text: /*
  * Base class for message authentiction codes
  * (C) 1999-2007 Jack Lloyd
  *
  * Botan is released under the Simplified BSD License (see license.txt)
  */
  
  #ifndef BOTAN_MESSAGE_AUTH_CODE_BASE_H__
  #define BOTAN_MESSAGE_AUTH_CODE_BASE_H__
  
  #include <botan/buf_comp.h>
  #include <botan/sym_algo.h>
  #include <string>
  
  namespace Botan {
  
  /**
  * This class represents Message Authentication Code (MAC) objects.
  */
  class BOTAN_DLL MessageAuthenticationCode : public Buffered_Computation,
                                              public SymmetricAlgorithm
     {
     public:
        /**
        * Create an instance based on a name
        * If provider is empty then best available is chosen.
        * @param algo_spec algorithm name
        * @param provider provider implementation to use
        * @return a null pointer if the algo/provider combination cannot be found
        */
        static std::unique_ptr<MessageAuthenticationCode>
           create(const std::string& algo_spec,
                  const std::string& provider = "");
  
        /*
        * Create an instance based on a name
        * If provider is empty then best available is chosen.
        * @param algo_spec algorithm name
        * @param provider provider implementation to use
        * Throws a Lookup_Error if algo/provider combination cannot be found
        */
        static std::unique_ptr<MessageAuthenticationCode>
           create_or_throw(const std::string& algo_spec,
                           const std::string& provider = "");
  
        /**
        * @return list of available providers for this algorithm, empty if not available
        */
        static std::vector<std::string> providers(const std::string& algo_spec);
  
        virtual ~MessageAuthenticationCode() {}
  
        /**
        * Prepare for processing a message under the specified nonce
        *
        * Most MACs neither require nor support a nonce; for these algorithms
        * calling `start_msg` is optional and calling it with anything other than
        * an empty string is an error. One MAC which *requires* a per-message
        * nonce be specified is GMAC.
        *
        * @param nonce the message nonce bytes
        * @param nonce_len the size of len in bytes
        * Default implementation simply rejects all non-empty nonces
        * since most hash/MAC algorithms do not support randomization
        */
        virtual void start_msg(const uint8_t nonce[], size_t nonce_len)
           {
           BOTAN_UNUSED(nonce);
           if(nonce_len > 0)
              throw Invalid_IV_Length(name(), nonce_len);
           }
  
        /**
        * Begin processing a message with a nonce
        *
        * @param nonce the per message nonce
        */
        template<typename Alloc>
        void start(const std::vector<uint8_t, Alloc>& nonce)
           {
           start_msg(nonce.data(), nonce.size());
           }
  
        /**
        * Begin processing a message.
        * @param nonce the per message nonce
        * @param nonce_len length of nonce
        */
        void start(const uint8_t nonce[], size_t nonce_len)
           {
           start_msg(nonce, nonce_len);
           }
  
        /**
        * Begin processing a message.
        */
        void start()
           {
           return start_msg(nullptr, 0);
           }
  
        /**
        * Verify a MAC.
        * @param in the MAC to verify as a byte array
        * @param length the length of param in
        * @return true if the MAC is valid, false otherwise
        */
        virtual bool verify_mac(const uint8_t in[], size_t length);
  
        /**
        * Verify a MAC.
        * @param in the MAC to verify as a byte array
        * @return true if the MAC is valid, false otherwise
        */
        virtual bool verify_mac(const std::vector<uint8_t>& in)
           {
           return verify_mac(in.data(), in.size());
           }
  
        /**
        * Verify a MAC.
        * @param in the MAC to verify as a byte array
        * @return true if the MAC is valid, false otherwise
        */
        virtual bool verify_mac(const secure_vector<uint8_t>& in)
           {
           return verify_mac(in.data(), in.size());
           }
  
        /**
        * Get a new object representing the same algorithm as *this
        */
        virtual MessageAuthenticationCode* clone() const = 0;
  
        /**
        * @return provider information about this implementation. Default is "base",
        * might also return "sse2", "avx2", "openssl", or some other arbitrary string.
        */
        virtual std::string provider() const { return "base"; }
  
     };
  
  typedef MessageAuthenticationCode MAC;
  
  }
  
  #endif
  