1 /*
2 * SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 #include <unistd.h>
8 #include <errno.h>
9 #include <string.h>
10 #include <stdlib.h>
11 #include <assert.h>
12 #include <sys/param.h>
13
14 /* realpath logic:
15 * 1. prepend CWD (/)
16 * 2. iterate over components (search until next '/' or end of line)
17 * - empty, skip the component
18 * - if it is '.', skip the component
19 * - if it is '..'
20 * - and out_level == 0, ??? ('/..')
21 * - otherwise, reverse-search for '/', set out_pos to that - 1, decrement out_level
22 * - otherwise, add the component to output, increment out_level
23 */
24
realpath(const char * file_name,char * resolved_name)25 char * realpath(const char *file_name, char *resolved_name)
26 {
27 char * out_path = resolved_name;
28 if (out_path == NULL) {
29 /* allowed as an extension, allocate memory for the output path */
30 out_path = malloc(PATH_MAX);
31 if (out_path == NULL) {
32 errno = ENOMEM;
33 return NULL;
34 }
35 }
36
37 /* canonical path starts with / */
38 strlcpy(out_path, "/", PATH_MAX);
39
40 /* pointers moving over the input and output path buffers */
41 const char* in_ptr = file_name;
42 char* out_ptr = out_path + 1;
43 /* number of path components in the output buffer */
44 size_t out_depth = 0;
45
46
47 while (*in_ptr) {
48 /* "path component" is the part between two '/' path separators.
49 * locate the next path component in the input path:
50 */
51 const char* end_of_path_component = strchrnul(in_ptr, '/');
52 size_t path_component_len = end_of_path_component - in_ptr;
53
54 if (path_component_len == 0 ||
55 (path_component_len == 1 && in_ptr[0] == '.')) {
56 /* empty path component or '.' - nothing to do */
57 } else if (path_component_len == 2 && in_ptr[0] == '.' && in_ptr[1] == '.') {
58 /* '..' - remove one path component from the output */
59 if (out_depth == 0) {
60 /* nothing to remove */
61 } else if (out_depth == 1) {
62 /* there is only one path component in output;
63 * remove it, but keep the leading separator
64 */
65 out_ptr = out_path + 1;
66 *out_ptr = '\0';
67 out_depth = 0;
68 } else {
69 /* remove last path component and the separator preceding it */
70 char * prev_sep = strrchr(out_path, '/');
71 assert(prev_sep > out_path); /* this shouldn't be the leading separator */
72 out_ptr = prev_sep;
73 *out_ptr = '\0';
74 --out_depth;
75 }
76 } else {
77 /* copy path component to output; +1 is for the separator */
78 if (out_ptr - out_path + 1 + path_component_len > PATH_MAX - 1) {
79 /* output buffer insufficient */
80 errno = E2BIG;
81 goto fail;
82 } else {
83 /* add separator if necessary */
84 if (out_depth > 0) {
85 *out_ptr = '/';
86 ++out_ptr;
87 }
88 memcpy(out_ptr, in_ptr, path_component_len);
89 out_ptr += path_component_len;
90 *out_ptr = '\0';
91 ++out_depth;
92 }
93 }
94 /* move input pointer to separator right after this path component */
95 in_ptr += path_component_len;
96 if (*in_ptr != '\0') {
97 /* move past it unless already at the end of the input string */
98 ++in_ptr;
99 }
100 }
101 return out_path;
102
103 fail:
104 if (resolved_name == NULL) {
105 /* out_path was allocated, free it */
106 free(out_path);
107 }
108 return NULL;
109 }
110
getcwd(char * buf,size_t size)111 char * getcwd(char *buf, size_t size)
112 {
113 if (buf == NULL) {
114 return strdup("/");
115 }
116 strlcpy(buf, "/", size);
117 return buf;
118 }
119
chdir(const char * path)120 int chdir(const char *path)
121 {
122 (void) path;
123 errno = ENOSYS;
124 return -1;
125 }
126
