f loop until writes return 0 + nit

Author: valentinewallace

lightning/src/util/chacha20poly1305rfc.rs

@@ -130,12 +130,16 @@ impl<'a, W: Writer> Writer for ChaChaPolyWriter<'a, W> {
 	// `ChaCha20Poly1305RFC::finish_and_get_tag` can be called to retrieve the tag after all writes
 	// complete.
 	fn write_all(&mut self, src: &[u8]) -> Result<(), io::Error> {
-		let num_writes = (src.len() + (8192 - 1)) / 8192;
-		for i in 0..num_writes {
+		let mut src_idx = 0;
+		loop {
 			let mut write_buffer = [0; 8192];
-			let bytes_written = (&mut write_buffer[..]).write(&src[i * 8192..])?;
+			let bytes_written = (&mut write_buffer[..]).write(&src[src_idx..]).expect("In-memory writes can't fail");
+			if bytes_written == 0 {
+				break
+			}
 			self.chacha.encrypt_in_place(&mut write_buffer[..bytes_written]);
 			self.write.write_all(&write_buffer[..bytes_written])?;
+			src_idx += bytes_written;
 		}
 		Ok(())
 	}