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// Copyright 2009 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.
//go:build linux && !baremetal && !wasi
// +build linux,!baremetal,!wasi
package os
import (
"io"
"sync"
"syscall"
"unsafe"
)
// Auxiliary information if the File describes a directory
type dirInfo struct {
buf *[]byte // buffer for directory I/O
nbuf int // length of buf; return value from Getdirentries
bufp int // location of next record in buf.
}
const (
// More than 5760 to work around https://golang.org/issue/24015.
blockSize = 8192
)
var dirBufPool = sync.Pool{
New: func() interface{} {
// The buffer must be at least a block long.
buf := make([]byte, blockSize)
return &buf
},
}
func (d *dirInfo) close() {
if d.buf != nil {
dirBufPool.Put(d.buf)
d.buf = nil
}
}
func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
// If this file has no dirinfo, create one.
if f.dirinfo == nil {
f.dirinfo = new(dirInfo)
f.dirinfo.buf = dirBufPool.Get().(*[]byte)
}
d := f.dirinfo
// Change the meaning of n for the implementation below.
//
// The n above was for the public interface of "if n <= 0,
// Readdir returns all the FileInfo from the directory in a
// single slice".
//
// But below, we use only negative to mean looping until the
// end and positive to mean bounded, with positive
// terminating at 0.
if n == 0 {
n = -1
}
for n != 0 {
// Refill the buffer if necessary
if d.bufp >= d.nbuf {
d.bufp = 0
var errno error
d.nbuf, errno = syscall.ReadDirent(syscallFd(f.handle.(unixFileHandle)), *d.buf)
if d.nbuf < 0 {
errno = handleSyscallError(errno)
}
if errno != nil {
return names, dirents, infos, &PathError{Op: "readdirent", Path: f.name, Err: errno}
}
if d.nbuf <= 0 {
break // EOF
}
}
// Drain the buffer
buf := (*d.buf)[d.bufp:d.nbuf]
reclen, ok := direntReclen(buf)
if !ok || reclen > uint64(len(buf)) {
break
}
rec := buf[:reclen]
d.bufp += int(reclen)
ino, ok := direntIno(rec)
if !ok {
break
}
if ino == 0 {
continue
}
const namoff = uint64(unsafe.Offsetof(syscall.Dirent{}.Name))
namlen, ok := direntNamlen(rec)
if !ok || namoff+namlen > uint64(len(rec)) {
break
}
name := rec[namoff : namoff+namlen]
for i, c := range name {
if c == 0 {
name = name[:i]
break
}
}
// Check for useless names before allocating a string.
if string(name) == "." || string(name) == ".." {
continue
}
if n > 0 { // see 'n == 0' comment above
n--
}
if mode == readdirName {
names = append(names, string(name))
} else if mode == readdirDirEntry {
de, err := newUnixDirent(f.name, string(name), direntType(rec))
if IsNotExist(err) {
// File disappeared between readdir and stat.
// Treat as if it didn't exist.
continue
}
if err != nil {
return nil, dirents, nil, err
}
dirents = append(dirents, de)
} else {
info, err := lstat(f.name + "/" + string(name))
if IsNotExist(err) {
// File disappeared between readdir + stat.
// Treat as if it didn't exist.
continue
}
if err != nil {
return nil, nil, infos, err
}
infos = append(infos, info)
}
}
if n > 0 && len(names)+len(dirents)+len(infos) == 0 {
return nil, nil, nil, io.EOF
}
return names, dirents, infos, nil
}
// readInt returns the size-bytes unsigned integer in native byte order at offset off.
func readInt(b []byte, off, size uintptr) (u uint64, ok bool) {
if len(b) < int(off+size) {
return 0, false
}
if isBigEndian {
return readIntBE(b[off:], size), true
}
return readIntLE(b[off:], size), true
}
func readIntBE(b []byte, size uintptr) uint64 {
switch size {
case 1:
return uint64(b[0])
case 2:
_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
return uint64(b[1]) | uint64(b[0])<<8
case 4:
_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
return uint64(b[3]) | uint64(b[2])<<8 | uint64(b[1])<<16 | uint64(b[0])<<24
case 8:
_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
default:
panic("syscall: readInt with unsupported size")
}
}
func readIntLE(b []byte, size uintptr) uint64 {
switch size {
case 1:
return uint64(b[0])
case 2:
_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
return uint64(b[0]) | uint64(b[1])<<8
case 4:
_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24
case 8:
_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
default:
panic("syscall: readInt with unsupported size")
}
}
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