flock.rs

// Copyright 2014-2015 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.

//! Simple file-locking apis for each OS.
//!
//! This is not meant to be in the standard library, it does nothing with
//! green/native threading. This is just a bare-bones enough solution for
//! librustdoc, it is not production quality at all.

#![allow(non_camel_case_types)]
use std::path::Path;

pub use self::imp::Lock;

#[cfg(unix)]
mod imp {
    use std::ffi::{CString, OsStr};
    use std::os::unix::prelude::*;
    use std::path::Path;
    use std::io;
    use libc;

    #[cfg(any(target_os = "linux", target_os = "android"))]
    mod os {
        use libc;

        #[repr(C)]
        pub struct flock {
            pub l_type: libc::c_short,
            pub l_whence: libc::c_short,
            pub l_start: libc::off_t,
            pub l_len: libc::off_t,
            pub l_pid: libc::pid_t,

            // not actually here, but brings in line with freebsd
            pub l_sysid: libc::c_int,
        }

        pub const F_RDLCK: libc::c_short = 0;
        pub const F_WRLCK: libc::c_short = 1;
        pub const F_UNLCK: libc::c_short = 2;
        pub const F_SETLK: libc::c_int = 6;
        pub const F_SETLKW: libc::c_int = 7;
    }

    #[cfg(target_os = "freebsd")]
    mod os {
        use libc;

        #[repr(C)]
        pub struct flock {
            pub l_start: libc::off_t,
            pub l_len: libc::off_t,
            pub l_pid: libc::pid_t,
            pub l_type: libc::c_short,
            pub l_whence: libc::c_short,
            pub l_sysid: libc::c_int,
        }

        pub const F_RDLCK: libc::c_short = 1;
        pub const F_UNLCK: libc::c_short = 2;
        pub const F_WRLCK: libc::c_short = 3;
        pub const F_SETLK: libc::c_int = 12;
        pub const F_SETLKW: libc::c_int = 13;
    }

    #[cfg(any(target_os = "dragonfly",
              target_os = "bitrig",
              target_os = "netbsd",
              target_os = "openbsd"))]
    mod os {
        use libc;

        #[repr(C)]
        pub struct flock {
            pub l_start: libc::off_t,
            pub l_len: libc::off_t,
            pub l_pid: libc::pid_t,
            pub l_type: libc::c_short,
            pub l_whence: libc::c_short,

            // not actually here, but brings in line with freebsd
            pub l_sysid: libc::c_int,
        }

        pub const F_RDLCK: libc::c_short = 1;
        pub const F_UNLCK: libc::c_short = 2;
        pub const F_WRLCK: libc::c_short = 3;
        pub const F_SETLK: libc::c_int = 8;
        pub const F_SETLKW: libc::c_int = 9;
    }

    #[cfg(target_os = "haiku")]
    mod os {
        use libc;

        #[repr(C)]
        pub struct flock {
            pub l_type: libc::c_short,
            pub l_whence: libc::c_short,
            pub l_start: libc::off_t,
            pub l_len: libc::off_t,
            pub l_pid: libc::pid_t,

            // not actually here, but brings in line with freebsd
            pub l_sysid: libc::c_int,
        }

        pub const F_RDLCK: libc::c_short = 0x0040;
        pub const F_UNLCK: libc::c_short = 0x0200;
        pub const F_WRLCK: libc::c_short = 0x0400;
        pub const F_SETLK: libc::c_int = 0x0080;
        pub const F_SETLKW: libc::c_int = 0x0100;
    }

    #[cfg(any(target_os = "macos", target_os = "ios"))]
    mod os {
        use libc;

        #[repr(C)]
        pub struct flock {
            pub l_start: libc::off_t,
            pub l_len: libc::off_t,
            pub l_pid: libc::pid_t,
            pub l_type: libc::c_short,
            pub l_whence: libc::c_short,

            // not actually here, but brings in line with freebsd
            pub l_sysid: libc::c_int,
        }

        pub const F_RDLCK: libc::c_short = 1;
        pub const F_UNLCK: libc::c_short = 2;
        pub const F_WRLCK: libc::c_short = 3;
        pub const F_SETLK: libc::c_int = 8;
        pub const F_SETLKW: libc::c_int = 9;
    }

    #[cfg(target_os = "solaris")]
    mod os {
        use libc;

        #[repr(C)]
        pub struct flock {
            pub l_type: libc::c_short,
            pub l_whence: libc::c_short,
            pub l_start: libc::off_t,
            pub l_len: libc::off_t,
            pub l_sysid: libc::c_int,
            pub l_pid: libc::pid_t,
        }

        pub const F_RDLCK: libc::c_short = 1;
        pub const F_WRLCK: libc::c_short = 2;
        pub const F_UNLCK: libc::c_short = 3;
        pub const F_SETLK: libc::c_int = 6;
        pub const F_SETLKW: libc::c_int = 7;
    }

    #[derive(Debug)]
    pub struct Lock {
        fd: libc::c_int,
    }

    impl Lock {
        pub fn new(p: &Path,
                   wait: bool,
                   create: bool,
                   exclusive: bool)
                   -> io::Result<Lock> {
            let os: &OsStr = p.as_ref();
            let buf = CString::new(os.as_bytes()).unwrap();
            let open_flags = if create {
                libc::O_RDWR | libc::O_CREAT
            } else {
                libc::O_RDWR
            };

            let fd = unsafe {
                libc::open(buf.as_ptr(), open_flags,
                           libc::S_IRWXU as libc::c_int)
            };

            if fd < 0 {
                return Err(io::Error::last_os_error());
            }

            let lock_type = if exclusive {
                os::F_WRLCK
            } else {
                os::F_RDLCK
            };

            let flock = os::flock {
                l_start: 0,
                l_len: 0,
                l_pid: 0,
                l_whence: libc::SEEK_SET as libc::c_short,
                l_type: lock_type,
                l_sysid: 0,
            };
            let cmd = if wait { os::F_SETLKW } else { os::F_SETLK };
            let ret = unsafe {
                libc::fcntl(fd, cmd, &flock)
            };
            if ret == -1 {
                let err = io::Error::last_os_error();
                unsafe { libc::close(fd); }
                Err(err)
            } else {
                Ok(Lock { fd: fd })
            }
        }
    }

    impl Drop for Lock {
        fn drop(&mut self) {
            let flock = os::flock {
                l_start: 0,
                l_len: 0,
                l_pid: 0,
                l_whence: libc::SEEK_SET as libc::c_short,
                l_type: os::F_UNLCK,
                l_sysid: 0,
            };
            unsafe {
                libc::fcntl(self.fd, os::F_SETLK, &flock);
                libc::close(self.fd);
            }
        }
    }
}

#[cfg(windows)]
#[allow(bad_style)]
mod imp {
    use std::io;
    use std::mem;
    use std::os::windows::prelude::*;
    use std::os::windows::raw::HANDLE;
    use std::path::Path;
    use std::fs::{File, OpenOptions};
    use std::os::raw::{c_ulong, c_ulonglong, c_int};

    type DWORD = c_ulong;
    type BOOL = c_int;
    type ULONG_PTR = c_ulonglong;

    type LPOVERLAPPED = *mut OVERLAPPED;
    const LOCKFILE_EXCLUSIVE_LOCK: DWORD = 0x00000002;
    const LOCKFILE_FAIL_IMMEDIATELY: DWORD = 0x00000001;

    const FILE_SHARE_DELETE: DWORD = 0x4;
    const FILE_SHARE_READ: DWORD = 0x1;
    const FILE_SHARE_WRITE: DWORD = 0x2;

    #[repr(C)]
    struct OVERLAPPED {
        Internal: ULONG_PTR,
        InternalHigh: ULONG_PTR,
        Offset: DWORD,
        OffsetHigh: DWORD,
        hEvent: HANDLE,
    }

    extern "system" {
        fn LockFileEx(hFile: HANDLE,
                      dwFlags: DWORD,
                      dwReserved: DWORD,
                      nNumberOfBytesToLockLow: DWORD,
                      nNumberOfBytesToLockHigh: DWORD,
                      lpOverlapped: LPOVERLAPPED) -> BOOL;
    }

    #[derive(Debug)]
    pub struct Lock {
        _file: File,
    }

    impl Lock {
        pub fn new(p: &Path,
                   wait: bool,
                   create: bool,
                   exclusive: bool)
                   -> io::Result<Lock> {
            assert!(p.parent().unwrap().exists(),
                "Parent directory of lock-file must exist: {}",
                p.display());

            let share_mode = FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE;

            let mut open_options = OpenOptions::new();
            open_options.read(true)
                        .share_mode(share_mode);

            if create {
                open_options.create(true)
                            .write(true);
            }

            debug!("Attempting to open lock file `{}`", p.display());
            let file = match open_options.open(p) {
                Ok(file) => {
                    debug!("Lock file opened successfully");
                    file
                }
                Err(err) => {
                    debug!("Error opening lock file: {}", err);
                    return Err(err)
                }
            };

            let ret = unsafe {
                let mut overlapped: OVERLAPPED = mem::zeroed();

                let mut dwFlags = 0;
                if !wait {
                    dwFlags |= LOCKFILE_FAIL_IMMEDIATELY;
                }

                if exclusive {
                    dwFlags |= LOCKFILE_EXCLUSIVE_LOCK;
                }

                debug!("Attempting to acquire lock on lock file `{}`",
                       p.display());
                LockFileEx(file.as_raw_handle(),
                           dwFlags,
                           0,
                           0xFFFF_FFFF,
                           0xFFFF_FFFF,
                           &mut overlapped)
            };
            if ret == 0 {
                let err = io::Error::last_os_error();
                debug!("Failed acquiring file lock: {}", err);
                Err(err)
            } else {
                debug!("Successfully acquired lock.");
                Ok(Lock { _file: file })
            }
        }
    }

    // Note that we don't need a Drop impl on the Windows: The file is unlocked
    // automatically when it's closed.
}

impl imp::Lock {
    pub fn panicking_new(p: &Path,
                         wait: bool,
                         create: bool,
                         exclusive: bool)
                         -> Lock {
        Lock::new(p, wait, create, exclusive).unwrap_or_else(|err| {
            panic!("could not lock `{}`: {}", p.display(), err);
        })
    }
}