Rollup merge of rust-lang#57860 - jethrogb:jb/sgx-os-ffi, r=joshtriplett

Add os::fortanix_sgx::ffi module

This uses the same byte slice accessors that Unix has. The [ABI specifies](https://docs.rs/fortanix-sgx-abi/0.3.2/fortanix_sgx_abi/struct.ByteBuffer.html) byte slices.

src/libstd/os/fortanix_sgx/mod.rs

@@ -56,4 +56,4 @@ pub mod mem {
     pub use sys::abi::mem::*;
 }
 
-pub use sys::ext::{io, arch};
+pub use sys::ext::{io, arch, ffi};

src/libstd/sys/sgx/ext/ffi.rs

@@ -0,0 +1,109 @@
+//! SGX-specific extension to the primitives in the `std::ffi` module
+
+#![unstable(feature = "sgx_platform", issue = "56975")]
+
+use ffi::{OsStr, OsString};
+use mem;
+use sys::os_str::Buf;
+use sys_common::{FromInner, IntoInner, AsInner};
+
+/// SGX-specific extensions to [`OsString`].
+///
+/// [`OsString`]: ../../../../std/ffi/struct.OsString.html
+#[unstable(feature = "sgx_platform", issue = "56975")]
+pub trait OsStringExt {
+    /// Creates an [`OsString`] from a byte vector.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsString;
+    /// use std::os::unix::ffi::OsStringExt;
+    ///
+    /// let bytes = b"foo".to_vec();
+    /// let os_string = OsString::from_vec(bytes);
+    /// assert_eq!(os_string.to_str(), Some("foo"));
+    /// ```
+    ///
+    /// [`OsString`]: ../../../ffi/struct.OsString.html
+    #[unstable(feature = "sgx_platform", issue = "56975")]
+    fn from_vec(vec: Vec<u8>) -> Self;
+
+    /// Yields the underlying byte vector of this [`OsString`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsString;
+    /// use std::os::unix::ffi::OsStringExt;
+    ///
+    /// let mut os_string = OsString::new();
+    /// os_string.push("foo");
+    /// let bytes = os_string.into_vec();
+    /// assert_eq!(bytes, b"foo");
+    /// ```
+    ///
+    /// [`OsString`]: ../../../ffi/struct.OsString.html
+    #[unstable(feature = "sgx_platform", issue = "56975")]
+    fn into_vec(self) -> Vec<u8>;
+}
+
+#[unstable(feature = "sgx_platform", issue = "56975")]
+impl OsStringExt for OsString {
+    fn from_vec(vec: Vec<u8>) -> OsString {
+        FromInner::from_inner(Buf { inner: vec })
+    }
+    fn into_vec(self) -> Vec<u8> {
+        self.into_inner().inner
+    }
+}
+
+/// SGX-specific extensions to [`OsStr`].
+///
+/// [`OsStr`]: ../../../../std/ffi/struct.OsStr.html
+#[unstable(feature = "sgx_platform", issue = "56975")]
+pub trait OsStrExt {
+    #[unstable(feature = "sgx_platform", issue = "56975")]
+    /// Creates an [`OsStr`] from a byte slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsStr;
+    /// use std::os::unix::ffi::OsStrExt;
+    ///
+    /// let bytes = b"foo";
+    /// let os_str = OsStr::from_bytes(bytes);
+    /// assert_eq!(os_str.to_str(), Some("foo"));
+    /// ```
+    ///
+    /// [`OsStr`]: ../../../ffi/struct.OsStr.html
+    fn from_bytes(slice: &[u8]) -> &Self;
+
+    /// Gets the underlying byte view of the [`OsStr`] slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsStr;
+    /// use std::os::unix::ffi::OsStrExt;
+    ///
+    /// let mut os_str = OsStr::new("foo");
+    /// let bytes = os_str.as_bytes();
+    /// assert_eq!(bytes, b"foo");
+    /// ```
+    ///
+    /// [`OsStr`]: ../../../ffi/struct.OsStr.html
+    #[unstable(feature = "sgx_platform", issue = "56975")]
+    fn as_bytes(&self) -> &[u8];
+}
+
+#[unstable(feature = "sgx_platform", issue = "56975")]
+impl OsStrExt for OsStr {
+    fn from_bytes(slice: &[u8]) -> &OsStr {
+        unsafe { mem::transmute(slice) }
+    }
+    fn as_bytes(&self) -> &[u8] {
+        &self.as_inner().inner
+    }
+}

src/libstd/sys/sgx/ext/mod.rs

@@ -2,3 +2,4 @@
 
 pub mod arch;
 pub mod io;
+pub mod ffi;