Replace replace(..., None) with take()

This is strictly for simplicity, since Option::take() is imlemented with replace().

src/broadcast_stage.rs

@@ -8,7 +8,6 @@ use log::Level;
 use packet::BlobRecycler;
 use result::{Error, Result};
 use service::Service;
-use std::mem;
 use std::net::UdpSocket;
 use std::sync::atomic::AtomicUsize;
 use std::sync::mpsc::RecvTimeoutError;
@@ -60,7 +59,7 @@ fn broadcast(
             for b in &blobs {
                 let ix = b.read().unwrap().get_index().expect("blob index");
                 let pos = (ix % WINDOW_SIZE) as usize;
-                if let Some(x) = mem::replace(&mut win[pos].data, None) {
+                if let Some(x) = win[pos].data.take() {
                     trace!(
                         "{} popped {} at {}",
                         id,
@@ -69,7 +68,7 @@ fn broadcast(
                     );
                     recycler.recycle(x, "broadcast-data");
                 }
-                if let Some(x) = mem::replace(&mut win[pos].coding, None) {
+                if let Some(x) = win[pos].coding.take() {
                     trace!(
                         "{} popped {} at {}",
                         id,

src/erasure.rs

@@ -363,7 +363,7 @@ fn is_missing(
     recycler: &BlobRecycler,
     c_or_d: &str,
 ) -> bool {
-    if let Some(blob) = mem::replace(window_slot, None) {
+    if let Some(blob) = window_slot.take() {
         let blob_idx = blob.read().unwrap().get_index().unwrap();
         if blob_idx == idx {
             trace!("recover {}: idx: {} good {}", id, idx, c_or_d);

src/window.rs

@@ -34,7 +34,7 @@ impl WindowSlot {
     }
 
     fn clear_data(&mut self, recycler: &BlobRecycler) {
-        if let Some(blob) = mem::replace(&mut self.data, None) {
+        if let Some(blob) = self.data.take() {
             recycler.recycle(blob, "WindowSlot::clear_data");
         }
     }