// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package pot see doc.go
package pot
import (
"encoding/binary"
"fmt"
"math/rand"
"strconv"
"strings"
"github.com/ethereum/go-ethereum/common"
)
var (
zerosBin = Address{}.Bin()
)
// Address is an alias for common.Hash
type Address common.Hash
// NewAddressFromBytes constructs an Address from a byte slice
func NewAddressFromBytes(b []byte) Address {
h := common.Hash{}
copy(h[:], b)
return Address(h)
}
func (a Address) IsZero() bool {
return a.Bin() == zerosBin
}
func (a Address) String() string {
return fmt.Sprintf("%x", a[:])
}
// MarshalJSON Address serialisation
func (a *Address) MarshalJSON() (out []byte, err error) {
return []byte(`"` + a.String() + `"`), nil
}
// UnmarshalJSON Address deserialisation
func (a *Address) UnmarshalJSON(value []byte) error {
*a = Address(common.HexToHash(string(value[1 : len(value)-1])))
return nil
}
// Bin returns the string form of the binary representation of an address (only first 8 bits)
func (a Address) Bin() string {
return ToBin(a[:])
}
// ToBin converts a byteslice to the string binary representation
func ToBin(a []byte) string {
var bs []string
for _, b := range a {
bs = append(bs, fmt.Sprintf("%08b", b))
}
return strings.Join(bs, "")
}
// Bytes returns the Address as a byte slice
func (a Address) Bytes() []byte {
return a[:]
}
/*
Proximity(x, y) returns the proximity order of the MSB distance between x and y
The distance metric MSB(x, y) of two equal length byte sequences x an y is the
value of the binary integer cast of the x^y, ie., x and y bitwise xor-ed.
the binary cast is big endian: most significant bit first (=MSB).
Proximity(x, y) is a discrete logarithmic scaling of the MSB distance.
It is defined as the reverse rank of the integer part of the base 2
logarithm of the distance.
It is calculated by counting the number of common leading zeros in the (MSB)
binary representation of the x^y.
(0 farthest, 255 closest, 256 self)
*/
func proximity(one, other Address) (ret int, eq bool) {
return posProximity(one, other, 0)
}
// posProximity(a, b, pos) returns proximity order of b wrt a (symmetric) pretending
// the first pos bits match, checking only bits index >= pos
func posProximity(one, other Address, pos int) (ret int, eq bool) {
for i := pos / 8; i < len(one); i++ {
if one[i] == other[i] {
continue
}
oxo := one[i] ^ other[i]
start := 0
if i == pos/8 {
start = pos % 8
}
for j := start; j < 8; j++ {
if (oxo>>uint8(7-j))&0x01 != 0 {
return i*8 + j, false
}
}
}
return len(one) * 8, true
}
// ProxCmp compares the distances a->target and b->target.
// Returns -1 if a is closer to target, 1 if b is closer to target
// and 0 if they are equal.
func ProxCmp(a, x, y interface{}) int {
return proxCmp(ToBytes(a), ToBytes(x), ToBytes(y))
}
func proxCmp(a, x, y []byte) int {
for i := range a {
dx := x[i] ^ a[i]
dy := y[i] ^ a[i]
if dx > dy {
return 1
} else if dx < dy {
return -1
}
}
return 0
}
// RandomAddressAt (address, prox) generates a random address
// at proximity order prox relative to address
// if prox is negative a random address is generated
func RandomAddressAt(self Address, prox int) (addr Address) {
addr = self
pos := -1
if prox >= 0 {
pos = prox / 8
trans := prox % 8
transbytea := byte(0)
for j := 0; j <= trans; j++ {
transbytea |= 1 << uint8(7-j)
}
flipbyte := byte(1 << uint8(7-trans))
transbyteb := transbytea ^ byte(255)
randbyte := byte(rand.Intn(255))
addr[pos] = ((addr[pos] & transbytea) ^ flipbyte) | randbyte&transbyteb
}
for i := pos + 1; i < len(addr); i++ {
addr[i] = byte(rand.Intn(255))
}
return
}
// RandomAddress generates a random address
func RandomAddress() Address {
return RandomAddressAt(Address{}, -1)
}
// NewAddressFromString creates a byte slice from a string in binary representation
func NewAddressFromString(s string) []byte {
ha := [32]byte{}
t := s + zerosBin[:len(zerosBin)-len(s)]
for i := 0; i < 4; i++ {
n, err := strconv.ParseUint(t[i*64:(i+1)*64], 2, 64)
if err != nil {
panic("wrong format: " + err.Error())
}
binary.BigEndian.PutUint64(ha[i*8:(i+1)*8], n)
}
return ha[:]
}
// BytesAddress is an interface for elements addressable by a byte slice
type BytesAddress interface {
Address() []byte
}
// ToBytes turns the Val into bytes
func ToBytes(v Val) []byte {
if v == nil {
return nil
}
b, ok := v.([]byte)
if !ok {
ba, ok := v.(BytesAddress)
if !ok {
panic(fmt.Sprintf("unsupported value type %T", v))
}
b = ba.Address()
}
return b
}
// DefaultPof returns a proximity order comparison operator function
// where all
func DefaultPof(max int) func(one, other Val, pos int) (int, bool) {
return func(one, other Val, pos int) (int, bool) {
po, eq := proximityOrder(ToBytes(one), ToBytes(other), pos)
if po >= max {
eq = true
po = max
}
return po, eq
}
}
func proximityOrder(one, other []byte, pos int) (int, bool) {
for i := pos / 8; i < len(one); i++ {
if one[i] == other[i] {
continue
}
oxo := one[i] ^ other[i]
start := 0
if i == pos/8 {
start = pos % 8
}
for j := start; j < 8; j++ {
if (oxo>>uint8(7-j))&0x01 != 0 {
return i*8 + j, false
}
}
}
return len(one) * 8, true
}
// Label displays the node's key in binary format
func Label(v Val) string {
if v == nil {
return "<nil>"
}
if s, ok := v.(fmt.Stringer); ok {
return s.String()
}
if b, ok := v.([]byte); ok {
return ToBin(b)
}
panic(fmt.Sprintf("unsupported value type %T", v))
}
