Rework object refs tracking to reduce memory usage
[git/git.git] / refs.c
CommitLineData
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1#include "refs.h"
2#include "cache.h"
3
4#include <errno.h>
5
ca8db142
LT
6/* We allow "recursive" symbolic refs. Only within reason, though */
7#define MAXDEPTH 5
8
8098a178
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9#ifndef USE_SYMLINK_HEAD
10#define USE_SYMLINK_HEAD 1
11#endif
12
13int validate_symref(const char *path)
14{
15 struct stat st;
16 char *buf, buffer[256];
17 int len, fd;
18
19 if (lstat(path, &st) < 0)
20 return -1;
21
22 /* Make sure it is a "refs/.." symlink */
23 if (S_ISLNK(st.st_mode)) {
24 len = readlink(path, buffer, sizeof(buffer)-1);
25 if (len >= 5 && !memcmp("refs/", buffer, 5))
26 return 0;
27 return -1;
28 }
29
30 /*
31 * Anything else, just open it and try to see if it is a symbolic ref.
32 */
33 fd = open(path, O_RDONLY);
34 if (fd < 0)
35 return -1;
36 len = read(fd, buffer, sizeof(buffer)-1);
37 close(fd);
38
39 /*
40 * Is it a symbolic ref?
41 */
42 if (len < 4 || memcmp("ref:", buffer, 4))
43 return -1;
44 buf = buffer + 4;
45 len -= 4;
46 while (len && isspace(*buf))
47 buf++, len--;
85912b06 48 if (len >= 5 && !memcmp("refs/", buf, 5))
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49 return 0;
50 return -1;
51}
52
a876ed83 53const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
8a65ff76 54{
a876ed83
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55 int depth = MAXDEPTH, len;
56 char buffer[256];
ca8db142 57
a876ed83
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58 for (;;) {
59 struct stat st;
60 char *buf;
61 int fd;
8a65ff76 62
a876ed83
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63 if (--depth < 0)
64 return NULL;
ca8db142 65
a876ed83
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66 /* Special case: non-existing file.
67 * Not having the refs/heads/new-branch is OK
68 * if we are writing into it, so is .git/HEAD
69 * that points at refs/heads/master still to be
70 * born. It is NOT OK if we are resolving for
71 * reading.
72 */
73 if (lstat(path, &st) < 0) {
74 if (reading || errno != ENOENT)
75 return NULL;
76 memset(sha1, 0, 20);
77 return path;
78 }
ca8db142 79
a876ed83
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80 /* Follow "normalized" - ie "refs/.." symlinks by hand */
81 if (S_ISLNK(st.st_mode)) {
82 len = readlink(path, buffer, sizeof(buffer)-1);
83 if (len >= 5 && !memcmp("refs/", buffer, 5)) {
84 path = git_path("%.*s", len, buffer);
85 continue;
86 }
ca8db142 87 }
a876ed83
JH
88
89 /*
90 * Anything else, just open it and try to use it as
91 * a ref
92 */
93 fd = open(path, O_RDONLY);
94 if (fd < 0)
95 return NULL;
96 len = read(fd, buffer, sizeof(buffer)-1);
97 close(fd);
98
99 /*
100 * Is it a symbolic ref?
101 */
102 if (len < 4 || memcmp("ref:", buffer, 4))
103 break;
104 buf = buffer + 4;
105 len -= 4;
106 while (len && isspace(*buf))
107 buf++, len--;
108 while (len && isspace(buf[len-1]))
109 buf[--len] = 0;
110 path = git_path("%.*s", len, buf);
8a65ff76 111 }
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112 if (len < 40 || get_sha1_hex(buffer, sha1))
113 return NULL;
114 return path;
115}
116
8098a178
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117int create_symref(const char *git_HEAD, const char *refs_heads_master)
118{
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119 const char *lockpath;
120 char ref[1000];
121 int fd, len, written;
122
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JS
123#if USE_SYMLINK_HEAD
124 unlink(git_HEAD);
125 if (!symlink(refs_heads_master, git_HEAD))
126 return 0;
127 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
128#endif
129
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130 len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
131 if (sizeof(ref) <= len) {
132 error("refname too long: %s", refs_heads_master);
133 return -1;
134 }
135 lockpath = mkpath("%s.lock", git_HEAD);
136 fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
137 written = write(fd, ref, len);
138 close(fd);
139 if (written != len) {
140 unlink(lockpath);
141 error("Unable to write to %s", lockpath);
142 return -2;
143 }
144 if (rename(lockpath, git_HEAD) < 0) {
145 unlink(lockpath);
146 error("Unable to create %s", git_HEAD);
147 return -3;
148 }
149 return 0;
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150}
151
a876ed83
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152int read_ref(const char *filename, unsigned char *sha1)
153{
154 if (resolve_ref(filename, sha1, 1))
155 return 0;
156 return -1;
8a65ff76
LT
157}
158
944d8589 159static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
8a65ff76
LT
160{
161 int retval = 0;
4ec99bf0 162 DIR *dir = opendir(git_path("%s", base));
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LT
163
164 if (dir) {
165 struct dirent *de;
166 int baselen = strlen(base);
167 char *path = xmalloc(baselen + 257);
6cada6a9
LT
168
169 if (!strncmp(base, "./", 2)) {
170 base += 2;
171 baselen -= 2;
172 }
8a65ff76 173 memcpy(path, base, baselen);
944d8589
LT
174 if (baselen && base[baselen-1] != '/')
175 path[baselen++] = '/';
8a65ff76
LT
176
177 while ((de = readdir(dir)) != NULL) {
178 unsigned char sha1[20];
179 struct stat st;
180 int namelen;
181
182 if (de->d_name[0] == '.')
183 continue;
184 namelen = strlen(de->d_name);
185 if (namelen > 255)
186 continue;
187 memcpy(path + baselen, de->d_name, namelen+1);
a7e66ae3 188 if (stat(git_path("%s", path), &st) < 0)
8a65ff76
LT
189 continue;
190 if (S_ISDIR(st.st_mode)) {
8a65ff76
LT
191 retval = do_for_each_ref(path, fn);
192 if (retval)
193 break;
194 continue;
195 }
ca8db142 196 if (read_ref(git_path("%s", path), sha1) < 0)
8a65ff76
LT
197 continue;
198 if (!has_sha1_file(sha1))
199 continue;
200 retval = fn(path, sha1);
201 if (retval)
202 break;
203 }
204 free(path);
205 closedir(dir);
206 }
207 return retval;
208}
209
723c31fe
LT
210int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
211{
212 unsigned char sha1[20];
ca8db142 213 if (!read_ref(git_path("HEAD"), sha1))
99a0a6e0 214 return fn("HEAD", sha1);
2f34ba32 215 return 0;
723c31fe
LT
216}
217
944d8589 218int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
8a65ff76 219{
99a0a6e0 220 return do_for_each_ref("refs", fn);
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LT
221}
222
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DB
223static char *ref_file_name(const char *ref)
224{
225 char *base = get_refs_directory();
226 int baselen = strlen(base);
227 int reflen = strlen(ref);
228 char *ret = xmalloc(baselen + 2 + reflen);
229 sprintf(ret, "%s/%s", base, ref);
230 return ret;
231}
232
233static char *ref_lock_file_name(const char *ref)
234{
235 char *base = get_refs_directory();
236 int baselen = strlen(base);
237 int reflen = strlen(ref);
238 char *ret = xmalloc(baselen + 7 + reflen);
239 sprintf(ret, "%s/%s.lock", base, ref);
240 return ret;
241}
242
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DB
243int get_ref_sha1(const char *ref, unsigned char *sha1)
244{
ca8db142
LT
245 const char *filename;
246
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DB
247 if (check_ref_format(ref))
248 return -1;
ca8db142
LT
249 filename = git_path("refs/%s", ref);
250 return read_ref(filename, sha1);
95fc7512
DB
251}
252
253static int lock_ref_file(const char *filename, const char *lock_filename,
254 const unsigned char *old_sha1)
255{
256 int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
257 unsigned char current_sha1[20];
258 int retval;
259 if (fd < 0) {
260 return error("Couldn't open lock file for %s: %s",
261 filename, strerror(errno));
262 }
ca8db142 263 retval = read_ref(filename, current_sha1);
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DB
264 if (old_sha1) {
265 if (retval) {
266 close(fd);
267 unlink(lock_filename);
268 return error("Could not read the current value of %s",
269 filename);
270 }
271 if (memcmp(current_sha1, old_sha1, 20)) {
272 close(fd);
273 unlink(lock_filename);
274 error("The current value of %s is %s",
275 filename, sha1_to_hex(current_sha1));
276 return error("Expected %s",
277 sha1_to_hex(old_sha1));
278 }
279 } else {
280 if (!retval) {
281 close(fd);
282 unlink(lock_filename);
283 return error("Unexpectedly found a value of %s for %s",
284 sha1_to_hex(current_sha1), filename);
285 }
286 }
287 return fd;
288}
289
290int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
291{
292 char *filename;
293 char *lock_filename;
294 int retval;
295 if (check_ref_format(ref))
296 return -1;
297 filename = ref_file_name(ref);
298 lock_filename = ref_lock_file_name(ref);
299 retval = lock_ref_file(filename, lock_filename, old_sha1);
300 free(filename);
301 free(lock_filename);
302 return retval;
303}
304
305static int write_ref_file(const char *filename,
306 const char *lock_filename, int fd,
307 const unsigned char *sha1)
308{
309 char *hex = sha1_to_hex(sha1);
310 char term = '\n';
311 if (write(fd, hex, 40) < 40 ||
312 write(fd, &term, 1) < 1) {
313 error("Couldn't write %s\n", filename);
314 close(fd);
315 return -1;
316 }
317 close(fd);
318 rename(lock_filename, filename);
319 return 0;
320}
321
322int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
323{
324 char *filename;
325 char *lock_filename;
326 int retval;
327 if (fd < 0)
328 return -1;
329 if (check_ref_format(ref))
330 return -1;
331 filename = ref_file_name(ref);
332 lock_filename = ref_lock_file_name(ref);
333 retval = write_ref_file(filename, lock_filename, fd, sha1);
334 free(filename);
335 free(lock_filename);
336 return retval;
337}
338
03feddd6
JH
339/*
340 * Make sure "ref" is something reasonable to have under ".git/refs/";
341 * We do not like it if:
342 *
343 * - any path component of it begins with ".", or
344 * - it has double dots "..", or
345 * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
346 * - it ends with a "/".
347 */
348
349static inline int bad_ref_char(int ch)
350{
351 return (((unsigned) ch) <= ' ' ||
352 ch == '~' || ch == '^' || ch == ':');
353}
354
95fc7512
DB
355int check_ref_format(const char *ref)
356{
03feddd6
JH
357 int ch, level;
358 const char *cp = ref;
359
360 level = 0;
361 while (1) {
362 while ((ch = *cp++) == '/')
363 ; /* tolerate duplicated slashes */
364 if (!ch)
365 return -1; /* should not end with slashes */
366
367 /* we are at the beginning of the path component */
368 if (ch == '.' || bad_ref_char(ch))
369 return -1;
370
371 /* scan the rest of the path component */
372 while ((ch = *cp++) != 0) {
373 if (bad_ref_char(ch))
374 return -1;
375 if (ch == '/')
376 break;
377 if (ch == '.' && *cp == '.')
378 return -1;
379 }
380 level++;
381 if (!ch) {
382 if (level < 2)
383 return -1; /* at least of form "heads/blah" */
384 return 0;
385 }
386 }
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DB
387}
388
389int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
390{
391 char *filename;
392 char *lock_filename;
393 int fd;
394 int retval;
395 if (check_ref_format(ref))
396 return -1;
397 filename = ref_file_name(ref);
398 lock_filename = ref_lock_file_name(ref);
399 fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
400 if (fd < 0) {
401 error("Writing %s", lock_filename);
402 perror("Open");
403 }
404 retval = write_ref_file(filename, lock_filename, fd, sha1);
405 free(filename);
406 free(lock_filename);
407 return retval;
408}