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/*
* Copyright 2018 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef RTC_BASE_UNIQUE_ID_GENERATOR_H_
#define RTC_BASE_UNIQUE_ID_GENERATOR_H_
#include <cstdint>
#include <limits>
#include <set>
#include <string>
#include <type_traits>
#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "api/sequence_checker.h"
#include "rtc_base/checks.h"
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/system/no_unique_address.h"
#include "rtc_base/thread_annotations.h"
namespace webrtc {
// This class will generate numbers. A common use case is for identifiers.
// The generated numbers will be unique, in the local scope of the generator.
// This means that a generator will never generate the same number twice.
// The generator can also be initialized with a sequence of known ids.
// In such a case, it will never generate an id from that list.
// Recommendedations:
// * Prefer unsigned types.
// * Prefer larger types (uint8_t will run out quickly).
template <typename TIntegral>
class UniqueNumberGenerator {
public:
typedef TIntegral value_type;
UniqueNumberGenerator();
// Creates a generator that will never return any value from the given list.
explicit UniqueNumberGenerator(ArrayView<TIntegral> known_ids);
~UniqueNumberGenerator();
// Generates a number that this generator has never produced before.
// If there are no available numbers to generate, this method will fail
// with an `RTC_CHECK`.
TIntegral GenerateNumber();
// Alias for GenerateId, used for allowing typed testing
TIntegral Generate() { return GenerateNumber(); }
// Adds an id that this generator should no longer generate.
// Return value indicates whether the ID was hitherto unknown.
bool AddKnownId(TIntegral value);
private:
RTC_NO_UNIQUE_ADDRESS SequenceChecker sequence_checker_{
SequenceChecker::kDetached};
static_assert(std::is_integral<TIntegral>::value, "Must be integral type.");
TIntegral counter_ RTC_GUARDED_BY(sequence_checker_);
std::set<TIntegral> known_ids_ RTC_GUARDED_BY(sequence_checker_);
};
// This class will generate unique ids. Ids are 32 bit unsigned integers.
// The generated ids will be unique, in the local scope of the generator.
// This means that a generator will never generate the same id twice.
// The generator can also be initialized with a sequence of known ids.
// In such a case, it will never generate an id from that list.
class UniqueRandomIdGenerator {
public:
typedef uint32_t value_type;
UniqueRandomIdGenerator();
// Create a generator that will never return any value from the given list.
explicit UniqueRandomIdGenerator(ArrayView<uint32_t> known_ids);
~UniqueRandomIdGenerator();
// Generates a random id that this generator has never produced before.
// This method becomes more expensive with each use, as the probability of
// collision for the randomly generated numbers increases.
uint32_t GenerateId();
// Alias for GenerateId, used for allowing typed testing
uint32_t Generate() { return GenerateId(); }
// Adds an id that this generator should no longer generate.
// Return value indicates whether the ID was hitherto unknown.
bool AddKnownId(uint32_t value);
private:
// TODO(bugs.webrtc.org/12666): This lock is needed due to an instance in
// SdpOfferAnswerHandler being shared between threads.
Mutex mutex_;
std::set<uint32_t> known_ids_ RTC_GUARDED_BY(&mutex_);
};
// This class will generate strings. A common use case is for identifiers.
// The generated strings will be unique, in the local scope of the generator.
// This means that a generator will never generate the same string twice.
// The generator can also be initialized with a sequence of known ids.
// In such a case, it will never generate an id from that list.
class UniqueStringGenerator {
public:
typedef std::string value_type;
UniqueStringGenerator();
explicit UniqueStringGenerator(ArrayView<std::string> known_ids);
~UniqueStringGenerator();
std::string GenerateString();
// Alias for GenerateString, used for allowing typed testing
std::string Generate() { return GenerateString(); }
// Adds an id that this generator should no longer generate.
// Return value indicates whether the ID was hitherto unknown.
bool AddKnownId(absl::string_view value);
private:
// This implementation will be simple and will generate "0", "1", ...
UniqueNumberGenerator<uint32_t> unique_number_generator_;
};
template <typename TIntegral>
UniqueNumberGenerator<TIntegral>::UniqueNumberGenerator() : counter_(0) {}
template <typename TIntegral>
UniqueNumberGenerator<TIntegral>::UniqueNumberGenerator(
ArrayView<TIntegral> known_ids)
: counter_(0), known_ids_(known_ids.begin(), known_ids.end()) {}
template <typename TIntegral>
UniqueNumberGenerator<TIntegral>::~UniqueNumberGenerator() {}
template <typename TIntegral>
TIntegral UniqueNumberGenerator<TIntegral>::GenerateNumber() {
RTC_DCHECK_RUN_ON(&sequence_checker_);
while (true) {
RTC_CHECK_LT(counter_, std::numeric_limits<TIntegral>::max());
auto pair = known_ids_.insert(counter_++);
if (pair.second) {
return *pair.first;
}
}
}
template <typename TIntegral>
bool UniqueNumberGenerator<TIntegral>::AddKnownId(TIntegral value) {
RTC_DCHECK_RUN_ON(&sequence_checker_);
return known_ids_.insert(value).second;
}
} // namespace webrtc
// Re-export symbols from the webrtc namespace for backwards compatibility.
// TODO(bugs.webrtc.org/4222596): Remove once all references are updated.
#ifdef WEBRTC_ALLOW_DEPRECATED_NAMESPACES
namespace rtc {
using ::webrtc::UniqueNumberGenerator;
using ::webrtc::UniqueRandomIdGenerator;
using ::webrtc::UniqueStringGenerator;
} // namespace rtc
#endif // WEBRTC_ALLOW_DEPRECATED_NAMESPACES
#endif // RTC_BASE_UNIQUE_ID_GENERATOR_H_
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