Add `Read::initializer`.

This is an API that allows types to indicate that they can be passed
buffers of uninitialized memory which can improve performance.

1 files changed, 16 insertions, 1 deletions

diff --git a/src/libstd/io/impls.rs b/src/libstd/io/impls.rs
index f691289811b..d6b41ceda43 100644
--- a/src/libstd/io/impls.rs
+++ b/src/libstd/io/impls.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 use cmp;
-use io::{self, SeekFrom, Read, Write, Seek, BufRead, Error, ErrorKind};
+use io::{self, SeekFrom, Read, Initializer, Write, Seek, BufRead, Error, ErrorKind};
 use fmt;
 use mem;
 
@@ -24,6 +24,11 @@ impl<'a, R: Read + ?Sized> Read for &'a mut R {
     }
 
     #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        (**self).initializer()
+    }
+
+    #[inline]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
         (**self).read_to_end(buf)
     }
@@ -88,6 +93,11 @@ impl<R: Read + ?Sized> Read for Box<R> {
     }
 
     #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        (**self).initializer()
+    }
+
+    #[inline]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
         (**self).read_to_end(buf)
     }
@@ -172,6 +182,11 @@ impl<'a> Read for &'a [u8] {
     }
 
     #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        Initializer::nop()
+    }
+
+    #[inline]
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         if buf.len() > self.len() {
             return Err(Error::new(ErrorKind::UnexpectedEof,