It can exist at any address since alignment is one and all numbers are evenly divisible by one. Next, look at the layout of some user-defined structs by adding the following to the playground: For these basic types, the size is the same as the stride. When you pack a bunch of Int16s together, they pack at an interval of stride. That means it has to start on even addresses - that is, addresses divisible by two.įor example, it’s legal to allocate an Int16 at address 100, but not at 101 - an odd number violates the required alignment. It determines the size, alignment and stride of each specified Type and returns a number in bytes.įor example, an Int16 is two bytes in size and has an alignment of two as well. MemoryLayout is a generic type evaluated at compile time. MemoryLayout.stride // returns 8 (on 64-bit) MemoryLayout.alignment // returns 8 (on 64-bit) MemoryLayout.size // returns 8 (on 64-bit) To see this in action, you’ll use MemoryLayout to tell you the size and alignment of components of some native Swift types. On a 64-bit system, for example, a word is 8 bytes or 64 bits. Processors can also efficiently access words of memory, which are typically more than one byte. The smallest addressable unit of storage is a byte, which usually consists of eight bits.Įight-bit bytes can store values from 0-255.
Detectx swift tutorial series#
You can visualize memory as a series of boxes - billions of boxes, actually - each containing a number.Įach box has a unique memory address. Unsafe Swift works directly with the memory system. Exploring Memory Layout With Unsafe Swift
Detectx swift tutorial code#
Since all the code in this tutorial is platform-agnostic, you may select any platform. Start by opening the UnsafeSwift playground. It uses unsafe Swift, but hides that detail from users. In the final playground, you’ll create a platform-independent alternative to arc4random to generate random numbers.In the second, you’ll take a low-level C API that performs streaming data compression and wrap it with a Swifty interface.In the first playground, you’ll use several short snippets of code to explore memory layout.This tutorial consists of three empty Swift playgrounds:
Getting Startedĭownload the begin project by clicking the Download Materials button at the top or bottom of the tutorial. C experience is beneficial but not necessary.
If you need to brush up on your skills, please check out our iOS and Swift for Beginners series. Note: While this is an advanced topic, you’ll be able to follow along if you have reasonable competency in Swift.
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