From d52acbe37f69a2ebc9d161c479ed628da1cbea4e Mon Sep 17 00:00:00 2001
From: Florian Hartwig <florian.j.hartwig@gmail.com>
Date: Sat, 7 Oct 2017 14:49:42 +0200
Subject: [PATCH] Add read_to_end implementation to &[u8]'s Read impl

The default impl for read_to_end does a bunch of bookkeeping
that isn't necessary for slices and is about 4 times slower
on my machine.
---
 src/libstd/io/impls.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/libstd/io/impls.rs b/src/libstd/io/impls.rs
index d6b41ceda4392..fe1179a3b4a18 100644
--- a/src/libstd/io/impls.rs
+++ b/src/libstd/io/impls.rs
@@ -206,6 +206,14 @@ impl<'a> Read for &'a [u8] {
         *self = b;
         Ok(())
     }
+
+    #[inline]
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        buf.extend_from_slice(*self);
+        let len = self.len();
+        *self = &self[len..];
+        Ok(len)
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]