Simon Willison's Weblog: objective-c

Tagged Pointer Strings (2015)

2024-05-08T14:23:13+00:00

Tagged Pointer Strings (2015)

Mike Ash digs into a fascinating implementation detail of macOS.

Tagged pointers provide a way to embed a literal value in a pointer reference. Objective-C pointers on macOS are 64 bit, providing plenty of space for representing entire values. If the least significant bit is 1 (the pointer is a 64 bit odd number) then the pointer is "tagged" and represents a value, not a memory reference.

Here's where things get really clever. Storing an integer value up to 60 bits is easy. But what about strings?

There's enough space for three UTF-16 characters, with 12 bits left over. But if the string fits ASCII we can store 7 characters.

Drop everything except a-z A-Z.0-9 and we need 6 bits per character, allowing 10 characters to fit in the pointer.

Apple take this a step further: if the string contains just eilotrm.apdnsIc ufkMShjTRxgC4013 ("b" is apparently uncommon enough to be ignored here) they can store 11 characters in that 60 bits!

Via Lobste.rs

Tags: c, objective-c, strings

10 Uses for Blocks in C/Objective-C

2009-11-16T14:27:15+00:00

10 Uses for Blocks in C/Objective-C

Part of the Cocoa for Scientists series, which is by far the best free Objective-C / Cocoa tutorial I’ve seen anywhere.

Tags: blocks, closures, cocoa, macos, objective-c, science

Mac OS X 10.6 Snow Leopard: the Ars Technica review

2009-09-01T19:05:25+00:00

Mac OS X 10.6 Snow Leopard: the Ars Technica review

The essential review: 23 pages of information-dense but readable goodness. Pretty much everything I know about Mac OS X internals I learnt from reading John Siracusa’s reviews—this one is particularly juice when it gets to Grand Central Dispatch and blocks (aka closures) in C and Objective-C.

Tags: apple, blocks, c, closures, grandcentraldispatch, john-siracusa, macos, objective-c, snowleopard

Switching from scripting languages to Objective C and iPhone: useful libraries

2009-01-27T17:50:04+00:00

Switching from scripting languages to Objective C and iPhone: useful libraries

Matt Biddulph collects together some very useful libraries for developers just getting started with Objective-C (though I’m not too keen on the title).

Tags: iphone, matt-biddulph, objective-c, programming

Blocks in Objective-C

2008-12-29T19:38:08+00:00

Blocks in Objective-C

Closures are coming soon to Objective-C - interesting syntax, a regular curly brace block preceded by a caret ^{ ... }.

Tags: blocks, closures, objective-c, programming, syntax

Cappuccino Web Framework

2008-09-05T15:27:54+00:00

Cappuccino Web Framework

Now open source (LGPL)—the Objective-C-in-JavaScript web application toolkit from 280 North, who are speaking at this year’s FOWA in October. Beautiful logo.

Tags: cappuccino, javascript, lgpl, objective-c, objective-j, open-source

An interview with 280 North on Objective-J and Cappuccino

2008-06-07T19:40:11+00:00

An interview with 280 North on Objective-J and Cappuccino

Fantastic comment thread with involvement from the guys who created Objective-J. Just like Objective-C, Objective-J is a preprocessor that runs against regular JavaScript source files so you can use JavaScript and Objective-J idioms interchangeably.

Tags: 280north, ajaxian, javascript, objective-c, objective-j

280slides and Objective-J

2008-06-07T16:09:37+00:00

280slides and Objective-J

280 slides uses an Objective-C clone written in 13KB of JavaScript. I have to admit I’m completely baffled as to why you would want to use Objective C instead of JavaScript, but evidently it worked fantastically well for them.

Tags: 280slides, compiler, javascript, ned-batchelder, objective-c

Programming Nu

2007-10-01T21:49:06+00:00

Programming Nu

Interesting new programming language—Lisp style syntax, Ruby style semantics, built in Objective C bridge so you can access Cocoa APIs directly.

Via John Gruber

Tags: cocoa, lisp, nu, objective-c, programming, ruby

Targets for 2004

2004-01-01T22:55:03+00:00

Looking back on 2003, one thing really stuck out for me: I didn't learn a new programming language. The Pragmatic Programmers recommend learning at least one new language every year, and I've heard similar advice from other notable authorities; Ruby's Matz made a similar point in an article published just the other day.

I learned a number of new skills and technologies in 2003, and improved on my existing knowledge in more ways than I can count. Unfortunately, everything was building on stuff I already had experience with: I didn't really learn anything completely new.

2004 will be very different, mainly because I will finally have access to a Mac. Objective C and AppleScript are both on my list, and I'm looking forward to doing some serious messing around with GUIs as well.

Other than that, my two main geeky goals for this year are to become more active in the open source world (hopefully contributing some useful code) and to do a lot more writing outside of my blog. On a personal note, I plan to see at least some of America outside of Kansas. I'm only here until October and I want to make the most of it.

Tags: objective-c, applescript