blob: dc0befee37eb29947e6ae64728ad026ddc6887a0 [file] [log] [blame]
Andrea Campanella3614a922021-02-25 12:40:42 +01001// 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// +build darwin,go1.13
6
7package unix
8
9import (
10 "unsafe"
11
12 "golang.org/x/sys/internal/unsafeheader"
13)
14
15//sys closedir(dir uintptr) (err error)
16//sys readdir_r(dir uintptr, entry *Dirent, result **Dirent) (res Errno)
17
18func fdopendir(fd int) (dir uintptr, err error) {
19 r0, _, e1 := syscall_syscallPtr(funcPC(libc_fdopendir_trampoline), uintptr(fd), 0, 0)
20 dir = uintptr(r0)
21 if e1 != 0 {
22 err = errnoErr(e1)
23 }
24 return
25}
26
27func libc_fdopendir_trampoline()
28
29//go:linkname libc_fdopendir libc_fdopendir
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}