3 releases
0.0.3 | Sep 21, 2024 |
---|---|
0.0.2 | Jan 29, 2024 |
0.0.1 | Jan 25, 2024 |
#572 in Filesystem
1,391 downloads per month
Used in fsblobstore
18KB
262 lines
tmpfile
TmpFile
is an object representing a temporary file that can optionally be
persisted.
lib.rs
:
Temporary file object that can be persisted.
Usage overview
The main type of this crate is TmpFile
, which represents a (temporary)
file being written to, that may optionally be persisted (or it will be
removed).
To use TmpFile
an application must first implement the TmpProc
trait
on a type. [TmpProc::update()
] will be called each time a block of data
is written to the TmpFile
. [TmpProc::finalize()
] will be called if the
application chooses to persist the TmpFile
.
When a TmpFile
is created, the application must pass along the file's
temporary location and an object whose type implements TmpProc
. The
instantiated TmpFile
object implements std::io::Write
, which is used
to write data to it.
If the entire file can not be completed, the TmpFile
object is dropped,
which will automatically remove the temporary file.
If the entire file has been written, and the application wants to persist
it, it calls [TmpFile::persist()
]. This will call the
TmpProc::finalize()
trait method, whose responsibility it is to return
the file's persistent location (and application-defined data). Information
about the persisted file is finally returned to the application via an
instantion of Persisted
.
"Small file" special case
An application may not want to store small files in its filesystem.
For this purpose, the TmpFile
can be set up to have a minimum file size.
If a TmpFile
does not reach this size before being persisted, a memory
buffer of the file's contents will be returned instead of a file name of
the persisted file.
The [TmpFile::with_minsize()
] factory method can be used to use this
feature.
Deferred persist
There may be cases where it's impractical to call [TmpFile::persist()
] on
a TmpFile
, but where the originator of the TmpFile
wants to manage the
results from the TmpFile
when it is pesisted. This crate has means to
handle such situations, but it drastically changes the semantics of
TmpFile
: The defer_persist()
method returns a wait context that can be
used to wait for the TmpFile
to finalize and send its results. In this
scenario, the finalization occurrs implicitly when the TmpFile
is
dropped.
This means that deferred persist shifts the default assumption of
"drop-before-persist implies failure" to "drop means persist", with no
means to trigger "abort without finalization" (unless the TmpProc
's
finalization is able to determine that the file is incomplete).
Features
Feature | Function |
---|---|
defer-persist |
Allow Drop to finalize TmpFile . |
Dependencies
~0–4.5MB