Base58Address.go

package btcaddress

import (
	"errors"
	"crypto/sha256"
	"github.com/chainlibs/btcaddress/base58"
)

// ErrChecksum indicates that the checksum of a check-encoded string does not verify against
// the checksum.
var ErrChecksum = errors.New("checksum error")

// ErrInvalidFormat indicates that the check-encoded string has an invalid format.
var ErrInvalidFormat = errors.New("invalid format: version and/or checksum bytes missing")

// checksum: first four bytes of sha256^2
func checksum(input []byte) (cksum [4]byte) {
	h := sha256.Sum256(input)
	h2 := sha256.Sum256(h[:])
	copy(cksum[:], h2[:4])
	return
}

// DecodeAddressToH160 decodes a string that was encoded with CheckEncode and verifies the checksum.
func DecodeAddressToH160(input string) (result []byte, version byte, err error) {
	decoded := base58.Decode(input)
	if len(decoded) < 5 {
		return nil, 0, ErrInvalidFormat
	}
	version = decoded[0]
	var cksum [4]byte
	copy(cksum[:], decoded[len(decoded)-4:])
	if checksum(decoded[:len(decoded)-4]) != cksum {
		return nil, 0, ErrChecksum
	}
	payload := decoded[1 : len(decoded)-4]
	result = append(result, payload...)
	return
}

// encodeAddressFromH160 returns a human-readable payment address given a ripemd160 hash
// and magic which encodes the bitcoin network and address type.  It is used
// in both pay-to-pubkey-hash (P2PKH) and pay-to-script-hash (P2SH) address
// encoding.
func EncodeAddressFromH160(hash160 []byte, magic Magic) string {
	// Format is 1 byte for a network and address class (i.e. P2PKH vs
	// P2SH), 20 bytes for a RIPEMD160 hash, and 4 bytes of checksum.
	b := make([]byte, 0, 1+len(hash160)+4)
	b = append(b, byte(magic))
	b = append(b, hash160[:]...)
	cksum := checksum(b)
	b = append(b, cksum[:]...)
	return base58.Encode(b)
}