Add specializations of read_to_end for Stdin, TcpStream and File,

allowing them to read into a buffer containing uninitialized data,
rather than pay the cost of zeroing.

2 files changed, 15 insertions, 0 deletions

diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 50c44299dc7..d0453c2e776 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -906,6 +906,8 @@ mod tests {
     use io::prelude::*;
     use io;
     use super::Cursor;
+    use test;
+    use super::repeat;
 
     #[test]
     fn read_until() {
@@ -1024,4 +1026,13 @@ mod tests {
         let mut buf = [0; 1];
         assert_eq!(0, R.take(0).read(&mut buf).unwrap());
     }
+
+    #[bench]
+    fn bench_read_to_end(b: &mut test::Bencher) {
+        b.iter(|| {
+            let mut lr = repeat(1).take(10000000);
+            let mut vec = Vec::with_capacity(1024);
+            super::read_to_end(&mut lr, &mut vec);
+        });
+    }
 }
diff --git a/src/libstd/io/stdio.rs b/src/libstd/io/stdio.rs
index 62bbb939a71..d8b7c8a282c 100644
--- a/src/libstd/io/stdio.rs
+++ b/src/libstd/io/stdio.rs
@@ -18,6 +18,7 @@ use io::lazy::Lazy;
 use io::{self, BufReader, LineWriter};
 use sync::{Arc, Mutex, MutexGuard};
 use sys::stdio;
+use sys_common::io::{read_to_end_uninitialized};
 use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
 use libc;
 
@@ -277,6 +278,9 @@ impl<'a> Read for StdinLock<'a> {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         self.inner.read(buf)
     }
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        unsafe { read_to_end_uninitialized(self, buf) }
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]