text: // Copyright (c) 2017 The Bitcoin Core developers
  // Copyright (c) 2021 The Mobolith developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_CRYPTO_CHACHA20_H
  #define BITCOIN_CRYPTO_CHACHA20_H
  
  #include <stdint.h>
  #include <stdlib.h>
  
  /** A PRNG class for ChaCha20. */
  class ChaCha20
  {
  private:
      uint32_t input[16];
  
  public:
      ChaCha20();
      ChaCha20(const unsigned char* key, size_t keylen);
      void SetKey(const unsigned char* key, size_t keylen);
      void SetIV(uint64_t iv);
      void Seek(uint64_t pos);
      void Output(unsigned char* output, size_t bytes);
  };
  
  #endif // BITCOIN_CRYPTO_CHACHA20_H
  