mempool: export isDust for use in other projects

This changes isDust to IsDust so other golang projects (btcwallet
or lnd) can use the precise dust calculation used by btcd.

mempool/policy.go

@@ -172,12 +172,12 @@ func checkPkScriptStandard(pkScript []byte, scriptClass txscript.ScriptClass) er
 	return nil
 }
 
-// isDust returns whether or not the passed transaction output amount is
+// IsDust returns whether or not the passed transaction output amount is
 // considered dust or not based on the passed minimum transaction relay fee.
 // Dust is defined in terms of the minimum transaction relay fee.  In
 // particular, if the cost to the network to spend coins is more than 1/3 of the
 // minimum transaction relay fee, it is considered dust.
-func isDust(txOut *wire.TxOut, minRelayTxFee btcutil.Amount) bool {
+func IsDust(txOut *wire.TxOut, minRelayTxFee btcutil.Amount) bool {
 	// Unspendable outputs are considered dust.
 	if txscript.IsUnspendable(txOut.PkScript) {
 		return true
@@ -351,7 +351,7 @@ func checkTransactionStandard(tx *btcutil.Tx, height int32,
 		// "dust".
 		if scriptClass == txscript.NullDataTy {
 			numNullDataOutputs++
-		} else if isDust(txOut, minRelayTxFee) {
+		} else if IsDust(txOut, minRelayTxFee) {
 			str := fmt.Sprintf("transaction output %d: payment "+
 				"of %d is dust", i, txOut.Value)
 			return txRuleError(wire.RejectDust, str)

mempool/policy_test.go

@@ -204,7 +204,7 @@ func TestCheckPkScriptStandard(t *testing.T) {
 	}
 }
 
-// TestDust tests the isDust API.
+// TestDust tests the IsDust API.
 func TestDust(t *testing.T) {
 	pkScript := []byte{0x76, 0xa9, 0x21, 0x03, 0x2f, 0x7e, 0x43,
 		0x0a, 0xa4, 0xc9, 0xd1, 0x59, 0x43, 0x7e, 0x84, 0xb9,
@@ -268,7 +268,7 @@ func TestDust(t *testing.T) {
 		},
 	}
 	for _, test := range tests {
-		res := isDust(&test.txOut, test.relayFee)
+		res := IsDust(&test.txOut, test.relayFee)
 		if res != test.isDust {
 			t.Fatalf("Dust test '%s' failed: want %v got %v",
 				test.name, test.isDust, res)