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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/download/public/common/desktop/desktop_auto_resumption_handler.h"
#include "base/no_destructor.h"
#include "base/rand_util.h"
#include "base/task/single_thread_task_runner.h"
#include "components/download/public/common/download_item_impl.h"
namespace download {
// static
DesktopAutoResumptionHandler* DesktopAutoResumptionHandler::Get() {
static base::NoDestructor<DesktopAutoResumptionHandler> handler;
return handler.get();
}
DesktopAutoResumptionHandler::DesktopAutoResumptionHandler() {}
DesktopAutoResumptionHandler::~DesktopAutoResumptionHandler() = default;
base::TimeDelta DesktopAutoResumptionHandler::ComputeBackoffDelay(
int retry_count) {
// Implement exponential backoff algorithm
const base::TimeDelta kInitialDelay = base::Milliseconds(500);
int64_t delay = kInitialDelay.InMilliseconds() * (1 << retry_count);
// Add random jitter of +/- 15% of the calculated delay to avoid thundering
// herd
int64_t jitter_ms = (delay * 15) / 100; // 15% of delay
delay += base::RandInt(-jitter_ms, jitter_ms);
return base::Milliseconds(delay);
}
void DesktopAutoResumptionHandler::OnDownloadUpdated(DownloadItem* item) {
if (item->GetState() == DownloadItem::INTERRUPTED &&
IsAutoResumableDownload(item)) {
resumable_downloads_[item->GetGuid()] = item;
base::TimeDelta delay = ComputeBackoffDelay(item->GetAutoResumeCount());
base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
FROM_HERE,
base::BindOnce(&DesktopAutoResumptionHandler::MaybeResumeDownload,
weak_factory_.GetWeakPtr(), item->GetGuid()),
delay);
}
}
void DesktopAutoResumptionHandler::OnDownloadDestroyed(DownloadItem* item) {
item->RemoveObserver(this);
resumable_downloads_.erase(item->GetGuid());
}
bool DesktopAutoResumptionHandler::IsAutoResumableDownload(
DownloadItem* item) const {
if (!item) {
return false;
}
switch (item->GetState()) {
case DownloadItem::IN_PROGRESS:
return !item->IsPaused();
case DownloadItem::COMPLETE:
case DownloadItem::CANCELLED:
return false;
case DownloadItem::INTERRUPTED:
return !item->IsPaused();
case DownloadItem::MAX_DOWNLOAD_STATE:
NOTREACHED();
}
return false;
}
void DesktopAutoResumptionHandler::MaybeResumeDownload(std::string guid) {
// Check if the download is still resumable
if (resumable_downloads_.find(guid) == resumable_downloads_.end()) {
return;
}
auto item = resumable_downloads_[guid];
if (!IsAutoResumableDownload(item)) {
resumable_downloads_.erase(guid);
return;
}
item->Resume(false);
}
} // namespace download
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