21 

    22 //sys	closedir(dir uintptr) (err error)

    23 //sys	readdir_r(dir uintptr, entry *Dirent, result **Dirent) (res Errno)

    24 

    25 func fdopendir(fd int) (dir uintptr, err error) {

    26 	r0, _, e1 := syscall_syscallPtr(libc_fdopendir_trampoline_addr, uintptr(fd), 0, 0)

    27 	dir = uintptr(r0)

    28 	if e1 != 0 {

    29 		err = errnoErr(e1)

    30 	}

    31 	return

    32 }

    33 

    34 var libc_fdopendir_trampoline_addr uintptr

    35 

    36 //go:cgo_import_dynamic libc_fdopendir fdopendir "/usr/lib/libSystem.B.dylib"

    37 

    38 func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {

    39 	// Simulate Getdirentries using fdopendir/readdir_r/closedir.

    40 	// We store the number of entries to skip in the seek

    41 	// offset of fd. See issue #31368.

    42 	// It's not the full required semantics, but should handle the case

    43 	// of calling Getdirentries or ReadDirent repeatedly.

    44 	// It won't handle assigning the results of lseek to *basep, or handle

    45 	// the directory being edited underfoot.

    46 	skip, err := Seek(fd, 0, 1 /* SEEK_CUR */)

    47 	if err != nil {

    48 		return 0, err

    49 	}

    50 

    51 	// We need to duplicate the incoming file descriptor

    52 	// because the caller expects to retain control of it, but

    53 	// fdopendir expects to take control of its argument.

    54 	// Just Dup'ing the file descriptor is not enough, as the

    55 	// result shares underlying state. Use Openat to make a really

    56 	// new file descriptor referring to the same directory.

    57 	fd2, err := Openat(fd, ".", O_RDONLY, 0)

    58 	if err != nil {

    59 		return 0, err

    60 	}

    61 	d, err := fdopendir(fd2)

    62 	if err != nil {

    63 		Close(fd2)

    64 		return 0, err

    65 	}

    66 	defer closedir(d)

    67 

    68 	var cnt int64

    69 	for {

    70 		var entry Dirent

    71 		var entryp *Dirent

    72 		e := readdir_r(d, &entry, &entryp)

    73 		if e != 0 {

    74 			return n, errnoErr(e)

    75 		}

    76 		if entryp == nil {

    77 			break

    78 		}

    79 		if skip > 0 {

    80 			skip--

    81 			cnt++

    82 			continue

    83 		}

    84 

    85 		reclen := int(entry.Reclen)

    86 		if reclen > len(buf) {

    87 			// Not enough room. Return for now.

    88 			// The counter will let us know where we should start up again.

    89 			// Note: this strategy for suspending in the middle and

    90 			// restarting is O(n^2) in the length of the directory. Oh well.

    91 			break

    92 		}

    93 

    94 		// Copy entry into return buffer.

    95 		s := unsafe.Slice((*byte)(unsafe.Pointer(&entry)), reclen)

    96 		copy(buf, s)

    97 

    98 		buf = buf[reclen:]

    99 		n += reclen

   100 		cnt++

   101 	}

   102 	// Set the seek offset of the input fd to record

   103 	// how many files we've already returned.

   104 	_, err = Seek(fd, cnt, 0 /* SEEK_SET */)

   105 	if err != nil {

   106 		return n, err

   107 	}

   108 

   109 	return n, nil

   110 }