| 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 | //go:build (linux || freebsd || openbsd || netbsd || (darwin && !cgo)) && !appengine |
| 6 | // +build linux freebsd openbsd netbsd darwin,!cgo |
| 7 | // +build !appengine |
| 8 | |
| 9 | package fastwalk |
| 10 | |
| 11 | import ( |
| 12 | "fmt" |
| 13 | "os" |
| 14 | "syscall" |
| 15 | "unsafe" |
| 16 | ) |
| 17 | |
| 18 | const blockSize = 8 << 10 |
| 19 | |
| 20 | // unknownFileMode is a sentinel (and bogus) os.FileMode |
| 21 | // value used to represent a syscall.DT_UNKNOWN Dirent.Type. |
| 22 | const unknownFileMode os.FileMode = os.ModeNamedPipe | os.ModeSocket | os.ModeDevice |
| 23 | |
| 24 | func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error { |
| 25 | fd, err := 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 | skipFiles := false |
| 36 | for { |
| 37 | if bufp >= nbuf { |
| 38 | bufp = 0 |
| 39 | nbuf, err = readDirent(fd, buf) |
| 40 | if err != nil { |
| 41 | return os.NewSyscallError("readdirent", err) |
| 42 | } |
| 43 | if nbuf <= 0 { |
| 44 | return nil |
| 45 | } |
| 46 | } |
| 47 | consumed, name, typ := parseDirEnt(buf[bufp:nbuf]) |
| 48 | bufp += consumed |
| 49 | if name == "" || name == "." || name == ".." { |
| 50 | continue |
| 51 | } |
| 52 | // Fallback for filesystems (like old XFS) that don't |
| 53 | // support Dirent.Type and have DT_UNKNOWN (0) there |
| 54 | // instead. |
| 55 | if typ == unknownFileMode { |
| 56 | fi, err := os.Lstat(dirName + "/" + name) |
| 57 | if err != nil { |
| 58 | // It got deleted in the meantime. |
| 59 | if os.IsNotExist(err) { |
| 60 | continue |
| 61 | } |
| 62 | return err |
| 63 | } |
| 64 | typ = fi.Mode() & os.ModeType |
| 65 | } |
| 66 | if skipFiles && typ.IsRegular() { |
| 67 | continue |
| 68 | } |
| 69 | if err := fn(dirName, name, typ); err != nil { |
| 70 | if err == ErrSkipFiles { |
| 71 | skipFiles = true |
| 72 | continue |
| 73 | } |
| 74 | return err |
| 75 | } |
| 76 | } |
| 77 | } |
| 78 | |
| 79 | func parseDirEnt(buf []byte) (consumed int, name string, typ os.FileMode) { |
| 80 | // golang.org/issue/37269 |
| 81 | dirent := &syscall.Dirent{} |
| 82 | copy((*[unsafe.Sizeof(syscall.Dirent{})]byte)(unsafe.Pointer(dirent))[:], buf) |
| 83 | if v := unsafe.Offsetof(dirent.Reclen) + unsafe.Sizeof(dirent.Reclen); uintptr(len(buf)) < v { |
| 84 | panic(fmt.Sprintf("buf size of %d smaller than dirent header size %d", len(buf), v)) |
| 85 | } |
| 86 | if len(buf) < int(dirent.Reclen) { |
| 87 | panic(fmt.Sprintf("buf size %d < record length %d", len(buf), dirent.Reclen)) |
| 88 | } |
| 89 | consumed = int(dirent.Reclen) |
| 90 | if direntInode(dirent) == 0 { // File absent in directory. |
| 91 | return |
| 92 | } |
| 93 | switch dirent.Type { |
| 94 | case syscall.DT_REG: |
| 95 | typ = 0 |
| 96 | case syscall.DT_DIR: |
| 97 | typ = os.ModeDir |
| 98 | case syscall.DT_LNK: |
| 99 | typ = os.ModeSymlink |
| 100 | case syscall.DT_BLK: |
| 101 | typ = os.ModeDevice |
| 102 | case syscall.DT_FIFO: |
| 103 | typ = os.ModeNamedPipe |
| 104 | case syscall.DT_SOCK: |
| 105 | typ = os.ModeSocket |
| 106 | case syscall.DT_UNKNOWN: |
| 107 | typ = unknownFileMode |
| 108 | default: |
| 109 | // Skip weird things. |
| 110 | // It's probably a DT_WHT (http://lwn.net/Articles/325369/) |
| 111 | // or something. Revisit if/when this package is moved outside |
| 112 | // of goimports. goimports only cares about regular files, |
| 113 | // symlinks, and directories. |
| 114 | return |
| 115 | } |
| 116 | |
| 117 | nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0])) |
| 118 | nameLen := direntNamlen(dirent) |
| 119 | |
| 120 | // Special cases for common things: |
| 121 | if nameLen == 1 && nameBuf[0] == '.' { |
| 122 | name = "." |
| 123 | } else if nameLen == 2 && nameBuf[0] == '.' && nameBuf[1] == '.' { |
| 124 | name = ".." |
| 125 | } else { |
| 126 | name = string(nameBuf[:nameLen]) |
| 127 | } |
| 128 | return |
| 129 | } |
| 130 | |
| 131 | // According to https://golang.org/doc/go1.14#runtime |
| 132 | // A consequence of the implementation of preemption is that on Unix systems, including Linux and macOS |
| 133 | // systems, programs built with Go 1.14 will receive more signals than programs built with earlier releases. |
| 134 | // |
| 135 | // This causes syscall.Open and syscall.ReadDirent sometimes fail with EINTR errors. |
| 136 | // We need to retry in this case. |
| 137 | func open(path string, mode int, perm uint32) (fd int, err error) { |
| 138 | for { |
| 139 | fd, err := syscall.Open(path, mode, perm) |
| 140 | if err != syscall.EINTR { |
| 141 | return fd, err |
| 142 | } |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | func readDirent(fd int, buf []byte) (n int, err error) { |
| 147 | for { |
| 148 | nbuf, err := syscall.ReadDirent(fd, buf) |
| 149 | if err != syscall.EINTR { |
| 150 | return nbuf, err |
| 151 | } |
| 152 | } |
| 153 | } |
| 154 |
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