Blockchain C++ STL-Like Container

Usage

Include the Blockchain.h header. Requires C++20.

#include "Blockchain.h"

Creating a Blockchain

Create a Blockchain with std::string Blocks and add the Genesis Block:

Blockchain<std::string> blockchain("Genesis");

Pushing new blocks/transactions

blockchain.push_back("Transaction 1");
blockchain.push_back("Transaction 2");
blockchain.push_back("Last transaction");

Iterating the Blockchain and print the Hash of each Block/Transaction

Range-Based for loop:

for(auto& block : blockchain)
    std::cout << block.GetTransaction() << ":\t" << block.GetHash() << std::endl;

Indexed for loop:

for(int i = 0; i < blockchain.size(); I++)
    std::cout << blockchain[i].GetTransaction() << ":\t" << blockchain[i].GetHash() << std::endl;

Iterators:

for (Blockchain<std::string>::iterator iter = blockchain.begin(); iter != blockchain.end(); iter++) 
    std::cout << iter->GetTransaction() << ":\t" << iter->GetHash() << std::endl;

Checking the Blockchain

Blockchain<...>::Check() checks if the hashes are consistent:

if(blockchain.Check())
    std::cout << "Blockchain hashes checked. ALL GOOD" << std::endl;

Blockchain<...>::Revalidate() checks if the hashes and transactions are consistent:

if(blockchain.Revalidate())
    std::cout << "Blockchain hashes and transactions revalidated. ALL GOOD" << std::endl;

If a transaction or hash in the chain would be altered, the corresponding check/revalidate function would fail.

Using a custom Hash-Function

The Blockchain uses std::hash<...> by default. You can use a custom hash function for the chain. Your custom Hasher can return any data type as the hash and must overload the () operator:

template <typename T>
class MyHashFunction
{
public:
    std::string operator()(T input)
    {
        // Here calculate your hash based on the input
        // and return your calculated hash
        return "MyCalculatedHashFromInput";
    }
};

To use the custom Hasher, simply specify it as a template argument when creating the Blockchain:

Blockchain<std::string, MyHashFunction<std::string>> customBlockchain("Genesis");