Rust: test copy reader-writer

rust/example_0003_copy_reader_to_writer/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "example_0003_copy_reader_to_writer"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

rust/example_0003_copy_reader_to_writer/src/lib.rs

@@ -0,0 +1,21 @@
+use std::io::{Read, Write, self, ErrorKind};
+
+const DEFAULT_BUFFER_SIZE: usize = 8 * 1024;
+
+pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> io::Result<u64>
+where R: Read, W: Write
+{
+    let mut buf = [0; DEFAULT_BUFFER_SIZE];
+    let mut written = 0;
+
+    loop {
+        let len = match reader.read(&mut buf) {
+            Ok(0) => return Ok(written),
+            Ok(len) => len,
+            Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
+            Err(e) => return Err(e),
+        };
+        writer.write_all(&buf[..len])?;
+        written += len as u64;
+    }
+}