github.com/keltia/go-ipfs@v0.3.8-0.20150909044612-210793031c63/routing/kbucket/util.go (about)

     1  package kbucket
     2  
     3  import (
     4  	"bytes"
     5  	"crypto/sha256"
     6  	"errors"
     7  
     8  	key "github.com/ipfs/go-ipfs/blocks/key"
     9  	peer "github.com/ipfs/go-ipfs/p2p/peer"
    10  	ks "github.com/ipfs/go-ipfs/routing/keyspace"
    11  	u "github.com/ipfs/go-ipfs/util"
    12  )
    13  
    14  // Returned if a routing table query returns no results. This is NOT expected
    15  // behaviour
    16  var ErrLookupFailure = errors.New("failed to find any peer in table")
    17  
    18  // ID for IpfsDHT is in the XORKeySpace
    19  //
    20  // The type dht.ID signifies that its contents have been hashed from either a
    21  // peer.ID or a util.Key. This unifies the keyspace
    22  type ID []byte
    23  
    24  func (id ID) equal(other ID) bool {
    25  	return bytes.Equal(id, other)
    26  }
    27  
    28  func (id ID) less(other ID) bool {
    29  	a := ks.Key{Space: ks.XORKeySpace, Bytes: id}
    30  	b := ks.Key{Space: ks.XORKeySpace, Bytes: other}
    31  	return a.Less(b)
    32  }
    33  
    34  func xor(a, b ID) ID {
    35  	return ID(u.XOR(a, b))
    36  }
    37  
    38  func commonPrefixLen(a, b ID) int {
    39  	return ks.ZeroPrefixLen(u.XOR(a, b))
    40  }
    41  
    42  // ConvertPeerID creates a DHT ID by hashing a Peer ID (Multihash)
    43  func ConvertPeerID(id peer.ID) ID {
    44  	hash := sha256.Sum256([]byte(id))
    45  	return hash[:]
    46  }
    47  
    48  // ConvertKey creates a DHT ID by hashing a local key (String)
    49  func ConvertKey(id key.Key) ID {
    50  	hash := sha256.Sum256([]byte(id))
    51  	return hash[:]
    52  }
    53  
    54  // Closer returns true if a is closer to key than b is
    55  func Closer(a, b peer.ID, key key.Key) bool {
    56  	aid := ConvertPeerID(a)
    57  	bid := ConvertPeerID(b)
    58  	tgt := ConvertKey(key)
    59  	adist := xor(aid, tgt)
    60  	bdist := xor(bid, tgt)
    61  
    62  	return adist.less(bdist)
    63  }