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package chunk
import (
"errors"
"fmt"
"github.com/ethereum/go-ethereum/common"
)
const (
DefaultSize = 4096
MaxPO = 16
AddressLength = 32
)
var (
ErrChunkNotFound = errors.New("chunk not found")
ErrChunkInvalid = errors.New("invalid chunk")
)
type Chunk interface {
Address() Address
Data() []byte
}
type chunk struct {
addr Address
sdata []byte
}
func NewChunk(addr Address, data []byte) *chunk {
return &chunk{
addr: addr,
sdata: data,
}
}
func (c *chunk) Address() Address {
return c.addr
}
func (c *chunk) Data() []byte {
return c.sdata
}
func (self *chunk) String() string {
return fmt.Sprintf("Address: %v Chunksize: %v", self.addr.Log(), len(self.sdata))
}
type Address []byte
var ZeroAddr = Address(common.Hash{}.Bytes())
func (a Address) Hex() string {
return fmt.Sprintf("%064x", []byte(a[:]))
}
func (a Address) Log() string {
if len(a[:]) < 8 {
return fmt.Sprintf("%x", []byte(a[:]))
}
return fmt.Sprintf("%016x", []byte(a[:8]))
}
func (a Address) String() string {
return fmt.Sprintf("%064x", []byte(a))
}
func (a Address) MarshalJSON() (out []byte, err error) {
return []byte(`"` + a.String() + `"`), nil
}
func (a *Address) UnmarshalJSON(value []byte) error {
s := string(value)
*a = make([]byte, 32)
h := common.Hex2Bytes(s[1 : len(s)-1])
copy(*a, h)
return nil
}
// Proximity 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 []byte) (ret int) {
b := (MaxPO-1)/8 + 1
if b > len(one) {
b = len(one)
}
m := 8
for i := 0; i < b; i++ {
oxo := one[i] ^ other[i]
for j := 0; j < m; j++ {
if (oxo>>uint8(7-j))&0x01 != 0 {
return i*8 + j
}
}
}
return MaxPO
}
|
