HashGenerator.h

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#ifndef Hash_Generator_h
#define Hash_Generator_h
 
// Local includes.
#include "Configuration.h"
 
// Library includes.
#if THINGSBOARD_USE_MBED_TLS
#include <mbedtls/md.h>
#else
#include <Seeed_mbedtls.h>
#endif // THINGSBOARD_USE_MBED_TLS
#include <stdint.h>
#include <stddef.h>
 
// Maximum size of the hash string representation, consists of size required for byte representation of the hash * 2 because every byte is 2 hex characters + 1 for null termination character
size_t constexpr MAX_STRING_HASH_SIZE = (MBEDTLS_MD_MAX_SIZE * 2U) + 1U;
 
 
class HashGenerator {
  public:
    struct HashString
    {
      char hash[MAX_STRING_HASH_SIZE];
    };
 
    HashGenerator(void) = default;
 
    HashGenerator(HashGenerator const & other) = delete;
 
    void operator=(HashGenerator const & other) = delete;
 
    ~HashGenerator(void);
 
    bool start(mbedtls_md_type_t const & type);
 
    bool update(uint8_t const * data, size_t const & length);
 
    HashString finish();
 
  private:
    void free();
 
    size_t mbedtls_type_to_size(mbedtls_md_type_t const & type);
 
    size_t               m_size = {}; // Actual size in bytes, depend on the mbedtls_md_type_t given in the start method
    mbedtls_md_context_t m_ctx = {};  // Context used to access the already written bytes and update them latter
};
 
#endif // Hash_Generator_h