Scrooge Coin 取引の実装

「Scrooge Coin 取引の有効性確認」の続きです.

ここでは, 前回まで見てきた Scrooge Coin 取引の理論を Java で実装してみます.
これは Princeton 大学の講義 “Bitcoin and Cryptocurrency Technologies” のプログラミング課題の1つです.

下表に, 使用するクラス一覧とその説明を纏めました.

表1 クラスの仕様 (概要)

今回は, 次のような API を実装する TxHandler クラスを作成します.
ただし, ここでは処理の流れを分かりやすく表現するために擬似コードで書きました.

public class TxHandler {

    Declares the field utxoPool;

    public TxHandler(UTXOPool utxoPool) {
        Initializes the field utxoPool with the argument value utxoPool;
    }

    public boolean isValidTx(Transaction tx) {
        Declare the HashSet with UTXO type;
        Initializes the input value is 0.0;
        Initializes the output value is 0.0;

        Loop i = 0, 1, ..., number of elements stored in the input of tx
            Creates a new UTXO corresponding to the output 
            with index outputIndex in the transaction whose hash is prevTxHash;

            if (!all outputs claimed by tx are in the current UTXO pool) {
                return false;
            }

            if (!the signatures on each input of tx are valid) {
                return false;
            }

            if (UTXO is claimed multiple times by tx) {
                return false;
            }
            Adds the UTXO to Set;
            Adds the previous output value to the input value;
        End i Loop

        Loop i = 0, 1, ..., number of elements stored in the output of tx
            if (!all of txs output values are non-negative) {
                return false;
            }
            Adds the value to the output value;
        End i Loop

        if (output value > input value) {
            return false;
        }

        return true;
    }

    public Transaction[] handleTxs(Transaction[] possibleTxs) {
        Declares the HashSet with Transaction type;

        Loop i = 0, 1, ..., number of elements stored in the possibleTxs
            if (transaction is valid) {
                Adds the transaction to Set;

                    Loop i = 0, 1, ..., number of elements stored in the input of transacion
                        Creates a new UTXO corresponding to the output with 
                        index outputIndex in the transaction whose hash is prevTxHash;
                        Removes the UTXO from the utxoPool;
                    End i Loop
                    Loop i = 0, 1, ..., number of elements stored in the output of transacion
                        Creates a new UTXO corresponding to the output with 
                        index i in the transaction;
                        Adds a mapping from UTXO to transaction output to the utxoPool;
                    End i Loop
            }
        End i Loop

        return a valid transaction array;
    }
}