Merge branch 'ew/packfile-syscall-optim'
[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  * 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                            const unsigned char *sha1)
48 {
49         struct hashfile *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         uint32_t index_version;
55
56         if (nr_objects) {
57                 sorted_by_sha = objects;
58                 list = sorted_by_sha;
59                 last = sorted_by_sha + nr_objects;
60                 for (i = 0; i < nr_objects; ++i) {
61                         if (objects[i]->offset > last_obj_offset)
62                                 last_obj_offset = objects[i]->offset;
63                 }
64                 QSORT(sorted_by_sha, nr_objects, sha1_compare);
65         }
66         else
67                 sorted_by_sha = list = last = NULL;
68
69         if (opts->flags & WRITE_IDX_VERIFY) {
70                 assert(index_name);
71                 f = hashfd_check(index_name);
72         } else {
73                 if (!index_name) {
74                         struct strbuf tmp_file = STRBUF_INIT;
75                         fd = odb_mkstemp(&tmp_file, "pack/tmp_idx_XXXXXX");
76                         index_name = strbuf_detach(&tmp_file, NULL);
77                 } else {
78                         unlink(index_name);
79                         fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
80                         if (fd < 0)
81                                 die_errno("unable to create '%s'", index_name);
82                 }
83                 f = hashfd(fd, index_name);
84         }
85
86         /* if last object's offset is >= 2^31 we should use index V2 */
87         index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
88
89         /* index versions 2 and above need a header */
90         if (index_version >= 2) {
91                 struct pack_idx_header hdr;
92                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
93                 hdr.idx_version = htonl(index_version);
94                 hashwrite(f, &hdr, sizeof(hdr));
95         }
96
97         /*
98          * Write the first-level table (the list is sorted,
99          * but we use a 256-entry lookup to be able to avoid
100          * having to do eight extra binary search iterations).
101          */
102         for (i = 0; i < 256; i++) {
103                 struct pack_idx_entry **next = list;
104                 while (next < last) {
105                         struct pack_idx_entry *obj = *next;
106                         if (obj->oid.hash[0] != i)
107                                 break;
108                         next++;
109                 }
110                 array[i] = htonl(next - sorted_by_sha);
111                 list = next;
112         }
113         hashwrite(f, array, 256 * 4);
114
115         /*
116          * Write the actual SHA1 entries..
117          */
118         list = sorted_by_sha;
119         for (i = 0; i < nr_objects; i++) {
120                 struct pack_idx_entry *obj = *list++;
121                 if (index_version < 2) {
122                         uint32_t offset = htonl(obj->offset);
123                         hashwrite(f, &offset, 4);
124                 }
125                 hashwrite(f, obj->oid.hash, the_hash_algo->rawsz);
126                 if ((opts->flags & WRITE_IDX_STRICT) &&
127                     (i && oideq(&list[-2]->oid, &obj->oid)))
128                         die("The same object %s appears twice in the pack",
129                             oid_to_hex(&obj->oid));
130         }
131
132         if (index_version >= 2) {
133                 unsigned int nr_large_offset = 0;
134
135                 /* write the crc32 table */
136                 list = sorted_by_sha;
137                 for (i = 0; i < nr_objects; i++) {
138                         struct pack_idx_entry *obj = *list++;
139                         uint32_t crc32_val = htonl(obj->crc32);
140                         hashwrite(f, &crc32_val, 4);
141                 }
142
143                 /* write the 32-bit offset table */
144                 list = sorted_by_sha;
145                 for (i = 0; i < nr_objects; i++) {
146                         struct pack_idx_entry *obj = *list++;
147                         uint32_t offset;
148
149                         offset = (need_large_offset(obj->offset, opts)
150                                   ? (0x80000000 | nr_large_offset++)
151                                   : obj->offset);
152                         offset = htonl(offset);
153                         hashwrite(f, &offset, 4);
154                 }
155
156                 /* write the large offset table */
157                 list = sorted_by_sha;
158                 while (nr_large_offset) {
159                         struct pack_idx_entry *obj = *list++;
160                         uint64_t offset = obj->offset;
161                         uint32_t split[2];
162
163                         if (!need_large_offset(offset, opts))
164                                 continue;
165                         split[0] = htonl(offset >> 32);
166                         split[1] = htonl(offset & 0xffffffff);
167                         hashwrite(f, split, 8);
168                         nr_large_offset--;
169                 }
170         }
171
172         hashwrite(f, sha1, the_hash_algo->rawsz);
173         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_CLOSE |
174                                     ((opts->flags & WRITE_IDX_VERIFY)
175                                     ? 0 : CSUM_FSYNC));
176         return index_name;
177 }
178
179 off_t write_pack_header(struct hashfile *f, uint32_t nr_entries)
180 {
181         struct pack_header hdr;
182
183         hdr.hdr_signature = htonl(PACK_SIGNATURE);
184         hdr.hdr_version = htonl(PACK_VERSION);
185         hdr.hdr_entries = htonl(nr_entries);
186         hashwrite(f, &hdr, sizeof(hdr));
187         return sizeof(hdr);
188 }
189
190 /*
191  * Update pack header with object_count and compute new SHA1 for pack data
192  * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
193  * is also returned in new_pack_sha1.
194  *
195  * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
196  * (without the header update) is computed and validated against the
197  * one provided in partial_pack_sha1.  The validation is performed at
198  * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
199  * data (i.e. from partial_pack_offset to the end) is then computed and
200  * returned in partial_pack_sha1.
201  *
202  * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
203  * partial_pack_sha1 can refer to the same buffer if the caller is not
204  * interested in the resulting SHA1 of pack data above partial_pack_offset.
205  */
206 void fixup_pack_header_footer(int pack_fd,
207                          unsigned char *new_pack_hash,
208                          const char *pack_name,
209                          uint32_t object_count,
210                          unsigned char *partial_pack_hash,
211                          off_t partial_pack_offset)
212 {
213         int aligned_sz, buf_sz = 8 * 1024;
214         git_hash_ctx old_hash_ctx, new_hash_ctx;
215         struct pack_header hdr;
216         char *buf;
217         ssize_t read_result;
218
219         the_hash_algo->init_fn(&old_hash_ctx);
220         the_hash_algo->init_fn(&new_hash_ctx);
221
222         if (lseek(pack_fd, 0, SEEK_SET) != 0)
223                 die_errno("Failed seeking to start of '%s'", pack_name);
224         read_result = read_in_full(pack_fd, &hdr, sizeof(hdr));
225         if (read_result < 0)
226                 die_errno("Unable to reread header of '%s'", pack_name);
227         else if (read_result != sizeof(hdr))
228                 die_errno("Unexpected short read for header of '%s'",
229                           pack_name);
230         if (lseek(pack_fd, 0, SEEK_SET) != 0)
231                 die_errno("Failed seeking to start of '%s'", pack_name);
232         the_hash_algo->update_fn(&old_hash_ctx, &hdr, sizeof(hdr));
233         hdr.hdr_entries = htonl(object_count);
234         the_hash_algo->update_fn(&new_hash_ctx, &hdr, sizeof(hdr));
235         write_or_die(pack_fd, &hdr, sizeof(hdr));
236         partial_pack_offset -= sizeof(hdr);
237
238         buf = xmalloc(buf_sz);
239         aligned_sz = buf_sz - sizeof(hdr);
240         for (;;) {
241                 ssize_t m, n;
242                 m = (partial_pack_hash && partial_pack_offset < aligned_sz) ?
243                         partial_pack_offset : aligned_sz;
244                 n = xread(pack_fd, buf, m);
245                 if (!n)
246                         break;
247                 if (n < 0)
248                         die_errno("Failed to checksum '%s'", pack_name);
249                 the_hash_algo->update_fn(&new_hash_ctx, buf, n);
250
251                 aligned_sz -= n;
252                 if (!aligned_sz)
253                         aligned_sz = buf_sz;
254
255                 if (!partial_pack_hash)
256                         continue;
257
258                 the_hash_algo->update_fn(&old_hash_ctx, buf, n);
259                 partial_pack_offset -= n;
260                 if (partial_pack_offset == 0) {
261                         unsigned char hash[GIT_MAX_RAWSZ];
262                         the_hash_algo->final_fn(hash, &old_hash_ctx);
263                         if (!hasheq(hash, partial_pack_hash))
264                                 die("Unexpected checksum for %s "
265                                     "(disk corruption?)", pack_name);
266                         /*
267                          * Now let's compute the SHA1 of the remainder of the
268                          * pack, which also means making partial_pack_offset
269                          * big enough not to matter anymore.
270                          */
271                         the_hash_algo->init_fn(&old_hash_ctx);
272                         partial_pack_offset = ~partial_pack_offset;
273                         partial_pack_offset -= MSB(partial_pack_offset, 1);
274                 }
275         }
276         free(buf);
277
278         if (partial_pack_hash)
279                 the_hash_algo->final_fn(partial_pack_hash, &old_hash_ctx);
280         the_hash_algo->final_fn(new_pack_hash, &new_hash_ctx);
281         write_or_die(pack_fd, new_pack_hash, the_hash_algo->rawsz);
282         fsync_or_die(pack_fd, pack_name);
283 }
284
285 char *index_pack_lockfile(int ip_out)
286 {
287         char packname[GIT_MAX_HEXSZ + 6];
288         const int len = the_hash_algo->hexsz + 6;
289
290         /*
291          * The first thing we expect from index-pack's output
292          * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
293          * %40s is the newly created pack SHA1 name.  In the "keep"
294          * case, we need it to remove the corresponding .keep file
295          * later on.  If we don't get that then tough luck with it.
296          */
297         if (read_in_full(ip_out, packname, len) == len && packname[len-1] == '\n') {
298                 const char *name;
299                 packname[len-1] = 0;
300                 if (skip_prefix(packname, "keep\t", &name))
301                         return xstrfmt("%s/pack/pack-%s.keep",
302                                        get_object_directory(), name);
303         }
304         return NULL;
305 }
306
307 /*
308  * The per-object header is a pretty dense thing, which is
309  *  - first byte: low four bits are "size", then three bits of "type",
310  *    and the high bit is "size continues".
311  *  - each byte afterwards: low seven bits are size continuation,
312  *    with the high bit being "size continues"
313  */
314 int encode_in_pack_object_header(unsigned char *hdr, int hdr_len,
315                                  enum object_type type, uintmax_t size)
316 {
317         int n = 1;
318         unsigned char c;
319
320         if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
321                 die("bad type %d", type);
322
323         c = (type << 4) | (size & 15);
324         size >>= 4;
325         while (size) {
326                 if (n == hdr_len)
327                         die("object size is too enormous to format");
328                 *hdr++ = c | 0x80;
329                 c = size & 0x7f;
330                 size >>= 7;
331                 n++;
332         }
333         *hdr = c;
334         return n;
335 }
336
337 struct hashfile *create_tmp_packfile(char **pack_tmp_name)
338 {
339         struct strbuf tmpname = STRBUF_INIT;
340         int fd;
341
342         fd = odb_mkstemp(&tmpname, "pack/tmp_pack_XXXXXX");
343         *pack_tmp_name = strbuf_detach(&tmpname, NULL);
344         return hashfd(fd, *pack_tmp_name);
345 }
346
347 void finish_tmp_packfile(struct strbuf *name_buffer,
348                          const char *pack_tmp_name,
349                          struct pack_idx_entry **written_list,
350                          uint32_t nr_written,
351                          struct pack_idx_option *pack_idx_opts,
352                          unsigned char hash[])
353 {
354         const char *idx_tmp_name;
355         int basename_len = name_buffer->len;
356
357         if (adjust_shared_perm(pack_tmp_name))
358                 die_errno("unable to make temporary pack file readable");
359
360         idx_tmp_name = write_idx_file(NULL, written_list, nr_written,
361                                       pack_idx_opts, hash);
362         if (adjust_shared_perm(idx_tmp_name))
363                 die_errno("unable to make temporary index file readable");
364
365         strbuf_addf(name_buffer, "%s.pack", hash_to_hex(hash));
366
367         if (rename(pack_tmp_name, name_buffer->buf))
368                 die_errno("unable to rename temporary pack file");
369
370         strbuf_setlen(name_buffer, basename_len);
371
372         strbuf_addf(name_buffer, "%s.idx", hash_to_hex(hash));
373         if (rename(idx_tmp_name, name_buffer->buf))
374                 die_errno("unable to rename temporary index file");
375
376         strbuf_setlen(name_buffer, basename_len);
377
378         free((void *)idx_tmp_name);
379 }