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