compiler/rustc_data_structures/src/flock.rs

   1 //! Simple file-locking apis for each OS.
   2 //!
   3 //! This is not meant to be in the standard library, it does nothing with
   4 //! green/native threading. This is just a bare-bones enough solution for
   5 //! librustdoc, it is not production quality at all.
   6
   7 #![allow(non_camel_case_types)]
   8 #![allow(nonstandard_style)]
   9
  10 use std::fs::{File, OpenOptions};
  11 use std::io;
  12 use std::path::Path;
  13
  14 cfg_if! {
  15     // We use `flock` rather than `fcntl` on Linux, because WSL1 does not support
  16     // `fcntl`-style advisory locks properly (rust-lang/rust#72157).
  17     //
  18     // For other Unix targets we still use `fcntl` because it's more portable than
  19     // `flock`.
  20     if #[cfg(target_os = "linux")] {
  21         use std::os::unix::prelude::*;
  22
  23         #[derive(Debug)]
  24         pub struct Lock {
  25             _file: File,
  26         }
  27
  28         impl Lock {
  29             pub fn new(p: &Path,
  30                        wait: bool,
  31                        create: bool,
  32                        exclusive: bool)
  33                        -> io::Result<Lock> {
  34                 let file = OpenOptions::new()
  35                     .read(true)
  36                     .write(true)
  37                     .create(create)
  38                     .mode(libc::S_IRWXU as u32)
  39                     .open(p)?;
  40
  41                 let mut operation = if exclusive {
  42                     libc::LOCK_EX
  43                 } else {
  44                     libc::LOCK_SH
  45                 };
  46                 if !wait {
  47                     operation |= libc::LOCK_NB
  48                 }
  49
  50                 let ret = unsafe { libc::flock(file.as_raw_fd(), operation) };
  51                 if ret == -1 {
  52                     Err(io::Error::last_os_error())
  53                 } else {
  54                     Ok(Lock { _file: file })
  55                 }
  56             }
  57         }
  58
  59         // Note that we don't need a Drop impl to execute `flock(fd, LOCK_UN)`. Lock acquired by
  60         // `flock` is associated with the file descriptor and closing the file release it
  61         // automatically.
  62     } else if #[cfg(unix)] {
  63         use std::mem;
  64         use std::os::unix::prelude::*;
  65
  66         #[derive(Debug)]
  67         pub struct Lock {
  68             file: File,
  69         }
  70
  71         impl Lock {
  72             pub fn new(p: &Path,
  73                        wait: bool,
  74                        create: bool,
  75                        exclusive: bool)
  76                        -> io::Result<Lock> {
  77                 let file = OpenOptions::new()
  78                     .read(true)
  79                     .write(true)
  80                     .create(create)
  81                     .mode(libc::S_IRWXU as u32)
  82                     .open(p)?;
  83
  84                 let lock_type = if exclusive {
  85                     libc::F_WRLCK
  86                 } else {
  87                     libc::F_RDLCK
  88                 };
  89
  90                 let mut flock: libc::flock = unsafe { mem::zeroed() };
  91                 flock.l_type = lock_type as libc::c_short;
  92                 flock.l_whence = libc::SEEK_SET as libc::c_short;
  93                 flock.l_start = 0;
  94                 flock.l_len = 0;
  95
  96                 let cmd = if wait { libc::F_SETLKW } else { libc::F_SETLK };
  97                 let ret = unsafe {
  98                     libc::fcntl(file.as_raw_fd(), cmd, &flock)
  99                 };
 100                 if ret == -1 {
 101                     Err(io::Error::last_os_error())
 102                 } else {
 103                     Ok(Lock { file })
 104                 }
 105             }
 106         }
 107
 108         impl Drop for Lock {
 109             fn drop(&mut self) {
 110                 let mut flock: libc::flock = unsafe { mem::zeroed() };
 111                 flock.l_type = libc::F_UNLCK as libc::c_short;
 112                 flock.l_whence = libc::SEEK_SET as libc::c_short;
 113                 flock.l_start = 0;
 114                 flock.l_len = 0;
 115
 116                 unsafe {
 117                     libc::fcntl(self.file.as_raw_fd(), libc::F_SETLK, &flock);
 118                 }
 119             }
 120         }
 121     } else if #[cfg(windows)] {
 122         use std::mem;
 123         use std::os::windows::prelude::*;
 124
 125         use winapi::um::minwinbase::{OVERLAPPED, LOCKFILE_FAIL_IMMEDIATELY, LOCKFILE_EXCLUSIVE_LOCK};
 126         use winapi::um::fileapi::LockFileEx;
 127         use winapi::um::winnt::{FILE_SHARE_DELETE, FILE_SHARE_READ, FILE_SHARE_WRITE};
 128
 129         #[derive(Debug)]
 130         pub struct Lock {
 131             _file: File,
 132         }
 133
 134         impl Lock {
 135             pub fn new(p: &Path,
 136                        wait: bool,
 137                        create: bool,
 138                        exclusive: bool)
 139                        -> io::Result<Lock> {
 140                 assert!(p.parent().unwrap().exists(),
 141                     "Parent directory of lock-file must exist: {}",
 142                     p.display());
 143
 144                 let share_mode = FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE;
 145
 146                 let mut open_options = OpenOptions::new();
 147                 open_options.read(true)
 148                             .share_mode(share_mode);
 149
 150                 if create {
 151                     open_options.create(true)
 152                                 .write(true);
 153                 }
 154
 155                 debug!("attempting to open lock file `{}`", p.display());
 156                 let file = match open_options.open(p) {
 157                     Ok(file) => {
 158                         debug!("lock file opened successfully");
 159                         file
 160                     }
 161                     Err(err) => {
 162                         debug!("error opening lock file: {}", err);
 163                         return Err(err)
 164                     }
 165                 };
 166
 167                 let ret = unsafe {
 168                     let mut overlapped: OVERLAPPED = mem::zeroed();
 169
 170                     let mut dwFlags = 0;
 171                     if !wait {
 172                         dwFlags |= LOCKFILE_FAIL_IMMEDIATELY;
 173                     }
 174
 175                     if exclusive {
 176                         dwFlags |= LOCKFILE_EXCLUSIVE_LOCK;
 177                     }
 178
 179                     debug!("attempting to acquire lock on lock file `{}`",
 180                            p.display());
 181                     LockFileEx(file.as_raw_handle(),
 182                                dwFlags,
 183                                0,
 184                                0xFFFF_FFFF,
 185                                0xFFFF_FFFF,
 186                                &mut overlapped)
 187                 };
 188                 if ret == 0 {
 189                     let err = io::Error::last_os_error();
 190                     debug!("failed acquiring file lock: {}", err);
 191                     Err(err)
 192                 } else {
 193                     debug!("successfully acquired lock");
 194                     Ok(Lock { _file: file })
 195                 }
 196             }
 197         }
 198
 199         // Note that we don't need a Drop impl on the Windows: The file is unlocked
 200         // automatically when it's closed.
 201     } else {
 202         #[derive(Debug)]
 203         pub struct Lock(());
 204
 205         impl Lock {
 206             pub fn new(_p: &Path, _wait: bool, _create: bool, _exclusive: bool)
 207                 -> io::Result<Lock>
 208             {
 209                 let msg = "file locks not supported on this platform";
 210                 Err(io::Error::new(io::ErrorKind::Other, msg))
 211             }
 212         }
 213     }
 214 }