128 lines
3.3 KiB
Go
128 lines
3.3 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build linux darwin freebsd openbsd netbsd
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// +build !appengine
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package fastwalk
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import (
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"fmt"
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"os"
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"syscall"
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"unsafe"
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)
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const blockSize = 8 << 10
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// unknownFileMode is a sentinel (and bogus) os.FileMode
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// value used to represent a syscall.DT_UNKNOWN Dirent.Type.
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const unknownFileMode os.FileMode = os.ModeNamedPipe | os.ModeSocket | os.ModeDevice
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func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error {
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fd, err := syscall.Open(dirName, 0, 0)
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if err != nil {
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return &os.PathError{Op: "open", Path: dirName, Err: err}
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}
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defer syscall.Close(fd)
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// The buffer must be at least a block long.
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buf := make([]byte, blockSize) // stack-allocated; doesn't escape
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bufp := 0 // starting read position in buf
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nbuf := 0 // end valid data in buf
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skipFiles := false
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for {
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if bufp >= nbuf {
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bufp = 0
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nbuf, err = syscall.ReadDirent(fd, buf)
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if err != nil {
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return os.NewSyscallError("readdirent", err)
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}
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if nbuf <= 0 {
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return nil
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}
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}
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consumed, name, typ := parseDirEnt(buf[bufp:nbuf])
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bufp += consumed
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if name == "" || name == "." || name == ".." {
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continue
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}
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// Fallback for filesystems (like old XFS) that don't
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// support Dirent.Type and have DT_UNKNOWN (0) there
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// instead.
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if typ == unknownFileMode {
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fi, err := os.Lstat(dirName + "/" + name)
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if err != nil {
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// It got deleted in the meantime.
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if os.IsNotExist(err) {
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continue
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}
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return err
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}
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typ = fi.Mode() & os.ModeType
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}
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if skipFiles && typ.IsRegular() {
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continue
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}
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if err := fn(dirName, name, typ); err != nil {
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if err == SkipFiles {
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skipFiles = true
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continue
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}
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return err
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}
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}
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}
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func parseDirEnt(buf []byte) (consumed int, name string, typ os.FileMode) {
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// golang.org/issue/15653
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dirent := (*syscall.Dirent)(unsafe.Pointer(&buf[0]))
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if v := unsafe.Offsetof(dirent.Reclen) + unsafe.Sizeof(dirent.Reclen); uintptr(len(buf)) < v {
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panic(fmt.Sprintf("buf size of %d smaller than dirent header size %d", len(buf), v))
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}
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if len(buf) < int(dirent.Reclen) {
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panic(fmt.Sprintf("buf size %d < record length %d", len(buf), dirent.Reclen))
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}
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consumed = int(dirent.Reclen)
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if direntInode(dirent) == 0 { // File absent in directory.
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return
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}
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switch dirent.Type {
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case syscall.DT_REG:
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typ = 0
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case syscall.DT_DIR:
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typ = os.ModeDir
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case syscall.DT_LNK:
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typ = os.ModeSymlink
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case syscall.DT_BLK:
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typ = os.ModeDevice
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case syscall.DT_FIFO:
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typ = os.ModeNamedPipe
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case syscall.DT_SOCK:
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typ = os.ModeSocket
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case syscall.DT_UNKNOWN:
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typ = unknownFileMode
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default:
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// Skip weird things.
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// It's probably a DT_WHT (http://lwn.net/Articles/325369/)
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// or something. Revisit if/when this package is moved outside
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// of goimports. goimports only cares about regular files,
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// symlinks, and directories.
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return
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}
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nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
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nameLen := direntNamlen(dirent)
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// Special cases for common things:
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if nameLen == 1 && nameBuf[0] == '.' {
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name = "."
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} else if nameLen == 2 && nameBuf[0] == '.' && nameBuf[1] == '.' {
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name = ".."
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} else {
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name = string(nameBuf[:nameLen])
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}
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return
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}
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