text: // 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.
  //
  ////////////////////////////////////////////////////////////////////////////////
  
  #ifndef TINK_SUBTLE_PRF_HKDF_STREAMING_PRF_H_
  #define TINK_SUBTLE_PRF_HKDF_STREAMING_PRF_H_
  
  #include <memory>
  #include <string>
  #include <utility>
  
  #include "absl/strings/string_view.h"
  #include "openssl/base.h"
  #include "tink/subtle/common_enums.h"
  #include "tink/subtle/prf/streaming_prf.h"
  #include "tink/util/secret_data.h"
  #include "tink/util/statusor.h"
  
  namespace crypto {
  namespace tink {
  namespace subtle {
  
  class HkdfStreamingPrf : public StreamingPrf {
   public:
    static crypto::tink::util::StatusOr<std::unique_ptr<StreamingPrf>> New(
        HashType hash, util::SecretData secret, absl::string_view salt);
  
    std::unique_ptr<InputStream> ComputePrf(
        absl::string_view input) const override;
  
   private:
    HkdfStreamingPrf(const EVP_MD* hash, util::SecretData secret,
                     absl::string_view salt)
        : hash_(hash), secret_(std::move(secret)), salt_(salt) {}
  
    const EVP_MD* hash_;
    const util::SecretData secret_;
    const std::string salt_;
  };
  
  }  // namespace subtle
  }  // namespace tink
  }  // namespace crypto
  
  #endif  // TINK_SUBTLE_PRF_HKDF_STREAMING_PRF_H_
  