raw_hash.h

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/*
* (C) 2023 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#ifndef BOTAN_RAW_HASH_FN_H_
#define BOTAN_RAW_HASH_FN_H_
 
#include <botan/hash.h>
#include <memory>
 
namespace Botan {
 
/**
* This is not an actual hash function; it simply emits as the "hash"
* the value it is given as input. This is useful when implementing
* certain protocols where the hash is provided externally somehow to
* the unit which is generating the signature.
*
* This is exposed as the "Raw" padding scheme for signatures.
*/
class RawHashFunction final : public HashFunction {
   public:
      explicit RawHashFunction(std::unique_ptr<HashFunction> hash) :
            RawHashFunction(hash->name(), hash->output_length()) {}
 
      RawHashFunction(std::string_view name, size_t output_length) : m_name(name), m_output_length(output_length) {}
 
      void add_data(std::span<const uint8_t> input) override;
 
      void final_result(std::span<uint8_t> out) override;
 
      void clear() override;
 
      std::unique_ptr<HashFunction> copy_state() const override;
 
      std::unique_ptr<HashFunction> new_object() const override;
 
      size_t output_length() const override;
 
      std::string name() const override { return m_name; }
 
   private:
      const std::string m_name;
      const size_t m_output_length;
      std::vector<uint8_t> m_bits;
};
 
}  // namespace Botan
 
#endif