Contents of /trunk/mkinitrd-magellan/busybox/libbb/xreadlink.c
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Revision 816 -
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Fri Apr 24 18:33:46 2009 UTC (15 years, 5 months ago) by niro
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File size: 2441 byte(s)
Fri Apr 24 18:33:46 2009 UTC (15 years, 5 months ago) by niro
File MIME type: text/plain
File size: 2441 byte(s)
-updated to busybox-1.13.4
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * xreadlink.c - safe implementation of readlink. |
4 | * Returns a NULL on failure... |
5 | */ |
6 | |
7 | #include "libbb.h" |
8 | |
9 | /* |
10 | * NOTE: This function returns a malloced char* that you will have to free |
11 | * yourself. |
12 | */ |
13 | char* FAST_FUNC xmalloc_readlink(const char *path) |
14 | { |
15 | enum { GROWBY = 80 }; /* how large we will grow strings by */ |
16 | |
17 | char *buf = NULL; |
18 | int bufsize = 0, readsize = 0; |
19 | |
20 | do { |
21 | bufsize += GROWBY; |
22 | buf = xrealloc(buf, bufsize); |
23 | readsize = readlink(path, buf, bufsize); |
24 | if (readsize == -1) { |
25 | free(buf); |
26 | return NULL; |
27 | } |
28 | } while (bufsize < readsize + 1); |
29 | |
30 | buf[readsize] = '\0'; |
31 | |
32 | return buf; |
33 | } |
34 | |
35 | /* |
36 | * This routine is not the same as realpath(), which |
37 | * canonicalizes the given path completely. This routine only |
38 | * follows trailing symlinks until a real file is reached and |
39 | * returns its name. If the path ends in a dangling link or if |
40 | * the target doesn't exist, the path is returned in any case. |
41 | * Intermediate symlinks in the path are not expanded -- only |
42 | * those at the tail. |
43 | * A malloced char* is returned, which must be freed by the caller. |
44 | */ |
45 | char* FAST_FUNC xmalloc_follow_symlinks(const char *path) |
46 | { |
47 | char *buf; |
48 | char *lpc; |
49 | char *linkpath; |
50 | int bufsize; |
51 | int looping = MAXSYMLINKS + 1; |
52 | |
53 | buf = xstrdup(path); |
54 | goto jump_in; |
55 | |
56 | while (1) { |
57 | linkpath = xmalloc_readlink(buf); |
58 | if (!linkpath) { |
59 | /* not a symlink, or doesn't exist */ |
60 | if (errno == EINVAL || errno == ENOENT) |
61 | return buf; |
62 | goto free_buf_ret_null; |
63 | } |
64 | |
65 | if (!--looping) { |
66 | free(linkpath); |
67 | free_buf_ret_null: |
68 | free(buf); |
69 | return NULL; |
70 | } |
71 | |
72 | if (*linkpath != '/') { |
73 | bufsize += strlen(linkpath); |
74 | buf = xrealloc(buf, bufsize); |
75 | lpc = bb_get_last_path_component_strip(buf); |
76 | strcpy(lpc, linkpath); |
77 | free(linkpath); |
78 | } else { |
79 | free(buf); |
80 | buf = linkpath; |
81 | jump_in: |
82 | bufsize = strlen(buf) + 1; |
83 | } |
84 | } |
85 | } |
86 | |
87 | char* FAST_FUNC xmalloc_readlink_or_warn(const char *path) |
88 | { |
89 | char *buf = xmalloc_readlink(path); |
90 | if (!buf) { |
91 | /* EINVAL => "file: Invalid argument" => puzzled user */ |
92 | bb_error_msg("%s: cannot read link (not a symlink?)", path); |
93 | } |
94 | return buf; |
95 | } |
96 | |
97 | /* UNUSED */ |
98 | #if 0 |
99 | char* FAST_FUNC xmalloc_realpath(const char *path) |
100 | { |
101 | #if defined(__GLIBC__) && !defined(__UCLIBC__) |
102 | /* glibc provides a non-standard extension */ |
103 | return realpath(path, NULL); |
104 | #else |
105 | char buf[PATH_MAX+1]; |
106 | |
107 | /* on error returns NULL (xstrdup(NULL) ==NULL) */ |
108 | return xstrdup(realpath(path, buf)); |
109 | #endif |
110 | } |
111 | #endif |