Add big_file example.

Cargo.toml

@@ -122,7 +122,8 @@ serde = { version = "1.0", features = ["derive"] }
 libflate = "0.1"
 brotli_crate = { package = "brotli", version = "3.3.0" }
 doc-comment = "0.3"
-tokio = { version = "0.2.0", default-features = false, features = ["macros"] }
+tokio = { version = "0.2.0", default-features = false, features = ["fs", "io-std", "macros"] }
+tokio-util = { version = "0.3", features = ["codec"] }
 
 [target.'cfg(windows)'.dependencies]
 winreg = "0.6"
@@ -150,6 +151,11 @@ name = "blocking"
 path = "examples/blocking.rs"
 required-features = ["blocking"]
 
+[[example]]
+name = "big_file"
+path = "examples/big_file.rs"
+required-features = ["stream"]
+
 [[example]]
 name = "json_dynamic"
 path = "examples/json_dynamic.rs"

examples/big_file.json

@@ -0,0 +1,5 @@
+{
+  "user_id": 1,
+  "title": "very long title",
+  "body": "very long body"
+}

examples/big_file.rs

@@ -0,0 +1,44 @@
+//! `cargo run --example big_file --features=stream`
+//! This example illustrates the way to send and receive big file by chunks.
+#![deny(warnings)]
+
+use reqwest::{
+    header::{HeaderMap, HeaderValue, CONTENT_TYPE},
+    Body,
+};
+use tokio::{
+    fs::File,
+    io::{self, AsyncWriteExt},
+    stream::StreamExt,
+};
+use tokio_util::codec::{BytesCodec, FramedRead};
+
+static FILE_PATH: &str = "examples/big_file.json";
+
+// This is using the `tokio` runtime. You'll need the following dependency:
+//
+// `tokio = { version = "0.2", features = ["fs", "io-std", "macros"] }`
+//
+// for reading file by chunks this example uses tokio-util dependency:
+//
+// `tokio-util = { version = "0.3", features = ["codec"] }`
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let file = File::open(FILE_PATH).await?;
+    let stream = FramedRead::new(file, BytesCodec::new());
+    let body = Body::wrap_stream(stream);
+    let mut headers = HeaderMap::new();
+    headers.insert(CONTENT_TYPE, HeaderValue::from_static("application/json"));
+    let mut response_stream = reqwest::Client::new()
+        .post("https://jsonplaceholder.typicode.com/posts")
+        .headers(headers)
+        .body(body)
+        .send()
+        .await?
+        .bytes_stream();
+    while let Some(chunk) = response_stream.next().await {
+        let chunk = chunk?;
+        io::stdout().write_all(&chunk).await?;
+    }
+    Ok(())
+}