asp.Net application 16 Oct 2008

C# version of isxdigit - is a character a hex digit? 15 Sep 2008

Geocoding part 1 - Getting the longitude and latitude of all australian postcodes from google maps 26 Aug 2008

Converting HSV to RGB colour using C# 14 Aug 2008

Opening a TCP connection in C# with a custom timeout 11 Aug 2008

Oracle Explorer - a very simple C# open source Toad alternative 31 Jul 2008

Linking DigitalMars' D with a C library (Mongrel's HTTP parser) 23 Jun 2008

Connecting to Oracle from C# / Winforms / Asp.net without tnsnames.ora 16 Jun 2008

A simple server: DigitalMars' D + Libev 6 Jun 2008

Travelling from Rails 1 to Rails 2 9 Apr 2008

Online Rostering System 9 Apr 2008

DanceInforma 9 Apr 2008

Using RSS or Atom to keep an eye on your company's heartbeat 10 Nov 2007

Easy Integrated Active Directory Security in ASP.Net 24 Oct 2007