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// Copyright 2013 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.
#ifndef COMPONENTS_PREFS_PREF_FILTER_H_
#define COMPONENTS_PREFS_PREF_FILTER_H_
#include <memory>
#include <string>
#include <utility>
#include "base/callback_forward.h"
#include "components/prefs/base_prefs_export.h"
namespace base {
class DictionaryValue;
} // namespace base
// Filters preferences as they are loaded from disk or updated at runtime.
// Currently supported only by JsonPrefStore.
class COMPONENTS_PREFS_EXPORT PrefFilter {
public:
// A pair of pre-write and post-write callbacks.
using OnWriteCallbackPair =
std::pair<base::Closure, base::Callback<void(bool success)>>;
// A callback to be invoked when |prefs| have been read (and possibly
// pre-modified) and are now ready to be handed back to this callback's
// builder. |schedule_write| indicates whether a write should be immediately
// scheduled (typically because the |prefs| were pre-modified).
using PostFilterOnLoadCallback =
base::Callback<void(std::unique_ptr<base::DictionaryValue> prefs,
bool schedule_write)>;
virtual ~PrefFilter() {}
// This method is given ownership of the |pref_store_contents| read from disk
// before the underlying PersistentPrefStore gets to use them. It must hand
// them back via |post_filter_on_load_callback|, but may modify them first.
// Note: This method is asynchronous, which may make calls like
// PersistentPrefStore::ReadPrefs() asynchronous. The owner of filtered
// PersistentPrefStores should handle this to make the reads look synchronous
// to external users (see SegregatedPrefStore::ReadPrefs() for an example).
virtual void FilterOnLoad(
const PostFilterOnLoadCallback& post_filter_on_load_callback,
std::unique_ptr<base::DictionaryValue> pref_store_contents) = 0;
// Receives notification when a pref store value is changed, before Observers
// are notified.
virtual void FilterUpdate(const std::string& path) = 0;
// Receives notification when the pref store is about to serialize data
// contained in |pref_store_contents| to a string. Modifications to
// |pref_store_contents| will be persisted to disk and also affect the
// in-memory state.
// If the returned callbacks are non-null, they will be registered to be
// invoked synchronously after the next write (from the I/O TaskRunner so they
// must not be bound to thread-unsafe member state).
virtual OnWriteCallbackPair FilterSerializeData(
base::DictionaryValue* pref_store_contents) = 0;
};
#endif // COMPONENTS_PREFS_PREF_FILTER_H_
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