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Locking documentation updates #136876

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merged 4 commits into from
Feb 19, 2025
Merged

Locking documentation updates #136876

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16abb39
Reword file lock documentation to clarify advisory vs mandatory
joshtriplett Feb 11, 2025
bc59397
Document that locking a file fails on Windows if the file is opened o…
joshtriplett Feb 11, 2025
35674ef
Clarify that locking on Windows also works for files opened with `.re…
joshtriplett Feb 18, 2025
ec2034d
Reorder "This lock may be advisory or mandatory." earlier in the lock…
joshtriplett Feb 18, 2025
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96 changes: 58 additions & 38 deletions library/std/src/fs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -624,20 +624,20 @@ impl File {
self.inner.datasync()
}

/// Acquire an exclusive advisory lock on the file. Blocks until the lock can be acquired.
/// Acquire an exclusive lock on the file. Blocks until the lock can be acquired.
///
/// This acquires an exclusive advisory lock; no other file handle to this file may acquire
/// another lock.
/// This acquires an exclusive lock; no other file handle to this file may acquire another lock.
///
/// If this file handle/descriptor, or a clone of it, already holds an advisory lock the exact
/// behavior is unspecified and platform dependent, including the possibility that it will
/// deadlock. However, if this method returns, then an exclusive lock is held.
/// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
/// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
/// other methods, such as [`read`] and [`write`] are platform specific, and it may or may not
/// cause non-lockholders to block.
///
/// If the file not open for writing, it is unspecified whether this function returns an error.
/// If this file handle/descriptor, or a clone of it, already holds an lock the exact behavior
/// is unspecified and platform dependent, including the possibility that it will deadlock.
/// However, if this method returns, then an exclusive lock is held.
///
/// Note, this is an advisory lock meant to interact with [`lock_shared`], [`try_lock`],
/// [`try_lock_shared`], and [`unlock`]. Its interactions with other methods, such as [`read`]
/// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
/// If the file not open for writing, it is unspecified whether this function returns an error.
///
/// The lock will be released when this file (along with any other file descriptors/handles
/// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
Expand All @@ -648,8 +648,12 @@ impl File {
/// and the `LockFileEx` function on Windows with the `LOCKFILE_EXCLUSIVE_LOCK` flag. Note that,
/// this [may change in the future][changes].
///
/// On Windows, locking a file will fail if the file is opened only for append. To lock a file,
/// open it with one of `.read(true)`, `.read(true).append(true)`, or `.write(true)`.
///
/// [changes]: io#platform-specific-behavior
///
/// [`lock`]: File::lock
/// [`lock_shared`]: File::lock_shared
/// [`try_lock`]: File::try_lock
/// [`try_lock_shared`]: File::try_lock_shared
Expand All @@ -674,18 +678,19 @@ impl File {
self.inner.lock()
}

/// Acquire a shared (non-exclusive) advisory lock on the file. Blocks until the lock can be acquired.
/// Acquire a shared (non-exclusive) lock on the file. Blocks until the lock can be acquired.
///
/// This acquires a shared advisory lock; more than one file handle may hold a shared lock, but
/// none may hold an exclusive lock at the same time.
/// This acquires a shared lock; more than one file handle may hold a shared lock, but none may
/// hold an exclusive lock at the same time.
///
/// If this file handle/descriptor, or a clone of it, already holds an advisory lock, the exact
/// behavior is unspecified and platform dependent, including the possibility that it will
/// deadlock. However, if this method returns, then a shared lock is held.
/// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
/// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
/// other methods, such as [`read`] and [`write`] are platform specific, and it may or may not
/// cause non-lockholders to block.
///
/// Note, this is an advisory lock meant to interact with [`lock`], [`try_lock`],
/// [`try_lock_shared`], and [`unlock`]. Its interactions with other methods, such as [`read`]
/// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
/// If this file handle/descriptor, or a clone of it, already holds an lock, the exact behavior
/// is unspecified and platform dependent, including the possibility that it will deadlock.
/// However, if this method returns, then a shared lock is held.
///
/// The lock will be released when this file (along with any other file descriptors/handles
/// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
Expand All @@ -696,9 +701,13 @@ impl File {
/// and the `LockFileEx` function on Windows. Note that, this
/// [may change in the future][changes].
///
/// On Windows, locking a file will fail if the file is opened only for append. To lock a file,
/// open it with one of `.read(true)`, `.read(true).append(true)`, or `.write(true)`.
///
/// [changes]: io#platform-specific-behavior
///
/// [`lock`]: File::lock
/// [`lock_shared`]: File::lock_shared
/// [`try_lock`]: File::try_lock
/// [`try_lock_shared`]: File::try_lock_shared
/// [`unlock`]: File::unlock
Expand All @@ -722,24 +731,23 @@ impl File {
self.inner.lock_shared()
}

/// Try to acquire an exclusive advisory lock on the file.
/// Try to acquire an exclusive lock on the file.
///
/// Returns `Ok(false)` if a different lock is already held on this file (via another
/// handle/descriptor).
///
/// This acquires an exclusive advisory lock; no other file handle to this file may acquire
/// another lock.
/// This acquires an exclusive lock; no other file handle to this file may acquire another lock.
///
/// If this file handle/descriptor, or a clone of it, already holds an advisory lock, the exact
/// behavior is unspecified and platform dependent, including the possibility that it will
/// deadlock. However, if this method returns `Ok(true)`, then it has acquired an exclusive
/// lock.
/// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
/// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
/// other methods, such as [`read`] and [`write`] are platform specific, and it may or may not
/// cause non-lockholders to block.
///
/// If the file not open for writing, it is unspecified whether this function returns an error.
/// If this file handle/descriptor, or a clone of it, already holds an lock, the exact behavior
/// is unspecified and platform dependent, including the possibility that it will deadlock.
/// However, if this method returns `Ok(true)`, then it has acquired an exclusive lock.
///
/// Note, this is an advisory lock meant to interact with [`lock`], [`lock_shared`],
/// [`try_lock_shared`], and [`unlock`]. Its interactions with other methods, such as [`read`]
/// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
/// If the file not open for writing, it is unspecified whether this function returns an error.
///
/// The lock will be released when this file (along with any other file descriptors/handles
/// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
Expand All @@ -751,10 +759,14 @@ impl File {
/// and `LOCKFILE_FAIL_IMMEDIATELY` flags. Note that, this
/// [may change in the future][changes].
///
/// On Windows, locking a file will fail if the file is opened only for append. To lock a file,
/// open it with one of `.read(true)`, `.read(true).append(true)`, or `.write(true)`.
///
/// [changes]: io#platform-specific-behavior
///
/// [`lock`]: File::lock
/// [`lock_shared`]: File::lock_shared
/// [`try_lock`]: File::try_lock
/// [`try_lock_shared`]: File::try_lock_shared
/// [`unlock`]: File::unlock
/// [`read`]: Read::read
Expand All @@ -777,22 +789,23 @@ impl File {
self.inner.try_lock()
}

/// Try to acquire a shared (non-exclusive) advisory lock on the file.
/// Try to acquire a shared (non-exclusive) lock on the file.
///
/// Returns `Ok(false)` if an exclusive lock is already held on this file (via another
/// handle/descriptor).
///
/// This acquires a shared advisory lock; more than one file handle may hold a shared lock, but
/// none may hold an exclusive lock at the same time.
/// This acquires a shared lock; more than one file handle may hold a shared lock, but none may
/// hold an exclusive lock at the same time.
///
/// If this file handle, or a clone of it, already holds an advisory lock, the exact behavior is
/// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
/// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
/// other methods, such as [`read`] and [`write`] are platform specific, and it may or may not
/// cause non-lockholders to block.
///
/// If this file handle, or a clone of it, already holds an lock, the exact behavior is
/// unspecified and platform dependent, including the possibility that it will deadlock.
/// However, if this method returns `Ok(true)`, then it has acquired a shared lock.
///
/// Note, this is an advisory lock meant to interact with [`lock`], [`try_lock`],
/// [`try_lock`], and [`unlock`]. Its interactions with other methods, such as [`read`]
/// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
///
/// The lock will be released when this file (along with any other file descriptors/handles
/// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
///
Expand All @@ -803,11 +816,15 @@ impl File {
/// `LOCKFILE_FAIL_IMMEDIATELY` flag. Note that, this
/// [may change in the future][changes].
///
/// On Windows, locking a file will fail if the file is opened only for append. To lock a file,
/// open it with one of `.read(true)`, `.read(true).append(true)`, or `.write(true)`.
///
/// [changes]: io#platform-specific-behavior
///
/// [`lock`]: File::lock
/// [`lock_shared`]: File::lock_shared
/// [`try_lock`]: File::try_lock
/// [`try_lock_shared`]: File::try_lock_shared
/// [`unlock`]: File::unlock
/// [`read`]: Read::read
/// [`write`]: Write::write
Expand Down Expand Up @@ -844,6 +861,9 @@ impl File {
/// and the `UnlockFile` function on Windows. Note that, this
/// [may change in the future][changes].
///
/// On Windows, locking a file will fail if the file is opened only for append. To lock a file,
/// open it with one of `.read(true)`, `.read(true).append(true)`, or `.write(true)`.
///
/// [changes]: io#platform-specific-behavior
///
/// # Examples
Expand Down
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