Implement read_buf for a few more types

Implement read_buf for TcpStream, Stdin, StdinLock, ChildStdout,
ChildStderr (and internally for AnonPipe, Handle, Socket), so
that it skips buffer initialization.

The other provided methods like read_to_string and read_to_end are
implemented in terms of read_buf and so benefit from the optimization
as well.

This commit also implements read_vectored and is_read_vectored where
applicable.

2 files changed, 10 insertions, 2 deletions

diff --git a/library/std/src/sys/sgx/fd.rs b/library/std/src/sys/sgx/fd.rs
index e5dc5b5adaa..0c02a107691 100644
--- a/library/std/src/sys/sgx/fd.rs
+++ b/library/std/src/sys/sgx/fd.rs
@@ -1,7 +1,7 @@
 use fortanix_sgx_abi::Fd;
 
 use super::abi::usercalls;
-use crate::io::{self, IoSlice, IoSliceMut};
+use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::mem;
 use crate::sys::{AsInner, FromInner, IntoInner};
 
@@ -30,6 +30,10 @@ impl FileDesc {
         usercalls::read(self.fd, &mut [IoSliceMut::new(buf)])
     }
 
+    pub fn read_buf(&self, buf: BorrowedCursor<'_>) -> io::Result<()> {
+        crate::io::default_read_buf(|b| self.read(b), buf)
+    }
+
     pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
         usercalls::read(self.fd, bufs)
     }
diff --git a/library/std/src/sys/sgx/net.rs b/library/std/src/sys/sgx/net.rs
index 4c4cd7d1d1d..923be5eb944 100644
--- a/library/std/src/sys/sgx/net.rs
+++ b/library/std/src/sys/sgx/net.rs
@@ -1,6 +1,6 @@
 use crate::error;
 use crate::fmt;
-use crate::io::{self, IoSlice, IoSliceMut};
+use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use crate::sync::Arc;
 use crate::sys::fd::FileDesc;
@@ -144,6 +144,10 @@ impl TcpStream {
         self.inner.inner.read(buf)
     }
 
+    pub fn read_buf(&self, buf: BorrowedCursor<'_>) -> io::Result<()> {
+        self.inner.inner.read_buf(buf)
+    }
+
     pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
         self.inner.inner.read_vectored(bufs)
     }