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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/browser/chromeos/drive/drive_prefetcher.h"
#include "base/bind.h"
#include "base/command_line.h"
#include "base/location.h"
#include "base/message_loop_proxy.h"
#include "chrome/browser/chromeos/drive/drive_file_system_interface.h"
#include "chrome/browser/chromeos/drive/drive_file_system_util.h"
#include "chrome/common/chrome_switches.h"
#include "content/public/browser/browser_thread.h"
using content::BrowserThread;
namespace drive {
namespace {
const int kInitialPrefetchCount = 100;
const int64 kPrefetchFileSizeLimit = 10 << 20; // 10MB
// Returns true if prefetching is disabled by a command line option.
bool IsPrefetchDisabled() {
return CommandLine::ForCurrentProcess()->HasSwitch(
switches::kDisableDrivePrefetch);
}
// Returns true if |left| has lower priority than |right|.
bool ComparePrefetchPriority(const DriveEntryProto& left,
const DriveEntryProto& right) {
// First, compare last access time. The older entry has less priority.
if (left.file_info().last_accessed() != right.file_info().last_accessed())
return left.file_info().last_accessed() < right.file_info().last_accessed();
// When the entries have the same last access time (which happens quite often
// because Drive server doesn't set the field until an entry is viewed via
// drive.google.com), we use last modified time as the tie breaker.
if (left.file_info().last_modified() != right.file_info().last_modified())
return left.file_info().last_modified() < right.file_info().last_modified();
// Two entries have the same priority. To make this function a valid
// comparator for std::set, we need to differentiate them anyhow.
return left.resource_id() < right.resource_id();
}
}
DrivePrefetcherOptions::DrivePrefetcherOptions()
: initial_prefetch_count(kInitialPrefetchCount),
prefetch_file_size_limit(kPrefetchFileSizeLimit) {
}
DrivePrefetcher::DrivePrefetcher(DriveFileSystemInterface* file_system,
const DrivePrefetcherOptions& options)
: latest_files_(&ComparePrefetchPriority),
number_of_inflight_prefetches_(0),
number_of_inflight_traversals_(0),
should_suspend_prefetch_(true),
initial_prefetch_count_(options.initial_prefetch_count),
prefetch_file_size_limit_(options.prefetch_file_size_limit),
file_system_(file_system),
weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
file_system_->AddObserver(this);
}
DrivePrefetcher::~DrivePrefetcher() {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
file_system_->RemoveObserver(this);
}
void DrivePrefetcher::OnInitialLoadFinished(DriveFileError error) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
if (error == DRIVE_FILE_OK)
DoFullScan();
}
void DrivePrefetcher::OnDirectoryChanged(const FilePath& directory_path) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
// TODO(kinaba): crbug.com/156270.
// Update the list of latest files and the prefetch queue if needed.
}
void DrivePrefetcher::OnSyncTaskStarted() {
should_suspend_prefetch_ = true;
}
void DrivePrefetcher::OnSyncClientStopped() {
should_suspend_prefetch_ = true;
}
void DrivePrefetcher::OnSyncClientIdle() {
should_suspend_prefetch_ = IsPrefetchDisabled();
DoPrefetch();
}
void DrivePrefetcher::DoFullScan() {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
if (IsPrefetchDisabled())
return;
FilePath root(util::ExtractDrivePath(util::GetDriveMountPointPath()));
VisitDirectory(root);
}
void DrivePrefetcher::DoPrefetch() {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
if (should_suspend_prefetch_ ||
queue_.empty() ||
number_of_inflight_prefetches_ > 0)
return;
std::string resource_id = queue_.front();
queue_.pop_front();
++number_of_inflight_prefetches_;
file_system_->GetFileByResourceId(
resource_id,
base::Bind(&DrivePrefetcher::OnPrefetchFinished,
weak_ptr_factory_.GetWeakPtr()),
google_apis::GetContentCallback());
}
void DrivePrefetcher::OnPrefetchFinished(DriveFileError error,
const FilePath& file_path,
const std::string& mime_type,
DriveFileType file_type) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
if (error != DRIVE_FILE_OK) {
LOG(WARNING) << "Prefetch failed: " << error;
}
--number_of_inflight_prefetches_;
DoPrefetch(); // Start next prefetch.
}
void DrivePrefetcher::ReconstructQueue() {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
// Put the files with latest timestamp into the queue.
queue_.clear();
for (LatestFileSet::reverse_iterator it = latest_files_.rbegin();
it != latest_files_.rend(); ++it) {
queue_.push_back(it->resource_id());
}
}
void DrivePrefetcher::VisitFile(const DriveEntryProto& entry) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
// Excessively large files will not be fetched.
if (entry.file_info().size() > prefetch_file_size_limit_)
return;
// Remember the file in the set ordered by the |last_accessed| field.
latest_files_.insert(entry);
// If the set become too big, forget the oldest entry.
if (latest_files_.size() > static_cast<size_t>(initial_prefetch_count_))
latest_files_.erase(latest_files_.begin());
}
void DrivePrefetcher::VisitDirectory(const FilePath& directory_path) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
++number_of_inflight_traversals_;
file_system_->ReadDirectoryByPath(
directory_path,
base::Bind(&DrivePrefetcher::OnReadDirectory,
weak_ptr_factory_.GetWeakPtr(),
directory_path));
}
void DrivePrefetcher::OnReadDirectory(
const FilePath& directory_path,
DriveFileError error,
bool hide_hosted_documents,
scoped_ptr<DriveEntryProtoVector> entries) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
if (error != DRIVE_FILE_OK) {
LOG(WARNING) << "Directory cannot be scanned by prefetcher: "
<< directory_path.value();
OnReadDirectoryFinished();
return;
}
// TODO(kinaba): if entries->size() is so big and it does not contain any
// directories, the loop below may run on UI thread long time. Consider
// splitting it into a smaller asynchronous tasks.
for (size_t i = 0; i < entries->size(); ++i) {
const DriveEntryProto& entry = (*entries)[i];
if (entry.file_info().is_directory()) {
VisitDirectory(directory_path.Append(entry.base_name()));
} else if (entry.has_file_specific_info() &&
!entry.file_specific_info().is_hosted_document()) {
VisitFile(entry);
}
}
OnReadDirectoryFinished();
}
void DrivePrefetcher::OnReadDirectoryFinished() {
DCHECK(number_of_inflight_traversals_ > 0);
--number_of_inflight_traversals_;
if (number_of_inflight_traversals_ == 0) {
ReconstructQueue();
DoPrefetch(); // Start prefetching.
}
}
} // namespace drive
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