1// Copyright 2019 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 darwin && go1.13
  6// +build darwin,go1.13
  7
  8package unix
  9
 10import (
 11	"unsafe"
 12
 13	"golang.org/x/sys/internal/unsafeheader"
 14)
 15
 16//sys	closedir(dir uintptr) (err error)
 17//sys	readdir_r(dir uintptr, entry *Dirent, result **Dirent) (res Errno)
 18
 19func fdopendir(fd int) (dir uintptr, err error) {
 20	r0, _, e1 := syscall_syscallPtr(funcPC(libc_fdopendir_trampoline), uintptr(fd), 0, 0)
 21	dir = uintptr(r0)
 22	if e1 != 0 {
 23		err = errnoErr(e1)
 24	}
 25	return
 26}
 27
 28func libc_fdopendir_trampoline()
 29
 30//go:cgo_import_dynamic libc_fdopendir fdopendir "/usr/lib/libSystem.B.dylib"
 31
 32func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 33	// Simulate Getdirentries using fdopendir/readdir_r/closedir.
 34	// We store the number of entries to skip in the seek
 35	// offset of fd. See issue #31368.
 36	// It's not the full required semantics, but should handle the case
 37	// of calling Getdirentries or ReadDirent repeatedly.
 38	// It won't handle assigning the results of lseek to *basep, or handle
 39	// the directory being edited underfoot.
 40	skip, err := Seek(fd, 0, 1 /* SEEK_CUR */)
 41	if err != nil {
 42		return 0, err
 43	}
 44
 45	// We need to duplicate the incoming file descriptor
 46	// because the caller expects to retain control of it, but
 47	// fdopendir expects to take control of its argument.
 48	// Just Dup'ing the file descriptor is not enough, as the
 49	// result shares underlying state. Use Openat to make a really
 50	// new file descriptor referring to the same directory.
 51	fd2, err := Openat(fd, ".", O_RDONLY, 0)
 52	if err != nil {
 53		return 0, err
 54	}
 55	d, err := fdopendir(fd2)
 56	if err != nil {
 57		Close(fd2)
 58		return 0, err
 59	}
 60	defer closedir(d)
 61
 62	var cnt int64
 63	for {
 64		var entry Dirent
 65		var entryp *Dirent
 66		e := readdir_r(d, &entry, &entryp)
 67		if e != 0 {
 68			return n, errnoErr(e)
 69		}
 70		if entryp == nil {
 71			break
 72		}
 73		if skip > 0 {
 74			skip--
 75			cnt++
 76			continue
 77		}
 78
 79		reclen := int(entry.Reclen)
 80		if reclen > len(buf) {
 81			// Not enough room. Return for now.
 82			// The counter will let us know where we should start up again.
 83			// Note: this strategy for suspending in the middle and
 84			// restarting is O(n^2) in the length of the directory. Oh well.
 85			break
 86		}
 87
 88		// Copy entry into return buffer.
 89		var s []byte
 90		hdr := (*unsafeheader.Slice)(unsafe.Pointer(&s))
 91		hdr.Data = unsafe.Pointer(&entry)
 92		hdr.Cap = reclen
 93		hdr.Len = reclen
 94		copy(buf, s)
 95
 96		buf = buf[reclen:]
 97		n += reclen
 98		cnt++
 99	}
100	// Set the seek offset of the input fd to record
101	// how many files we've already returned.
102	_, err = Seek(fd, cnt, 0 /* SEEK_SET */)
103	if err != nil {
104		return n, err
105	}
106
107	return n, nil
108}