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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_PREFS_PREF_REGISTRY_H_
#define COMPONENTS_PREFS_PREF_REGISTRY_H_
#include <stdint.h>
#include <string>
#include <string_view>
#include <unordered_map>
#include "base/memory/ref_counted.h"
#include "components/prefs/pref_value_map.h"
#include "components/prefs/prefs_export.h"
#include "components/prefs/transparent_unordered_string_map.h"
namespace base {
class Value;
}
class DefaultPrefStore;
class PrefStore;
// Preferences need to be registered with a type and default value
// before they are used.
//
// The way you use a PrefRegistry is that you register all required
// preferences on it (via one of its subclasses), then pass it as a
// construction parameter to PrefService.
//
// Currently, registrations after constructing the PrefService will
// also work, but this is being deprecated.
class COMPONENTS_PREFS_EXPORT PrefRegistry
: public base::RefCounted<PrefRegistry> {
public:
// Registration flags that can be specified which impact how the pref will
// behave or be stored. This will be passed in a bitmask when the pref is
// registered. Subclasses of PrefRegistry can specify their own flags. Care
// must be taken to ensure none of these overlap with the flags below.
using PrefRegistrationFlags = uint32_t;
// No flags are specified.
static constexpr PrefRegistrationFlags NO_REGISTRATION_FLAGS = 0;
// The first 8 bits are reserved for subclasses of PrefRegistry to use.
// This marks the pref as "lossy". There is no strict time guarantee on when
// a lossy pref will be persisted to permanent storage when it is modified.
static constexpr PrefRegistrationFlags LOSSY_PREF = 1 << 8;
// Registering a pref as public allows other services to access it.
static constexpr PrefRegistrationFlags PUBLIC = 1 << 9;
// Enum for pref types that are stored as string but have different semantic
// meaning. This is used to prevent accidentally reading a pref as a wrong
// type.
enum class RegisteredPrefType {
// For all prefs that are not registered as any of the more specific types
// below.
kOther,
kInt64,
kTime,
};
using const_iterator = PrefValueMap::const_iterator;
using PrefRegistrationFlagsMap = TransparentUnorderedStringMap<uint32_t>;
PrefRegistry();
PrefRegistry(const PrefRegistry&) = delete;
PrefRegistry& operator=(const PrefRegistry&) = delete;
// Retrieve the set of registration flags for the given preference. The return
// value is a bitmask of PrefRegistrationFlags.
uint32_t GetRegistrationFlags(std::string_view pref_name) const;
// Retrieve the registered type for the given preference.
//
// TODO(crbug.com/438680281): Fix all test code to always register preferences
// before Get/Set calls, then remove the std::optional from the return value.
std::optional<RegisteredPrefType> GetRegisteredPrefType(
std::string_view pref_name) const;
// Gets the registered defaults.
scoped_refptr<PrefStore> defaults();
// Allows iteration over defaults.
const_iterator begin() const;
const_iterator end() const;
// Changes the default value for a preference.
//
// `pref_name` must be a previously registered preference.
void SetDefaultPrefValue(std::string_view pref_name, base::Value value);
protected:
friend class base::RefCounted<PrefRegistry>;
virtual ~PrefRegistry();
// Used by subclasses to register a default value and registration flags for
// a preference. `flags` is a bitmask of `PrefRegistrationFlags`. `type` can
// be specified for prefs that need more specific type-checking than their
// storage `base::Value::Type`.
//
// TODO(crbug.com/438680281): Migrate all pref types to specify the `type`
// parameter, then remove the default value.
void RegisterPreference(std::string_view path,
base::Value default_value,
uint32_t flags,
RegisteredPrefType type = RegisteredPrefType::kOther);
// Allows subclasses to hook into pref registration.
virtual void OnPrefRegistered(std::string_view path, uint32_t flags);
scoped_refptr<DefaultPrefStore> defaults_;
// A map of pref name to a bitmask of PrefRegistrationFlags.
PrefRegistrationFlagsMap registration_flags_;
// A map of pref name to its registered type.
using PrefRegistrationTypeMap =
TransparentUnorderedStringMap<RegisteredPrefType>;
PrefRegistrationTypeMap registration_types_;
};
#endif // COMPONENTS_PREFS_PREF_REGISTRY_H_
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