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// Copyright 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 "sync/engine/update_applicator.h"
#include <vector>
#include "base/logging.h"
#include "sync/engine/syncer_util.h"
#include "sync/syncable/entry.h"
#include "sync/syncable/mutable_entry.h"
#include "sync/syncable/syncable_id.h"
#include "sync/syncable/syncable_write_transaction.h"
using std::vector;
namespace syncer {
using syncable::ID;
UpdateApplicator::UpdateApplicator(Cryptographer* cryptographer)
: cryptographer_(cryptographer),
updates_applied_(0),
encryption_conflicts_(0),
hierarchy_conflicts_(0) {
}
UpdateApplicator::~UpdateApplicator() {
}
// Attempt to apply all updates, using multiple passes if necessary.
//
// Some updates must be applied in order. For example, children must be created
// after their parent folder is created. This function runs an O(n^2) algorithm
// that will keep trying until there is nothing left to apply, or it stops
// making progress, which would indicate that the hierarchy is invalid.
//
// The update applicator also has to deal with simple conflicts, which occur
// when an item is modified on both the server and the local model. We remember
// their IDs so they can be passed to the conflict resolver after all the other
// applications are complete.
//
// Finally, there are encryption conflicts, which can occur when we don't have
// access to all the Nigori keys. There's nothing we can do about them here.
void UpdateApplicator::AttemptApplications(
syncable::WriteTransaction* trans,
const std::vector<int64>& handles) {
std::vector<int64> to_apply = handles;
DVLOG(1) << "UpdateApplicator running over " << to_apply.size() << " items.";
while (!to_apply.empty()) {
std::vector<int64> to_reapply;
for (std::vector<int64>::iterator i = to_apply.begin();
i != to_apply.end(); ++i) {
syncable::MutableEntry entry(trans, syncable::GET_BY_HANDLE, *i);
UpdateAttemptResponse result = AttemptToUpdateEntry(
trans, &entry, cryptographer_);
switch (result) {
case SUCCESS:
updates_applied_++;
break;
case CONFLICT_SIMPLE:
simple_conflict_ids_.insert(entry.GetId());
break;
case CONFLICT_ENCRYPTION:
encryption_conflicts_++;
break;
case CONFLICT_HIERARCHY:
// The decision to classify these as hierarchy conflcits is tentative.
// If we make any progress this round, we'll clear the hierarchy
// conflict count and attempt to reapply these updates.
to_reapply.push_back(*i);
break;
default:
NOTREACHED();
break;
}
}
if (to_reapply.size() == to_apply.size()) {
// We made no progress. Must be stubborn hierarchy conflicts.
hierarchy_conflicts_ = to_apply.size();
break;
}
// We made some progress, so prepare for what might be another iteration.
// If everything went well, to_reapply will be empty and we'll break out on
// the while condition.
to_apply.swap(to_reapply);
to_reapply.clear();
}
}
} // namespace syncer
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