1 /*
2 * Copyright (c) 2005, Junio C Hamano
3 */
4 #include "cache.h"
6 static struct lock_file *lock_file_list;
7 static const char *alternate_index_output;
9 static void remove_lock_file(void)
10 {
11 pid_t me = getpid();
13 while (lock_file_list) {
14 if (lock_file_list->owner == me &&
15 lock_file_list->filename[0]) {
16 if (lock_file_list->fd >= 0)
17 close(lock_file_list->fd);
18 unlink(lock_file_list->filename);
19 }
20 lock_file_list = lock_file_list->next;
21 }
22 }
24 static void remove_lock_file_on_signal(int signo)
25 {
26 remove_lock_file();
27 signal(SIGINT, SIG_DFL);
28 raise(signo);
29 }
31 /*
32 * p = absolute or relative path name
33 *
34 * Return a pointer into p showing the beginning of the last path name
35 * element. If p is empty or the root directory ("/"), just return p.
36 */
37 static char *last_path_elm(char *p)
38 {
39 /* r starts pointing to null at the end of the string */
40 char *r = strchr(p, '\0');
42 if (r == p)
43 return p; /* just return empty string */
45 r--; /* back up to last non-null character */
47 /* back up past trailing slashes, if any */
48 while (r > p && *r == '/')
49 r--;
51 /*
52 * then go backwards until I hit a slash, or the beginning of
53 * the string
54 */
55 while (r > p && *(r-1) != '/')
56 r--;
57 return r;
58 }
61 /* We allow "recursive" symbolic links. Only within reason, though */
62 #define MAXDEPTH 5
64 /*
65 * p = path that may be a symlink
66 * s = full size of p
67 *
68 * If p is a symlink, attempt to overwrite p with a path to the real
69 * file or directory (which may or may not exist), following a chain of
70 * symlinks if necessary. Otherwise, leave p unmodified.
71 *
72 * This is a best-effort routine. If an error occurs, p will either be
73 * left unmodified or will name a different symlink in a symlink chain
74 * that started with p's initial contents.
75 *
76 * Always returns p.
77 */
79 static char *resolve_symlink(char *p, size_t s)
80 {
81 int depth = MAXDEPTH;
83 while (depth--) {
84 char link[PATH_MAX];
85 int link_len = readlink(p, link, sizeof(link));
86 if (link_len < 0) {
87 /* not a symlink anymore */
88 return p;
89 }
90 else if (link_len < sizeof(link))
91 /* readlink() never null-terminates */
92 link[link_len] = '\0';
93 else {
94 warning("%s: symlink too long", p);
95 return p;
96 }
98 if (is_absolute_path(link)) {
99 /* absolute path simply replaces p */
100 if (link_len < s)
101 strcpy(p, link);
102 else {
103 warning("%s: symlink too long", p);
104 return p;
105 }
106 } else {
107 /*
108 * link is a relative path, so I must replace the
109 * last element of p with it.
110 */
111 char *r = (char*)last_path_elm(p);
112 if (r - p + link_len < s)
113 strcpy(r, link);
114 else {
115 warning("%s: symlink too long", p);
116 return p;
117 }
118 }
119 }
120 return p;
121 }
124 static int lock_file(struct lock_file *lk, const char *path)
125 {
126 if (strlen(path) >= sizeof(lk->filename)) return -1;
127 strcpy(lk->filename, path);
128 /*
129 * subtract 5 from size to make sure there's room for adding
130 * ".lock" for the lock file name
131 */
132 resolve_symlink(lk->filename, sizeof(lk->filename)-5);
133 strcat(lk->filename, ".lock");
134 lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
135 if (0 <= lk->fd) {
136 if (!lock_file_list) {
137 signal(SIGINT, remove_lock_file_on_signal);
138 atexit(remove_lock_file);
139 }
140 lk->owner = getpid();
141 if (!lk->on_list) {
142 lk->next = lock_file_list;
143 lock_file_list = lk;
144 lk->on_list = 1;
145 }
146 if (adjust_shared_perm(lk->filename))
147 return error("cannot fix permission bits on %s",
148 lk->filename);
149 }
150 else
151 lk->filename[0] = 0;
152 return lk->fd;
153 }
155 int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on_error)
156 {
157 int fd = lock_file(lk, path);
158 if (fd < 0 && die_on_error)
159 die("unable to create '%s.lock': %s", path, strerror(errno));
160 return fd;
161 }
163 int close_lock_file(struct lock_file *lk)
164 {
165 int fd = lk->fd;
166 lk->fd = -1;
167 return close(fd);
168 }
170 int commit_lock_file(struct lock_file *lk)
171 {
172 char result_file[PATH_MAX];
173 size_t i;
174 if (lk->fd >= 0 && close_lock_file(lk))
175 return -1;
176 strcpy(result_file, lk->filename);
177 i = strlen(result_file) - 5; /* .lock */
178 result_file[i] = 0;
179 if (rename(lk->filename, result_file))
180 return -1;
181 lk->filename[0] = 0;
182 return 0;
183 }
185 int hold_locked_index(struct lock_file *lk, int die_on_error)
186 {
187 return hold_lock_file_for_update(lk, get_index_file(), die_on_error);
188 }
190 void set_alternate_index_output(const char *name)
191 {
192 alternate_index_output = name;
193 }
195 int commit_locked_index(struct lock_file *lk)
196 {
197 if (alternate_index_output) {
198 if (lk->fd >= 0 && close_lock_file(lk))
199 return -1;
200 if (rename(lk->filename, alternate_index_output))
201 return -1;
202 lk->filename[0] = 0;
203 return 0;
204 }
205 else
206 return commit_lock_file(lk);
207 }
209 void rollback_lock_file(struct lock_file *lk)
210 {
211 if (lk->filename[0]) {
212 if (lk->fd >= 0)
213 close(lk->fd);
214 unlink(lk->filename);
215 }
216 lk->filename[0] = 0;
217 }