1 files changed, 105 insertions, 1 deletions
diff --git a/swarm/chunk/chunk.go b/swarm/chunk/chunk.go
index 1449efccd..7540af8ce 100644
--- a/swarm/chunk/chunk.go
+++ b/swarm/chunk/chunk.go
@@ -1,5 +1,109 @@
 package chunk
 
+import (
+	"errors"
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
 const (
-	DefaultSize = 4096
+	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
+}