Update for latest nightly 2018-06-09 (#70)

* Update for latest nightly 2018-06-09
* We now have a proper horizon os and sys modules in libstd

1 files changed, 928 insertions, 0 deletions

diff --git a/ctr-std/src/sys/horizon/fs.rs b/ctr-std/src/sys/horizon/fs.rs
new file mode 100644
index 0000000..f370d9c
--- /dev/null
+++ b/ctr-std/src/sys/horizon/fs.rs
@@ -0,0 +1,928 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use os::unix::prelude::*;
+
+use ffi::{CString, CStr, OsString, OsStr};
+use fmt;
+use io::{self, Error, ErrorKind, SeekFrom};
+use libc::{self, c_int, mode_t};
+use mem;
+use path::{Path, PathBuf};
+use ptr;
+use sync::Arc;
+use sys::fd::FileDesc;
+use sys::time::SystemTime;
+use sys::{cvt, cvt_r};
+use sys_common::{AsInner, FromInner};
+
+#[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "l4re"))]
+use libc::{stat64, fstat64, lstat64, off64_t, ftruncate64, lseek64, dirent64, readdir64_r, open64};
+#[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "android"))]
+use libc::{fstatat, dirfd};
+#[cfg(target_os = "android")]
+use libc::{stat as stat64, fstat as fstat64, lstat as lstat64, lseek64,
+           dirent as dirent64, open as open64};
+#[cfg(not(any(target_os = "linux",
+              target_os = "emscripten",
+              target_os = "l4re",
+              target_os = "android")))]
+use libc::{stat as stat64, fstat as fstat64, lstat as lstat64, off_t as off64_t,
+           ftruncate as ftruncate64, lseek as lseek64, dirent as dirent64, open as open64};
+#[cfg(not(any(target_os = "linux",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "l4re",
+              target_os = "fuchsia")))]
+use libc::{readdir_r as readdir64_r};
+
+pub struct File(FileDesc);
+
+#[derive(Clone)]
+pub struct FileAttr {
+    stat: stat64,
+}
+
+// all DirEntry's will have a reference to this struct
+struct InnerReadDir {
+    dirp: Dir,
+    root: PathBuf,
+}
+
+#[derive(Clone)]
+pub struct ReadDir(Arc<InnerReadDir>);
+
+struct Dir(*mut libc::DIR);
+
+unsafe impl Send for Dir {}
+unsafe impl Sync for Dir {}
+
+pub struct DirEntry {
+    entry: dirent64,
+    dir: ReadDir,
+    // We need to store an owned copy of the entry name
+    // on Solaris and Fuchsia because a) it uses a zero-length
+    // array to store the name, b) its lifetime between readdir
+    // calls is not guaranteed.
+    #[cfg(any(target_os = "solaris", target_os = "fuchsia"))]
+    name: Box<[u8]>
+}
+
+#[derive(Clone, Debug)]
+pub struct OpenOptions {
+    // generic
+    read: bool,
+    write: bool,
+    append: bool,
+    truncate: bool,
+    create: bool,
+    create_new: bool,
+    // system-specific
+    custom_flags: i32,
+    mode: mode_t,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct FilePermissions { mode: mode_t }
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct FileType { mode: mode_t }
+
+#[derive(Debug)]
+pub struct DirBuilder { mode: mode_t }
+
+impl FileAttr {
+    pub fn size(&self) -> u64 { self.stat.st_size as u64 }
+    pub fn perm(&self) -> FilePermissions {
+        FilePermissions { mode: (self.stat.st_mode as mode_t) }
+    }
+
+    pub fn file_type(&self) -> FileType {
+        FileType { mode: self.stat.st_mode as mode_t }
+    }
+}
+
+#[cfg(target_os = "netbsd")]
+impl FileAttr {
+    pub fn modified(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from(libc::timespec {
+            tv_sec: self.stat.st_mtime as libc::time_t,
+            tv_nsec: self.stat.st_mtimensec as libc::c_long,
+        }))
+    }
+
+    pub fn accessed(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from(libc::timespec {
+            tv_sec: self.stat.st_atime as libc::time_t,
+            tv_nsec: self.stat.st_atimensec as libc::c_long,
+        }))
+    }
+
+    pub fn created(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from(libc::timespec {
+            tv_sec: self.stat.st_birthtime as libc::time_t,
+            tv_nsec: self.stat.st_birthtimensec as libc::c_long,
+        }))
+    }
+}
+
+#[cfg(not(target_os = "netbsd"))]
+impl FileAttr {
+    pub fn modified(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from(libc::timespec {
+            tv_sec: self.stat.st_mtime as libc::time_t,
+            tv_nsec: 0 as _,
+        }))
+    }
+
+    pub fn accessed(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from(libc::timespec {
+            tv_sec: self.stat.st_atime as libc::time_t,
+            tv_nsec: 0 as _,
+        }))
+    }
+
+    #[cfg(any(target_os = "bitrig",
+              target_os = "freebsd",
+              target_os = "openbsd",
+              target_os = "macos",
+              target_os = "ios"))]
+    pub fn created(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from(libc::timespec {
+            tv_sec: self.stat.st_birthtime as libc::time_t,
+            tv_nsec: self.stat.st_birthtime_nsec as libc::c_long,
+        }))
+    }
+
+    #[cfg(not(any(target_os = "bitrig",
+                  target_os = "freebsd",
+                  target_os = "openbsd",
+                  target_os = "macos",
+                  target_os = "ios")))]
+    pub fn created(&self) -> io::Result<SystemTime> {
+        Err(io::Error::new(io::ErrorKind::Other,
+                           "creation time is not available on this platform \
+                            currently"))
+    }
+}
+
+impl AsInner<stat64> for FileAttr {
+    fn as_inner(&self) -> &stat64 { &self.stat }
+}
+
+impl FilePermissions {
+    pub fn readonly(&self) -> bool {
+        // check if any class (owner, group, others) has write permission
+        self.mode & 0o222 == 0
+    }
+
+    pub fn set_readonly(&mut self, readonly: bool) {
+        if readonly {
+            // remove write permission for all classes; equivalent to `chmod a-w <file>`
+            self.mode &= !0o222;
+        } else {
+            // add write permission for all classes; equivalent to `chmod a+w <file>`
+            self.mode |= 0o222;
+        }
+    }
+    pub fn mode(&self) -> u32 { self.mode as u32 }
+}
+
+impl FileType {
+    pub fn is_dir(&self) -> bool { self.is(libc::S_IFDIR) }
+    pub fn is_file(&self) -> bool { self.is(libc::S_IFREG) }
+    pub fn is_symlink(&self) -> bool { self.is(libc::S_IFLNK) }
+
+    pub fn is(&self, mode: mode_t) -> bool { self.mode & libc::S_IFMT == mode }
+}
+
+impl FromInner<u32> for FilePermissions {
+    fn from_inner(mode: u32) -> FilePermissions {
+        FilePermissions { mode: mode as mode_t }
+    }
+}
+
+impl fmt::Debug for ReadDir {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // This will only be called from std::fs::ReadDir, which will add a "ReadDir()" frame.
+        // Thus the result will be e g 'ReadDir("/home")'
+        fmt::Debug::fmt(&*self.0.root, f)
+    }
+}
+
+impl Iterator for ReadDir {
+    type Item = io::Result<DirEntry>;
+
+    #[cfg(any(target_os = "solaris", target_os = "fuchsia"))]
+    fn next(&mut self) -> Option<io::Result<DirEntry>> {
+        unsafe {
+            loop {
+                // Although readdir_r(3) would be a correct function to use here because
+                // of the thread safety, on Illumos and Fuchsia the readdir(3C) function
+                // is safe to use in threaded applications and it is generally preferred
+                // over the readdir_r(3C) function.
+                super::os::set_errno(0);
+                let entry_ptr = libc::readdir(self.0.dirp.0);
+                if entry_ptr.is_null() {
+                    // NULL can mean either the end is reached or an error occurred.
+                    // So we had to clear errno beforehand to check for an error now.
+                    return match super::os::errno() {
+                        0 => None,
+                        e => Some(Err(Error::from_raw_os_error(e))),
+                    }
+                }
+
+                let name = (*entry_ptr).d_name.as_ptr() as *const u8;
+                let namelen = libc::strlen(name) as usize;
+
+                let ret = DirEntry {
+                    entry: *entry_ptr,
+                    name: ::slice::from_raw_parts(name as *const u8,
+                                                  namelen as usize).to_owned().into_boxed_slice(),
+                    dir: self.clone()
+                };
+                if ret.name_bytes() != b"." && ret.name_bytes() != b".." {
+                    return Some(Ok(ret))
+                }
+            }
+        }
+    }
+
+    #[cfg(not(any(target_os = "solaris", target_os = "fuchsia")))]
+    fn next(&mut self) -> Option<io::Result<DirEntry>> {
+        unsafe {
+            let mut ret = DirEntry {
+                entry: mem::zeroed(),
+                dir: self.clone(),
+            };
+            let mut entry_ptr = ptr::null_mut();
+            loop {
+                if readdir64_r(self.0.dirp.0, &mut ret.entry, &mut entry_ptr) != 0 {
+                    return Some(Err(Error::last_os_error()))
+                }
+                if entry_ptr.is_null() {
+                    return None
+                }
+                if ret.name_bytes() != b"." && ret.name_bytes() != b".." {
+                    return Some(Ok(ret))
+                }
+            }
+        }
+    }
+}
+
+impl Drop for Dir {
+    fn drop(&mut self) {
+        let r = unsafe { libc::closedir(self.0) };
+        debug_assert_eq!(r, 0);
+    }
+}
+
+impl DirEntry {
+    pub fn path(&self) -> PathBuf {
+        self.dir.0.root.join(OsStr::from_bytes(self.name_bytes()))
+    }
+
+    pub fn file_name(&self) -> OsString {
+        OsStr::from_bytes(self.name_bytes()).to_os_string()
+    }
+
+    #[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "android"))]
+    pub fn metadata(&self) -> io::Result<FileAttr> {
+        let fd = cvt(unsafe {dirfd(self.dir.0.dirp.0)})?;
+        let mut stat: stat64 = unsafe { mem::zeroed() };
+        cvt(unsafe {
+            fstatat(fd,
+                    self.entry.d_name.as_ptr() as *const u8,
+                    &mut stat as *mut _ as *mut _,
+                    libc::AT_SYMLINK_NOFOLLOW)
+        })?;
+        Ok(FileAttr { stat: stat })
+    }
+
+    #[cfg(not(any(target_os = "linux", target_os = "emscripten", target_os = "android")))]
+    pub fn metadata(&self) -> io::Result<FileAttr> {
+        lstat(&self.path())
+    }
+
+    #[cfg(any(target_os = "solaris", target_os = "haiku"))]
+    pub fn file_type(&self) -> io::Result<FileType> {
+        lstat(&self.path()).map(|m| m.file_type())
+    }
+
+    #[cfg(not(any(target_os = "solaris", target_os = "haiku")))]
+    pub fn file_type(&self) -> io::Result<FileType> {
+        match self.entry.d_type {
+            libc::DT_CHR => Ok(FileType { mode: libc::S_IFCHR }),
+            libc::DT_FIFO => Ok(FileType { mode: libc::S_IFIFO }),
+            libc::DT_LNK => Ok(FileType { mode: libc::S_IFLNK }),
+            libc::DT_REG => Ok(FileType { mode: libc::S_IFREG }),
+            libc::DT_SOCK => Ok(FileType { mode: libc::S_IFSOCK }),
+            libc::DT_DIR => Ok(FileType { mode: libc::S_IFDIR }),
+            libc::DT_BLK => Ok(FileType { mode: libc::S_IFBLK }),
+            _ => lstat(&self.path()).map(|m| m.file_type()),
+        }
+    }
+
+    #[cfg(any(target_os = "macos",
+              target_os = "ios",
+              target_os = "linux",
+              target_os = "emscripten",
+              target_os = "android",
+              target_os = "solaris",
+              target_os = "haiku",
+              target_os = "l4re",
+              target_os = "fuchsia"))]
+    pub fn ino(&self) -> u64 {
+        self.entry.d_ino as u64
+    }
+
+    #[cfg(any(target_os = "freebsd",
+              target_os = "openbsd",
+              target_os = "bitrig",
+              target_os = "netbsd",
+              target_os = "dragonfly"))]
+    pub fn ino(&self) -> u64 {
+        self.entry.d_fileno as u64
+    }
+
+    #[cfg(any(target_os = "macos",
+              target_os = "ios",
+              target_os = "netbsd",
+              target_os = "openbsd",
+              target_os = "freebsd",
+              target_os = "dragonfly",
+              target_os = "bitrig"))]
+    fn name_bytes(&self) -> &[u8] {
+        unsafe {
+            ::slice::from_raw_parts(self.entry.d_name.as_ptr() as *const u8 as *const u8,
+                                    self.entry.d_namlen as usize)
+        }
+    }
+    #[cfg(any(target_os = "android",
+              target_os = "linux",
+              target_os = "emscripten",
+              target_os = "l4re",
+              target_os = "haiku",
+              target_os = "horizon"))]
+    fn name_bytes(&self) -> &[u8] {
+        unsafe {
+            CStr::from_ptr(self.entry.d_name.as_ptr() as *const i8).to_bytes()
+        }
+    }
+    #[cfg(any(target_os = "solaris",
+              target_os = "fuchsia"))]
+    fn name_bytes(&self) -> &[u8] {
+        &*self.name
+    }
+}
+
+impl OpenOptions {
+    pub fn new() -> OpenOptions {
+        OpenOptions {
+            // generic
+            read: false,
+            write: false,
+            append: false,
+            truncate: false,
+            create: false,
+            create_new: false,
+            // system-specific
+            custom_flags: 0,
+            mode: 0o666,
+        }
+    }
+
+    pub fn read(&mut self, read: bool) { self.read = read; }
+    pub fn write(&mut self, write: bool) { self.write = write; }
+    pub fn append(&mut self, append: bool) { self.append = append; }
+    pub fn truncate(&mut self, truncate: bool) { self.truncate = truncate; }
+    pub fn create(&mut self, create: bool) { self.create = create; }
+    pub fn create_new(&mut self, create_new: bool) { self.create_new = create_new; }
+
+    pub fn custom_flags(&mut self, flags: i32) { self.custom_flags = flags; }
+    pub fn mode(&mut self, mode: u32) { self.mode = mode as mode_t; }
+
+    fn get_access_mode(&self) -> io::Result<c_int> {
+        match (self.read, self.write, self.append) {
+            (true,  false, false) => Ok(libc::O_RDONLY),
+            (false, true,  false) => Ok(libc::O_WRONLY),
+            (true,  true,  false) => Ok(libc::O_RDWR),
+            (false, _,     true)  => Ok(libc::O_WRONLY | libc::O_APPEND),
+            (true,  _,     true)  => Ok(libc::O_RDWR | libc::O_APPEND),
+            (false, false, false) => Err(Error::from_raw_os_error(libc::EINVAL)),
+        }
+    }
+
+    fn get_creation_mode(&self) -> io::Result<c_int> {
+        match (self.write, self.append) {
+            (true, false) => {}
+            (false, false) =>
+                if self.truncate || self.create || self.create_new {
+                    return Err(Error::from_raw_os_error(libc::EINVAL));
+                },
+            (_, true) =>
+                if self.truncate && !self.create_new {
+                    return Err(Error::from_raw_os_error(libc::EINVAL));
+                },
+        }
+
+        Ok(match (self.create, self.truncate, self.create_new) {
+                (false, false, false) => 0,
+                (true,  false, false) => libc::O_CREAT,
+                (false, true,  false) => libc::O_TRUNC,
+                (true,  true,  false) => libc::O_CREAT | libc::O_TRUNC,
+                (_,      _,    true)  => libc::O_CREAT | libc::O_EXCL,
+           })
+    }
+}
+
+impl File {
+    pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
+        let path = cstr(path)?;
+        File::open_c(&path, opts)
+    }
+
+    pub fn open_c(path: &CStr, opts: &OpenOptions) -> io::Result<File> {
+        let flags = libc::O_CLOEXEC |
+                    opts.get_access_mode()? |
+                    opts.get_creation_mode()? |
+                    (opts.custom_flags as c_int & !libc::O_ACCMODE);
+        let fd = cvt_r(|| unsafe {
+            open64(path.as_ptr() as *const u8, flags, opts.mode as c_int)
+        })?;
+        let fd = FileDesc::new(fd);
+
+        // Currently the standard library supports Linux 2.6.18 which did not
+        // have the O_CLOEXEC flag (passed above). If we're running on an older
+        // Linux kernel then the flag is just ignored by the OS. After we open
+        // the first file, we check whether it has CLOEXEC set. If it doesn't,
+        // we will explicitly ask for a CLOEXEC fd for every further file we
+        // open, if it does, we will skip that step.
+        //
+        // The CLOEXEC flag, however, is supported on versions of macOS/BSD/etc
+        // that we support, so we only do this on Linux currently.
+        #[cfg(target_os = "linux")]
+        fn ensure_cloexec(fd: &FileDesc) -> io::Result<()> {
+            use sync::atomic::{AtomicUsize, Ordering};
+
+            const OPEN_CLOEXEC_UNKNOWN: usize = 0;
+            const OPEN_CLOEXEC_SUPPORTED: usize = 1;
+            const OPEN_CLOEXEC_NOTSUPPORTED: usize = 2;
+            static OPEN_CLOEXEC: AtomicUsize = AtomicUsize::new(OPEN_CLOEXEC_UNKNOWN);
+
+            let need_to_set;
+            match OPEN_CLOEXEC.load(Ordering::Relaxed) {
+                OPEN_CLOEXEC_UNKNOWN => {
+                    need_to_set = !fd.get_cloexec()?;
+                    OPEN_CLOEXEC.store(if need_to_set {
+                        OPEN_CLOEXEC_NOTSUPPORTED
+                    } else {
+                        OPEN_CLOEXEC_SUPPORTED
+                    }, Ordering::Relaxed);
+                },
+                OPEN_CLOEXEC_SUPPORTED => need_to_set = false,
+                OPEN_CLOEXEC_NOTSUPPORTED => need_to_set = true,
+                _ => unreachable!(),
+            }
+            if need_to_set {
+                fd.set_cloexec()?;
+            }
+            Ok(())
+        }
+
+        #[cfg(not(target_os = "linux"))]
+        fn ensure_cloexec(_: &FileDesc) -> io::Result<()> {
+            Ok(())
+        }
+
+        ensure_cloexec(&fd)?;
+        Ok(File(fd))
+    }
+
+    pub fn file_attr(&self) -> io::Result<FileAttr> {
+        let mut stat: stat64 = unsafe { mem::zeroed() };
+        cvt(unsafe {
+            fstat64(self.0.raw(), &mut stat)
+        })?;
+        Ok(FileAttr { stat: stat })
+    }
+
+    pub fn fsync(&self) -> io::Result<()> {
+        cvt_r(|| unsafe { libc::fsync(self.0.raw()) })?;
+        Ok(())
+    }
+
+    pub fn datasync(&self) -> io::Result<()> {
+        cvt_r(|| unsafe { os_datasync(self.0.raw()) })?;
+        return Ok(());
+
+        #[cfg(any(target_os = "macos", target_os = "ios"))]
+        unsafe fn os_datasync(fd: c_int) -> c_int {
+            libc::fcntl(fd, libc::F_FULLFSYNC)
+        }
+        #[cfg(target_os = "linux")]
+        unsafe fn os_datasync(fd: c_int) -> c_int { libc::fdatasync(fd) }
+        #[cfg(not(any(target_os = "macos",
+                      target_os = "ios",
+                      target_os = "linux")))]
+        unsafe fn os_datasync(fd: c_int) -> c_int { libc::fsync(fd) }
+    }
+
+    pub fn truncate(&self, size: u64) -> io::Result<()> {
+        #[cfg(target_os = "android")]
+        return ::sys::android::ftruncate64(self.0.raw(), size);
+
+        #[cfg(not(target_os = "android"))]
+        return cvt_r(|| unsafe {
+            ftruncate64(self.0.raw(), size as off64_t)
+        }).map(|_| ());
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.0.read(buf)
+    }
+
+    pub fn read_at(&self, buf: &mut [u8], offset: u64) -> io::Result<usize> {
+        self.0.read_at(buf, offset)
+    }
+
+    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
+        self.0.write(buf)
+    }
+
+    pub fn write_at(&self, buf: &[u8], offset: u64) -> io::Result<usize> {
+        self.0.write_at(buf, offset)
+    }
+
+    pub fn flush(&self) -> io::Result<()> { Ok(()) }
+
+    pub fn seek(&self, pos: SeekFrom) -> io::Result<u64> {
+        let (whence, pos) = match pos {
+            // Casting to `i64` is fine, too large values will end up as
+            // negative which will cause an error in `lseek64`.
+            SeekFrom::Start(off) => (libc::SEEK_SET, off as i64),
+            SeekFrom::End(off) => (libc::SEEK_END, off),
+            SeekFrom::Current(off) => (libc::SEEK_CUR, off),
+        };
+        #[cfg(target_os = "emscripten")]
+        let pos = pos as i32;
+        let n = cvt(unsafe { lseek64(self.0.raw(), pos, whence) })?;
+        Ok(n as u64)
+    }
+
+    pub fn duplicate(&self) -> io::Result<File> {
+        self.0.duplicate().map(File)
+    }
+
+    pub fn fd(&self) -> &FileDesc { &self.0 }
+
+    pub fn into_fd(self) -> FileDesc { self.0 }
+
+    pub fn set_permissions(&self, perm: FilePermissions) -> io::Result<()> {
+        cvt_r(|| unsafe { libc::fchmod(self.0.raw(), perm.mode) })?;
+        Ok(())
+    }
+}
+
+impl DirBuilder {
+    pub fn new() -> DirBuilder {
+        DirBuilder { mode: 0o777 }
+    }
+
+    pub fn mkdir(&self, p: &Path) -> io::Result<()> {
+        let p = cstr(p)?;
+        cvt(unsafe { libc::mkdir(p.as_ptr() as *const u8, self.mode) })?;
+        Ok(())
+    }
+
+    pub fn set_mode(&mut self, mode: u32) {
+        self.mode = mode as mode_t;
+    }
+}
+
+fn cstr(path: &Path) -> io::Result<CString> {
+    Ok(CString::new(path.as_os_str().as_bytes())?)
+}
+
+impl FromInner<c_int> for File {
+    fn from_inner(fd: c_int) -> File {
+        File(FileDesc::new(fd))
+    }
+}
+
+impl fmt::Debug for File {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        #[cfg(target_os = "linux")]
+        fn get_path(fd: c_int) -> Option<PathBuf> {
+            let mut p = PathBuf::from("/proc/self/fd");
+            p.push(&fd.to_string());
+            readlink(&p).ok()
+        }
+
+        #[cfg(target_os = "macos")]
+        fn get_path(fd: c_int) -> Option<PathBuf> {
+            // FIXME: The use of PATH_MAX is generally not encouraged, but it
+            // is inevitable in this case because macOS defines `fcntl` with
+            // `F_GETPATH` in terms of `MAXPATHLEN`, and there are no
+            // alternatives. If a better method is invented, it should be used
+            // instead.
+            let mut buf = vec![0;libc::PATH_MAX as usize];
+            let n = unsafe { libc::fcntl(fd, libc::F_GETPATH, buf.as_ptr() as *const u8) };
+            if n == -1 {
+                return None;
+            }
+            let l = buf.iter().position(|&c| c == 0).unwrap();
+            buf.truncate(l as usize);
+            buf.shrink_to_fit();
+            Some(PathBuf::from(OsString::from_vec(buf)))
+        }
+
+        #[cfg(not(any(target_os = "linux", target_os = "macos")))]
+        fn get_path(_fd: c_int) -> Option<PathBuf> {
+            // FIXME(#24570): implement this for other Unix platforms
+            None
+        }
+
+        #[cfg(any(target_os = "linux", target_os = "macos"))]
+        fn get_mode(fd: c_int) -> Option<(bool, bool)> {
+            let mode = unsafe { libc::fcntl(fd, libc::F_GETFL) };
+            if mode == -1 {
+                return None;
+            }
+            match mode & libc::O_ACCMODE {
+                libc::O_RDONLY => Some((true, false)),
+                libc::O_RDWR => Some((true, true)),
+                libc::O_WRONLY => Some((false, true)),
+                _ => None
+            }
+        }
+
+        #[cfg(not(any(target_os = "linux", target_os = "macos")))]
+        fn get_mode(_fd: c_int) -> Option<(bool, bool)> {
+            // FIXME(#24570): implement this for other Unix platforms
+            None
+        }
+
+        let fd = self.0.raw();
+        let mut b = f.debug_struct("File");
+        b.field("fd", &fd);
+        if let Some(path) = get_path(fd) {
+            b.field("path", &path);
+        }
+        if let Some((read, write)) = get_mode(fd) {
+            b.field("read", &read).field("write", &write);
+        }
+        b.finish()
+    }
+}
+
+pub fn readdir(p: &Path) -> io::Result<ReadDir> {
+    let root = p.to_path_buf();
+    let p = cstr(p)?;
+    unsafe {
+        let ptr = libc::opendir(p.as_ptr() as *const u8);
+        if ptr.is_null() {
+            Err(Error::last_os_error())
+        } else {
+            let inner = InnerReadDir { dirp: Dir(ptr), root };
+            Ok(ReadDir(Arc::new(inner)))
+        }
+    }
+}
+
+pub fn unlink(p: &Path) -> io::Result<()> {
+    let p = cstr(p)?;
+    cvt(unsafe { libc::unlink(p.as_ptr() as *const u8) })?;
+    Ok(())
+}
+
+pub fn rename(old: &Path, new: &Path) -> io::Result<()> {
+    let old = cstr(old)?;
+    let new = cstr(new)?;
+    cvt(unsafe { libc::rename(old.as_ptr() as *const u8, new.as_ptr() as *const u8) })?;
+    Ok(())
+}
+
+pub fn set_perm(p: &Path, perm: FilePermissions) -> io::Result<()> {
+    let p = cstr(p)?;
+    cvt_r(|| unsafe { libc::chmod(p.as_ptr() as *const u8, perm.mode) })?;
+    Ok(())
+}
+
+pub fn rmdir(p: &Path) -> io::Result<()> {
+    let p = cstr(p)?;
+    cvt(unsafe { libc::rmdir(p.as_ptr() as *const u8) })?;
+    Ok(())
+}
+
+pub fn remove_dir_all(path: &Path) -> io::Result<()> {
+    let filetype = lstat(path)?.file_type();
+    if filetype.is_symlink() {
+        unlink(path)
+    } else {
+        remove_dir_all_recursive(path)
+    }
+}
+
+fn remove_dir_all_recursive(path: &Path) -> io::Result<()> {
+    for child in readdir(path)? {
+        let child = child?;
+        if child.file_type()?.is_dir() {
+            remove_dir_all_recursive(&child.path())?;
+        } else {
+            unlink(&child.path())?;
+        }
+    }
+    rmdir(path)
+}
+
+pub fn readlink(p: &Path) -> io::Result<PathBuf> {
+    let c_path = cstr(p)?;
+    let p = c_path.as_ptr() as *const u8;
+
+    let mut buf = Vec::with_capacity(256);
+
+    loop {
+        let buf_read = cvt(unsafe {
+            libc::readlink(p, buf.as_mut_ptr() as *mut _, buf.capacity())
+        })? as usize;
+
+        unsafe { buf.set_len(buf_read); }
+
+        if buf_read != buf.capacity() {
+            buf.shrink_to_fit();
+
+            return Ok(PathBuf::from(OsString::from_vec(buf)));
+        }
+
+        // Trigger the internal buffer resizing logic of `Vec` by requiring
+        // more space than the current capacity. The length is guaranteed to be
+        // the same as the capacity due to the if statement above.
+        buf.reserve(1);
+    }
+}
+
+pub fn symlink(src: &Path, dst: &Path) -> io::Result<()> {
+    let src = cstr(src)?;
+    let dst = cstr(dst)?;
+    cvt(unsafe { libc::symlink(src.as_ptr() as *const u8, dst.as_ptr() as *const u8) })?;
+    Ok(())
+}
+
+pub fn link(src: &Path, dst: &Path) -> io::Result<()> {
+    let src = cstr(src)?;
+    let dst = cstr(dst)?;
+    cvt(unsafe { libc::link(src.as_ptr() as *const u8, dst.as_ptr() as *const u8) })?;
+    Ok(())
+}
+
+pub fn stat(p: &Path) -> io::Result<FileAttr> {
+    let p = cstr(p)?;
+    let mut stat: stat64 = unsafe { mem::zeroed() };
+    cvt(unsafe {
+        stat64(p.as_ptr() as *const u8, &mut stat as *mut _ as *mut _)
+    })?;
+    Ok(FileAttr { stat: stat })
+}
+
+pub fn lstat(p: &Path) -> io::Result<FileAttr> {
+    let p = cstr(p)?;
+    let mut stat: stat64 = unsafe { mem::zeroed() };
+    cvt(unsafe {
+        lstat64(p.as_ptr() as *const u8, &mut stat as *mut _ as *mut _)
+    })?;
+    Ok(FileAttr { stat: stat })
+}
+
+pub fn canonicalize(p: &Path) -> io::Result<PathBuf> {
+    let path = CString::new(p.as_os_str().as_bytes())?;
+    let buf;
+    unsafe {
+        let r = libc::realpath(path.as_ptr() as *const u8, ptr::null_mut());
+        if r.is_null() {
+            return Err(io::Error::last_os_error())
+        }
+        buf = CStr::from_ptr(r as *const i8).to_bytes().to_vec();
+        libc::free(r as *mut _);
+    }
+    Ok(PathBuf::from(OsString::from_vec(buf)))
+}
+
+#[cfg(not(any(target_os = "linux", target_os = "android")))]
+pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
+    use fs::File;
+    if !from.is_file() {
+        return Err(Error::new(ErrorKind::InvalidInput,
+                              "the source path is not an existing regular file"))
+    }
+
+    let mut reader = File::open(from)?;
+    let mut writer = File::create(to)?;
+    let perm = reader.metadata()?.permissions();
+
+    let ret = io::copy(&mut reader, &mut writer)?;
+    writer.set_permissions(perm)?;
+    Ok(ret)
+}
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
+    use cmp;
+    use fs::File;
+    use sync::atomic::{AtomicBool, Ordering};
+
+    // Kernel prior to 4.5 don't have copy_file_range
+    // We store the availability in a global to avoid unneccessary syscalls
+    static HAS_COPY_FILE_RANGE: AtomicBool = AtomicBool::new(true);
+
+    unsafe fn copy_file_range(
+        fd_in: libc::c_int,
+        off_in: *mut libc::loff_t,
+        fd_out: libc::c_int,
+        off_out: *mut libc::loff_t,
+        len: libc::size_t,
+        flags: libc::c_uint,
+    ) -> libc::c_long {
+        libc::syscall(
+            libc::SYS_copy_file_range,
+            fd_in,
+            off_in,
+            fd_out,
+            off_out,
+            len,
+            flags,
+        )
+    }
+
+    if !from.is_file() {
+        return Err(Error::new(ErrorKind::InvalidInput,
+                              "the source path is not an existing regular file"))
+    }
+
+    let mut reader = File::open(from)?;
+    let mut writer = File::create(to)?;
+    let (perm, len) = {
+        let metadata = reader.metadata()?;
+        (metadata.permissions(), metadata.size())
+    };
+
+    let has_copy_file_range = HAS_COPY_FILE_RANGE.load(Ordering::Relaxed);
+    let mut written = 0u64;
+    while written < len {
+        let copy_result = if has_copy_file_range {
+            let bytes_to_copy = cmp::min(len - written, usize::max_value() as u64) as usize;
+            let copy_result = unsafe {
+                // We actually don't have to adjust the offsets,
+                // because copy_file_range adjusts the file offset automatically
+                cvt(copy_file_range(reader.as_raw_fd(),
+                                    ptr::null_mut(),
+                                    writer.as_raw_fd(),
+                                    ptr::null_mut(),
+                                    bytes_to_copy,
+                                    0)
+                    )
+            };
+            if let Err(ref copy_err) = copy_result {
+                match copy_err.raw_os_error() {
+                    Some(libc::ENOSYS) | Some(libc::EPERM) => {
+                        HAS_COPY_FILE_RANGE.store(false, Ordering::Relaxed);
+                    }
+                    _ => {}
+                }
+            }
+            copy_result
+        } else {
+            Err(io::Error::from_raw_os_error(libc::ENOSYS))
+        };
+        match copy_result {
+            Ok(ret) => written += ret as u64,
+            Err(err) => {
+                match err.raw_os_error() {
+                    Some(os_err) if os_err == libc::ENOSYS
+                                 || os_err == libc::EXDEV
+                                 || os_err == libc::EPERM => {
+                        // Try fallback io::copy if either:
+                        // - Kernel version is < 4.5 (ENOSYS)
+                        // - Files are mounted on different fs (EXDEV)
+                        // - copy_file_range is disallowed, for example by seccomp (EPERM)
+                        assert_eq!(written, 0);
+                        let ret = io::copy(&mut reader, &mut writer)?;
+                        writer.set_permissions(perm)?;
+                        return Ok(ret)
+                    },
+                    _ => return Err(err),
+                }
+            }
+        }
+    }
+    writer.set_permissions(perm)?;
+    Ok(written)
+}