AsyncRead

AsyncRead is a trait in the Rust programming language that defines an interface for asynchronous reading operations. It is part of the async-std and tokio runtimes, which are popular frameworks for writing asynchronous code in Rust.

The core of AsyncRead is the poll_read method. This method is called by the asynchronous runtime to attempt to read data from the source into a buffer. It returns a Poll<Result<usize>>, where usize represents the number of bytes read and Result indicates whether the operation was successful or encountered an error. If no data is immediately available, poll_read returns Poll::Pending, signaling that the operation should be retried later.

Implementors of AsyncRead typically provide their own asynchronous streams or file handles. For instance, a network socket or a file opened asynchronously would implement AsyncRead. The trait is designed to be efficient, allowing the runtime to manage multiple I/O operations concurrently without blocking threads.

Key characteristics of AsyncRead include its non-blocking nature and its integration with Rust's asynchronous programming model, using futures and `async`/`await` syntax. This allows developers to write efficient and scalable I/O-bound applications. The trait is fundamental for building asynchronous applications that interact with external data sources.