Export CheckConnectBlock function.

This commit makes a slight variant of the existing checkConnectBlock
function available to external callers.  The new exported version checks
if the passed block will connect to the end of the current main chain.

In order to support this, a few other small modifications have been made
to the initial index generation and the existing checkConnectBlock since
it previously made some assumptions about the state of genesis block which
can no longer be assumed due accepting blocks from callers directly.

Also, add a quick test to ensure the new function fails when checking if
the genesis block will connect again when it's already inserted.

chain.go

@@ -340,7 +340,7 @@ func (b *BlockChain) GenerateInitialIndex() error {
 
 	// Calculate the starting height based on the minimum number of nodes
 	// needed in memory.
-	startHeight := endHeight - (minMemoryNodes + 1)
+	startHeight := endHeight - minMemoryNodes
 	if startHeight < 0 {
 		startHeight = 0
 	}
@@ -353,7 +353,7 @@ func (b *BlockChain) GenerateInitialIndex() error {
 	// is going to be nuked eventually, the bug isn't being fixed in the
 	// driver.  In the mean time, work around the issue by calling
 	// FetchBlockBySha multiple times with the appropriate indices as needed.
-	for start := startHeight; start < endHeight; {
+	for start := startHeight; start <= endHeight; {
 		hashList, err := b.db.FetchHeightRange(start, endHeight+1)
 		if err != nil {
 			return err
@@ -368,8 +368,8 @@ func (b *BlockChain) GenerateInitialIndex() error {
 		// Loop forwards through each block loading the node into the
 		// index for the block.
 		for _, hash := range hashList {
-			// Make a copy of the hash to make sure there are no references
+			// Make a copy of the hash to make sure there are no
-			// into the list so it can be freed.
+			// references into the list so it can be freed.
 			hashCopy := hash
 			node, err := b.loadBlockNode(&hashCopy)
 			if err != nil {

test_coverage.txt

@@ -2,27 +2,28 @@
 github.com/conformal/btcchain/validate.go	 checkSerializedHeight			 100.00% (17/17)
 github.com/conformal/btcchain/chain.go		 BlockChain.removeOrphanBlock		 100.00% (16/16)
 github.com/conformal/btcchain/txlookup.go	 disconnectTransactions			 100.00% (13/13)
-github.com/conformal/btcchain/validate.go	 countSigOps				 100.00% (9/9)
+github.com/conformal/btcchain/validate.go	 CountSigOps				 100.00% (9/9)
+github.com/conformal/btcchain/validate.go	 BlockChain.CheckConnectBlock		 100.00% (7/7)
 github.com/conformal/btcchain/checkpoints.go	 init					 100.00% (6/6)
-github.com/conformal/btcchain/merkle.go		 hashMerkleBranches			 100.00% (5/5)
 github.com/conformal/btcchain/difficulty.go	 ShaHashToBig				 100.00% (5/5)
+github.com/conformal/btcchain/merkle.go		 hashMerkleBranches			 100.00% (5/5)
 github.com/conformal/btcchain/chain.go		 BlockChain.IsKnownOrphan		 100.00% (5/5)
 github.com/conformal/btcchain/merkle.go		 nextPowerOfTwo				 100.00% (4/4)
 github.com/conformal/btcchain/chain.go		 newBlockNode				 100.00% (3/3)
 github.com/conformal/btcchain/process.go	 BlockChain.blockExists			 100.00% (3/3)
-github.com/conformal/btcchain/checkpoints.go	 newShaHashFromStr			 100.00% (2/2)
 github.com/conformal/btcchain/chain.go		 New					 100.00% (2/2)
-github.com/conformal/btcchain/timesorter.go	 timeSorter.Swap			 100.00% (1/1)
+github.com/conformal/btcchain/checkpoints.go	 newShaHashFromStr			 100.00% (2/2)
-github.com/conformal/btcchain/validate.go	 BlockChain.calcBlockSubsidy		 100.00% (1/1)
+github.com/conformal/btcchain/timesorter.go	 timeSorter.Less			 100.00% (1/1)
 github.com/conformal/btcchain/chain.go		 BlockChain.HaveBlock			 100.00% (1/1)
 github.com/conformal/btcchain/log.go		 init					 100.00% (1/1)
-github.com/conformal/btcchain/timesorter.go	 timeSorter.Less			 100.00% (1/1)
+github.com/conformal/btcchain/timesorter.go	 timeSorter.Swap			 100.00% (1/1)
 github.com/conformal/btcchain/timesorter.go	 timeSorter.Len				 100.00% (1/1)
-github.com/conformal/btcchain/scriptval.go	 newTxValidator				 100.00% (1/1)
 github.com/conformal/btcchain/checkpoints.go	 BlockChain.DisableCheckpoints		 100.00% (1/1)
+github.com/conformal/btcchain/scriptval.go	 newTxValidator				 100.00% (1/1)
 github.com/conformal/btcchain/scriptval.go	 txValidator.sendResult			 100.00% (1/1)
-github.com/conformal/btcchain/log.go		 DisableLog				 100.00% (1/1)
 github.com/conformal/btcchain/params.go		 BlockChain.chainParams			 100.00% (1/1)
+github.com/conformal/btcchain/log.go		 DisableLog				 100.00% (1/1)
+github.com/conformal/btcchain/validate.go	 CalcBlockSubsidy			 100.00% (1/1)
 github.com/conformal/btcchain/txlookup.go	 fetchTxStoreMain			 95.65% (22/23)
 github.com/conformal/btcchain/merkle.go		 BuildMerkleTreeStore			 93.33% (14/15)
 github.com/conformal/btcchain/chain.go		 BlockChain.getReorganizeNodes		 92.86% (13/14)
@@ -35,19 +36,21 @@ github.com/conformal/btcchain/chain.go		 BlockChain.reorganizeChain		 85.29% (29
 github.com/conformal/btcchain/process.go	 BlockChain.processOrphans		 84.21% (16/19)
 github.com/conformal/btcchain/chain.go		 BlockChain.connectBlock		 83.33% (10/12)
 github.com/conformal/btcchain/chain.go		 BlockChain.calcPastMedianTime		 82.35% (14/17)
+github.com/conformal/btcchain/validate.go	 BlockChain.checkBIP0030		 82.35% (14/17)
 github.com/conformal/btcchain/chain.go		 BlockChain.isMajorityVersion		 80.00% (8/10)
 github.com/conformal/btcchain/difficulty.go	 CalcWork				 80.00% (4/5)
 github.com/conformal/btcchain/chain.go		 BlockChain.addOrphanBlock		 77.78% (14/18)
 github.com/conformal/btcchain/chain.go		 BlockChain.getPrevNodeFromBlock	 77.78% (7/9)
+github.com/conformal/btcchain/chain.go		 BlockChain.GenerateInitialIndex	 77.27% (17/22)
 github.com/conformal/btcchain/chain.go		 BlockChain.disconnectBlock		 76.92% (10/13)
 github.com/conformal/btcchain/txlookup.go	 BlockChain.fetchInputTransactions	 75.00% (18/24)
 github.com/conformal/btcchain/difficulty.go	 BigToCompact				 75.00% (12/16)
 github.com/conformal/btcchain/difficulty.go	 CompactToBig				 75.00% (9/12)
-github.com/conformal/btcchain/validate.go	 BlockChain.checkConnectBlock		 69.23% (36/52)
+github.com/conformal/btcchain/validate.go	 isTransactionSpent			 75.00% (3/4)
+github.com/conformal/btcchain/validate.go	 BlockChain.checkConnectBlock		 71.15% (37/52)
 github.com/conformal/btcchain/validate.go	 CheckBlockSanity			 67.44% (29/43)
 github.com/conformal/btcchain/validate.go	 isNullOutpoint				 66.67% (2/3)
 github.com/conformal/btcchain/validate.go	 CheckTransactionInputs			 65.12% (28/43)
-github.com/conformal/btcchain/validate.go	 BlockChain.checkBIP0030		 64.71% (11/17)
 github.com/conformal/btcchain/txlookup.go	 connectTransactions			 61.54% (8/13)
 github.com/conformal/btcchain/validate.go	 CheckTransactionSanity			 61.11% (22/36)
 github.com/conformal/btcchain/validate.go	 isBIP0030Node				 60.00% (3/5)
@@ -63,12 +66,11 @@ github.com/conformal/btcchain/notifications.go	 BlockChain.sendNotification		 50
 github.com/conformal/btcchain/chain.go		 BlockChain.pruneBlockNodes		 41.18% (7/17)
 github.com/conformal/btcchain/validate.go	 IsFinalizedTransaction			 28.57% (4/14)
 github.com/conformal/btcchain/checkpoints.go	 BlockChain.verifyCheckpoint		 22.22% (2/9)
-github.com/conformal/btcchain/difficulty.go	 BlockChain.calcNextRequiredDifficulty	 17.07% (7/41)
+github.com/conformal/btcchain/difficulty.go	 BlockChain.calcNextRequiredDifficulty	 17.50% (7/40)
 github.com/conformal/btcchain/checkpoints.go	 BlockChain.findPreviousCheckpoint	 4.88% (2/41)
 github.com/conformal/btcchain/blocklocator.go	 BlockChain.BlockLocatorFromHash	 0.00% (0/39)
 github.com/conformal/btcchain/checkpoints.go	 BlockChain.IsCheckpointCandidate	 0.00% (0/32)
-github.com/conformal/btcchain/validate.go	 countP2SHSigOps			 0.00% (0/26)
+github.com/conformal/btcchain/validate.go	 CountP2SHSigOps			 0.00% (0/26)
-github.com/conformal/btcchain/chain.go		 BlockChain.GenerateInitialIndex	 0.00% (0/22)
 github.com/conformal/btcchain/difficulty.go	 BlockChain.calcEasiestDifficulty	 0.00% (0/15)
 github.com/conformal/btcchain/difficulty.go	 BlockChain.findPrevTestNetDifficulty	 0.00% (0/12)
 github.com/conformal/btcchain/chain.go		 BlockChain.removeBlockNode		 0.00% (0/12)
@@ -81,14 +83,14 @@ github.com/conformal/btcchain/blocklocator.go	 BlockChain.LatestBlockLocator		 0
 github.com/conformal/btcchain/txlookup.go	 BlockChain.FetchTransactionStore	 0.00% (0/6)
 github.com/conformal/btcchain/checkpoints.go	 isNonstandardTransaction		 0.00% (0/5)
 github.com/conformal/btcchain/checkpoints.go	 BlockChain.checkpointData		 0.00% (0/4)
-github.com/conformal/btcchain/validate.go	 isTransactionSpent			 0.00% (0/4)
-github.com/conformal/btcchain/chain.go		 addChildrenWork			 0.00% (0/3)
 github.com/conformal/btcchain/notifications.go	 NotificationType.String		 0.00% (0/3)
+github.com/conformal/btcchain/chain.go		 addChildrenWork			 0.00% (0/3)
 github.com/conformal/btcchain/checkpoints.go	 BlockChain.Checkpoints			 0.00% (0/3)
-github.com/conformal/btcchain/log.go		 logClosure.String			 0.00% (0/1)
-github.com/conformal/btcchain/log.go		 newLogClosure				 0.00% (0/1)
 github.com/conformal/btcchain/chain.go		 BlockChain.DisableVerify		 0.00% (0/1)
-github.com/conformal/btcchain/log.go		 UseLogger				 0.00% (0/1)
 github.com/conformal/btcchain/process.go	 RuleError.Error			 0.00% (0/1)
-github.com/conformal/btcchain			 -------------------------------------	 53.75% (666/1239)
+github.com/conformal/btcchain/difficulty.go	 BlockChain.CalcNextRequiredDifficulty	 0.00% (0/1)
+github.com/conformal/btcchain/log.go		 logClosure.String			 0.00% (0/1)
+github.com/conformal/btcchain/log.go		 UseLogger				 0.00% (0/1)
+github.com/conformal/btcchain/log.go		 newLogClosure				 0.00% (0/1)
+github.com/conformal/btcchain			 -------------------------------------	 55.94% (697/1246)
 

validate.go

@@ -711,6 +711,15 @@ func CheckTransactionInputs(tx *btcutil.Tx, txHeight int64, txStore TxStore) (in
 // checkConnectBlock performs several checks to confirm connecting the passed
 // block to the main chain (including whatever reorganization might be necessary
 // to get this node to the main chain) does not violate any rules.
+//
+// The CheckConnectBlock function makes use of this function to perform the
+// bulk of its work.  The only difference is this function accepts a node which
+// may or may not require reorganization to connect it to the main chain whereas
+// CheckConnectBlock creates a new node which specifically connects to the end
+// of the current main chain and then calls this function with that node.
+//
+// See the comments for CheckConnectBlock for some examples of the type of
+// checks performed by this function.
 func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block) error {
 	// If the side chain blocks end up in the database, a call to
 	// checkBlockSanity should be done here in case a previous version
@@ -718,12 +727,9 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block) er
 	// implementation only currently uses memory for the side chain blocks,
 	// it isn't currently necessary.
 
-	// TODO(davec): Keep a flag if this has already been done to avoid
-	// multiple runs.
-
 	// The coinbase for the Genesis block is not spendable, so just return
 	// now.
-	if node.hash.IsEqual(b.chainParams().GenesisHash) {
+	if node.hash.IsEqual(b.chainParams().GenesisHash) && b.bestChain == nil {
 		return nil
 	}
 
@@ -864,3 +870,24 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block) er
 
 	return nil
 }
+
+// CheckConnectBlock performs several checks to confirm connecting the passed
+// block to the main chain does not violate any rules.  An example of some of
+// the checks performed are ensuring connecting the block would not cause any
+// duplicate transaction hashes for old transactions that aren't already fully
+// spent, double spends, exceeding the maximum allowed signature operations
+// per block, invalid values in relation to the expected block subisidy, or
+// fail transaction script validation.
+//
+// This function is NOT safe for concurrent access.
+func (b *BlockChain) CheckConnectBlock(block *btcutil.Block) error {
+	prevNode := b.bestChain
+	blockSha, _ := block.Sha()
+	newNode := newBlockNode(&block.MsgBlock().Header, blockSha, block.Height())
+	if prevNode != nil {
+		newNode.parent = prevNode
+		newNode.workSum.Add(prevNode.workSum, newNode.workSum)
+	}
+
+	return b.checkConnectBlock(newNode, block)
+}

validate_test.go

@@ -14,6 +14,30 @@ import (
 	"time"
 )
 
+// TestCheckConnectBlock tests the CheckConnectBlock function to ensure it
+// fails
+func TestCheckConnectBlock(t *testing.T) {
+	// Create a new database and chain instance to run tests against.
+	chain, teardownFunc, err := chainSetup("checkconnectblock")
+	if err != nil {
+		t.Errorf("Failed to setup chain instance: %v", err)
+		return
+	}
+	defer teardownFunc()
+
+	err = chain.GenerateInitialIndex()
+	if err != nil {
+		t.Errorf("GenerateInitialIndex: %v", err)
+	}
+
+	// The genesis block should fail to connect since it's already
+	// inserted.
+	err = chain.CheckConnectBlock(btcutil.NewBlock(&btcwire.GenesisBlock))
+	if err == nil {
+		t.Errorf("CheckConnectBlock: Did not received expected error")
+	}
+}
+
 func TestCheckBlockSanity(t *testing.T) {
 	powLimit := btcchain.ChainParams(btcwire.MainNet).PowLimit
 	block := btcutil.NewBlock(&Block100000)