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
|
// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package fastwalk provides a faster version of filepath.Walk for file system
// scanning tools.
package fastwalk
import (
"errors"
"os"
"path/filepath"
"runtime"
"sync"
)
// ErrTraverseLink is used as a return value from WalkFuncs to indicate that the
// symlink named in the call may be traversed.
var ErrTraverseLink = errors.New("fastwalk: traverse symlink, assuming target is a directory")
// ErrSkipFiles is a used as a return value from WalkFuncs to indicate that the
// callback should not be called for any other files in the current directory.
// Child directories will still be traversed.
var ErrSkipFiles = errors.New("fastwalk: skip remaining files in directory")
// Walk is a faster implementation of filepath.Walk.
//
// filepath.Walk's design necessarily calls os.Lstat on each file,
// even if the caller needs less info.
// Many tools need only the type of each file.
// On some platforms, this information is provided directly by the readdir
// system call, avoiding the need to stat each file individually.
// fastwalk_unix.go contains a fork of the syscall routines.
//
// See golang.org/issue/16399
//
// Walk walks the file tree rooted at root, calling walkFn for
// each file or directory in the tree, including root.
//
// If fastWalk returns filepath.SkipDir, the directory is skipped.
//
// Unlike filepath.Walk:
// * file stat calls must be done by the user.
// The only provided metadata is the file type, which does not include
// any permission bits.
// * multiple goroutines stat the filesystem concurrently. The provided
// walkFn must be safe for concurrent use.
// * fastWalk can follow symlinks if walkFn returns the TraverseLink
// sentinel error. It is the walkFn's responsibility to prevent
// fastWalk from going into symlink cycles.
func Walk(root string, walkFn func(path string, typ os.FileMode) error) error {
// TODO(bradfitz): make numWorkers configurable? We used a
// minimum of 4 to give the kernel more info about multiple
// things we want, in hopes its I/O scheduling can take
// advantage of that. Hopefully most are in cache. Maybe 4 is
// even too low of a minimum. Profile more.
numWorkers := 4
if n := runtime.NumCPU(); n > numWorkers {
numWorkers = n
}
// Make sure to wait for all workers to finish, otherwise
// walkFn could still be called after returning. This Wait call
// runs after close(e.donec) below.
var wg sync.WaitGroup
defer wg.Wait()
w := &walker{
fn: walkFn,
enqueuec: make(chan walkItem, numWorkers), // buffered for performance
workc: make(chan walkItem, numWorkers), // buffered for performance
donec: make(chan struct{}),
// buffered for correctness & not leaking goroutines:
resc: make(chan error, numWorkers),
}
defer close(w.donec)
for i := 0; i < numWorkers; i++ {
wg.Add(1)
go w.doWork(&wg)
}
todo := []walkItem{{dir: root}}
out := 0
for {
workc := w.workc
var workItem walkItem
if len(todo) == 0 {
workc = nil
} else {
workItem = todo[len(todo)-1]
}
select {
case workc <- workItem:
todo = todo[:len(todo)-1]
out++
case it := <-w.enqueuec:
todo = append(todo, it)
case err := <-w.resc:
out--
if err != nil {
return err
}
if out == 0 && len(todo) == 0 {
// It's safe to quit here, as long as the buffered
// enqueue channel isn't also readable, which might
// happen if the worker sends both another unit of
// work and its result before the other select was
// scheduled and both w.resc and w.enqueuec were
// readable.
select {
case it := <-w.enqueuec:
todo = append(todo, it)
default:
return nil
}
}
}
}
}
// doWork reads directories as instructed (via workc) and runs the
// user's callback function.
func (w *walker) doWork(wg *sync.WaitGroup) {
defer wg.Done()
for {
select {
case <-w.donec:
return
case it := <-w.workc:
select {
case <-w.donec:
return
case w.resc <- w.walk(it.dir, !it.callbackDone):
}
}
}
}
type walker struct {
fn func(path string, typ os.FileMode) error
donec chan struct{} // closed on fastWalk's return
workc chan walkItem // to workers
enqueuec chan walkItem // from workers
resc chan error // from workers
}
type walkItem struct {
dir string
callbackDone bool // callback already called; don't do it again
}
func (w *walker) enqueue(it walkItem) {
select {
case w.enqueuec <- it:
case <-w.donec:
}
}
func (w *walker) onDirEnt(dirName, baseName string, typ os.FileMode) error {
joined := dirName + string(os.PathSeparator) + baseName
if typ == os.ModeDir {
w.enqueue(walkItem{dir: joined})
return nil
}
err := w.fn(joined, typ)
if typ == os.ModeSymlink {
if err == ErrTraverseLink {
// Set callbackDone so we don't call it twice for both the
// symlink-as-symlink and the symlink-as-directory later:
w.enqueue(walkItem{dir: joined, callbackDone: true})
return nil
}
if err == filepath.SkipDir {
// Permit SkipDir on symlinks too.
return nil
}
}
return err
}
func (w *walker) walk(root string, runUserCallback bool) error {
if runUserCallback {
err := w.fn(root, os.ModeDir)
if err == filepath.SkipDir {
return nil
}
if err != nil {
return err
}
}
return readDir(root, w.onDirEnt)
}
|
