Repository: tokio-rs/tokio
File: tokio-util/src/io/sync_bridge.rs (Rust)

Code before:
///     hasher.update(&data[..len]);
/// }
/// let hash = hasher.finalize();
/// ```
///
/// ## Example 2: Compressing Data
///
/// When compressing data, avoid using `SyncIoBridge`` with non-async compression libraries, as it may lead to inefficient and blocking code.
/// Instead, use `async-compression`, which is designed to work with asynchronous data streams.
///
/// ```rust, no_run
/// use async_compression::tokio::write::GzipEncoder;
///
/// let mut encoder = GzipEncoder::new(writer);
/// tokio::io::copy(&mut reader, &mut encoder).await?;
/// ```
///
/// ## Example 3: Parsing `JSON`
///
/// When parsing `JSON` data, avoid using `SyncIoBridge` with `serde_json::from_reader` as it may cause blocking operations.
/// Instead, read the data into a `Vec<u8>` and parse it using `serde_json::from_slice`.
///
/// ```rust, no_run
/// let mut data = Vec::new();
/// reader.read_to_end(&mut data).await?;
/// let value: MyStruct = serde_json::from_slice(&data)?;
/// ```
///
/// ## Correct Usage of `SyncIoBridge` inside `spawn_blocking`
///
/// `SyncIoBridge` is mainly useful when you need to interface with synchronous libraries from an asynchronous context.
/// Here is how you can do it correctly:
///
/// ```rust, no_run
/// use tokio::task::spawn_blocking;
/// use tokio::io::AsyncReadExt;
/// use tokio_util::io::SyncIoBridge;
/// use std::fs::File;
/// use std::io::Read;
///
/// let reader = tokio::fs::File::open("data.txt").await?;
/// let sync_reader = SyncIoBridge::new(reader);
///
/// let result = spawn_blocking(move || {
///    let mut file = File::open("output.txt")?;
///    std::io::copy(&mut sync_reader, &mut file)?;
///    Ok::<_, std::io::Error>(())
/// })
/// .await??;
/// ```
///

Review comment (suggestion):
this won't compile because `reader` is undefined, and `serde_json` is not a dependency of the example.

Code after:
///
/// The use of `SyncIoBridge` is unnecessary when hashing data. Instead, you can
/// process the data asynchronously by reading it into memory, which avoids blocking
/// the async runtime.
///
/// There are two strategies for avoiding `SyncIoBridge` when hashing data. When
/// the data fits into memory, the easiest is to read the data into a `Vec<u8>`
/// and hash it:
///
/// Explanation: This example demonstrates how to asynchronously read data from a
/// reader into memory and hash it using a synchronous hashing function. The
/// `SyncIoBridge` is avoided, ensuring that the async runtime is not blocked.
/// ```rust
/// use tokio::io::AsyncReadExt;
/// use tokio::io::AsyncRead;
/// use std::io::Cursor;
/// # mod blake3 { pub fn hash(_: &[u8]) {} }
///
/// async fn hash_contents(mut reader: impl AsyncRead + Unpin) -> Result<(), std::io::Error> {
///    // Read all data from the reader into a Vec<u8>.
///    let mut data = Vec::new();
///    reader.read_to_end(&mut data).await?;
///
///    // Hash the data using the blake3 hashing function.
///    let hash = blake3::hash(&data);
///
///    Ok(hash)
///}
///
/// #[tokio::main]
/// async fn main() -> Result<(), std::io::Error> {
///     // Example: In-memory data.
///     let data = b"Hello, world!"; // A byte slice.
///     let reader = Cursor::new(data); // Create an in-memory AsyncRead.
///     hash_contents(reader).await
/// }
/// ```
///
/// When the data doesn't fit into memory, the hashing library will usually
/// provide a `hasher` that you can repeatedly call `update` on to hash the data
/// one chunk at the time.
///
/// Explanation: This example demonstrates how to asynchronously stream data in
/// chunks for hashing. Each chunk is read asynchronously, and the hash is updated
/// incrementally. This avoids blocking and improves performance over using
/// `SyncIoBridge`.
///
/// ```rust
/// use tokio::io::AsyncReadExt;
/// use tokio::io::AsyncRead;
/// use std::io::Cursor;