1 files changed, 60 insertions, 0 deletions
diff --git a/pkg/blockchain/chainwriter/undoblock.go b/pkg/blockchain/chainwriter/undoblock.go
new file mode 100644
index 0000000..5827f57
--- /dev/null
+++ b/pkg/blockchain/chainwriter/undoblock.go
@@ -0,0 +1,60 @@
+package chainwriter
+
+import "Chain/pkg/pro"
+
+// UndoBlock is used to reverse the side effects causes by a Block.
+// When the chain reverts a block's Transactions, it must both (1)
+// remove newly created TransactionOutputs and (2) convert
+// TransactionInputs back into available TransactionOutputs.
+// This struct helps with (2).
+// TransactionInputHashes are the hashes of the TransactionInputs that
+// the UndoBlock must revert.
+// OutputIndexes are the OutputIndexes of the TransactionInputs.
+// Amounts are the amounts of the parent TransactionOutputs.
+// LockingScripts are the locking scripts of the parent TransactionOutputs.
+type UndoBlock struct {
+	TransactionInputHashes []string
+	OutputIndexes          []uint32
+	Amounts                []uint32
+	LockingScripts         []string
+}
+
+// EncodeUndoBlock returns a pro.UndoBlock given an UndoBlock.
+func EncodeUndoBlock(ub *UndoBlock) *pro.UndoBlock {
+	var transactionInputHashes []string
+	var outputIndexes []uint32
+	var amounts []uint32
+	var lockingScripts []string
+	for i := 0; i < len(ub.TransactionInputHashes); i++ {
+		transactionInputHashes = append(transactionInputHashes, ub.TransactionInputHashes[i])
+		outputIndexes = append(outputIndexes, ub.OutputIndexes[i])
+		amounts = append(amounts, ub.Amounts[i])
+		lockingScripts = append(lockingScripts, ub.LockingScripts[i])
+	}
+	return &pro.UndoBlock{
+		TransactionInputHashes: transactionInputHashes,
+		OutputIndexes:          outputIndexes,
+		Amounts:                amounts,
+		LockingScripts:         lockingScripts,
+	}
+}
+
+// DecodeUndoBlock returns an UndoBlock given a pro.UndoBlock
+func DecodeUndoBlock(pub *pro.UndoBlock) *UndoBlock {
+	var transactionInputHashes []string
+	var outputIndexes []uint32
+	var amounts []uint32
+	var lockingScripts []string
+	for i := 0; i < len(pub.GetTransactionInputHashes()); i++ {
+		transactionInputHashes = append(transactionInputHashes, pub.GetTransactionInputHashes()[i])
+		outputIndexes = append(outputIndexes, pub.GetOutputIndexes()[i])
+		amounts = append(amounts, pub.GetAmounts()[i])
+		lockingScripts = append(lockingScripts, pub.GetLockingScripts()[i])
+	}
+	return &UndoBlock{
+		TransactionInputHashes: transactionInputHashes,
+		OutputIndexes:          outputIndexes,
+		Amounts:                amounts,
+		LockingScripts:         lockingScripts,
+	}
+}