chaincfg: Add IsBech32SegwitPrefix utility method.

The IsBech32SegwitPrefix method takes a string prefix and
determines if it is a valid prefix for a Bech32 encoded segwit
address for any of the default or registered networks.

chaincfg/params.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"math"
 	"math/big"
+	"strings"
 	"time"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -195,8 +196,8 @@ type Params struct {
 	// Mempool parameters
 	RelayNonStdTxs bool
 
-	// Human-readable part for Bech32 encoded segwit addresses, as defined in
+	// Human-readable part for Bech32 encoded segwit addresses, as defined
-	// BIP 173.
+	// in BIP 173.
 	Bech32HRPSegwit string
 
 	// Address encoding magics
@@ -547,10 +548,11 @@ var (
 )
 
 var (
-	registeredNets    = make(map[wire.BitcoinNet]struct{})
+	registeredNets       = make(map[wire.BitcoinNet]struct{})
-	pubKeyHashAddrIDs = make(map[byte]struct{})
+	pubKeyHashAddrIDs    = make(map[byte]struct{})
-	scriptHashAddrIDs = make(map[byte]struct{})
+	scriptHashAddrIDs    = make(map[byte]struct{})
-	hdPrivToPubKeyIDs = make(map[[4]byte][]byte)
+	bech32SegwitPrefixes = make(map[string]struct{})
+	hdPrivToPubKeyIDs    = make(map[[4]byte][]byte)
 )
 
 // String returns the hostname of the DNS seed in human-readable form.
@@ -575,6 +577,10 @@ func Register(params *Params) error {
 	pubKeyHashAddrIDs[params.PubKeyHashAddrID] = struct{}{}
 	scriptHashAddrIDs[params.ScriptHashAddrID] = struct{}{}
 	hdPrivToPubKeyIDs[params.HDPrivateKeyID] = params.HDPublicKeyID[:]
+
+	// A valid Bech32 encoded segwit address always has as prefix the
+	// human-readable part for the given net followed by '1'.
+	bech32SegwitPrefixes[params.Bech32HRPSegwit+"1"] = struct{}{}
 	return nil
 }
 
@@ -608,6 +614,15 @@ func IsScriptHashAddrID(id byte) bool {
 	return ok
 }
 
+// IsBech32SegwitPrefix returns whether the prefix is a known prefix for segwit
+// addresses on any default or registered network.  This is used when decoding
+// an address string into a specific address type.
+func IsBech32SegwitPrefix(prefix string) bool {
+	prefix = strings.ToLower(prefix)
+	_, ok := bech32SegwitPrefixes[prefix]
+	return ok
+}
+
 // HDPrivateKeyToPublicKeyID accepts a private hierarchical deterministic
 // extended key id and returns the associated public key id.  When the provided
 // id is not registered, the ErrUnknownHDKeyID error will be returned.

chaincfg/register_test.go

@@ -3,6 +3,7 @@ package chaincfg_test
 import (
 	"bytes"
 	"reflect"
+	"strings"
 	"testing"
 
 	. "github.com/btcsuite/btcd/chaincfg"
@@ -16,6 +17,7 @@ var mockNetParams = Params{
 	Net:              1<<32 - 1,
 	PubKeyHashAddrID: 0x9f,
 	ScriptHashAddrID: 0xf9,
+	Bech32HRPSegwit:  "tc",
 	HDPrivateKeyID:   [4]byte{0x01, 0x02, 0x03, 0x04},
 	HDPublicKeyID:    [4]byte{0x05, 0x06, 0x07, 0x08},
 }
@@ -30,6 +32,10 @@ func TestRegister(t *testing.T) {
 		magic byte
 		valid bool
 	}
+	type prefixTest struct {
+		prefix string
+		valid  bool
+	}
 	type hdTest struct {
 		priv []byte
 		want []byte
@@ -37,11 +43,12 @@ func TestRegister(t *testing.T) {
 	}
 
 	tests := []struct {
-		name        string
+		name           string
-		register    []registerTest
+		register       []registerTest
-		p2pkhMagics []magicTest
+		p2pkhMagics    []magicTest
-		p2shMagics  []magicTest
+		p2shMagics     []magicTest
-		hdMagics    []hdTest
+		segwitPrefixes []prefixTest
+		hdMagics       []hdTest
 	}{
 		{
 			name: "default networks",
@@ -119,6 +126,44 @@ func TestRegister(t *testing.T) {
 					valid: false,
 				},
 			},
+			segwitPrefixes: []prefixTest{
+				{
+					prefix: MainNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: TestNet3Params.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: RegressionNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: SimNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: strings.ToUpper(MainNetParams.Bech32HRPSegwit + "1"),
+					valid:  true,
+				},
+				{
+					prefix: mockNetParams.Bech32HRPSegwit + "1",
+					valid:  false,
+				},
+				{
+					prefix: "abc1",
+					valid:  false,
+				},
+				{
+					prefix: "1",
+					valid:  false,
+				},
+				{
+					prefix: MainNetParams.Bech32HRPSegwit,
+					valid:  false,
+				},
+			},
 			hdMagics: []hdTest{
 				{
 					priv: MainNetParams.HDPrivateKeyID[:],
@@ -215,6 +260,44 @@ func TestRegister(t *testing.T) {
 					valid: false,
 				},
 			},
+			segwitPrefixes: []prefixTest{
+				{
+					prefix: MainNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: TestNet3Params.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: RegressionNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: SimNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: strings.ToUpper(MainNetParams.Bech32HRPSegwit + "1"),
+					valid:  true,
+				},
+				{
+					prefix: mockNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: "abc1",
+					valid:  false,
+				},
+				{
+					prefix: "1",
+					valid:  false,
+				},
+				{
+					prefix: MainNetParams.Bech32HRPSegwit,
+					valid:  false,
+				},
+			},
 			hdMagics: []hdTest{
 				{
 					priv: mockNetParams.HDPrivateKeyID[:],
@@ -304,6 +387,44 @@ func TestRegister(t *testing.T) {
 					valid: false,
 				},
 			},
+			segwitPrefixes: []prefixTest{
+				{
+					prefix: MainNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: TestNet3Params.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: RegressionNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: SimNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: strings.ToUpper(MainNetParams.Bech32HRPSegwit + "1"),
+					valid:  true,
+				},
+				{
+					prefix: mockNetParams.Bech32HRPSegwit + "1",
+					valid:  true,
+				},
+				{
+					prefix: "abc1",
+					valid:  false,
+				},
+				{
+					prefix: "1",
+					valid:  false,
+				},
+				{
+					prefix: MainNetParams.Bech32HRPSegwit,
+					valid:  false,
+				},
+			},
 			hdMagics: []hdTest{
 				{
 					priv: MainNetParams.HDPrivateKeyID[:],
@@ -364,6 +485,13 @@ func TestRegister(t *testing.T) {
 					test.name, i, valid, magTest.valid)
 			}
 		}
+		for i, prxTest := range test.segwitPrefixes {
+			valid := IsBech32SegwitPrefix(prxTest.prefix)
+			if valid != prxTest.valid {
+				t.Errorf("%s: segwit prefix %s (%d) valid mismatch: got %v expected %v",
+					test.name, prxTest.prefix, i, valid, prxTest.valid)
+			}
+		}
 		for i, magTest := range test.hdMagics {
 			pubKey, err := HDPrivateKeyToPublicKeyID(magTest.priv[:])
 			if !reflect.DeepEqual(err, magTest.err) {