Struct advisory_lock::AdvisoryFileLock

pub struct AdvisoryFileLock { /* fields omitted */ }

An advisory lock for files.

An advisory lock provides a mutual-exclusion mechanism among processes which explicitly acquires and releases the lock. Processes that are not aware of the lock will ignore it.

AdvisoryFileLock provides following features:

• Blocking or non-blocking operations.
• Shared or exclusive modes.
• All operations are thread-safe.

Notes

AdvisoryFileLock has following limitations:

• Locks are allowed only on files, but not directories.

Implementations

impl AdvisoryFileLock

pub fn new<P: AsRef<Path>>(
    path: P,
    file_lock_mode: FileLockMode
) -> Result<Self, FileLockError>

Create a new FileLock.

pub fn is_shared(&self) -> bool

Return true if the advisory lock is acquired by shared mode.

pub fn is_exclusive(&self) -> bool

Return true if the advisory lock is acquired by exclusive mode.

pub fn lock(&mut self) -> Result<(), FileLockError>

Acquire the advisory file lock.

lock is blocking; it will block the current thread until it succeeds or errors.

pub fn try_lock(&mut self) -> Result<(), FileLockError>

Try to acquire the advisory file lock.

try_lock returns immediately.

pub fn unlock(&mut self) -> Result<(), FileLockError>

Unlock this advisory file lock.

Methods from Deref<Target = File>

pub fn sync_all(&self) -> Result<(), Error>

Attempts to sync all OS-internal metadata to disk.

This function will attempt to ensure that all in-memory data reaches the filesystem before returning.

This can be used to handle errors that would otherwise only be caught when the File is closed. Dropping a file will ignore errors in synchronizing this in-memory data.

Examples

use std::fs::File;
use std::io::prelude::*;

fn main() -> std::io::Result<()> {
    let mut f = File::create("foo.txt")?;
    f.write_all(b"Hello, world!")?;

    f.sync_all()?;
    Ok(())
}

pub fn sync_data(&self) -> Result<(), Error>

This function is similar to sync_all, except that it may not synchronize file metadata to the filesystem.

This is intended for use cases that must synchronize content, but don't need the metadata on disk. The goal of this method is to reduce disk operations.

Note that some platforms may simply implement this in terms of sync_all.

Examples

use std::fs::File;
use std::io::prelude::*;

fn main() -> std::io::Result<()> {
    let mut f = File::create("foo.txt")?;
    f.write_all(b"Hello, world!")?;

    f.sync_data()?;
    Ok(())
}

pub fn set_len(&self, size: u64) -> Result<(), Error>

Truncates or extends the underlying file, updating the size of this file to become size.

If the size is less than the current file's size, then the file will be shrunk. If it is greater than the current file's size, then the file will be extended to size and have all of the intermediate data filled in with 0s.

The file's cursor isn't changed. In particular, if the cursor was at the end and the file is shrunk using this operation, the cursor will now be past the end.

Errors

This function will return an error if the file is not opened for writing. Also, std::io::ErrorKind::InvalidInput will be returned if the desired length would cause an overflow due to the implementation specifics.

Examples

use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut f = File::create("foo.txt")?;
    f.set_len(10)?;
    Ok(())
}

Note that this method alters the content of the underlying file, even though it takes &self rather than &mut self.

pub fn metadata(&self) -> Result<Metadata, Error>

Queries metadata about the underlying file.

Examples

use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut f = File::open("foo.txt")?;
    let metadata = f.metadata()?;
    Ok(())
}

pub fn try_clone(&self) -> Result<File, Error>

Creates a new File instance that shares the same underlying file handle as the existing File instance. Reads, writes, and seeks will affect both File instances simultaneously.

Examples

Creates two handles for a file named foo.txt:

use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut file = File::open("foo.txt")?;
    let file_copy = file.try_clone()?;
    Ok(())
}

Assuming there’s a file named foo.txt with contents abcdef\n, create two handles, seek one of them, and read the remaining bytes from the other handle:

use std::fs::File;
use std::io::SeekFrom;
use std::io::prelude::*;

fn main() -> std::io::Result<()> {
    let mut file = File::open("foo.txt")?;
    let mut file_copy = file.try_clone()?;

    file.seek(SeekFrom::Start(3))?;

    let mut contents = vec![];
    file_copy.read_to_end(&mut contents)?;
    assert_eq!(contents, b"def\n");
    Ok(())
}

pub fn set_permissions(&self, perm: Permissions) -> Result<(), Error>

Changes the permissions on the underlying file.

Platform-specific behavior

This function currently corresponds to the fchmod function on Unix and the SetFileInformationByHandle function on Windows. Note that, this may change in the future.

Errors

This function will return an error if the user lacks permission change attributes on the underlying file. It may also return an error in other os-specific unspecified cases.

Examples

fn main() -> std::io::Result<()> {
    use std::fs::File;

    let file = File::open("foo.txt")?;
    let mut perms = file.metadata()?.permissions();
    perms.set_readonly(true);
    file.set_permissions(perms)?;
    Ok(())
}

Note that this method alters the permissions of the underlying file, even though it takes &self rather than &mut self.

Trait Implementations

impl Deref for AdvisoryFileLock

type Target = File

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl DerefMut for AdvisoryFileLock

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl Drop for AdvisoryFileLock

fn drop(&mut self)

Executes the destructor for this type.