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nearby/presence/implementation/advertisement_decoder.h
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2022-11-03 12:14:16 -07:00

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// Copyright 2022 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 THIRD_PARTY_NEARBY_PRESENCE_ADVERTISEMENT_DECODER_H_
#define THIRD_PARTY_NEARBY_PRESENCE_ADVERTISEMENT_DECODER_H_
#include <string>
#include <vector>
#include "absl/container/flat_hash_set.h"
#include "absl/log/die_if_null.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "presence/data_element.h"
#include "presence/implementation/credential_manager.h"
#include "presence/scan_request.h"
namespace nearby {
namespace presence {
// Decodes BLE NP advertisements
class AdvertisementDecoder {
public:
AdvertisementDecoder(CredentialManager* credential_manager,
ScanRequest scan_request)
: credential_manager_(*ABSL_DIE_IF_NULL(credential_manager)),
scan_request_(scan_request) {
AddBannedDataTypes();
}
// Returns a list of Data Elements decoded from the advertisement.
// Returns an error if the advertisement is misformatted or if it couldn't be
// decrypted.
absl::StatusOr<std::vector<DataElement>> DecodeAdvertisement(
absl::string_view advertisement);
// Returns true if the decoded advertisement in `data_elements` matches the
// filters in `scan_request`.
bool MatchesScanFilter(const std::vector<DataElement>& data_elements);
private:
// Decrypts data elements stored inside encrypted `elem` and appends them to
// `result`.
absl::Status DecryptDataElements(const DataElement& elem,
std::vector<DataElement>& result);
absl::StatusOr<std::string> Decrypt(absl::string_view salt,
absl::string_view encrypted);
void AddBannedDataTypes();
bool MatchesScanFilter(const std::vector<DataElement>& data_elements,
const PresenceScanFilter& filter);
bool MatchesScanFilter(const std::vector<DataElement>& data_elements,
const LegacyPresenceScanFilter& filter);
CredentialManager& credential_manager_;
ScanRequest scan_request_;
absl::flat_hash_set<int> banned_data_types_;
};
} // namespace presence
} // namespace nearby
#endif // THIRD_PARTY_NEARBY_PRESENCE_ADVERTISEMENT_DECODER_H_