nix/src/lib.rs

//! Rust friendly bindings to the various *nix system functions.
//!
//! Modules are structured according to the C header file that they would be
//! defined in.
#![crate_name = "nix"]
#![cfg(unix)]
#![allow(non_camel_case_types)]
// latest bitflags triggers a rustc bug with cross-crate macro expansions causing dead_code
// warnings even though the macro expands into something with allow(dead_code)
#![allow(dead_code)]
#![cfg_attr(test, deny(warnings))]
#![recursion_limit = "500"]
#![deny(unused)]
#![deny(unstable_features)]
#![deny(missing_copy_implementations)]
#![deny(missing_debug_implementations)]

// Re-exported external crates
pub use libc;

// Private internal modules
#[macro_use] mod macros;

// Public crates
#[cfg(not(target_os = "redox"))]
pub mod dir;
pub mod env;
pub mod errno;
#[deny(missing_docs)]
pub mod features;
pub mod fcntl;
#[deny(missing_docs)]
#[cfg(any(target_os = "android",
          target_os = "dragonfly",
          target_os = "freebsd",
          target_os = "ios",
          target_os = "linux",
          target_os = "macos",
          target_os = "netbsd",
          target_os = "openbsd"))]
pub mod ifaddrs;
#[cfg(any(target_os = "android",
          target_os = "linux"))]
pub mod kmod;
#[cfg(any(target_os = "android",
          target_os = "linux"))]
pub mod mount;
#[cfg(any(target_os = "dragonfly",
          target_os = "freebsd",
          target_os = "fushsia",
          target_os = "linux",
          target_os = "netbsd"))]
pub mod mqueue;
#[deny(missing_docs)]
#[cfg(not(target_os = "redox"))]
pub mod net;
#[deny(missing_docs)]
pub mod poll;
#[deny(missing_docs)]
#[cfg(not(any(target_os = "redox", target_os = "fuchsia")))]
pub mod pty;
pub mod sched;
pub mod sys;
pub mod time;
// This can be implemented for other platforms as soon as libc
// provides bindings for them.
#[cfg(all(target_os = "linux",
          any(target_arch = "x86", target_arch = "x86_64")))]
pub mod ucontext;
pub mod unistd;

/*
 *
 * ===== Result / Error =====
 *
 */

use libc::{c_char, PATH_MAX};

use std::{error, fmt, ptr, result};
use std::ffi::{CStr, OsStr};
use std::os::unix::ffi::OsStrExt;
use std::path::{Path, PathBuf};

use errno::Errno;

/// Nix Result Type
pub type Result<T> = result::Result<T, Error>;

/// Nix Error Type
///
/// The nix error type provides a common way of dealing with
/// various system system/libc calls that might fail.  Each
/// error has a corresponding errno (usually the one from the
/// underlying OS) to which it can be mapped in addition to
/// implementing other common traits.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum Error {
    Sys(Errno),
    InvalidPath,
    /// The operation involved a conversion to Rust's native String type, which failed because the
    /// string did not contain all valid UTF-8.
    InvalidUtf8,
    /// The operation is not supported by Nix, in this instance either use the libc bindings or
    /// consult the module documentation to see if there is a more appropriate interface available.
    UnsupportedOperation,
}

impl Error {
    /// Convert this `Error` to an [`Errno`](enum.Errno.html).
    ///
    /// # Example
    ///
    /// ```
    /// # use nix::Error;
    /// # use nix::errno::Errno;
    /// let e = Error::from(Errno::EPERM);
    /// assert_eq!(Some(Errno::EPERM), e.as_errno());
    /// ```
    pub fn as_errno(self) -> Option<Errno> {
        if let Error::Sys(e) = self {
            Some(e)
        } else {
            None
        }
    }

    /// Create a nix Error from a given errno
    pub fn from_errno(errno: Errno) -> Error {
        Error::Sys(errno)
    }

    /// Get the current errno and convert it to a nix Error
    pub fn last() -> Error {
        Error::Sys(Errno::last())
    }

    /// Create a new invalid argument error (`EINVAL`)
    pub fn invalid_argument() -> Error {
        Error::Sys(Errno::EINVAL)
    }

}

impl From<Errno> for Error {
    fn from(errno: Errno) -> Error { Error::from_errno(errno) }
}

impl From<std::string::FromUtf8Error> for Error {
    fn from(_: std::string::FromUtf8Error) -> Error { Error::InvalidUtf8 }
}

impl error::Error for Error {}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Error::InvalidPath => write!(f, "Invalid path"),
            Error::InvalidUtf8 => write!(f, "Invalid UTF-8 string"),
            Error::UnsupportedOperation => write!(f, "Unsupported Operation"),
            Error::Sys(errno) => write!(f, "{:?}: {}", errno, errno.desc()),
        }
    }
}

pub trait NixPath {
    fn is_empty(&self) -> bool;

    fn len(&self) -> usize;

    fn with_nix_path<T, F>(&self, f: F) -> Result<T>
        where F: FnOnce(&CStr) -> T;
}

impl NixPath for str {
    fn is_empty(&self) -> bool {
        NixPath::is_empty(OsStr::new(self))
    }

    fn len(&self) -> usize {
        NixPath::len(OsStr::new(self))
    }

    fn with_nix_path<T, F>(&self, f: F) -> Result<T>
        where F: FnOnce(&CStr) -> T {
            OsStr::new(self).with_nix_path(f)
        }
}

impl NixPath for OsStr {
    fn is_empty(&self) -> bool {
        self.as_bytes().is_empty()
    }

    fn len(&self) -> usize {
        self.as_bytes().len()
    }

    fn with_nix_path<T, F>(&self, f: F) -> Result<T>
        where F: FnOnce(&CStr) -> T {
            self.as_bytes().with_nix_path(f)
        }
}

impl NixPath for CStr {
    fn is_empty(&self) -> bool {
        self.to_bytes().is_empty()
    }

    fn len(&self) -> usize {
        self.to_bytes().len()
    }

    fn with_nix_path<T, F>(&self, f: F) -> Result<T>
            where F: FnOnce(&CStr) -> T {
        // Equivalence with the [u8] impl.
        if self.len() >= PATH_MAX as usize {
            return Err(Error::InvalidPath);
        }

        Ok(f(self))
    }
}

impl NixPath for [u8] {
    fn is_empty(&self) -> bool {
        self.is_empty()
    }

    fn len(&self) -> usize {
        self.len()
    }

    fn with_nix_path<T, F>(&self, f: F) -> Result<T>
            where F: FnOnce(&CStr) -> T {
        let mut buf = [0u8; PATH_MAX as usize];

        if self.len() >= PATH_MAX as usize {
            return Err(Error::InvalidPath);
        }

        match self.iter().position(|b| *b == 0) {
            Some(_) => Err(Error::InvalidPath),
            None => {
                unsafe {
                    // TODO: Replace with bytes::copy_memory. rust-lang/rust#24028
                    ptr::copy_nonoverlapping(self.as_ptr(), buf.as_mut_ptr(), self.len());
                    Ok(f(CStr::from_ptr(buf.as_ptr() as *const c_char)))
                }

            }
        }
    }
}

impl NixPath for Path {
    fn is_empty(&self) -> bool {
        NixPath::is_empty(self.as_os_str())
    }

    fn len(&self) -> usize {
        NixPath::len(self.as_os_str())
    }

    fn with_nix_path<T, F>(&self, f: F) -> Result<T> where F: FnOnce(&CStr) -> T {
        self.as_os_str().with_nix_path(f)
    }
}

impl NixPath for PathBuf {
    fn is_empty(&self) -> bool {
        NixPath::is_empty(self.as_os_str())
    }

    fn len(&self) -> usize {
        NixPath::len(self.as_os_str())
    }

    fn with_nix_path<T, F>(&self, f: F) -> Result<T> where F: FnOnce(&CStr) -> T {
        self.as_os_str().with_nix_path(f)
    }
}