Struct zng_ext_fs_watcher::WriteFile
source · pub struct WriteFile { /* private fields */ }
Expand description
Represents an open write file provided by WATCHER.sync
.
This type actually writes to a temporary file and rename it over the actual file on commit only.
The dereferenced fs::File
is the temporary file, not the actual one.
§Transaction
To minimize the risk of file corruption exclusive locks are used, both the target file and the temp file are locked. An empty lock file is also used to cover the moment when both files are unlocked for the rename operation and the moment the temp file is acquired.
The temp file is the actual file path with file extension replaced with {path/.file-name.ext}.{GUID}-{n}.tmp
, the n
is a
number from 0 to 999, if a temp file exists unlocked it will be reused.
The lock file is {path/.file-name.ext}.{GUID}-lock.tmp
. Note that this
lock file only helps for apps that use WriteFile
, but even without it the risk is minimal as the slow
write operations are already flushed when it is time to commit.
Implementations§
source§impl WriteFile
impl WriteFile
sourcepub fn write_text(&mut self, txt: &str) -> Result<()>
pub fn write_text(&mut self, txt: &str) -> Result<()>
Write the text string.
sourcepub fn write_json<O: Serialize>(
&mut self,
value: &O,
pretty: bool,
) -> Result<()>
pub fn write_json<O: Serialize>( &mut self, value: &O, pretty: bool, ) -> Result<()>
Serialize and write.
If pretty
is true
the JSON is formatted for human reading.
sourcepub fn write_toml<O: Serialize>(
&mut self,
value: &O,
pretty: bool,
) -> Result<()>
pub fn write_toml<O: Serialize>( &mut self, value: &O, pretty: bool, ) -> Result<()>
Serialize and write.
If pretty
is true
the TOML is formatted for human reading.
sourcepub fn write_ron<O: Serialize>(&mut self, value: &O, pretty: bool) -> Result<()>
pub fn write_ron<O: Serialize>(&mut self, value: &O, pretty: bool) -> Result<()>
Serialize and write.
If pretty
is true
the RON if formatted for human reading using the default pretty config.
Methods from Deref<Target = File>§
1.0.0 · sourcepub fn sync_all(&self) -> Result<(), Error>
pub fn sync_all(&self) -> Result<(), Error>
Attempts to sync all OS-internal file content and 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, as dropping a File
will ignore all errors.
Note, however, that sync_all
is generally more expensive than closing
a file by dropping it, because the latter is not required to block until
the data has been written to the filesystem.
If synchronizing the metadata is not required, use sync_data
instead.
§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(())
}
1.0.0 · sourcepub fn sync_data(&self) -> Result<(), Error>
pub fn sync_data(&self) -> Result<(), Error>
This function is similar to sync_all
, except that it might 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(())
}
1.0.0 · sourcepub fn set_len(&self, size: u64) -> Result<(), Error>
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
.
1.0.0 · sourcepub fn metadata(&self) -> Result<Metadata, Error>
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(())
}
1.9.0 · sourcepub fn try_clone(&self) -> Result<File, Error>
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(())
}
1.16.0 · sourcepub fn set_permissions(&self, perm: Permissions) -> Result<(), Error>
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
.
1.75.0 · sourcepub fn set_times(&self, times: FileTimes) -> Result<(), Error>
pub fn set_times(&self, times: FileTimes) -> Result<(), Error>
Changes the timestamps of the underlying file.
§Platform-specific behavior
This function currently corresponds to the futimens
function on Unix (falling back to
futimes
on macOS before 10.13) and the SetFileTime
function on Windows. Note that this
may change in the future.
§Errors
This function will return an error if the user lacks permission to change timestamps on the underlying file. It may also return an error in other os-specific unspecified cases.
This function may return an error if the operating system lacks support to change one or
more of the timestamps set in the FileTimes
structure.
§Examples
fn main() -> std::io::Result<()> {
use std::fs::{self, File, FileTimes};
let src = fs::metadata("src")?;
let dest = File::options().write(true).open("dest")?;
let times = FileTimes::new()
.set_accessed(src.accessed()?)
.set_modified(src.modified()?);
dest.set_times(times)?;
Ok(())
}
1.75.0 · sourcepub fn set_modified(&self, time: SystemTime) -> Result<(), Error>
pub fn set_modified(&self, time: SystemTime) -> Result<(), Error>
Changes the modification time of the underlying file.
This is an alias for set_times(FileTimes::new().set_modified(time))
.
Trait Implementations§
Auto Trait Implementations§
impl Freeze for WriteFile
impl RefUnwindSafe for WriteFile
impl Send for WriteFile
impl Sync for WriteFile
impl Unpin for WriteFile
impl UnwindSafe for WriteFile
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
§impl<T> Instrument for T
impl<T> Instrument for T
§fn instrument(self, span: Span) -> Instrumented<Self>
fn instrument(self, span: Span) -> Instrumented<Self>
§fn in_current_span(self) -> Instrumented<Self>
fn in_current_span(self) -> Instrumented<Self>
source§impl<T> IntoEither for T
impl<T> IntoEither for T
source§fn into_either(self, into_left: bool) -> Either<Self, Self>
fn into_either(self, into_left: bool) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left
is true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read moresource§fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left(&self)
returns true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read more