Allows saving data to a file, while handling all the input/output on a
background thread, including the initial file name assignment and any
subsequent renaming of the target file.
This interface is designed for file downloads. Generally, they start in the
temporary directory, while the user is selecting the final name. Then, they
are moved to the chosen target directory with a “.part” extension appended to
the file name. Finally, they are renamed when the download is completed.
Components implementing both nsIBackgroundFileSaver and nsIStreamListener
allow data to be fed using an implementation of OnDataAvailable that never
blocks the calling thread. They suspend the request that drives the stream
listener in case too much data is being fed, and resume it when the data has
been written. Calling OnStopRequest does not necessarily close the target
file, and the Finish method must be called to complete the operation.
Components implementing both nsIBackgroundFileSaver and nsIAsyncOutputStream
allow data to be fed directly to the non-blocking output stream, that however
may return NS_BASE_STREAM_WOULD_BLOCK in case too much data is being fed.
Closing the output stream does not necessarily close the target file, and the
Finish method must be called to complete the operation.
@remarks Implementations may require the consumer to always call Finish. If
the object reference is released without calling Finish, a memory
leak may occur, and the target file might be kept locked. All
public methods of the interface may only be called from the main
thread.
Instructs the component to compute the signatureInfo of the target file,
and make it available in the signatureInfo property.
@remarks This must be set on the main thread before the first call to
setTarget.
Instructs the component to compute the SHA-256 hash of the target file, and
make it available in the sha256Hash property.
@remarks This must be set on the main thread before the first call to
setTarget.
Instructs the component to append data to the initial target file, that
will be specified by the first call to the setTarget method, instead of
overwriting the file.
If the initial target file does not exist, this method has no effect.
@remarks This must be set on the main thread before the first call to
setTarget.
Sets the name of the output file to be written. The target can be changed
after data has already been fed, in which case the existing file will be
moved to the new destination.
In case the specified file already exists, and this method is called for
the first time, the file may be either overwritten or appended to, based on
whether the enableAppend method was called. Subsequent calls always
overwrite the specified target file with the previously saved data.
No file will be written until this function is called at least once. It’s
recommended not to feed any data until the output file is set.
If an input/output error occurs with the specified file, the save operation
fails. Failure is notified asynchronously through the observer.
| aTarget | New output file to be written. |
| aKeepPartial | Indicates whether aFile should be kept as partially completed, rather than deleted, if the operation fails or is canceled. This is generally set for downloads that use temporary ".part" files. |
Terminates access to the output file, then notifies the observer with the
specified status code. A failure code will force the operation to be
canceled, in which case the output file will be deleted if requested.
This forces the involved streams to be closed, thus no more data should be
fed to the component after this method has been called.
This is the last method that should be called on this object, and the
target file name cannot be changed anymore after this method has been
called. Conversely, before calling this method, the file can still be
renamed even if all the data has been fed.
| aStatus | Result code that determines whether the operation should succeed or be canceled, and is notified to the observer. If the operation fails meanwhile for other reasons, or the observer has been already notified of completion, this status code is ignored. |
This observer receives notifications when the target file name changes and
when the operation completes, successfully or not.
@remarks A strong reference to the observer is held. Notification events
are dispatched to the thread that created the object that
implements nsIBackgroundFileSaver.
An nsIArray of nsIX509CertList, representing a chain of X.509 signatures on
the downloaded file. Each list may belong to a different signer and contain
certificates all the way up to the root.
@throws NS_ERROR_NOT_AVAILABLE
In case this is called before the onSaveComplete method has been
called to notify success, or enableSignatureInfo has not been
called.
The SHA-256 hash, in raw bytes, associated with the data that was saved.
In case the enableAppend method has been called, the hash computation
includes the contents of the existing file, if any.
@throws NS_ERROR_NOT_AVAILABLE
In case the enableSha256 method has not been called, or before the
onSaveComplete method has been called to notify success.