How’s does async stream work

Async streams in Swift are part of the language's concurrency model, which uses the async and await keywords to handle asynchronous operations. Here's a detailed explanation of how async functions and streams work:

1. Task Suspension: When a task is waiting for an asynchronous operation to complete, it suspends to yield the CPU to other tasks. This is modeled in code using the async and await keywords. A function that may suspend is marked with the async keyword, and the await keyword is used to indicate that a suspension can occur on that line. This allows the CPU to be used efficiently by other tasks while waiting for the asynchronous operation to complete. (A Swift Tour: Explore Swift’s features and design)

2. Memory Allocation: Async functions do not allocate memory out of a large contiguous stack like synchronous functions. Instead, they hold onto one or more slabs of memory. When an async function needs to allocate memory, it asks the task for memory from the current slab. If the slab is full, a new slab is allocated. This method is typically faster than using malloc because the allocator is only used by a single task and follows a stack discipline. (Explore Swift performance)

3. Partial Functions: Async functions are split into multiple partial functions at runtime, each spanning the gaps between potential suspension points. For example, if there is one await in the function, it results in two partial functions. The first partial function runs until the await, and the second picks up after the await. This ensures that only one partial function is on the C stack at any time, optimizing memory usage and performance. (Explore Swift performance)

4. Concurrency and Actors: Swift also introduces actors, which are reference types that encapsulate shared mutable state and automatically protect their state by serializing accesses. Calls to actor methods from outside the actor's context are asynchronous, ensuring safe concurrent access to shared resources. (A Swift Tour: Explore Swift’s features and design)

For a more comprehensive understanding, you can explore the following sessions:

• Explore Swift performance
• A Swift Tour: Explore Swift’s features and design

These sessions cover the intricacies of async functions, memory allocation, and concurrency in Swift.