Release v0.3.0

vendor/github.com/btcsuite/btcwallet/wallet/txrules/rules.go

@@ -0,0 +1,98 @@
+// Copyright (c) 2016 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+// Package txrules provides transaction rules that should be followed by
+// transaction authors for wide mempool acceptance and quick mining.
+package txrules
+
+import (
+	"errors"
+
+	"github.com/btcsuite/btcd/txscript"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/btcsuite/btcutil"
+)
+
+// DefaultRelayFeePerKb is the default minimum relay fee policy for a mempool.
+const DefaultRelayFeePerKb btcutil.Amount = 1e3
+
+// GetDustThreshold is used to define the amount below which output will be
+// determined as dust. Threshold is determined as 3 times the relay fee.
+func GetDustThreshold(scriptSize int, relayFeePerKb btcutil.Amount) btcutil.Amount {
+	// Calculate the total (estimated) cost to the network.  This is
+	// calculated using the serialize size of the output plus the serial
+	// size of a transaction input which redeems it.  The output is assumed
+	// to be compressed P2PKH as this is the most common script type.  Use
+	// the average size of a compressed P2PKH redeem input (148) rather than
+	// the largest possible (txsizes.RedeemP2PKHInputSize).
+	totalSize := 8 + wire.VarIntSerializeSize(uint64(scriptSize)) +
+		scriptSize + 148
+
+	byteFee := relayFeePerKb / 1000
+	relayFee := btcutil.Amount(totalSize) * byteFee
+	return 3 * relayFee
+}
+
+// IsDustAmount determines whether a transaction output value and script length would
+// cause the output to be considered dust.  Transactions with dust outputs are
+// not standard and are rejected by mempools with default policies.
+func IsDustAmount(amount btcutil.Amount, scriptSize int, relayFeePerKb btcutil.Amount) bool {
+	return amount < GetDustThreshold(scriptSize, relayFeePerKb)
+}
+
+// IsDustOutput determines whether a transaction output is considered dust.
+// Transactions with dust outputs are not standard and are rejected by mempools
+// with default policies.
+func IsDustOutput(output *wire.TxOut, relayFeePerKb btcutil.Amount) bool {
+	// Unspendable outputs which solely carry data are not checked for dust.
+	if txscript.GetScriptClass(output.PkScript) == txscript.NullDataTy {
+		return false
+	}
+
+	// All other unspendable outputs are considered dust.
+	if txscript.IsUnspendable(output.PkScript) {
+		return true
+	}
+
+	return IsDustAmount(btcutil.Amount(output.Value), len(output.PkScript),
+		relayFeePerKb)
+}
+
+// Transaction rule violations
+var (
+	ErrAmountNegative   = errors.New("transaction output amount is negative")
+	ErrAmountExceedsMax = errors.New("transaction output amount exceeds maximum value")
+	ErrOutputIsDust     = errors.New("transaction output is dust")
+)
+
+// CheckOutput performs simple consensus and policy tests on a transaction
+// output.
+func CheckOutput(output *wire.TxOut, relayFeePerKb btcutil.Amount) error {
+	if output.Value < 0 {
+		return ErrAmountNegative
+	}
+	if output.Value > btcutil.MaxSatoshi {
+		return ErrAmountExceedsMax
+	}
+	if IsDustOutput(output, relayFeePerKb) {
+		return ErrOutputIsDust
+	}
+	return nil
+}
+
+// FeeForSerializeSize calculates the required fee for a transaction of some
+// arbitrary size given a mempool's relay fee policy.
+func FeeForSerializeSize(relayFeePerKb btcutil.Amount, txSerializeSize int) btcutil.Amount {
+	fee := relayFeePerKb * btcutil.Amount(txSerializeSize) / 1000
+
+	if fee == 0 && relayFeePerKb > 0 {
+		fee = relayFeePerKb
+	}
+
+	if fee < 0 || fee > btcutil.MaxSatoshi {
+		fee = btcutil.MaxSatoshi
+	}
+
+	return fee
+}