1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <errno.h>
30 #include <malloc.h>
31 #include <string.h>
32 #include <unistd.h>
33
34 extern "C" int __getcwd(char* buf, size_t size);
35
getcwd(char * buf,size_t size)36 char* getcwd(char* buf, size_t size) {
37 // You can't specify size 0 unless you're asking us to allocate for you.
38 if (buf != nullptr && size == 0) {
39 errno = EINVAL;
40 return nullptr;
41 }
42
43 // Allocate a buffer if necessary.
44 char* allocated_buf = nullptr;
45 size_t allocated_size = size;
46 if (buf == nullptr) {
47 if (size == 0) {
48 // The Linux kernel won't return more than a page, so translate size 0 to 4KiB.
49 // TODO: if we need to support paths longer than that, we'll have to walk the tree ourselves.
50 allocated_size = getpagesize();
51 }
52 buf = allocated_buf = static_cast<char*>(malloc(allocated_size));
53 if (buf == nullptr) {
54 return nullptr;
55 }
56 }
57
58 // Ask the kernel to fill our buffer.
59 int rc = __getcwd(buf, allocated_size);
60 if (rc == -1) {
61 free(allocated_buf);
62 // __getcwd set errno.
63 return nullptr;
64 }
65
66 // If we allocated a whole page, only return as large an allocation as necessary.
67 if (allocated_buf != nullptr) {
68 if (size == 0) {
69 buf = strdup(allocated_buf);
70 free(allocated_buf);
71 } else {
72 buf = allocated_buf;
73 }
74 }
75
76 return buf;
77 }
78