Auto merge of #58357 - sfackler:vectored-io, r=alexcrichton

Add vectored read and write support

This functionality has lived for a while in the tokio ecosystem, where
it can improve performance by minimizing copies.

r? @alexcrichton

3 files changed, 53 insertions, 6 deletions

diff --git a/src/libstd/sys/redox/io.rs b/src/libstd/sys/redox/io.rs
new file mode 100644
index 00000000000..8b02d3fd19d
--- /dev/null
+++ b/src/libstd/sys/redox/io.rs
@@ -0,0 +1,32 @@
+pub struct IoVec<'a>(&'a [u8]);
+
+impl<'a> IoVec<'a> {
+    #[inline]
+    pub fn new(buf: &'a [u8]) -> IoVec<'a> {
+        IoVec(buf)
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &[u8] {
+        self.0
+    }
+}
+
+pub struct IoVecMut<'a>(&'a mut [u8]);
+
+impl<'a> IoVecMut<'a> {
+    #[inline]
+    pub fn new(buf: &'a mut [u8]) -> IoVecMut<'a> {
+        IoVecMut(buf)
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &[u8] {
+        self.0
+    }
+
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut [u8] {
+        self.0
+    }
+}
diff --git a/src/libstd/sys/redox/mod.rs b/src/libstd/sys/redox/mod.rs
index c106db8ddfa..c3878349bb3 100644
--- a/src/libstd/sys/redox/mod.rs
+++ b/src/libstd/sys/redox/mod.rs
@@ -1,6 +1,6 @@
 #![allow(dead_code, missing_docs, nonstandard_style)]
 
-use io::{self, ErrorKind};
+use ::io::{ErrorKind};
 
 pub use libc::strlen;
 pub use self::rand::hashmap_random_keys;
@@ -17,6 +17,7 @@ pub mod ext;
 pub mod fast_thread_local;
 pub mod fd;
 pub mod fs;
+pub mod io;
 pub mod memchr;
 pub mod mutex;
 pub mod net;
@@ -63,8 +64,8 @@ pub fn decode_error_kind(errno: i32) -> ErrorKind {
     }
 }
 
-pub fn cvt(result: Result<usize, syscall::Error>) -> io::Result<usize> {
-    result.map_err(|err| io::Error::from_raw_os_error(err.errno))
+pub fn cvt(result: Result<usize, syscall::Error>) -> ::io::Result<usize> {
+    result.map_err(|err| ::io::Error::from_raw_os_error(err.errno))
 }
 
 #[doc(hidden)]
@@ -82,9 +83,9 @@ macro_rules! impl_is_minus_one {
 
 impl_is_minus_one! { i8 i16 i32 i64 isize }
 
-pub fn cvt_libc<T: IsMinusOne>(t: T) -> io::Result<T> {
+pub fn cvt_libc<T: IsMinusOne>(t: T) -> ::io::Result<T> {
     if t.is_minus_one() {
-        Err(io::Error::last_os_error())
+        Err(::io::Error::last_os_error())
     } else {
         Ok(t)
     }
diff --git a/src/libstd/sys/redox/net/tcp.rs b/src/libstd/sys/redox/net/tcp.rs
index e0353b130bb..abb9f72c324 100644
--- a/src/libstd/sys/redox/net/tcp.rs
+++ b/src/libstd/sys/redox/net/tcp.rs
@@ -1,5 +1,5 @@
 use cmp;
-use io::{self, Error, ErrorKind, Result};
+use io::{self, Error, ErrorKind, Result, IoVec, IoVecMut};
 use mem;
 use net::{SocketAddr, Shutdown};
 use path::Path;
@@ -34,10 +34,24 @@ impl TcpStream {
         self.0.read(buf)
     }
 
+    pub fn read_vectored(&self, bufs: &mut [IoVecMut<'_>]) -> io::Result<usize> {
+        match bufs.iter_mut().find(|b| !b.is_empty()) {
+            Some(buf) => self.read(buf),
+            None => Ok(0),
+        }
+    }
+
     pub fn write(&self, buf: &[u8]) -> Result<usize> {
         self.0.write(buf)
     }
 
+    pub fn write_vectored(&self, bufs: &[IoVec<'_>]) -> io::Result<usize> {
+        match bufs.iter().find(|b| !b.is_empty()) {
+            Some(buf) => self.write(buf),
+            None => Ok(0),
+        }
+    }
+
     pub fn take_error(&self) -> Result<Option<Error>> {
         Ok(None)
     }