On Tue, Apr 14, 2009 at 7:09 PM, Michael Ash <michael....@gmail.com> wrote: > This is not so. It's extremely rare to find a platform which > *requires* aligned access, and you certainly won't find one running OS > X. What's more common is finding a platform which *prefers* aligned > access, punishing misaligned access with significantly slower > operation. Even in those cases, "misaligned" means using an address > that isn't a multiple of your data type's size. Since char is always > one byte by definition, it is impossible to have a misaligned char > pointer.
x64 requires certain alignments: http://software.intel.com/en-us/articles/data-alignment-when-migrating-to-64-bit-intel-architecture/ I originally had the length member as an integer, which is why I was concerned about alignment. I modified it at the last minute because it makes the pointer math easier and I can't imagine a prefix that requires more than 255 characters. The code I pasted is pretty roundabout anyway; I'm not recommending that anyone use it, I just wanted to convey my idea. Another consideration I didn't take into account is that the iPhone uses solid-state storage, whereas the kind of optimization I was recommending (read in the entire file) is mostly beneficial on mechanical disks. It also helps circumvent buffered IO--when you know you need the whole file anyway, there's no point in having the kernel, the C runtime, and potentially Foundation buffer your (sequential) reads. --Kyle Sluder _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
