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 "bytes"
12 "fmt"
13 "os"
14 "syscall"
15 "unsafe"
16)
17
18const blockSize = 8 << 10
19
20// unknownFileMode is a sentinel (and bogus) os.FileMode
21// value used to represent a syscall.DT_UNKNOWN Dirent.Type.
22const unknownFileMode os.FileMode = os.ModeNamedPipe | os.ModeSocket | os.ModeDevice
23
24func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error {
25 fd, err := syscall.Open(dirName, 0, 0)
26 if err != nil {
27 return &os.PathError{Op: "open", Path: dirName, Err: err}
28 }
29 defer syscall.Close(fd)
30
31 // The buffer must be at least a block long.
32 buf := make([]byte, blockSize) // stack-allocated; doesn't escape
33 bufp := 0 // starting read position in buf
34 nbuf := 0 // end valid data in buf
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 err := fn(dirName, name, typ); err != nil {
66 return err
67 }
68 }
69}
70
71func parseDirEnt(buf []byte) (consumed int, name string, typ os.FileMode) {
72 // golang.org/issue/15653
73 dirent := (*syscall.Dirent)(unsafe.Pointer(&buf[0]))
74 if v := unsafe.Offsetof(dirent.Reclen) + unsafe.Sizeof(dirent.Reclen); uintptr(len(buf)) < v {
75 panic(fmt.Sprintf("buf size of %d smaller than dirent header size %d", len(buf), v))
76 }
77 if len(buf) < int(dirent.Reclen) {
78 panic(fmt.Sprintf("buf size %d < record length %d", len(buf), dirent.Reclen))
79 }
80 consumed = int(dirent.Reclen)
81 if direntInode(dirent) == 0 { // File absent in directory.
82 return
83 }
84 switch dirent.Type {
85 case syscall.DT_REG:
86 typ = 0
87 case syscall.DT_DIR:
88 typ = os.ModeDir
89 case syscall.DT_LNK:
90 typ = os.ModeSymlink
91 case syscall.DT_BLK:
92 typ = os.ModeDevice
93 case syscall.DT_FIFO:
94 typ = os.ModeNamedPipe
95 case syscall.DT_SOCK:
96 typ = os.ModeSocket
97 case syscall.DT_UNKNOWN:
98 typ = unknownFileMode
99 default:
100 // Skip weird things.
101 // It's probably a DT_WHT (http://lwn.net/Articles/325369/)
102 // or something. Revisit if/when this package is moved outside
103 // of goimports. goimports only cares about regular files,
104 // symlinks, and directories.
105 return
106 }
107
108 nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
109 nameLen := bytes.IndexByte(nameBuf[:], 0)
110 if nameLen < 0 {
111 panic("failed to find terminating 0 byte in dirent")
112 }
113
114 // Special cases for common things:
115 if nameLen == 1 && nameBuf[0] == '.' {
116 name = "."
117 } else if nameLen == 2 && nameBuf[0] == '.' && nameBuf[1] == '.' {
118 name = ".."
119 } else {
120 name = string(nameBuf[:nameLen])
121 }
122 return
123}