Export chain parameters.

This commit exports the chain parameters used depending on the specific
bitcoin network so callers can have access to this information if desired.

chain.go

@@ -339,7 +339,7 @@ func (b *BlockChain) getPrevNodeFromNode(node *blockNode) (*blockNode, error) {
 	}
 
 	// Genesis block.
-	if node.hash.IsEqual(b.netParams().genesisHash) {
+	if node.hash.IsEqual(b.chainParams().GenesisHash) {
 		return nil, nil
 	}
 
@@ -393,7 +393,7 @@ func (b *BlockChain) isMajorityVersion(minVer uint32, startNode *blockNode, numR
 func (b *BlockChain) calcPastMedianTime(startNode *blockNode) (time.Time, error) {
 	// Genesis block.
 	if startNode == nil {
-		return b.netParams().genesisBlock.Header.Timestamp, nil
+		return b.chainParams().GenesisBlock.Header.Timestamp, nil
 	}
 
 	// Create a slice of the previous few block timestamps used to calculate

difficulty.go

@@ -188,7 +188,7 @@ func (b *BlockChain) calcEasiestDifficulty(bits uint32, duration time.Duration)
 	adjustmentFactor := big.NewInt(retargetAdjustmentFactor)
 
 	// Choose the correct proof of work limit for the active network.
-	powLimit := b.netParams().powLimit
+	powLimit := b.chainParams().PowLimit
 
 	// The test network rules allow minimum difficulty blocks after more
 	// than twice the desired amount of time needed to generate a block has
@@ -225,7 +225,7 @@ func (b *BlockChain) calcEasiestDifficulty(bits uint32, duration time.Duration)
 func (b *BlockChain) findPrevTestNetDifficulty(startNode *blockNode) (uint32, error) {
 	// Search backwards through the chain for the last block without
 	// the special rule applied.
-	powLimitBits := BigToCompact(b.netParams().powLimit)
+	powLimitBits := BigToCompact(b.chainParams().PowLimit)
 	iterNode := startNode
 	for iterNode != nil && iterNode.height%blocksPerRetarget != 0 && iterNode.bits == powLimitBits {
 		// Get the previous block node.  This function is used over
@@ -254,7 +254,7 @@ func (b *BlockChain) findPrevTestNetDifficulty(startNode *blockNode) (uint32, er
 // after the passed previous block node based on the difficulty retarget rules.
 func (b *BlockChain) calcNextRequiredDifficulty(lastNode *blockNode, block *btcutil.Block) (uint32, error) {
 	// Choose the correct proof of work limit for the active network.
-	powLimit := b.netParams().powLimit
+	powLimit := b.chainParams().PowLimit
 
 	// Genesis block.
 	if lastNode == nil {

params.go

@@ -9,50 +9,64 @@ import (
 	"math/big"
 )
 
-// params is used to group parameters for various networks such as the main
-// network and test networks.
-type params struct {
-	genesisBlock *btcwire.MsgBlock
-	genesisHash  *btcwire.ShaHash
-	powLimit     *big.Int
+// Params houses parameters unique to various bitcoin networks such as the main
+// network and test networks.  See ChainParams.
+type Params struct {
+	// GenesisBlock is the genesis block for the specific network.
+	GenesisBlock *btcwire.MsgBlock
+
+	// GenesisHash is the genesis block hash for the specific network.
+	GenesisHash *btcwire.ShaHash
+
+	// PowLimit is the highest proof of work value a bitcoin block can have
+	// for the specific network.
+	PowLimit *big.Int
 }
 
 // mainNetParams contains parameters specific to the main network
 // (btcwire.MainNet).
-var mainNetParams = params{
-	genesisBlock: &btcwire.GenesisBlock,
-	genesisHash:  &btcwire.GenesisHash,
+var mainNetParams = Params{
+	GenesisBlock: &btcwire.GenesisBlock,
+	GenesisHash:  &btcwire.GenesisHash,
 
-	// powLimit is the highest proof of work value a bitcoin block can have.
+	// PowLimit is the highest proof of work value a bitcoin block can have.
 	// It is the value 2^224 - 1 for the main network.
-	powLimit: new(big.Int).Sub(new(big.Int).Lsh(bigOne, 224), bigOne),
+	PowLimit: new(big.Int).Sub(new(big.Int).Lsh(bigOne, 224), bigOne),
 }
 
 // regressionParams contains parameters specific to the regression test network
 // (btcwire.TestNet).
-var regressionParams = params{
-	genesisBlock: &btcwire.TestNetGenesisBlock,
-	genesisHash:  &btcwire.TestNetGenesisHash,
+var regressionParams = Params{
+	GenesisBlock: &btcwire.TestNetGenesisBlock,
+	GenesisHash:  &btcwire.TestNetGenesisHash,
 
-	// powLimit is the highest proof of work value a bitcoin block can have.
+	// PowLimit is the highest proof of work value a bitcoin block can have.
 	// It is the value 2^256 - 1 for the regression test network.
-	powLimit: new(big.Int).Sub(new(big.Int).Lsh(bigOne, 255), bigOne),
+	PowLimit: new(big.Int).Sub(new(big.Int).Lsh(bigOne, 255), bigOne),
 }
 
 // testNet3Params contains parameters specific to the test network (version 3)
 // (btcwire.TestNet3).
-var testNet3Params = params{
-	genesisBlock: &btcwire.TestNet3GenesisBlock,
-	genesisHash:  &btcwire.TestNet3GenesisHash,
+var testNet3Params = Params{
+	GenesisBlock: &btcwire.TestNet3GenesisBlock,
+	GenesisHash:  &btcwire.TestNet3GenesisHash,
 
-	// powLimit is the highest proof of work value a bitcoin block can have.
+	// PowLimit is the highest proof of work value a bitcoin block can have.
 	// It is the value 2^224 - 1 for the test network (version 3).
-	powLimit: new(big.Int).Sub(new(big.Int).Lsh(bigOne, 224), bigOne),
+	PowLimit: new(big.Int).Sub(new(big.Int).Lsh(bigOne, 224), bigOne),
 }
 
-// netParams returns parameters specific to the passed bitcoin network.
-func (b *BlockChain) netParams() *params {
-	switch b.btcnet {
+// chainParams returns chain parameters specific to the bitcoin network
+// associated with the BlockChain instance.
+func (b *BlockChain) chainParams() *Params {
+	return ChainParams(b.btcnet)
+}
+
+// ChainParams returns chain parameters specific to the passed bitcoin network.
+// It returns the parameters for btcwire.MainNet if the passed network is not
+// supported.
+func ChainParams(btcnet btcwire.BitcoinNet) *Params {
+	switch btcnet {
 	case btcwire.TestNet:
 		return &regressionParams
 

validate.go

@@ -278,7 +278,7 @@ func (b *BlockChain) checkProofOfWork(block *btcutil.Block) error {
 	}
 
 	// The target difficulty must be less than the maximum allowed.
-	powLimit := b.netParams().powLimit
+	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)
@@ -712,7 +712,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block) er
 
 	// The coinbase for the Genesis block is not spendable, so just return
 	// now.
-	if node.hash.IsEqual(b.netParams().genesisHash) {
+	if node.hash.IsEqual(b.chainParams().GenesisHash) {
 		return nil
 	}