Make the CheckBlockSanity function context free.

Rather than defining CheckBlockSanity as a member of a BlockChain
instance, define it at the root level so it is truly context free as
intended.  In order to make it context free, the proof of work limit is
now a required parameter.

process.go

@@ -112,7 +112,7 @@ func (b *BlockChain) ProcessBlock(block *btcutil.Block) error {
 	}
 
 	// Perform preliminary sanity checks on the block and its transactions.
-	err = b.CheckBlockSanity(block)
+	err = CheckBlockSanity(block, b.chainParams().PowLimit)
 	if err != nil {
 		return err
 	}

validate.go

@@ -12,6 +12,7 @@ import (
 	"github.com/conformal/btcutil"
 	"github.com/conformal/btcwire"
 	"math"
+	"math/big"
 	"time"
 )
 
@@ -265,7 +266,7 @@ func CheckTransactionSanity(tx *btcutil.Tx) error {
 // checkProofOfWork ensures the block header bits which indicate the target
 // difficulty is in min/max range and that the block hash is less than the
 // target difficulty as claimed.
-func (b *BlockChain) checkProofOfWork(block *btcutil.Block) error {
+func checkProofOfWork(block *btcutil.Block, powLimit *big.Int) error {
 	// The target difficulty must be larger than zero.
 	header := block.MsgBlock().Header
 	target := CompactToBig(header.Bits)
@@ -276,7 +277,6 @@ func (b *BlockChain) checkProofOfWork(block *btcutil.Block) error {
 	}
 
 	// The target difficulty must be less than the maximum allowed.
-	powLimit := b.chainParams().PowLimit
 	if target.Cmp(powLimit) > 0 {
 		str := fmt.Sprintf("block target difficulty of %064x is "+
 			"higher than max of %064x", target, powLimit)
@@ -390,7 +390,7 @@ func countP2SHSigOps(tx *btcutil.Tx, isCoinBaseTx bool, txStore TxStore) (int, e
 
 // CheckBlockSanity performs some preliminary checks on a block to ensure it is
 // sane before continuing with block processing.  These checks are context free.
-func (b *BlockChain) CheckBlockSanity(block *btcutil.Block) error {
+func CheckBlockSanity(block *btcutil.Block, powLimit *big.Int) error {
 	// NOTE: bitcoind does size limits checking here, but the size limits
 	// have already been checked by btcwire for incoming blocks.  Also,
 	// btcwire checks the size limits on send too, so there is no need
@@ -399,7 +399,7 @@ func (b *BlockChain) CheckBlockSanity(block *btcutil.Block) error {
 	// Ensure the proof of work bits in the block header is in min/max range
 	// and the block hash is less than the target value described by the
 	// bits.
-	err := b.checkProofOfWork(block)
+	err := checkProofOfWork(block, powLimit)
 	if err != nil {
 		return err
 	}

validate_test.go

@@ -15,16 +15,9 @@ import (
 )
 
 func TestCheckBlockSanity(t *testing.T) {
-	// Create a new database and chain instance to run tests against.
-	chain, teardownFunc, err := chainSetup("cbsanity")
-	if err != nil {
-		t.Errorf("Failed to setup chain instance: %v", err)
-		return
-	}
-	defer teardownFunc()
-
+	powLimit := btcchain.ChainParams(btcwire.MainNet).PowLimit
 	block := btcutil.NewBlock(&Block100000)
-	err = chain.CheckBlockSanity(block)
+	err := btcchain.CheckBlockSanity(block, powLimit)
 	if err != nil {
 		t.Errorf("CheckBlockSanity: %v", err)
 	}