#![unstable(reason = "not public", issue = "0", feature = "fd")]

use io::{self, Read};
use mem;
use sys::{cvt, syscall};
use sys_common::AsInner;

pub struct FileDesc {
    fd: usize,
}

impl FileDesc {
    pub fn new(fd: usize) -> FileDesc {
        FileDesc { fd }
    }

    pub fn raw(&self) -> usize { self.fd }

    /// Extracts the actual file descriptor without closing it.
    pub fn into_raw(self) -> usize {
        let fd = self.fd;
        mem::forget(self);
        fd
    }

    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
        cvt(syscall::read(self.fd, buf))
    }

    pub fn read_to_end(&self, buf: &mut Vec<u8>) -> io::Result<usize> {
        let mut me = self;
        (&mut me).read_to_end(buf)
    }

    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
        cvt(syscall::write(self.fd, buf))
    }

    pub fn duplicate(&self) -> io::Result<FileDesc> {
        self.duplicate_path(&[])
    }
    pub fn duplicate_path(&self, path: &[u8]) -> io::Result<FileDesc> {
        let new_fd = cvt(syscall::dup(self.fd, path))?;
        Ok(FileDesc::new(new_fd))
    }

    pub fn nonblocking(&self) -> io::Result<bool> {
        let flags = cvt(syscall::fcntl(self.fd, syscall::F_GETFL, 0))?;
        Ok(flags & syscall::O_NONBLOCK == syscall::O_NONBLOCK)
    }

    pub fn set_cloexec(&self) -> io::Result<()> {
        let mut flags = cvt(syscall::fcntl(self.fd, syscall::F_GETFD, 0))?;
        flags |= syscall::O_CLOEXEC;
        cvt(syscall::fcntl(self.fd, syscall::F_SETFD, flags)).and(Ok(()))
    }

    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
        let mut flags = cvt(syscall::fcntl(self.fd, syscall::F_GETFL, 0))?;
        if nonblocking {
            flags |= syscall::O_NONBLOCK;
        } else {
            flags &= !syscall::O_NONBLOCK;
        }
        cvt(syscall::fcntl(self.fd, syscall::F_SETFL, flags)).and(Ok(()))
    }
}

impl<'a> Read for &'a FileDesc {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        (**self).read(buf)
    }
}

impl AsInner<usize> for FileDesc {
    fn as_inner(&self) -> &usize { &self.fd }
}

impl Drop for FileDesc {
    fn drop(&mut self) {
        // Note that errors are ignored when closing a file descriptor. The
        // reason for this is that if an error occurs we don't actually know if
        // the file descriptor was closed or not, and if we retried (for
        // something like EINTR), we might close another valid file descriptor
        // (opened after we closed ours.
        let _ = syscall::close(self.fd);
    }
}
