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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <sys/cdefs.h>
#include <chrono>
#include <limits>
#include <optional>
#include <string>
struct prop_info;
namespace android {
namespace base {
// Returns the current value of the system property `key`,
// or `default_value` if the property is empty or doesn't exist.
std::string GetProperty(const std::string& key, const std::string& default_value);
// Returns true if the system property `key` has the value "1", "y", "yes", "on", or "true",
// false for "0", "n", "no", "off", or "false", or `default_value` otherwise.
bool GetBoolProperty(const std::string& key, bool default_value);
// Returns the signed integer corresponding to the system property `key`.
// If the property is empty, doesn't exist, doesn't have an integer value, or is outside
// the optional bounds, returns `default_value`.
template <typename T> T GetIntProperty(const std::string& key,
T default_value,
T min = std::numeric_limits<T>::min(),
T max = std::numeric_limits<T>::max());
// Returns the unsigned integer corresponding to the system property `key`.
// If the property is empty, doesn't exist, doesn't have an integer value, or is outside
// the optional bound, returns `default_value`.
template <typename T> T GetUintProperty(const std::string& key,
T default_value,
T max = std::numeric_limits<T>::max());
// Sets the system property `key` to `value`.
bool SetProperty(const std::string& key, const std::string& value);
// Waits for the system property `key` to have the value `expected_value`.
// Times out after `relative_timeout`.
// Returns true on success, false on timeout.
#if defined(__BIONIC__)
bool WaitForProperty(const std::string& key, const std::string& expected_value,
std::chrono::milliseconds relative_timeout = std::chrono::milliseconds::max());
#endif
// Waits for the system property `key` to be created.
// Times out after `relative_timeout`.
// Returns true on success, false on timeout.
#if defined(__BIONIC__)
bool WaitForPropertyCreation(const std::string& key, std::chrono::milliseconds relative_timeout =
std::chrono::milliseconds::max());
#endif
#if defined(__BIONIC__) && __cplusplus >= 201703L
// Cached system property lookup. For code that needs to read the same property multiple times,
// this class helps optimize those lookups.
class CachedProperty {
public:
explicit CachedProperty(const char* property_name);
// Returns the current value of the underlying system property as cheaply as possible.
// The returned pointer is valid until the next call to Get. Because most callers are going
// to want to parse the string returned here and cached that as well, this function performs
// no locking, and is completely thread unsafe. It is the caller's responsibility to provide a
// lock for thread-safety.
//
// Note: *changed can be set to true even if the contents of the property remain the same.
const char* Get(bool* changed = nullptr);
private:
std::string property_name_;
const prop_info* prop_info_;
std::optional<uint32_t> cached_area_serial_;
std::optional<uint32_t> cached_property_serial_;
char cached_value_[92];
bool is_read_only_;
const char* read_only_property_;
};
#endif
} // namespace base
} // namespace android
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