style: replace split_to and split_off with better alternatives

This removes `let _ = ` from in front of `split_to` and `split_off`
and mostly follows the suggestions from the `#[must_use]` impls.
One of the uses of `split_to` is instead replaced with `take`.

src/codec/framed_read.rs

@@ -8,7 +8,7 @@ use crate::hpack;
 
 use futures_core::Stream;
 
-use bytes::BytesMut;
+use bytes::{Buf, BytesMut};
 
 use std::io;
 
@@ -146,8 +146,7 @@ fn decode_frame(
     macro_rules! header_block {
         ($frame:ident, $head:ident, $bytes:ident) => ({
             // Drop the frame header
-            // TODO: Change to drain: carllerche/bytes#130
-            let _ = $bytes.split_to(frame::HEADER_LEN);
+            $bytes.advance(frame::HEADER_LEN);
 
             // Parse the header frame w/o parsing the payload
             let (mut frame, mut payload) = match frame::$frame::load($head, $bytes) {
@@ -227,7 +226,7 @@ fn decode_frame(
             .into()
         }
         Kind::Data => {
-            let _ = bytes.split_to(frame::HEADER_LEN);
+            bytes.advance(frame::HEADER_LEN);
             let res = frame::Data::load(head, bytes.freeze());
 
             // TODO: Should this always be connection level? Probably not...

src/frame/headers.rs

@@ -6,7 +6,7 @@ use crate::hpack::{self, BytesStr};
 use http::header::{self, HeaderName, HeaderValue};
 use http::{uri, HeaderMap, Method, Request, StatusCode, Uri};
 
-use bytes::{BufMut, Bytes, BytesMut};
+use bytes::{Buf, BufMut, Bytes, BytesMut};
 
 use std::fmt;
 use std::io::Cursor;
@@ -166,7 +166,7 @@ impl Headers {
             pad = src[0] as usize;
 
             // Drop the padding
-            let _ = src.split_to(1);
+            src.advance(1);
         }
 
         // Read the stream dependency
@@ -181,7 +181,7 @@ impl Headers {
             }
 
             // Drop the next 5 bytes
-            let _ = src.split_to(5);
+            src.advance(5);
 
             Some(stream_dep)
         } else {
@@ -425,7 +425,7 @@ impl PushPromise {
             pad = src[0] as usize;
 
             // Drop the padding
-            let _ = src.split_to(1);
+            src.advance(1);
         }
 
         if src.len() < 5 {
@@ -434,7 +434,7 @@ impl PushPromise {
 
         let (promised_id, _) = StreamId::parse(&src[..4]);
         // Drop promised_id bytes
-        let _ = src.split_to(4);
+        src.advance(4);
 
         if pad > 0 {
             if pad > src.len() {
@@ -657,7 +657,7 @@ impl EncodingHeaderBlock {
 
         // Now, encode the header payload
         let continuation = if self.hpack.len() > dst.remaining_mut() {
-            dst.put_slice(&self.hpack.split_to(dst.remaining_mut()));
+            dst.put((&mut self.hpack).take(dst.remaining_mut()));
 
             Some(Continuation {
                 stream_id: head.stream_id(),

src/frame/util.rs

@@ -1,7 +1,7 @@
 use std::fmt;
 
 use super::Error;
-use bytes::Bytes;
+use bytes::{Buf, Bytes};
 
 /// Strip padding from the given payload.
 ///
@@ -32,8 +32,8 @@ pub fn strip_padding(payload: &mut Bytes) -> Result<u8, Error> {
         return Err(Error::TooMuchPadding);
     }
 
-    let _ = payload.split_to(1);
-    let _ = payload.split_off(payload_len - pad_len - 1);
+    payload.advance(1);
+    payload.truncate(payload_len - pad_len - 1);
 
     Ok(pad_len as u8)
 }