/
metadata.go
173 lines (156 loc) · 3.37 KB
/
metadata.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
package tor
import (
"crypto/sha1"
"errors"
"sort"
"github.com/jech/storrent/hash"
"github.com/jech/storrent/peer"
)
func metadataPeers(t *Torrent, count int) []*peer.Peer {
if len(t.peers) == 0 {
return nil
}
pn := t.rand.Perm(len(t.peers))
var peers []*peer.Peer
for n := range pn {
if t.peers[n].CanMetadata() {
peers = append(peers, t.peers[n])
if len(peers) >= count {
break
}
}
}
return peers
}
func metadataVote(t *Torrent, size uint32) error {
if t.infoComplete != 0 {
return errors.New("metadata complete")
}
if size <= 0 || size > 128*1024*1024 {
return errors.New("bad size")
}
if t.infoSizeVotes == nil {
t.infoSizeVotes = make(map[uint32]int)
}
t.infoSizeVotes[size]++
return nil
}
func metadataGuess(t *Torrent) uint32 {
if t.infoComplete != 0 {
panic("Eek!")
}
if t.infoSizeVotes == nil {
return 0
}
count := -1
var size uint32
for s, c := range t.infoSizeVotes {
if c > count {
count = c
size = s
}
}
return size
}
func resizeMetadata(t *Torrent, size uint32) error {
if t.infoComplete != 0 {
return errors.New("metadata complete")
}
if size <= 0 || size > 128*1024*1024 {
return errors.New("bad size")
}
if len(t.Info) != int(size) {
t.Info = make([]byte, size)
t.infoBitmap = nil
t.infoRequested = make([]uint8, (size+16*1024-1)/(16*1024))
}
return nil
}
func requestMetadata(t *Torrent, p *peer.Peer) error {
if t.infoComplete != 0 {
return errors.New("metadata complete")
}
guess := metadataGuess(t)
if guess == 0 {
return errors.New("unknown size")
}
if uint32(len(t.Info)) != guess {
err := resizeMetadata(t, guess)
if err != nil {
return err
}
}
var peers []*peer.Peer
if p == nil {
peers = metadataPeers(t, 8)
} else {
peers = []*peer.Peer{p}
}
cn := t.rand.Perm(len(t.infoRequested))
sort.Slice(cn, func(i, j int) bool {
if !t.infoBitmap.Get(cn[i]) && t.infoBitmap.Get(cn[j]) {
return true
}
if t.infoBitmap.Get(cn[i]) && !t.infoBitmap.Get(cn[j]) {
return false
}
return t.infoRequested[cn[i]] < t.infoRequested[cn[j]]
})
j := 0
for _, p := range peers {
if j >= len(cn) || t.infoBitmap.Get(cn[j]) {
return nil
}
err := maybeWritePeer(p, peer.PeerGetMetadata{uint32(cn[j])})
if err == nil {
t.infoRequested[cn[j]]++
j++
}
}
return nil
}
func gotMetadata(t *Torrent, index, size uint32, data []byte) (bool, error) {
if t.infoComplete != 0 {
return false, errors.New("metadata complete")
}
if size != uint32(len(t.Info)) {
return false, errors.New("inconsistent metadata size")
}
chunks := len(t.infoRequested)
if int(index) > chunks {
return false, errors.New("chunk beyond end of metadata")
}
if len(data) != 16*1024 &&
int(index)*16*1024+len(data) != len(t.Info) {
return false, errors.New("inconsistent metadata length")
}
if t.infoBitmap.Get(int(index)) {
return false, nil
}
copy(t.Info[index*16*1024:], data)
t.infoBitmap.Set(int(index))
for i := 0; i < chunks; i++ {
if !t.infoBitmap.Get(i) {
return false, nil
}
}
hsh := sha1.Sum(t.Info)
h := hash.Hash(hsh[:])
if !h.Equal(t.Hash) {
t.Info = nil
t.infoBitmap = nil
t.infoRequested = nil
return false, errors.New("hash mismatch")
}
err := t.MetadataComplete()
if err != nil {
t.Info = nil
t.infoBitmap = nil
t.infoRequested = nil
return false, err
}
t.infoSizeVotes = nil
t.infoBitmap = nil
t.infoRequested = nil
return true, nil
}