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// Copyright 2020 Google LLC
//
// 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
//
// https://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.
#ifndef CORE_INTERNAL_MEDIUMS_BLE_V2_ADVERTISEMENT_READ_RESULT_H_
#define CORE_INTERNAL_MEDIUMS_BLE_V2_ADVERTISEMENT_READ_RESULT_H_
#include <cstdint>
#include <vector>
#include "absl/container/flat_hash_map.h"
#include "absl/container/flat_hash_set.h"
#include "absl/time/clock.h"
#include "internal/platform/byte_array.h"
#include "internal/platform/mutex.h"
#include "internal/platform/system_clock.h"
namespace location {
namespace nearby {
namespace connections {
namespace mediums {
// Representation of a GATT/L2CAP advertisement read result. This object helps
// us determine whether or not we need to retry GATT reads.
class AdvertisementReadResult {
public:
struct Config {
// How much to multiply the backoff duration by with every failure to read
// from the advertisement GATT server. This should never be below 1!
float backoff_multiplier;
// The initial backoff duration when we fail to read from an advertisement
// GATT server.
absl::Duration base_backoff_duration;
// The maximum backoff duration allowed between advertisement GATT server
// reads.
absl::Duration max_backoff_duration;
};
static const Config kDefaultConfig;
explicit AdvertisementReadResult(const Config& config = kDefaultConfig)
: config_(config) {}
// Indicator for deciding if we should retry reading the advertisement.
enum class RetryStatus {
kUnknown = 0,
kRetry = 1,
kPreviouslySucceeded = 2,
kTooSoon = 3,
};
// Adds a successfully read advertisement for the specified slot to this read
// result. This is fundamentally different from RecordLastReadStatus()
// because we can report a read failure, but still manage to read some
// advertisements.
void AddAdvertisement(int slot, const ByteArray& advertisement)
ABSL_LOCKS_EXCLUDED(mutex_);
// Determines whether or not an advertisement was successfully read at the
// specified slot.
bool HasAdvertisement(int slot) const ABSL_LOCKS_EXCLUDED(mutex_);
// Retrieves all raw advertisements that were successfully read.
std::vector<const ByteArray*> GetAdvertisements() const
ABSL_LOCKS_EXCLUDED(mutex_);
// Determines what stage we're in for retrying a read from an advertisement
// GATT/L2CAP server.
RetryStatus EvaluateRetryStatus() const ABSL_LOCKS_EXCLUDED(mutex_);
// Records the status of the latest read, and updates the next backoff
// duration for subsequent reads. Be sure to also call AddAdvertisement(...)
// if any advertisements were read.
void RecordLastReadStatus(bool is_success) ABSL_LOCKS_EXCLUDED(mutex_);
// Returns how much time has passed since we last tried reading from an
// advertisement GATT server.
absl::Duration GetDurationSinceRead() const ABSL_LOCKS_EXCLUDED(mutex_);
private:
enum class Result {
kFailure = 0,
kSuccess = 1,
};
absl::Duration GetDurationSinceReadLocked() const
ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
mutable Mutex mutex_;
// Maps slot numbers to the GATT advertisement found in that slot.
absl::flat_hash_map<int, ByteArray> advertisements_ ABSL_GUARDED_BY(mutex_);
Config config_;
absl::Duration backoff_duration_ ABSL_GUARDED_BY(mutex_) =
config_.base_backoff_duration;
// We need a long enough duration such that we always trigger a read retry AND
// we always connect to it without delay. The former case helps us initialize
// an AdvertisementReadResult so that we unconditionally try reading on the
// first sighting. And the latter case helps us connect immediately when we
// initialize a dummy read result for fast advertisements (which don't use the
// GATT server).
absl::Time last_read_timestamp_ ABSL_GUARDED_BY(mutex_) =
SystemClock::ElapsedRealtime() - config_.max_backoff_duration;
absl::optional<Result> result_ ABSL_GUARDED_BY(mutex_);
};
} // namespace mediums
} // namespace connections
} // namespace nearby
} // namespace location
#endif // CORE_INTERNAL_MEDIUMS_BLE_V2_ADVERTISEMENT_READ_RESULT_H_
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