1// Copyright 2016 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// +build linux darwin freebsd openbsd netbsd
6// +build !appengine
7
8package fastwalk
9
10import (
11 "fmt"
12 "os"
13 "syscall"
14 "unsafe"
15)
16
17const blockSize = 8 << 10
18
19// unknownFileMode is a sentinel (and bogus) os.FileMode
20// value used to represent a syscall.DT_UNKNOWN Dirent.Type.
21const unknownFileMode os.FileMode = os.ModeNamedPipe | os.ModeSocket | os.ModeDevice
22
23func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error {
24 fd, err := syscall.Open(dirName, 0, 0)
25 if err != nil {
26 return &os.PathError{Op: "open", Path: dirName, Err: err}
27 }
28 defer syscall.Close(fd)
29
30 // The buffer must be at least a block long.
31 buf := make([]byte, blockSize) // stack-allocated; doesn't escape
32 bufp := 0 // starting read position in buf
33 nbuf := 0 // end valid data in buf
34 skipFiles := false
35 for {
36 if bufp >= nbuf {
37 bufp = 0
38 nbuf, err = syscall.ReadDirent(fd, buf)
39 if err != nil {
40 return os.NewSyscallError("readdirent", err)
41 }
42 if nbuf <= 0 {
43 return nil
44 }
45 }
46 consumed, name, typ := parseDirEnt(buf[bufp:nbuf])
47 bufp += consumed
48 if name == "" || name == "." || name == ".." {
49 continue
50 }
51 // Fallback for filesystems (like old XFS) that don't
52 // support Dirent.Type and have DT_UNKNOWN (0) there
53 // instead.
54 if typ == unknownFileMode {
55 fi, err := os.Lstat(dirName + "/" + name)
56 if err != nil {
57 // It got deleted in the meantime.
58 if os.IsNotExist(err) {
59 continue
60 }
61 return err
62 }
63 typ = fi.Mode() & os.ModeType
64 }
65 if skipFiles && typ.IsRegular() {
66 continue
67 }
68 if err := fn(dirName, name, typ); err != nil {
69 if err == SkipFiles {
70 skipFiles = true
71 continue
72 }
73 return err
74 }
75 }
76}
77
78func parseDirEnt(buf []byte) (consumed int, name string, typ os.FileMode) {
79 // golang.org/issue/15653
80 dirent := (*syscall.Dirent)(unsafe.Pointer(&buf[0]))
81 if v := unsafe.Offsetof(dirent.Reclen) + unsafe.Sizeof(dirent.Reclen); uintptr(len(buf)) < v {
82 panic(fmt.Sprintf("buf size of %d smaller than dirent header size %d", len(buf), v))
83 }
84 if len(buf) < int(dirent.Reclen) {
85 panic(fmt.Sprintf("buf size %d < record length %d", len(buf), dirent.Reclen))
86 }
87 consumed = int(dirent.Reclen)
88 if direntInode(dirent) == 0 { // File absent in directory.
89 return
90 }
91 switch dirent.Type {
92 case syscall.DT_REG:
93 typ = 0
94 case syscall.DT_DIR:
95 typ = os.ModeDir
96 case syscall.DT_LNK:
97 typ = os.ModeSymlink
98 case syscall.DT_BLK:
99 typ = os.ModeDevice
100 case syscall.DT_FIFO:
101 typ = os.ModeNamedPipe
102 case syscall.DT_SOCK:
103 typ = os.ModeSocket
104 case syscall.DT_UNKNOWN:
105 typ = unknownFileMode
106 default:
107 // Skip weird things.
108 // It's probably a DT_WHT (http://lwn.net/Articles/325369/)
109 // or something. Revisit if/when this package is moved outside
110 // of goimports. goimports only cares about regular files,
111 // symlinks, and directories.
112 return
113 }
114
115 nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
116 nameLen := direntNamlen(dirent)
117
118 // Special cases for common things:
119 if nameLen == 1 && nameBuf[0] == '.' {
120 name = "."
121 } else if nameLen == 2 && nameBuf[0] == '.' && nameBuf[1] == '.' {
122 name = ".."
123 } else {
124 name = string(nameBuf[:nameLen])
125 }
126 return
127}