An incremental download object attempts to fetch a file piecemeal over time
in an effort to minimize network bandwidth usage.
Canceling a background download does not cause the file on disk to be
deleted.
Initialize the incremental download object. If the destination file
already exists, then only the remaining portion of the file will be
fetched.
NOTE: The downloader will create the destination file if it does not
already exist. It will create the file with the permissions 0600 if
needed. To affect the permissions of the file, consumers of this
interface may create an empty file at the specified destination prior to
starting the incremental download.
NOTE: Since this class may create a temporary file at the specified
destination, it is advisable for the consumer of this interface to specify
a file name for the destination that would not tempt the user into
double-clicking it. For example, it might be wise to append a file
extension like “.part” to the end of the destination to protect users from
accidentally running “blah.exe” before it is a complete file.
| uri | The URI to fetch. |
| destination | The location where the file is to be stored. |
| chunkSize | The size of the chunks to fetch. A non-positive value results in the default chunk size being used. |
| intervalInSeconds | The amount of time to wait between fetching chunks. Pass a negative to use the default interval, or 0 to fetch the remaining part of the file in one chunk. |
Start the incremental download.
| observer | An observer to be notified of various events. OnStartRequest is called when finalURI and totalSize have been determined or when an error occurs. OnStopRequest is called when the file is completely downloaded or when an error occurs. If this object implements nsIProgressEventSink, then its OnProgress method will be called as data is written to the destination file. If this object implements nsIInterfaceRequestor, then it will be assigned as the underlying channel's notification callbacks, which allows it to provide a nsIAuthPrompt implementation if needed by the channel, for example. |
| ctxt | User defined object forwarded to the observer's methods. |
The URI being fetched.
The URI being fetched after any redirects have been followed. This
attribute is set just prior to calling OnStartRequest on the observer
passed to the start method.
The file where the download is being written.
The total number of bytes for the requested file. This attribute is set
just prior to calling OnStartRequest on the observer passed to the start
method.
This attribute has a value of -1 if the total size is unknown.
The current number of bytes downloaded so far. This attribute is set just
prior to calling OnStartRequest on the observer passed to the start
method.
This attribute has a value of -1 if the current size is unknown.