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#![cfg_attr(not(feature = "std"), no_std)] //! API to use files as a lock. Supports non-std crates by disabling feature //! `std`. //! //! # Types //! Currently, only one type is provided: [`LockFile`]. It does not destroy the //! file after closed and behaviour on locking different file handles owned by //! the same process is different between Unix and Windows. # Example: //! //! # Example //! ``` //! use fslock::LockFile; //! fn main() -> Result<(), fslock::Error> { //! //! let mut file = LockFile::open("mylock.test")?; //! file.lock()?; //! do_stuff(); //! file.unlock()?; //! //! Ok(()) //! } //! # fn do_stuff() { //! # // doing stuff here. //! # } //! ``` #[cfg(unix)] mod unix; #[cfg(unix)] use crate::unix as sys; #[cfg(windows)] mod windows; #[cfg(windows)] use crate::windows as sys; pub use crate::sys::{Error, OsStr, OsString}; use core::{fmt, ops::Deref}; impl fmt::Debug for OsString { fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { write!(fmt, "{:?}", self.as_ref()) } } impl fmt::Display for OsString { fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { write!(fmt, "{}", self.as_ref()) } } impl Deref for OsString { type Target = OsStr; fn deref(&self) -> &OsStr { self.as_ref() } } /// Either borrowed or owned allocation of an OS-native string. #[derive(Debug)] pub enum EitherOsStr<'str> { /// Borrowed allocation. Borrowed(&'str OsStr), /// Owned allocation. Owned(OsString), } impl<'str> AsRef<OsStr> for EitherOsStr<'str> { fn as_ref(&self) -> &OsStr { match self { Self::Borrowed(str) => str, Self::Owned(string) => string.as_ref(), } } } impl<'str> Deref for EitherOsStr<'str> { type Target = OsStr; fn deref(&self) -> &OsStr { self.as_ref() } } /// Conversion of anything into an owned OS-native string. If allocation fails, /// an error shall be returned. pub trait IntoOsString { /// Converts with possible allocation error. fn into_os_string(self) -> Result<OsString, Error>; } impl IntoOsString for OsString { fn into_os_string(self) -> Result<OsString, Error> { Ok(self) } } impl<'str> IntoOsString for EitherOsStr<'str> { fn into_os_string(self) -> Result<OsString, Error> { match self { Self::Borrowed(str) => str.into_os_string(), Self::Owned(string) => Ok(string), } } } impl<'str> IntoOsString for &'str str { fn into_os_string(self) -> Result<OsString, Error> { self.to_os_str()?.into_os_string() } } /// Conversion of anything to an either borrowed or owned OS-native string. If /// allocation fails, an error shall be returned. pub trait ToOsStr { /// Converts with possible allocation error. fn to_os_str(&self) -> Result<EitherOsStr, Error>; } impl ToOsStr for OsStr { fn to_os_str(&self) -> Result<EitherOsStr, Error> { Ok(EitherOsStr::Borrowed(self)) } } impl ToOsStr for OsString { fn to_os_str(&self) -> Result<EitherOsStr, Error> { Ok(EitherOsStr::Borrowed(self.as_ref())) } } #[derive(Debug)] /// A handle to a file that is lockable. Does not delete the file. /// /// # Multiple Handles/Descriptors To The Same File /// Windows will treat each handle as having their own lock, while Unix will /// have locks on a file for the whole process. This means that on Windows you /// may open a file, lock it, open it again, and when you try yo lock the second /// handle, it will block until the first lock is released. Meanwhile, unix will /// look if your process already owns the look, it will see that you already /// locked the file, and simply return as you already have it! It will only /// block if there is a different process holding the lock. Also, unlocking one /// file descriptor will unlock the file for the whole process. /// /// # Example /// ``` /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// file.lock()?; /// do_stuff(); /// file.unlock()?; /// /// # Ok(()) /// # } /// # fn do_stuff() { /// # // doing stuff here. /// # } /// ``` pub struct LockFile { locked: bool, desc: sys::FileDesc, } impl LockFile { /// Opens a file for locking. On Unix, if the path is nul-terminated (ends /// with 0), no extra allocation will be made. /// /// # Panics /// Panics if the path contains a nul-byte in a place other than the end. /// /// # Example /// /// ``` /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// /// # Ok(()) /// # } /// ``` /// /// # Panicking Example /// /// ```should_panic /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("my\0lock")?; /// /// # Ok(()) /// # } /// ``` pub fn open<P>(path: &P) -> Result<Self, Error> where P: ToOsStr + ?Sized, { let path = path.to_os_str()?; let desc = sys::open(path.as_ref())?; Ok(Self { locked: false, desc }) } /// Locks this file. Blocks while it is not possible to lock (i.e. someone /// else already owns a lock. After locked, if no attempt to unlock is made, /// it will be automatically unlocked on the file handle drop. /// /// # Panics /// Panics if this handle already owns the file. /// /// # Example /// /// ``` /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// file.lock()?; /// do_stuff(); /// file.unlock()?; /// /// # Ok(()) /// # } /// # fn do_stuff() { /// # // doing stuff here. /// # } /// ``` /// /// # Panicking Example /// /// ```should_panic /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// file.lock()?; /// file.lock()?; /// /// # Ok(()) /// # } /// ``` pub fn lock(&mut self) -> Result<(), Error> { if self.locked { panic!("Cannot lock if already owning a lock"); } sys::lock(self.desc)?; self.locked = true; Ok(()) } /// Locks this file. Does NOT block if it is not possible to lock (i.e. /// someone else already owns a lock. After locked, if no attempt to /// unlock is made, it will be automatically unlocked on the file handle /// drop. /// /// # Panics /// Panics if this handle already owns the file. /// /// # Example /// /// ``` /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// if file.try_lock()? { /// do_stuff(); /// file.unlock()?; /// } /// /// # Ok(()) /// # } /// # fn do_stuff() { /// # // doing stuff here. /// # } /// ``` /// /// # Panicking Example /// /// ```should_panic /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// file.lock()?; /// file.try_lock()?; /// /// # Ok(()) /// # } /// ``` pub fn try_lock(&mut self) -> Result<bool, Error> { if self.locked { panic!("Cannot lock if already owning a lock"); } let locked = sys::try_lock(self.desc)?; if locked { self.locked = true; } Ok(locked) } /// Returns whether this file handle owns the lock. /// /// # Example /// ``` /// use fslock::LockFile; /// # fn main() -> Result<(), fslock::Error> { /// /// let mut file = LockFile::open("mylock.test")?; /// do_stuff_with_lock(&mut file); /// if !file.owns_lock() { /// file.lock()?; /// do_stuff(); /// file.unlock()?; /// } /// /// # Ok(()) /// # } /// # fn do_stuff_with_lock(_lock: &mut LockFile) { /// # // doing stuff here. /// # } /// # fn do_stuff() { /// # // doing stuff here. /// # } /// ``` pub fn owns_lock(&self) -> bool { self.locked } /// Unlocks this file. This file handle must own the file lock. If not /// called manually, it is automatically called on `drop`. /// /// # Panics /// Panics if this handle does not own the file. /// /// # Example /// /// ``` /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// file.lock()?; /// do_stuff(); /// file.unlock()?; /// /// # Ok(()) /// # } /// # fn do_stuff() { /// # // doing stuff here. /// # } /// ``` /// /// # Panicking Example /// /// ```should_panic /// # fn main() -> Result<(), fslock::Error> { /// use fslock::LockFile; /// /// let mut file = LockFile::open("mylock.test")?; /// file.unlock()?; /// /// # Ok(()) /// # } /// ``` pub fn unlock(&mut self) -> Result<(), Error> { if !self.locked { panic!("Attempted to unlock already locked lockfile"); } sys::unlock(self.desc)?; self.locked = false; Ok(()) } } impl Drop for LockFile { fn drop(&mut self) { if self.locked { let _ = sys::unlock(self.desc); } sys::close(self.desc); } }