-
Notifications
You must be signed in to change notification settings - Fork 20.2k
/
iter.go
288 lines (256 loc) · 6.76 KB
/
iter.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
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
// Copyright 2019 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 enode
import (
"sync"
"time"
)
// Iterator represents a sequence of nodes. The Next method moves to the next node in the
// sequence. It returns false when the sequence has ended or the iterator is closed. Close
// may be called concurrently with Next and Node, and interrupts Next if it is blocked.
type Iterator interface {
Next() bool // moves to next node
Node() *Node // returns current node
Close() // ends the iterator
}
// ReadNodes reads at most n nodes from the given iterator. The return value contains no
// duplicates and no nil values. To prevent looping indefinitely for small repeating node
// sequences, this function calls Next at most n times.
func ReadNodes(it Iterator, n int) []*Node {
seen := make(map[ID]*Node, n)
for i := 0; i < n && it.Next(); i++ {
// Remove duplicates, keeping the node with higher seq.
node := it.Node()
prevNode, ok := seen[node.ID()]
if ok && prevNode.Seq() > node.Seq() {
continue
}
seen[node.ID()] = node
}
result := make([]*Node, 0, len(seen))
for _, node := range seen {
result = append(result, node)
}
return result
}
// IterNodes makes an iterator which runs through the given nodes once.
func IterNodes(nodes []*Node) Iterator {
return &sliceIter{nodes: nodes, index: -1}
}
// CycleNodes makes an iterator which cycles through the given nodes indefinitely.
func CycleNodes(nodes []*Node) Iterator {
return &sliceIter{nodes: nodes, index: -1, cycle: true}
}
type sliceIter struct {
mu sync.Mutex
nodes []*Node
index int
cycle bool
}
func (it *sliceIter) Next() bool {
it.mu.Lock()
defer it.mu.Unlock()
if len(it.nodes) == 0 {
return false
}
it.index++
if it.index == len(it.nodes) {
if it.cycle {
it.index = 0
} else {
it.nodes = nil
return false
}
}
return true
}
func (it *sliceIter) Node() *Node {
it.mu.Lock()
defer it.mu.Unlock()
if len(it.nodes) == 0 {
return nil
}
return it.nodes[it.index]
}
func (it *sliceIter) Close() {
it.mu.Lock()
defer it.mu.Unlock()
it.nodes = nil
}
// Filter wraps an iterator such that Next only returns nodes for which
// the 'check' function returns true.
func Filter(it Iterator, check func(*Node) bool) Iterator {
return &filterIter{it, check}
}
type filterIter struct {
Iterator
check func(*Node) bool
}
func (f *filterIter) Next() bool {
for f.Iterator.Next() {
if f.check(f.Node()) {
return true
}
}
return false
}
// FairMix aggregates multiple node iterators. The mixer itself is an iterator which ends
// only when Close is called. Source iterators added via AddSource are removed from the
// mix when they end.
//
// The distribution of nodes returned by Next is approximately fair, i.e. FairMix
// attempts to draw from all sources equally often. However, if a certain source is slow
// and doesn't return a node within the configured timeout, a node from any other source
// will be returned.
//
// It's safe to call AddSource and Close concurrently with Next.
type FairMix struct {
wg sync.WaitGroup
fromAny chan *Node
timeout time.Duration
cur *Node
mu sync.Mutex
closed chan struct{}
sources []*mixSource
last int
}
type mixSource struct {
it Iterator
next chan *Node
timeout time.Duration
}
// NewFairMix creates a mixer.
//
// The timeout specifies how long the mixer will wait for the next fairly-chosen source
// before giving up and taking a node from any other source. A good way to set the timeout
// is deciding how long you'd want to wait for a node on average. Passing a negative
// timeout makes the mixer completely fair.
func NewFairMix(timeout time.Duration) *FairMix {
m := &FairMix{
fromAny: make(chan *Node),
closed: make(chan struct{}),
timeout: timeout,
}
return m
}
// AddSource adds a source of nodes.
func (m *FairMix) AddSource(it Iterator) {
m.mu.Lock()
defer m.mu.Unlock()
if m.closed == nil {
return
}
m.wg.Add(1)
source := &mixSource{it, make(chan *Node), m.timeout}
m.sources = append(m.sources, source)
go m.runSource(m.closed, source)
}
// Close shuts down the mixer and all current sources.
// Calling this is required to release resources associated with the mixer.
func (m *FairMix) Close() {
m.mu.Lock()
defer m.mu.Unlock()
if m.closed == nil {
return
}
for _, s := range m.sources {
s.it.Close()
}
close(m.closed)
m.wg.Wait()
close(m.fromAny)
m.sources = nil
m.closed = nil
}
// Next returns a node from a random source.
func (m *FairMix) Next() bool {
m.cur = nil
var timeout <-chan time.Time
if m.timeout >= 0 {
timer := time.NewTimer(m.timeout)
timeout = timer.C
defer timer.Stop()
}
for {
source := m.pickSource()
if source == nil {
return m.nextFromAny()
}
select {
case n, ok := <-source.next:
if ok {
m.cur = n
source.timeout = m.timeout
return true
}
// This source has ended.
m.deleteSource(source)
case <-timeout:
source.timeout /= 2
return m.nextFromAny()
}
}
}
// Node returns the current node.
func (m *FairMix) Node() *Node {
return m.cur
}
// nextFromAny is used when there are no sources or when the 'fair' choice
// doesn't turn up a node quickly enough.
func (m *FairMix) nextFromAny() bool {
n, ok := <-m.fromAny
if ok {
m.cur = n
}
return ok
}
// pickSource chooses the next source to read from, cycling through them in order.
func (m *FairMix) pickSource() *mixSource {
m.mu.Lock()
defer m.mu.Unlock()
if len(m.sources) == 0 {
return nil
}
m.last = (m.last + 1) % len(m.sources)
return m.sources[m.last]
}
// deleteSource deletes a source.
func (m *FairMix) deleteSource(s *mixSource) {
m.mu.Lock()
defer m.mu.Unlock()
for i := range m.sources {
if m.sources[i] == s {
copy(m.sources[i:], m.sources[i+1:])
m.sources[len(m.sources)-1] = nil
m.sources = m.sources[:len(m.sources)-1]
break
}
}
}
// runSource reads a single source in a loop.
func (m *FairMix) runSource(closed chan struct{}, s *mixSource) {
defer m.wg.Done()
defer close(s.next)
for s.it.Next() {
n := s.it.Node()
select {
case s.next <- n:
case m.fromAny <- n:
case <-closed:
return
}
}
}