blockchain: Improve readability of parent approval.

This introduces two new functions to the blockchain package named
headerApprovesParent and voteBitsApproveParent and updates all call
sites in the package in order to improve the readability and more
clearly describe the intention of the code.

blockchain/chain.go

@@ -1169,10 +1169,8 @@ func countSpentOutputs(block *dcrutil.Block, parent *dcrutil.Block) int {
 	// We need to skip the regular tx tree if it's not valid.
 	// We also exclude the coinbase transaction since it can't
 	// spend anything.
-	regularTxTreeValid := dcrutil.IsFlagSet16(block.MsgBlock().Header.VoteBits,
-		dcrutil.BlockValid)
 	var numSpent int
-	if regularTxTreeValid {
+	if headerApprovesParent(&block.MsgBlock().Header) {
 		for _, tx := range parent.Transactions()[1:] {
 			numSpent += len(tx.MsgTx().TxIn)
 		}
@@ -1193,10 +1191,7 @@ func countSpentOutputs(block *dcrutil.Block, parent *dcrutil.Block) int {
 // adding the block.
 func countNumberOfTransactions(block, parent *dcrutil.Block) uint64 {
 	var numTxns uint64
-
-	regularTxTreeValid := dcrutil.IsFlagSet16(block.MsgBlock().Header.VoteBits,
-		dcrutil.BlockValid)
-	if regularTxTreeValid {
+	if headerApprovesParent(&block.MsgBlock().Header) {
 		numTxns += uint64(len(parent.Transactions()))
 	}
 	numTxns += uint64(len(block.STransactions()))
@@ -1696,9 +1691,7 @@ func (b *BlockChain) connectBestChain(node *blockNode, block, parent *dcrutil.Bl
 		}
 
 		validateStr := "validating"
-		txTreeRegularValid := dcrutil.IsFlagSet16(node.voteBits,
-			dcrutil.BlockValid)
-		if !txTreeRegularValid {
+		if !voteBitsApproveParent(node.voteBits) {
 			validateStr = "invalidating"
 		}
 

blockchain/chainio.go

@@ -518,9 +518,7 @@ func dbFetchSpendJournalEntry(dbTx database.Tx, block *dcrutil.Block, parent *dc
 	serialized := spendBucket.Get(block.Hash()[:])
 
 	var blockTxns []*wire.MsgTx
-	regularTxTreeValid := dcrutil.IsFlagSet16(block.MsgBlock().Header.VoteBits,
-		dcrutil.BlockValid)
-	if regularTxTreeValid {
+	if headerApprovesParent(&block.MsgBlock().Header) {
 		blockTxns = append(blockTxns, parent.MsgBlock().Transactions[1:]...)
 	}
 	blockTxns = append(blockTxns, block.MsgBlock().STransactions...)

blockchain/subsidy.go

@@ -328,10 +328,7 @@ func CoinbasePaysTax(subsidyCache *SubsidyCache, tx *dcrutil.Tx, height int64, v
 // network, or the function might panic.
 func CalculateAddedSubsidy(block, parent *dcrutil.Block) int64 {
 	var subsidy int64
-
-	regularTxTreeValid := dcrutil.IsFlagSet16(block.MsgBlock().Header.VoteBits,
-		dcrutil.BlockValid)
-	if regularTxTreeValid {
+	if headerApprovesParent(&block.MsgBlock().Header) {
 		subsidy += parent.MsgBlock().Transactions[0].TxIn[0].ValueIn
 	}
 

blockchain/utxoviewpoint.go

@@ -457,8 +457,7 @@ func (view *UtxoViewpoint) connectTransaction(tx *dcrutil.Tx, blockHeight int64,
 // In addition, when the 'stxos' argument is not nil, it will be updated to
 // append an entry for each spent txout.
 func (b *BlockChain) connectTransactions(view *UtxoViewpoint, block *dcrutil.Block, parent *dcrutil.Block, stxos *[]spentTxOut) error {
-	regularTxTreeValid := dcrutil.IsFlagSet16(block.MsgBlock().Header.VoteBits,
-		dcrutil.BlockValid)
+	regularTxTreeValid := headerApprovesParent(&block.MsgBlock().Header)
 	thisNodeStakeViewpoint := ViewpointPrevInvalidStake
 	if regularTxTreeValid {
 		thisNodeStakeViewpoint = ViewpointPrevValidStake
@@ -470,9 +469,6 @@ func (b *BlockChain) connectTransactions(view *UtxoViewpoint, block *dcrutil.Blo
 		if err != nil {
 			return err
 		}
-		mBlock := block.MsgBlock()
-		votebits := mBlock.Header.VoteBits
-		regularTxTreeValid := dcrutil.IsFlagSet16(votebits, dcrutil.BlockValid)
 		if regularTxTreeValid {
 			for i, tx := range parent.Transactions() {
 				err := view.connectTransaction(tx, parent.Height(), uint32(i),
@@ -521,8 +517,7 @@ func (b *BlockChain) disconnectTransactions(view *UtxoViewpoint, block *dcrutil.
 	// Loop backwards through all transactions so everything is unspent in
 	// reverse order.  This is necessary since transactions later in a block
 	// can spend from previous ones.
-	regularTxTreeValid := dcrutil.IsFlagSet16(block.MsgBlock().Header.VoteBits,
-		dcrutil.BlockValid)
+	regularTxTreeValid := headerApprovesParent(&block.MsgBlock().Header)
 	thisNodeStakeViewpoint := ViewpointPrevInvalidStake
 	if regularTxTreeValid {
 		thisNodeStakeViewpoint = ViewpointPrevValidStake

blockchain/validate.go

@@ -58,6 +58,19 @@ var (
 	zeroHash = &chainhash.Hash{}
 )
 
+// voteBitsApproveParent returns whether or not the passed vote bits indicate
+// the regular transaction tree of the parent block should be considered valid.
+func voteBitsApproveParent(voteBits uint16) bool {
+	return dcrutil.IsFlagSet16(voteBits, dcrutil.BlockValid)
+}
+
+// approvesParent returns whether or not the vote bits in the passed header
+// indicate the regular transaction tree of the parent block should be
+// considered valid.
+func headerApprovesParent(header *wire.BlockHeader) bool {
+	return voteBitsApproveParent(header.VoteBits)
+}
+
 // isNullOutpoint determines whether or not a previous transaction output point
 // is set.
 func isNullOutpoint(outpoint *wire.OutPoint) bool {
@@ -1030,8 +1043,7 @@ func (b *BlockChain) CheckBlockStakeSanity(stakeValidationHeight int64, node *bl
 
 	ticketsPerBlock := int(b.chainParams.TicketsPerBlock)
 
-	txTreeRegularValid := dcrutil.IsFlagSet16(msgBlock.Header.VoteBits,
-		dcrutil.BlockValid)
+	txTreeRegularValid := headerApprovesParent(&msgBlock.Header)
 
 	parentStakeNode, err := b.fetchStakeNode(node.parent)
 	if err != nil {
@@ -1113,8 +1125,7 @@ func (b *BlockChain) CheckBlockStakeSanity(stakeValidationHeight int64, node *bl
 			numSSGenTx++
 
 			// Check and store the vote for TxTreeRegular.
-			ssGenVoteBits := stake.SSGenVoteBits(msgTx)
-			if dcrutil.IsFlagSet16(ssGenVoteBits, dcrutil.BlockValid) {
+			if voteBitsApproveParent(stake.SSGenVoteBits(msgTx)) {
 				voteYea++
 			} else {
 				voteNay++
@@ -2451,8 +2462,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block, parent *dcrutil.B
 	// signature operations in each of the input transaction public key
 	// scripts.
 	// Do this for all TxTrees.
-	regularTxTreeValid := dcrutil.IsFlagSet16(node.voteBits,
-		dcrutil.BlockValid)
+	regularTxTreeValid := voteBitsApproveParent(node.voteBits)
 	thisNodeStakeViewpoint := ViewpointPrevInvalidStake
 	thisNodeRegularViewpoint := ViewpointPrevInvalidRegular
 	if regularTxTreeValid {