// Called on the worker thread.
nsresult
BackgroundFileSaver::ProcessAttention()
{
nsresult rv;
// This function is called whenever the attention of the worker thread has
// been requested. This may happen in these cases:
// * We are about to start the copy for the first time. In this case, we are
// called from an event posted on the worker thread from the control thread
// by GetWorkerThreadAttention, and mAsyncCopyContext is null.
// * We have interrupted the copy for some reason. In this case, we are
// called by AsyncCopyCallback, and mAsyncCopyContext is null.
// * We are currently executing ProcessStateChange, and attention is requested
// by the control thread, for example because SetTarget or Finish have been
// called. In this case, we are called from from an event posted through
// GetWorkerThreadAttention. While mAsyncCopyContext was always null when
// the event was posted, at this point mAsyncCopyContext may not be null
// anymore, because ProcessStateChange may have started the copy before the
// event that called this function was processed on the worker thread.
// If mAsyncCopyContext is not null, we interrupt the copy and re-enter
// through AsyncCopyCallback. This allows us to check if, for instance, we
// should rename the target file. We will then restart the copy if needed.
if (mAsyncCopyContext) {
NS_CancelAsyncCopy(mAsyncCopyContext, NS_ERROR_ABORT);
return NS_OK;
}
// Use the current shared state to determine the next operation to execute.
rv = ProcessStateChange();
if (NS_FAILED(rv)) {
// If something failed while processing, terminate the operation now.
{
MutexAutoLock lock(mLock);
if (NS_SUCCEEDED(mStatus)) {
mStatus = rv;
}
}
// Ensure we notify completion now that the operation failed.
CheckCompletion();
}
return NS_OK;
}
// Called on the control thread.
nsresult
BackgroundFileSaver::GetWorkerThreadAttention(bool aShouldInterruptCopy)
{
nsresult rv;
MutexAutoLock lock(mLock);
// We only require attention one time. If this function is called two times
// before the worker thread wakes up, and the first has aShouldInterruptCopy
// false and the second true, we won't forcibly interrupt the copy from the
// control thread. However, that never happens, because calling Finish with a
// success code is the only case that may result in aShouldInterruptCopy being
// false. In that case, we won't call this function again, because consumers
// should not invoke other methods on the control thread after calling Finish.
// And in any case, Finish already closes one end of the pipe, causing the
// copy to finish properly on its own.
if (mWorkerThreadAttentionRequested) {
return NS_OK;
}
if (!mAsyncCopyContext) {
// Copy is not in progress, post an event to handle the change manually.
nsCOMPtr<nsIRunnable> event =
NS_NewRunnableMethod(this, &BackgroundFileSaver::ProcessAttention);
NS_ENSURE_TRUE(event, NS_ERROR_FAILURE);
rv = mWorkerThread->Dispatch(event, NS_DISPATCH_NORMAL);
NS_ENSURE_SUCCESS(rv, rv);
} else if (aShouldInterruptCopy) {
// Interrupt the copy. The copy will be resumed, if needed, by the
// ProcessAttention function, invoked by the AsyncCopyCallback function.
NS_CancelAsyncCopy(mAsyncCopyContext, NS_ERROR_ABORT);
}
// Indicate that attention has been requested successfully, there is no need
// to post another event until the worker thread processes the current one.
mWorkerThreadAttentionRequested = true;
return NS_OK;
}
