Merge branch 'rp/blame-first-parent-doc'
[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 oidcmp(&a->oid, &b->oid);
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  * The *sha1 contains the pack content SHA1 hash.
42  * The objects array passed in will be sorted by SHA1 on exit.
43  */
44 const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
45                            int nr_objects, const struct pack_idx_option *opts,
46                            const unsigned char *sha1)
47 {
48         struct hashfile *f;
49         struct pack_idx_entry **sorted_by_sha, **list, **last;
50         off_t last_obj_offset = 0;
51         uint32_t array[256];
52         int i, fd;
53         uint32_t index_version;
54
55         if (nr_objects) {
56                 sorted_by_sha = objects;
57                 list = sorted_by_sha;
58                 last = sorted_by_sha + nr_objects;
59                 for (i = 0; i < nr_objects; ++i) {
60                         if (objects[i]->offset > last_obj_offset)
61                                 last_obj_offset = objects[i]->offset;
62                 }
63                 QSORT(sorted_by_sha, nr_objects, sha1_compare);
64         }
65         else
66                 sorted_by_sha = list = last = NULL;
67
68         if (opts->flags & WRITE_IDX_VERIFY) {
69                 assert(index_name);
70                 f = hashfd_check(index_name);
71         } else {
72                 if (!index_name) {
73                         struct strbuf tmp_file = STRBUF_INIT;
74                         fd = odb_mkstemp(&tmp_file, "pack/tmp_idx_XXXXXX");
75                         index_name = strbuf_detach(&tmp_file, NULL);
76                 } else {
77                         unlink(index_name);
78                         fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
79                         if (fd < 0)
80                                 die_errno("unable to create '%s'", index_name);
81                 }
82                 f = hashfd(fd, index_name);
83         }
84
85         /* if last object's offset is >= 2^31 we should use index V2 */
86         index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
87
88         /* index versions 2 and above need a header */
89         if (index_version >= 2) {
90                 struct pack_idx_header hdr;
91                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
92                 hdr.idx_version = htonl(index_version);
93                 hashwrite(f, &hdr, sizeof(hdr));
94         }
95
96         /*
97          * Write the first-level table (the list is sorted,
98          * but we use a 256-entry lookup to be able to avoid
99          * having to do eight extra binary search iterations).
100          */
101         for (i = 0; i < 256; i++) {
102                 struct pack_idx_entry **next = list;
103                 while (next < last) {
104                         struct pack_idx_entry *obj = *next;
105                         if (obj->oid.hash[0] != i)
106                                 break;
107                         next++;
108                 }
109                 array[i] = htonl(next - sorted_by_sha);
110                 list = next;
111         }
112         hashwrite(f, array, 256 * 4);
113
114         /*
115          * Write the actual SHA1 entries..
116          */
117         list = sorted_by_sha;
118         for (i = 0; i < nr_objects; i++) {
119                 struct pack_idx_entry *obj = *list++;
120                 if (index_version < 2) {
121                         uint32_t offset = htonl(obj->offset);
122                         hashwrite(f, &offset, 4);
123                 }
124                 hashwrite(f, obj->oid.hash, the_hash_algo->rawsz);
125                 if ((opts->flags & WRITE_IDX_STRICT) &&
126                     (i && oideq(&list[-2]->oid, &obj->oid)))
127                         die("The same object %s appears twice in the pack",
128                             oid_to_hex(&obj->oid));
129         }
130
131         if (index_version >= 2) {
132                 unsigned int nr_large_offset = 0;
133
134                 /* write the crc32 table */
135                 list = sorted_by_sha;
136                 for (i = 0; i < nr_objects; i++) {
137                         struct pack_idx_entry *obj = *list++;
138                         uint32_t crc32_val = htonl(obj->crc32);
139                         hashwrite(f, &crc32_val, 4);
140                 }
141
142                 /* write the 32-bit offset table */
143                 list = sorted_by_sha;
144                 for (i = 0; i < nr_objects; i++) {
145                         struct pack_idx_entry *obj = *list++;
146                         uint32_t offset;
147
148                         offset = (need_large_offset(obj->offset, opts)
149                                   ? (0x80000000 | nr_large_offset++)
150                                   : obj->offset);
151                         offset = htonl(offset);
152                         hashwrite(f, &offset, 4);
153                 }
154
155                 /* write the large offset table */
156                 list = sorted_by_sha;
157                 while (nr_large_offset) {
158                         struct pack_idx_entry *obj = *list++;
159                         uint64_t offset = obj->offset;
160                         uint32_t split[2];
161
162                         if (!need_large_offset(offset, opts))
163                                 continue;
164                         split[0] = htonl(offset >> 32);
165                         split[1] = htonl(offset & 0xffffffff);
166                         hashwrite(f, split, 8);
167                         nr_large_offset--;
168                 }
169         }
170
171         hashwrite(f, sha1, the_hash_algo->rawsz);
172         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_CLOSE |
173                                     ((opts->flags & WRITE_IDX_VERIFY)
174                                     ? 0 : CSUM_FSYNC));
175         return index_name;
176 }
177
178 off_t write_pack_header(struct hashfile *f, uint32_t nr_entries)
179 {
180         struct pack_header hdr;
181
182         hdr.hdr_signature = htonl(PACK_SIGNATURE);
183         hdr.hdr_version = htonl(PACK_VERSION);
184         hdr.hdr_entries = htonl(nr_entries);
185         hashwrite(f, &hdr, sizeof(hdr));
186         return sizeof(hdr);
187 }
188
189 /*
190  * Update pack header with object_count and compute new SHA1 for pack data
191  * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
192  * is also returned in new_pack_sha1.
193  *
194  * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
195  * (without the header update) is computed and validated against the
196  * one provided in partial_pack_sha1.  The validation is performed at
197  * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
198  * data (i.e. from partial_pack_offset to the end) is then computed and
199  * returned in partial_pack_sha1.
200  *
201  * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
202  * partial_pack_sha1 can refer to the same buffer if the caller is not
203  * interested in the resulting SHA1 of pack data above partial_pack_offset.
204  */
205 void fixup_pack_header_footer(int pack_fd,
206                          unsigned char *new_pack_hash,
207                          const char *pack_name,
208                          uint32_t object_count,
209                          unsigned char *partial_pack_hash,
210                          off_t partial_pack_offset)
211 {
212         int aligned_sz, buf_sz = 8 * 1024;
213         git_hash_ctx old_hash_ctx, new_hash_ctx;
214         struct pack_header hdr;
215         char *buf;
216         ssize_t read_result;
217
218         the_hash_algo->init_fn(&old_hash_ctx);
219         the_hash_algo->init_fn(&new_hash_ctx);
220
221         if (lseek(pack_fd, 0, SEEK_SET) != 0)
222                 die_errno("Failed seeking to start of '%s'", pack_name);
223         read_result = read_in_full(pack_fd, &hdr, sizeof(hdr));
224         if (read_result < 0)
225                 die_errno("Unable to reread header of '%s'", pack_name);
226         else if (read_result != sizeof(hdr))
227                 die_errno("Unexpected short read for header of '%s'",
228                           pack_name);
229         if (lseek(pack_fd, 0, SEEK_SET) != 0)
230                 die_errno("Failed seeking to start of '%s'", pack_name);
231         the_hash_algo->update_fn(&old_hash_ctx, &hdr, sizeof(hdr));
232         hdr.hdr_entries = htonl(object_count);
233         the_hash_algo->update_fn(&new_hash_ctx, &hdr, sizeof(hdr));
234         write_or_die(pack_fd, &hdr, sizeof(hdr));
235         partial_pack_offset -= sizeof(hdr);
236
237         buf = xmalloc(buf_sz);
238         aligned_sz = buf_sz - sizeof(hdr);
239         for (;;) {
240                 ssize_t m, n;
241                 m = (partial_pack_hash && partial_pack_offset < aligned_sz) ?
242                         partial_pack_offset : aligned_sz;
243                 n = xread(pack_fd, buf, m);
244                 if (!n)
245                         break;
246                 if (n < 0)
247                         die_errno("Failed to checksum '%s'", pack_name);
248                 the_hash_algo->update_fn(&new_hash_ctx, buf, n);
249
250                 aligned_sz -= n;
251                 if (!aligned_sz)
252                         aligned_sz = buf_sz;
253
254                 if (!partial_pack_hash)
255                         continue;
256
257                 the_hash_algo->update_fn(&old_hash_ctx, buf, n);
258                 partial_pack_offset -= n;
259                 if (partial_pack_offset == 0) {
260                         unsigned char hash[GIT_MAX_RAWSZ];
261                         the_hash_algo->final_fn(hash, &old_hash_ctx);
262                         if (!hasheq(hash, partial_pack_hash))
263                                 die("Unexpected checksum for %s "
264                                     "(disk corruption?)", pack_name);
265                         /*
266                          * Now let's compute the SHA1 of the remainder of the
267                          * pack, which also means making partial_pack_offset
268                          * big enough not to matter anymore.
269                          */
270                         the_hash_algo->init_fn(&old_hash_ctx);
271                         partial_pack_offset = ~partial_pack_offset;
272                         partial_pack_offset -= MSB(partial_pack_offset, 1);
273                 }
274         }
275         free(buf);
276
277         if (partial_pack_hash)
278                 the_hash_algo->final_fn(partial_pack_hash, &old_hash_ctx);
279         the_hash_algo->final_fn(new_pack_hash, &new_hash_ctx);
280         write_or_die(pack_fd, new_pack_hash, the_hash_algo->rawsz);
281         fsync_or_die(pack_fd, pack_name);
282 }
283
284 char *index_pack_lockfile(int ip_out)
285 {
286         char packname[GIT_MAX_HEXSZ + 6];
287         const int len = the_hash_algo->hexsz + 6;
288
289         /*
290          * The first thing we expect from index-pack's output
291          * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
292          * %40s is the newly created pack SHA1 name.  In the "keep"
293          * case, we need it to remove the corresponding .keep file
294          * later on.  If we don't get that then tough luck with it.
295          */
296         if (read_in_full(ip_out, packname, len) == len && packname[len-1] == '\n') {
297                 const char *name;
298                 packname[len-1] = 0;
299                 if (skip_prefix(packname, "keep\t", &name))
300                         return xstrfmt("%s/pack/pack-%s.keep",
301                                        get_object_directory(), name);
302         }
303         return NULL;
304 }
305
306 /*
307  * The per-object header is a pretty dense thing, which is
308  *  - first byte: low four bits are "size", then three bits of "type",
309  *    and the high bit is "size continues".
310  *  - each byte afterwards: low seven bits are size continuation,
311  *    with the high bit being "size continues"
312  */
313 int encode_in_pack_object_header(unsigned char *hdr, int hdr_len,
314                                  enum object_type type, uintmax_t size)
315 {
316         int n = 1;
317         unsigned char c;
318
319         if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
320                 die("bad type %d", type);
321
322         c = (type << 4) | (size & 15);
323         size >>= 4;
324         while (size) {
325                 if (n == hdr_len)
326                         die("object size is too enormous to format");
327                 *hdr++ = c | 0x80;
328                 c = size & 0x7f;
329                 size >>= 7;
330                 n++;
331         }
332         *hdr = c;
333         return n;
334 }
335
336 struct hashfile *create_tmp_packfile(char **pack_tmp_name)
337 {
338         struct strbuf tmpname = STRBUF_INIT;
339         int fd;
340
341         fd = odb_mkstemp(&tmpname, "pack/tmp_pack_XXXXXX");
342         *pack_tmp_name = strbuf_detach(&tmpname, NULL);
343         return hashfd(fd, *pack_tmp_name);
344 }
345
346 void finish_tmp_packfile(struct strbuf *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 hash[])
352 {
353         const char *idx_tmp_name;
354         int basename_len = name_buffer->len;
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, hash);
361         if (adjust_shared_perm(idx_tmp_name))
362                 die_errno("unable to make temporary index file readable");
363
364         strbuf_addf(name_buffer, "%s.pack", hash_to_hex(hash));
365
366         if (rename(pack_tmp_name, name_buffer->buf))
367                 die_errno("unable to rename temporary pack file");
368
369         strbuf_setlen(name_buffer, basename_len);
370
371         strbuf_addf(name_buffer, "%s.idx", hash_to_hex(hash));
372         if (rename(idx_tmp_name, name_buffer->buf))
373                 die_errno("unable to rename temporary index file");
374
375         strbuf_setlen(name_buffer, basename_len);
376
377         free((void *)idx_tmp_name);
378 }