1// Copyright 2009 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
5package os
6
7import (
8	"io"
9	"sync/atomic"
10	"syscall"
11	"unsafe"
12)
13
14//extern opendir
15func libc_opendir(*byte) *syscall.DIR
16
17//extern closedir
18func libc_closedir(*syscall.DIR) int
19
20// FIXME: pathconf returns long, not int.
21//extern pathconf
22func libc_pathconf(*byte, int) int
23
24func clen(n []byte) int {
25	for i := 0; i < len(n); i++ {
26		if n[i] == 0 {
27			return i
28		}
29	}
30	return len(n)
31}
32
33var nameMax int32
34
35func (file *File) readdirnames(n int) (names []string, err error) {
36	if file.dirinfo == nil {
37		p, err := syscall.BytePtrFromString(file.name)
38		if err != nil {
39			return nil, err
40		}
41
42		elen := int(atomic.LoadInt32(&nameMax))
43		if elen == 0 {
44			syscall.Entersyscall()
45			plen := libc_pathconf(p, syscall.PC_NAME_MAX)
46			syscall.Exitsyscall()
47			if plen < 1024 {
48				plen = 1024
49			}
50			var dummy syscall.Dirent
51			elen = int(unsafe.Offsetof(dummy.Name)) + plen + 1
52			atomic.StoreInt32(&nameMax, int32(elen))
53		}
54
55		syscall.Entersyscall()
56		r := libc_opendir(p)
57		errno := syscall.GetErrno()
58		syscall.Exitsyscall()
59		if r == nil {
60			return nil, &PathError{"opendir", file.name, errno}
61		}
62
63		file.dirinfo = new(dirInfo)
64		file.dirinfo.buf = make([]byte, elen)
65		file.dirinfo.dir = r
66	}
67
68	entryDirent := (*syscall.Dirent)(unsafe.Pointer(&file.dirinfo.buf[0]))
69
70	size := n
71	if size <= 0 {
72		size = 100
73		n = -1
74	}
75
76	names = make([]string, 0, size) // Empty with room to grow.
77
78	for n != 0 {
79		var dirent *syscall.Dirent
80		pr := &dirent
81		syscall.Entersyscall()
82		i := libc_readdir_r(file.dirinfo.dir, entryDirent, pr)
83		syscall.Exitsyscall()
84		if i != 0 {
85			return names, NewSyscallError("readdir_r", i)
86		}
87		if dirent == nil {
88			break // EOF
89		}
90		bytes := (*[10000]byte)(unsafe.Pointer(&dirent.Name[0]))
91		var name = string(bytes[0:clen(bytes[:])])
92		if name == "." || name == ".." { // Useless names
93			continue
94		}
95		names = append(names, name)
96		n--
97	}
98	if n >= 0 && len(names) == 0 {
99		return names, io.EOF
100	}
101	return names, nil
102}
103