describe: make own copy of refname
[git] / pack-write.c
1 #include "cache.h"
2 #include "pack.h"
3 #include "csum-file.h"
4
5 void reset_pack_idx_option(struct pack_idx_option *opts)
6 {
7         memset(opts, 0, sizeof(*opts));
8         opts->version = 2;
9         opts->off32_limit = 0x7fffffff;
10 }
11
12 static int sha1_compare(const void *_a, const void *_b)
13 {
14         struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
15         struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
16         return hashcmp(a->sha1, b->sha1);
17 }
18
19 static int cmp_uint32(const void *a_, const void *b_)
20 {
21         uint32_t a = *((uint32_t *)a_);
22         uint32_t b = *((uint32_t *)b_);
23
24         return (a < b) ? -1 : (a != b);
25 }
26
27 static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
28 {
29         uint32_t ofsval;
30
31         if ((offset >> 31) || (opts->off32_limit < offset))
32                 return 1;
33         if (!opts->anomaly_nr)
34                 return 0;
35         ofsval = offset;
36         return !!bsearch(&ofsval, opts->anomaly, opts->anomaly_nr,
37                          sizeof(ofsval), cmp_uint32);
38 }
39
40 /*
41  * On entry *sha1 contains the pack content SHA1 hash, on exit it is
42  * the SHA1 hash of sorted object names. The objects array passed in
43  * will be sorted by SHA1 on exit.
44  */
45 const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
46                            int nr_objects, const struct pack_idx_option *opts,
47                            unsigned char *sha1)
48 {
49         struct sha1file *f;
50         struct pack_idx_entry **sorted_by_sha, **list, **last;
51         off_t last_obj_offset = 0;
52         uint32_t array[256];
53         int i, fd;
54         git_SHA_CTX ctx;
55         uint32_t index_version;
56
57         if (nr_objects) {
58                 sorted_by_sha = objects;
59                 list = sorted_by_sha;
60                 last = sorted_by_sha + nr_objects;
61                 for (i = 0; i < nr_objects; ++i) {
62                         if (objects[i]->offset > last_obj_offset)
63                                 last_obj_offset = objects[i]->offset;
64                 }
65                 qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
66                       sha1_compare);
67         }
68         else
69                 sorted_by_sha = list = last = NULL;
70
71         if (opts->flags & WRITE_IDX_VERIFY) {
72                 assert(index_name);
73                 f = sha1fd_check(index_name);
74         } else {
75                 if (!index_name) {
76                         static char tmp_file[PATH_MAX];
77                         fd = odb_mkstemp(tmp_file, sizeof(tmp_file), "pack/tmp_idx_XXXXXX");
78                         index_name = xstrdup(tmp_file);
79                 } else {
80                         unlink(index_name);
81                         fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
82                 }
83                 if (fd < 0)
84                         die_errno("unable to create '%s'", index_name);
85                 f = sha1fd(fd, index_name);
86         }
87
88         /* if last object's offset is >= 2^31 we should use index V2 */
89         index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
90
91         /* index versions 2 and above need a header */
92         if (index_version >= 2) {
93                 struct pack_idx_header hdr;
94                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
95                 hdr.idx_version = htonl(index_version);
96                 sha1write(f, &hdr, sizeof(hdr));
97         }
98
99         /*
100          * Write the first-level table (the list is sorted,
101          * but we use a 256-entry lookup to be able to avoid
102          * having to do eight extra binary search iterations).
103          */
104         for (i = 0; i < 256; i++) {
105                 struct pack_idx_entry **next = list;
106                 while (next < last) {
107                         struct pack_idx_entry *obj = *next;
108                         if (obj->sha1[0] != i)
109                                 break;
110                         next++;
111                 }
112                 array[i] = htonl(next - sorted_by_sha);
113                 list = next;
114         }
115         sha1write(f, array, 256 * 4);
116
117         /* compute the SHA1 hash of sorted object names. */
118         git_SHA1_Init(&ctx);
119
120         /*
121          * Write the actual SHA1 entries..
122          */
123         list = sorted_by_sha;
124         for (i = 0; i < nr_objects; i++) {
125                 struct pack_idx_entry *obj = *list++;
126                 if (index_version < 2) {
127                         uint32_t offset = htonl(obj->offset);
128                         sha1write(f, &offset, 4);
129                 }
130                 sha1write(f, obj->sha1, 20);
131                 git_SHA1_Update(&ctx, obj->sha1, 20);
132                 if ((opts->flags & WRITE_IDX_STRICT) &&
133                     (i && !hashcmp(list[-2]->sha1, obj->sha1)))
134                         die("The same object %s appears twice in the pack",
135                             sha1_to_hex(obj->sha1));
136         }
137
138         if (index_version >= 2) {
139                 unsigned int nr_large_offset = 0;
140
141                 /* write the crc32 table */
142                 list = sorted_by_sha;
143                 for (i = 0; i < nr_objects; i++) {
144                         struct pack_idx_entry *obj = *list++;
145                         uint32_t crc32_val = htonl(obj->crc32);
146                         sha1write(f, &crc32_val, 4);
147                 }
148
149                 /* write the 32-bit offset table */
150                 list = sorted_by_sha;
151                 for (i = 0; i < nr_objects; i++) {
152                         struct pack_idx_entry *obj = *list++;
153                         uint32_t offset;
154
155                         offset = (need_large_offset(obj->offset, opts)
156                                   ? (0x80000000 | nr_large_offset++)
157                                   : obj->offset);
158                         offset = htonl(offset);
159                         sha1write(f, &offset, 4);
160                 }
161
162                 /* write the large offset table */
163                 list = sorted_by_sha;
164                 while (nr_large_offset) {
165                         struct pack_idx_entry *obj = *list++;
166                         uint64_t offset = obj->offset;
167                         uint32_t split[2];
168
169                         if (!need_large_offset(offset, opts))
170                                 continue;
171                         split[0] = htonl(offset >> 32);
172                         split[1] = htonl(offset & 0xffffffff);
173                         sha1write(f, split, 8);
174                         nr_large_offset--;
175                 }
176         }
177
178         sha1write(f, sha1, 20);
179         sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
180                             ? CSUM_CLOSE : CSUM_FSYNC));
181         git_SHA1_Final(sha1, &ctx);
182         return index_name;
183 }
184
185 off_t write_pack_header(struct sha1file *f, uint32_t nr_entries)
186 {
187         struct pack_header hdr;
188
189         hdr.hdr_signature = htonl(PACK_SIGNATURE);
190         hdr.hdr_version = htonl(PACK_VERSION);
191         hdr.hdr_entries = htonl(nr_entries);
192         if (sha1write(f, &hdr, sizeof(hdr)))
193                 return 0;
194         return sizeof(hdr);
195 }
196
197 /*
198  * Update pack header with object_count and compute new SHA1 for pack data
199  * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
200  * is also returned in new_pack_sha1.
201  *
202  * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
203  * (without the header update) is computed and validated against the
204  * one provided in partial_pack_sha1.  The validation is performed at
205  * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
206  * data (i.e. from partial_pack_offset to the end) is then computed and
207  * returned in partial_pack_sha1.
208  *
209  * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
210  * partial_pack_sha1 can refer to the same buffer if the caller is not
211  * interested in the resulting SHA1 of pack data above partial_pack_offset.
212  */
213 void fixup_pack_header_footer(int pack_fd,
214                          unsigned char *new_pack_sha1,
215                          const char *pack_name,
216                          uint32_t object_count,
217                          unsigned char *partial_pack_sha1,
218                          off_t partial_pack_offset)
219 {
220         int aligned_sz, buf_sz = 8 * 1024;
221         git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
222         struct pack_header hdr;
223         char *buf;
224
225         git_SHA1_Init(&old_sha1_ctx);
226         git_SHA1_Init(&new_sha1_ctx);
227
228         if (lseek(pack_fd, 0, SEEK_SET) != 0)
229                 die_errno("Failed seeking to start of '%s'", pack_name);
230         if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
231                 die_errno("Unable to reread header of '%s'", pack_name);
232         if (lseek(pack_fd, 0, SEEK_SET) != 0)
233                 die_errno("Failed seeking to start of '%s'", pack_name);
234         git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
235         hdr.hdr_entries = htonl(object_count);
236         git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
237         write_or_die(pack_fd, &hdr, sizeof(hdr));
238         partial_pack_offset -= sizeof(hdr);
239
240         buf = xmalloc(buf_sz);
241         aligned_sz = buf_sz - sizeof(hdr);
242         for (;;) {
243                 ssize_t m, n;
244                 m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
245                         partial_pack_offset : aligned_sz;
246                 n = xread(pack_fd, buf, m);
247                 if (!n)
248                         break;
249                 if (n < 0)
250                         die_errno("Failed to checksum '%s'", pack_name);
251                 git_SHA1_Update(&new_sha1_ctx, buf, n);
252
253                 aligned_sz -= n;
254                 if (!aligned_sz)
255                         aligned_sz = buf_sz;
256
257                 if (!partial_pack_sha1)
258                         continue;
259
260                 git_SHA1_Update(&old_sha1_ctx, buf, n);
261                 partial_pack_offset -= n;
262                 if (partial_pack_offset == 0) {
263                         unsigned char sha1[20];
264                         git_SHA1_Final(sha1, &old_sha1_ctx);
265                         if (hashcmp(sha1, partial_pack_sha1) != 0)
266                                 die("Unexpected checksum for %s "
267                                     "(disk corruption?)", pack_name);
268                         /*
269                          * Now let's compute the SHA1 of the remainder of the
270                          * pack, which also means making partial_pack_offset
271                          * big enough not to matter anymore.
272                          */
273                         git_SHA1_Init(&old_sha1_ctx);
274                         partial_pack_offset = ~partial_pack_offset;
275                         partial_pack_offset -= MSB(partial_pack_offset, 1);
276                 }
277         }
278         free(buf);
279
280         if (partial_pack_sha1)
281                 git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
282         git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
283         write_or_die(pack_fd, new_pack_sha1, 20);
284         fsync_or_die(pack_fd, pack_name);
285 }
286
287 char *index_pack_lockfile(int ip_out)
288 {
289         char packname[46];
290
291         /*
292          * The first thing we expect from index-pack's output
293          * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
294          * %40s is the newly created pack SHA1 name.  In the "keep"
295          * case, we need it to remove the corresponding .keep file
296          * later on.  If we don't get that then tough luck with it.
297          */
298         if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
299             memcmp(packname, "keep\t", 5) == 0) {
300                 char path[PATH_MAX];
301                 packname[45] = 0;
302                 snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
303                          get_object_directory(), packname + 5);
304                 return xstrdup(path);
305         }
306         return NULL;
307 }
308
309 /*
310  * The per-object header is a pretty dense thing, which is
311  *  - first byte: low four bits are "size", then three bits of "type",
312  *    and the high bit is "size continues".
313  *  - each byte afterwards: low seven bits are size continuation,
314  *    with the high bit being "size continues"
315  */
316 int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
317 {
318         int n = 1;
319         unsigned char c;
320
321         if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
322                 die("bad type %d", type);
323
324         c = (type << 4) | (size & 15);
325         size >>= 4;
326         while (size) {
327                 *hdr++ = c | 0x80;
328                 c = size & 0x7f;
329                 size >>= 7;
330                 n++;
331         }
332         *hdr = c;
333         return n;
334 }
335
336 struct sha1file *create_tmp_packfile(char **pack_tmp_name)
337 {
338         char tmpname[PATH_MAX];
339         int fd;
340
341         fd = odb_mkstemp(tmpname, sizeof(tmpname), "pack/tmp_pack_XXXXXX");
342         *pack_tmp_name = xstrdup(tmpname);
343         return sha1fd(fd, *pack_tmp_name);
344 }
345
346 void finish_tmp_packfile(char *name_buffer,
347                          const char *pack_tmp_name,
348                          struct pack_idx_entry **written_list,
349                          uint32_t nr_written,
350                          struct pack_idx_option *pack_idx_opts,
351                          unsigned char sha1[])
352 {
353         const char *idx_tmp_name;
354         char *end_of_name_prefix = strrchr(name_buffer, 0);
355
356         if (adjust_shared_perm(pack_tmp_name))
357                 die_errno("unable to make temporary pack file readable");
358
359         idx_tmp_name = write_idx_file(NULL, written_list, nr_written,
360                                       pack_idx_opts, sha1);
361         if (adjust_shared_perm(idx_tmp_name))
362                 die_errno("unable to make temporary index file readable");
363
364         sprintf(end_of_name_prefix, "%s.pack", sha1_to_hex(sha1));
365         free_pack_by_name(name_buffer);
366
367         if (rename(pack_tmp_name, name_buffer))
368                 die_errno("unable to rename temporary pack file");
369
370         sprintf(end_of_name_prefix, "%s.idx", sha1_to_hex(sha1));
371         if (rename(idx_tmp_name, name_buffer))
372                 die_errno("unable to rename temporary index file");
373
374         free((void *)idx_tmp_name);
375 }