chaincfg

README

chaincfg

Package chaincfg defines chain configuration parameters for the three standard Bitcoin networks and provides the ability for callers to define their own custom Bitcoin networks.

Although this package was primarily written for btcd, it has intentionally been designed so it can be used as a standalone package for any projects needing to use parameters for the standard Bitcoin networks or for projects needing to define their own network.

Sample Use

package main

import (
	"flag"
	"fmt"
	"log"

	"github.com/btcsuite/btcutil"
	"github.com/btcsuite/btcd/chaincfg"
)

var testnet = flag.Bool("testnet", false, "operate on the testnet Bitcoin network")

// By default (without -testnet), use mainnet.
var chainParams = &chaincfg.MainNetParams

func main() {
	flag.Parse()

	// Modify active network parameters if operating on testnet.
	if *testnet {
		chainParams = &chaincfg.TestNet3Params
	}

	// later...

	// Create and print new payment address, specific to the active network.
	pubKeyHash := make([]byte, 20)
	addr, err := btcutil.NewAddressPubKeyHash(pubKeyHash, chainParams)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(addr)
}

Installation and Updating

$ go get -u github.com/btcsuite/btcd/chaincfg

GPG Verification Key

All official release tags are signed by Conformal so users can ensure the code has not been tampered with and is coming from the btcsuite developers. To verify the signature perform the following:

• Download the public key from the Conformal website at https://opensource.conformal.com/GIT-GPG-KEY-conformal.txt

• Import the public key into your GPG keyring:

  gpg --import GIT-GPG-KEY-conformal.txt
  

• Verify the release tag with the following command where TAG_NAME is a placeholder for the specific tag:

  git tag -v TAG_NAME
  

License

Package chaincfg is licensed under the copyfree ISC License.

Documentation

Overview

Package chaincfg defines chain configuration parameters.

In addition to the main Bitcoin network, which is intended for the transfer of monetary value, there also exists two currently active standard networks: regression test and testnet (version 3). These networks are incompatible with each other (each sharing a different genesis block) and software should handle errors where input intended for one network is used on an application instance running on a different network.

For library packages, chaincfg provides the ability to lookup chain parameters and encoding magics when passed a *Params. Older APIs not updated to the new convention of passing a *Params may lookup the parameters for a wire.BitcoinNet using ParamsForNet, but be aware that this usage is deprecated and will be removed from chaincfg in the future.

For main packages, a (typically global) var may be assigned the address of one of the standard Param vars for use as the application's "active" network. When a network parameter is needed, it may then be looked up through this variable (either directly, or hidden in a library call).

package main

import (
        "flag"
        "fmt"
        "log"

        "github.com/btcsuite/btcutil"
        "github.com/btcsuite/btcd/chaincfg"
)

var testnet = flag.Bool("testnet", false, "operate on the testnet Bitcoin network")

// By default (without -testnet), use mainnet.
var chainParams = &chaincfg.MainNetParams

func main() {
        flag.Parse()

        // Modify active network parameters if operating on testnet.
        if *testnet {
                chainParams = &chaincfg.TestNet3Params
        }

        // later...

        // Create and print new payment address, specific to the active network.
        pubKeyHash := make([]byte, 20)
        addr, err := btcutil.NewAddressPubKeyHash(pubKeyHash, chainParams)
        if err != nil {
                log.Fatal(err)
        }
        fmt.Println(addr)
}

If an application does not use one of the three standard Bitcoin networks, a new Params struct may be created which defines the parameters for the non-standard network. As a general rule of thumb, all network parameters should be unique to the network, but parameter collisions can still occur (unfortunately, this is the case with regtest and testnet3 sharing magics).

Index

• Constants
• Variables
• func HDPrivateKeyToPublicKeyID(id []byte) ([]byte, error)
• func IsBech32SegwitPrefix(prefix string) bool
• func IsPubKeyHashAddrID(id byte) bool
• func IsScriptHashAddrID(id byte) bool
• func Register(params *Params) error
• type Checkpoint
• type ConsensusDeployment
• type DNSSeed
  • func (d DNSSeed) String() string
• type Params

Constants

const (
	// DeploymentTestDummy defines the rule change deployment ID for testing
	// purposes.
	DeploymentTestDummy = iota

	// DeploymentCSV defines the rule change deployment ID for the CSV
	// soft-fork package. The CSV package includes the deployment of BIPS
	// 68, 112, and 113.
	DeploymentCSV

	// DeploymentSegwit defines the rule change deployment ID for the
	// Segregated Witness (segwit) soft-fork package. The segwit package
	// includes the deployment of BIPS 141, 142, 144, 145, 147 and 173.
	DeploymentSegwit

	// DefinedDeployments is the number of currently defined deployments.
	DefinedDeployments
)

Constants that define the deployment offset in the deployments field of the parameters for each deployment. This is useful to be able to get the details of a specific deployment by name.

Variables

var (
	// ErrDuplicateNet describes an error where the parameters for a Bitcoin
	// network could not be set due to the network already being a standard
	// network or previously-registered into this package.
	ErrDuplicateNet = errors.New("duplicate Bitcoin network")

	// ErrUnknownHDKeyID describes an error where the provided id which
	// is intended to identify the network for a hierarchical deterministic
	// private extended key is not registered.
	ErrUnknownHDKeyID = errors.New("unknown hd private extended key bytes")
)

var MainNetParams = Params{
	Name:        "mainnet",
	Net:         wire.MainNet,
	DefaultPort: "8333",
	DNSSeeds: []DNSSeed{
		{"seed.bitcoin.sipa.be", true},
		{"dnsseed.bluematt.me", true},
		{"dnsseed.bitcoin.dashjr.org", false},
		{"seed.bitcoinstats.com", true},
		{"seed.bitnodes.io", false},
		{"seed.bitcoin.jonasschnelli.ch", true},
	},

	GenesisBlock:             &genesisBlock,
	GenesisHash:              &genesisHash,
	PowLimit:                 mainPowLimit,
	PowLimitBits:             0x1d00ffff,
	BIP0034Height:            227931,
	BIP0065Height:            388381,
	BIP0066Height:            363725,
	CoinbaseMaturity:         100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Hour * 24 * 14,
	TargetTimePerBlock:       time.Minute * 10,
	RetargetAdjustmentFactor: 4,
	ReduceMinDifficulty:      false,
	MinDiffReductionTime:     0,
	GenerateSupported:        false,

	Checkpoints: []Checkpoint{
		{11111, newHashFromStr("0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d")},
		{33333, newHashFromStr("000000002dd5588a74784eaa7ab0507a18ad16a236e7b1ce69f00d7ddfb5d0a6")},
		{74000, newHashFromStr("0000000000573993a3c9e41ce34471c079dcf5f52a0e824a81e7f953b8661a20")},
		{105000, newHashFromStr("00000000000291ce28027faea320c8d2b054b2e0fe44a773f3eefb151d6bdc97")},
		{134444, newHashFromStr("00000000000005b12ffd4cd315cd34ffd4a594f430ac814c91184a0d42d2b0fe")},
		{168000, newHashFromStr("000000000000099e61ea72015e79632f216fe6cb33d7899acb35b75c8303b763")},
		{193000, newHashFromStr("000000000000059f452a5f7340de6682a977387c17010ff6e6c3bd83ca8b1317")},
		{210000, newHashFromStr("000000000000048b95347e83192f69cf0366076336c639f9b7228e9ba171342e")},
		{216116, newHashFromStr("00000000000001b4f4b433e81ee46494af945cf96014816a4e2370f11b23df4e")},
		{225430, newHashFromStr("00000000000001c108384350f74090433e7fcf79a606b8e797f065b130575932")},
		{250000, newHashFromStr("000000000000003887df1f29024b06fc2200b55f8af8f35453d7be294df2d214")},
		{267300, newHashFromStr("000000000000000a83fbd660e918f218bf37edd92b748ad940483c7c116179ac")},
		{279000, newHashFromStr("0000000000000001ae8c72a0b0c301f67e3afca10e819efa9041e458e9bd7e40")},
		{300255, newHashFromStr("0000000000000000162804527c6e9b9f0563a280525f9d08c12041def0a0f3b2")},
		{319400, newHashFromStr("000000000000000021c6052e9becade189495d1c539aa37c58917305fd15f13b")},
		{343185, newHashFromStr("0000000000000000072b8bf361d01a6ba7d445dd024203fafc78768ed4368554")},
		{352940, newHashFromStr("000000000000000010755df42dba556bb72be6a32f3ce0b6941ce4430152c9ff")},
		{382320, newHashFromStr("00000000000000000a8dc6ed5b133d0eb2fd6af56203e4159789b092defd8ab2")},
	},

	RuleChangeActivationThreshold: 1916,
	MinerConfirmationWindow:       2016,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  1199145601,
			ExpireTime: 1230767999,
		},
		DeploymentCSV: {
			BitNumber:  0,
			StartTime:  1462060800,
			ExpireTime: 1493596800,
		},
		DeploymentSegwit: {
			BitNumber:  1,
			StartTime:  1479168000,
			ExpireTime: 1510704000,
		},
	},

	RelayNonStdTxs: false,

	Bech32HRPSegwit: "bc",

	PubKeyHashAddrID:        0x00,
	ScriptHashAddrID:        0x05,
	PrivateKeyID:            0x80,
	WitnessPubKeyHashAddrID: 0x06,
	WitnessScriptHashAddrID: 0x0A,

	HDPrivateKeyID: [4]byte{0x04, 0x88, 0xad, 0xe4},
	HDPublicKeyID:  [4]byte{0x04, 0x88, 0xb2, 0x1e},

	HDCoinType: 0,
}

MainNetParams defines the network parameters for the main Bitcoin network.

var RegressionNetParams = Params{
	Name:        "regtest",
	Net:         wire.TestNet,
	DefaultPort: "18444",
	DNSSeeds:    []DNSSeed{},

	GenesisBlock:             &regTestGenesisBlock,
	GenesisHash:              &regTestGenesisHash,
	PowLimit:                 regressionPowLimit,
	PowLimitBits:             0x207fffff,
	CoinbaseMaturity:         100,
	BIP0034Height:            100000000,
	BIP0065Height:            1351,
	BIP0066Height:            1251,
	SubsidyReductionInterval: 150,
	TargetTimespan:           time.Hour * 24 * 14,
	TargetTimePerBlock:       time.Minute * 10,
	RetargetAdjustmentFactor: 4,
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     time.Minute * 20,
	GenerateSupported:        true,

	Checkpoints: nil,

	RuleChangeActivationThreshold: 108,
	MinerConfirmationWindow:       144,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  0,
			ExpireTime: math.MaxInt64,
		},
		DeploymentCSV: {
			BitNumber:  0,
			StartTime:  0,
			ExpireTime: math.MaxInt64,
		},
		DeploymentSegwit: {
			BitNumber:  1,
			StartTime:  0,
			ExpireTime: math.MaxInt64,
		},
	},

	RelayNonStdTxs: true,

	Bech32HRPSegwit: "tb",

	PubKeyHashAddrID: 0x6f,
	ScriptHashAddrID: 0xc4,
	PrivateKeyID:     0xef,

	HDPrivateKeyID: [4]byte{0x04, 0x35, 0x83, 0x94},
	HDPublicKeyID:  [4]byte{0x04, 0x35, 0x87, 0xcf},

	HDCoinType: 1,
}

RegressionNetParams defines the network parameters for the regression test Bitcoin network. Not to be confused with the test Bitcoin network (version 3), this network is sometimes simply called "testnet".

var SimNetParams = Params{
	Name:        "simnet",
	Net:         wire.SimNet,
	DefaultPort: "18555",
	DNSSeeds:    []DNSSeed{},

	GenesisBlock:             &simNetGenesisBlock,
	GenesisHash:              &simNetGenesisHash,
	PowLimit:                 simNetPowLimit,
	PowLimitBits:             0x207fffff,
	BIP0034Height:            0,
	BIP0065Height:            0,
	BIP0066Height:            0,
	CoinbaseMaturity:         100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Hour * 24 * 14,
	TargetTimePerBlock:       time.Minute * 10,
	RetargetAdjustmentFactor: 4,
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     time.Minute * 20,
	GenerateSupported:        true,

	Checkpoints: nil,

	RuleChangeActivationThreshold: 75,
	MinerConfirmationWindow:       100,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  0,
			ExpireTime: math.MaxInt64,
		},
		DeploymentCSV: {
			BitNumber:  0,
			StartTime:  0,
			ExpireTime: math.MaxInt64,
		},
		DeploymentSegwit: {
			BitNumber:  1,
			StartTime:  0,
			ExpireTime: math.MaxInt64,
		},
	},

	RelayNonStdTxs: true,

	Bech32HRPSegwit: "sb",

	PubKeyHashAddrID:        0x3f,
	ScriptHashAddrID:        0x7b,
	PrivateKeyID:            0x64,
	WitnessPubKeyHashAddrID: 0x19,
	WitnessScriptHashAddrID: 0x28,

	HDPrivateKeyID: [4]byte{0x04, 0x20, 0xb9, 0x00},
	HDPublicKeyID:  [4]byte{0x04, 0x20, 0xbd, 0x3a},

	HDCoinType: 115,
}

SimNetParams defines the network parameters for the simulation test Bitcoin network. This network is similar to the normal test network except it is intended for private use within a group of individuals doing simulation testing. The functionality is intended to differ in that the only nodes which are specifically specified are used to create the network rather than following normal discovery rules. This is important as otherwise it would just turn into another public testnet.

var TestNet3Params = Params{
	Name:        "testnet3",
	Net:         wire.TestNet3,
	DefaultPort: "18333",
	DNSSeeds: []DNSSeed{
		{"testnet-seed.bitcoin.jonasschnelli.ch", true},
		{"testnet-seed.bitcoin.schildbach.de", false},
		{"seed.tbtc.petertodd.org", true},
		{"testnet-seed.bluematt.me", false},
	},

	GenesisBlock:             &testNet3GenesisBlock,
	GenesisHash:              &testNet3GenesisHash,
	PowLimit:                 testNet3PowLimit,
	PowLimitBits:             0x1d00ffff,
	BIP0034Height:            21111,
	BIP0065Height:            581885,
	BIP0066Height:            330776,
	CoinbaseMaturity:         100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Hour * 24 * 14,
	TargetTimePerBlock:       time.Minute * 10,
	RetargetAdjustmentFactor: 4,
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     time.Minute * 20,
	GenerateSupported:        false,

	Checkpoints: []Checkpoint{
		{546, newHashFromStr("000000002a936ca763904c3c35fce2f3556c559c0214345d31b1bcebf76acb70")},
		{100000, newHashFromStr("00000000009e2958c15ff9290d571bf9459e93b19765c6801ddeccadbb160a1e")},
		{200000, newHashFromStr("0000000000287bffd321963ef05feab753ebe274e1d78b2fd4e2bfe9ad3aa6f2")},
		{300001, newHashFromStr("0000000000004829474748f3d1bc8fcf893c88be255e6d7f571c548aff57abf4")},
		{400002, newHashFromStr("0000000005e2c73b8ecb82ae2dbc2e8274614ebad7172b53528aba7501f5a089")},
		{500011, newHashFromStr("00000000000929f63977fbac92ff570a9bd9e7715401ee96f2848f7b07750b02")},
		{600002, newHashFromStr("000000000001f471389afd6ee94dcace5ccc44adc18e8bff402443f034b07240")},
		{700000, newHashFromStr("000000000000406178b12a4dea3b27e13b3c4fe4510994fd667d7c1e6a3f4dc1")},
		{800010, newHashFromStr("000000000017ed35296433190b6829db01e657d80631d43f5983fa403bfdb4c1")},
		{900000, newHashFromStr("0000000000356f8d8924556e765b7a94aaebc6b5c8685dcfa2b1ee8b41acd89b")},
		{1000007, newHashFromStr("00000000001ccb893d8a1f25b70ad173ce955e5f50124261bbbc50379a612ddf")},
	},

	RuleChangeActivationThreshold: 1512,
	MinerConfirmationWindow:       2016,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  1199145601,
			ExpireTime: 1230767999,
		},
		DeploymentCSV: {
			BitNumber:  0,
			StartTime:  1456790400,
			ExpireTime: 1493596800,
		},
		DeploymentSegwit: {
			BitNumber:  1,
			StartTime:  1462060800,
			ExpireTime: 1493596800,
		},
	},

	RelayNonStdTxs: true,

	Bech32HRPSegwit: "tb",

	PubKeyHashAddrID:        0x6f,
	ScriptHashAddrID:        0xc4,
	WitnessPubKeyHashAddrID: 0x03,
	WitnessScriptHashAddrID: 0x28,
	PrivateKeyID:            0xef,

	HDPrivateKeyID: [4]byte{0x04, 0x35, 0x83, 0x94},
	HDPublicKeyID:  [4]byte{0x04, 0x35, 0x87, 0xcf},

	HDCoinType: 1,
}

TestNet3Params defines the network parameters for the test Bitcoin network (version 3). Not to be confused with the regression test network, this network is sometimes simply called "testnet".

Functions

func HDPrivateKeyToPublicKeyID

func HDPrivateKeyToPublicKeyID(id []byte) ([]byte, error)

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.

func IsBech32SegwitPrefix

func IsBech32SegwitPrefix(prefix string) bool

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 IsPubKeyHashAddrID

func IsPubKeyHashAddrID(id byte) bool

IsPubKeyHashAddrID returns whether the id is an identifier known to prefix a pay-to-pubkey-hash address on any default or registered network. This is used when decoding an address string into a specific address type. It is up to the caller to check both this and IsScriptHashAddrID and decide whether an address is a pubkey hash address, script hash address, neither, or undeterminable (if both return true).

func IsScriptHashAddrID

func IsScriptHashAddrID(id byte) bool

IsScriptHashAddrID returns whether the id is an identifier known to prefix a pay-to-script-hash address on any default or registered network. This is used when decoding an address string into a specific address type. It is up to the caller to check both this and IsPubKeyHashAddrID and decide whether an address is a pubkey hash address, script hash address, neither, or undeterminable (if both return true).

func Register

func Register(params *Params) error

Register registers the network parameters for a Bitcoin network. This may error with ErrDuplicateNet if the network is already registered (either due to a previous Register call, or the network being one of the default networks).

Network parameters should be registered into this package by a main package as early as possible. Then, library packages may lookup networks or network parameters based on inputs and work regardless of the network being standard or not.

Types

type Checkpoint

type Checkpoint struct {
	Height int32
	Hash   *chainhash.Hash
}

Checkpoint identifies a known good point in the block chain. Using checkpoints allows a few optimizations for old blocks during initial download and also prevents forks from old blocks.

Each checkpoint is selected based upon several factors. See the documentation for blockchain.IsCheckpointCandidate for details on the selection criteria.

type ConsensusDeployment

type ConsensusDeployment struct {
	// BitNumber defines the specific bit number within the block version
	// this particular soft-fork deployment refers to.
	BitNumber uint8

	// StartTime is the median block time after which voting on the
	// deployment starts.
	StartTime uint64

	// ExpireTime is the median block time after which the attempted
	// deployment expires.
	ExpireTime uint64
}

ConsensusDeployment defines details related to a specific consensus rule change that is voted in. This is part of BIP0009.

type DNSSeed

type DNSSeed struct {
	// Host defines the hostname of the seed.
	Host string

	// HasFiltering defines whether the seed supports filtering
	// by service flags (wire.ServiceFlag).
	HasFiltering bool
}

DNSSeed identifies a DNS seed.

func (DNSSeed) String

func (d DNSSeed) String() string

String returns the hostname of the DNS seed in human-readable form.

type Params

type Params struct {
	// Name defines a human-readable identifier for the network.
	Name string

	// Net defines the magic bytes used to identify the network.
	Net wire.BitcoinNet

	// DefaultPort defines the default peer-to-peer port for the network.
	DefaultPort string

	// DNSSeeds defines a list of DNS seeds for the network that are used
	// as one method to discover peers.
	DNSSeeds []DNSSeed

	// GenesisBlock defines the first block of the chain.
	GenesisBlock *wire.MsgBlock

	// GenesisHash is the starting block hash.
	GenesisHash *chainhash.Hash

	// PowLimit defines the highest allowed proof of work value for a block
	// as a uint256.
	PowLimit *big.Int

	// PowLimitBits defines the highest allowed proof of work value for a
	// block in compact form.
	PowLimitBits uint32

	// These fields define the block heights at which the specified softfork
	// BIP became active.
	BIP0034Height int32
	BIP0065Height int32
	BIP0066Height int32

	// CoinbaseMaturity is the number of blocks required before newly mined
	// coins (coinbase transactions) can be spent.
	CoinbaseMaturity uint16

	// SubsidyReductionInterval is the interval of blocks before the subsidy
	// is reduced.
	SubsidyReductionInterval int32

	// TargetTimespan is the desired amount of time that should elapse
	// before the block difficulty requirement is examined to determine how
	// it should be changed in order to maintain the desired block
	// generation rate.
	TargetTimespan time.Duration

	// TargetTimePerBlock is the desired amount of time to generate each
	// block.
	TargetTimePerBlock time.Duration

	// RetargetAdjustmentFactor is the adjustment factor used to limit
	// the minimum and maximum amount of adjustment that can occur between
	// difficulty retargets.
	RetargetAdjustmentFactor int64

	// ReduceMinDifficulty defines whether the network should reduce the
	// minimum required difficulty after a long enough period of time has
	// passed without finding a block.  This is really only useful for test
	// networks and should not be set on a main network.
	ReduceMinDifficulty bool

	// MinDiffReductionTime is the amount of time after which the minimum
	// required difficulty should be reduced when a block hasn't been found.
	//
	// NOTE: This only applies if ReduceMinDifficulty is true.
	MinDiffReductionTime time.Duration

	// GenerateSupported specifies whether or not CPU mining is allowed.
	GenerateSupported bool

	// Checkpoints ordered from oldest to newest.
	Checkpoints []Checkpoint

	// These fields are related to voting on consensus rule changes as
	// defined by BIP0009.
	//
	// RuleChangeActivationThreshold is the number of blocks in a threshold
	// state retarget window for which a positive vote for a rule change
	// must be cast in order to lock in a rule change. It should typically
	// be 95% for the main network and 75% for test networks.
	//
	// MinerConfirmationWindow is the number of blocks in each threshold
	// state retarget window.
	//
	// Deployments define the specific consensus rule changes to be voted
	// on.
	RuleChangeActivationThreshold uint32
	MinerConfirmationWindow       uint32
	Deployments                   [DefinedDeployments]ConsensusDeployment

	// Mempool parameters
	RelayNonStdTxs bool

	// Human-readable part for Bech32 encoded segwit addresses, as defined
	// in BIP 173.
	Bech32HRPSegwit string

	// Address encoding magics
	PubKeyHashAddrID        byte // First byte of a P2PKH address
	ScriptHashAddrID        byte // First byte of a P2SH address
	PrivateKeyID            byte // First byte of a WIF private key
	WitnessPubKeyHashAddrID byte // First byte of a P2WPKH address
	WitnessScriptHashAddrID byte // First byte of a P2WSH address

	// BIP32 hierarchical deterministic extended key magics
	HDPrivateKeyID [4]byte
	HDPublicKeyID  [4]byte

	// BIP44 coin type used in the hierarchical deterministic path for
	// address generation.
	HDCoinType uint32
}

Params defines a Bitcoin network by its parameters. These parameters may be used by Bitcoin applications to differentiate networks as well as addresses and keys for one network from those intended for use on another network.