docs(body): add example for to_bytes()

cc #2201

src/body/to_bytes.rs

@@ -13,6 +13,36 @@ use super::HttpBody;
 /// Care needs to be taken if the remote is untrusted. The function doesn't implement any length
 /// checks and an malicious peer might make it consume arbitrary amounts of memory. Checking the
 /// `Content-Length` is a possibility, but it is not strictly mandated to be present.
+///
+/// # Example
+///
+/// ```
+/// # async fn doc() -> hyper::Result<()> {
+/// use hyper::{body::HttpBody};
+///
+/// # let request = hyper::Request::builder()
+/// #        .method(hyper::Method::POST)
+/// #        .uri("http://httpbin.org/post")
+/// #        .header("content-type", "application/json")
+/// #        .body(hyper::Body::from(r#"{"library":"hyper"}"#)).unwrap();
+/// # let client = hyper::Client::new();
+/// let response = client.request(request).await?;
+///
+/// const MAX_ALLOWED_RESPONSE_SIZE: u64 = 1024;
+///
+/// let response_content_length = match response.body().size_hint().upper() {
+///     Some(v) => v,
+///     None => MAX_ALLOWED_RESPONSE_SIZE + 1 // Just to protect ourselves from a malicious response
+/// };
+///
+/// if response_content_length < MAX_ALLOWED_RESPONSE_SIZE {
+///     let body_bytes = hyper::body::to_bytes(response.into_body()).await?;
+///     println!("body: {:?}", body_bytes);
+/// }
+///
+/// # Ok(())
+/// # }
+/// ```
 pub async fn to_bytes<T>(body: T) -> Result<Bytes, T::Error>
 where
     T: HttpBody,