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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 PC_UNIQUE_ID_GENERATOR_H_
#define PC_UNIQUE_ID_GENERATOR_H_
#include <limits>
#include <set>
#include <string>
#include "api/array_view.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(rtc::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();
TIntegral operator()() { return GenerateNumber(); }
// Adds an id that this generator should no longer generate.
void AddKnownId(TIntegral value);
private:
static_assert(std::is_integral<TIntegral>::value, "Must be integral type.");
TIntegral counter_;
std::set<TIntegral> known_ids_;
};
// 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(rtc::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();
uint32_t operator()() { return GenerateId(); }
// Adds an id that this generator should no longer generate.
void AddKnownId(uint32_t value);
private:
std::set<uint32_t> known_ids_;
};
// 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(rtc::ArrayView<std::string> known_ids);
~UniqueStringGenerator();
std::string GenerateString();
std::string operator()() { return GenerateString(); }
// Adds an id that this generator should no longer generate.
void AddKnownId(const std::string& 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(
rtc::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() {
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>
void UniqueNumberGenerator<TIntegral>::AddKnownId(TIntegral value) {
known_ids_.insert(value);
}
} // namespace webrtc
#endif // PC_UNIQUE_ID_GENERATOR_H_