/*
* CTR-BE Mode
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_CTR_BE_H_
#define BOTAN_CTR_BE_H_

#include <botan/block_cipher.h>
#include <botan/stream_cipher.h>

namespace Botan {

/**
* CTR-BE (Counter mode, big-endian)
*/
class CTR_BE final : public StreamCipher {
   public:
      size_t default_iv_length() const override;

      bool valid_iv_length(size_t iv_len) const override;

      Key_Length_Specification key_spec() const override;

      std::string name() const override;

      std::unique_ptr<StreamCipher> new_object() const override;

      void clear() override;

      bool has_keying_material() const override;

      size_t buffer_size() const override;

      /**
      * @param cipher the block cipher to use
      */
      explicit CTR_BE(std::unique_ptr<BlockCipher> cipher);

      CTR_BE(std::unique_ptr<BlockCipher> cipher, size_t ctr_size);

      void seek(uint64_t offset) override;

      bool supports_seek() const override { return true; }

      std::optional<uint64_t> remaining_keystream_bytes() const override;

   private:
      void key_schedule(std::span<const uint8_t> key) override;
      void cipher_bytes(const uint8_t in[], uint8_t out[], size_t length) override;
      void generate_keystream(uint8_t out[], size_t length) override;
      void set_iv_bytes(const uint8_t iv[], size_t iv_len) override;
      void add_counter(uint64_t counter);

#if defined(BOTAN_HAS_CTR_BE_AVX2)
      size_t ctr_proc_bs16_ctr4_avx2(const uint8_t in[], uint8_t out[], size_t length);
#endif

#if defined(BOTAN_HAS_CTR_BE_SIMD32)
      size_t ctr_proc_bs16_ctr4_simd32(const uint8_t in[], uint8_t out[], size_t length);
#endif

      std::unique_ptr<BlockCipher> m_cipher;

      const size_t m_block_size;
      const size_t m_ctr_size;
      const size_t m_ctr_blocks;

      secure_vector<uint8_t> m_counter, m_pad;
      std::vector<uint8_t> m_iv;
      size_t m_pad_pos;
      // Valid only when m_ctr_size < 8: bytes the user can still
      // generate before the narrow counter would wrap.
      uint64_t m_bytes_remaining = 0;
};

}  // namespace Botan

#endif
