Teach update-ref about a symbolic ref stored in a textfile.
[git.git] / pack-objects.c
1 #include <ctype.h>
2 #include "cache.h"
3 #include "object.h"
4 #include "delta.h"
5 #include "pack.h"
6 #include "csum-file.h"
7
8 static const char pack_usage[] = "git-pack-objects [--incremental] [--window=N] [--depth=N] {--stdout | base-name} < object-list";
9
10 struct object_entry {
11         unsigned char sha1[20];
12         unsigned long size;
13         unsigned long offset;
14         unsigned int depth;
15         unsigned int hash;
16         enum object_type type;
17         unsigned long delta_size;
18         struct object_entry *delta;
19 };
20
21 static unsigned char object_list_sha1[20];
22 static int non_empty = 0;
23 static int incremental = 0;
24 static struct object_entry **sorted_by_sha, **sorted_by_type;
25 static struct object_entry *objects = NULL;
26 static int nr_objects = 0, nr_alloc = 0;
27 static const char *base_name;
28 static unsigned char pack_file_sha1[20];
29
30 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
31 {
32         unsigned long othersize, delta_size;
33         char type[10];
34         void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
35         void *delta_buf;
36
37         if (!otherbuf)
38                 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
39         delta_buf = diff_delta(otherbuf, othersize,
40                                buf, size, &delta_size, 0);
41         if (!delta_buf || delta_size != entry->delta_size)
42                 die("delta size changed");
43         free(buf);
44         free(otherbuf);
45         return delta_buf;
46 }
47
48 /*
49  * The per-object header is a pretty dense thing, which is
50  *  - first byte: low four bits are "size", then three bits of "type",
51  *    and the high bit is "size continues".
52  *  - each byte afterwards: low seven bits are size continuation,
53  *    with the high bit being "size continues"
54  */
55 static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
56 {
57         int n = 1;
58         unsigned char c;
59
60         if (type < OBJ_COMMIT || type > OBJ_DELTA)
61                 die("bad type %d", type);
62
63         c = (type << 4) | (size & 15);
64         size >>= 4;
65         while (size) {
66                 *hdr++ = c | 0x80;
67                 c = size & 0x7f;
68                 size >>= 7;
69                 n++;
70         }
71         *hdr = c;
72         return n;
73 }
74
75 static unsigned long write_object(struct sha1file *f, struct object_entry *entry)
76 {
77         unsigned long size;
78         char type[10];
79         void *buf = read_sha1_file(entry->sha1, type, &size);
80         unsigned char header[10];
81         unsigned hdrlen, datalen;
82         enum object_type obj_type;
83
84         if (!buf)
85                 die("unable to read %s", sha1_to_hex(entry->sha1));
86         if (size != entry->size)
87                 die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
88
89         /*
90          * The object header is a byte of 'type' followed by zero or
91          * more bytes of length.  For deltas, the 20 bytes of delta sha1
92          * follows that.
93          */
94         obj_type = entry->type;
95         if (entry->delta) {
96                 buf = delta_against(buf, size, entry);
97                 size = entry->delta_size;
98                 obj_type = OBJ_DELTA;
99         }
100         hdrlen = encode_header(obj_type, size, header);
101         sha1write(f, header, hdrlen);
102         if (entry->delta) {
103                 sha1write(f, entry->delta, 20);
104                 hdrlen += 20;
105         }
106         datalen = sha1write_compressed(f, buf, size);
107         free(buf);
108         return hdrlen + datalen;
109 }
110
111 static unsigned long write_one(struct sha1file *f,
112                                struct object_entry *e,
113                                unsigned long offset)
114 {
115         if (e->offset)
116                 /* offset starts from header size and cannot be zero
117                  * if it is written already.
118                  */
119                 return offset;
120         e->offset = offset;
121         offset += write_object(f, e);
122         /* if we are delitified, write out its base object. */
123         if (e->delta)
124                 offset = write_one(f, e->delta, offset);
125         return offset;
126 }
127
128 static void write_pack_file(void)
129 {
130         int i;
131         struct sha1file *f;
132         unsigned long offset;
133         unsigned long mb;
134         struct pack_header hdr;
135
136         if (!base_name)
137                 f = sha1fd(1, "<stdout>");
138         else
139                 f = sha1create("%s-%s.%s", base_name, sha1_to_hex(object_list_sha1), "pack");
140         hdr.hdr_signature = htonl(PACK_SIGNATURE);
141         hdr.hdr_version = htonl(PACK_VERSION);
142         hdr.hdr_entries = htonl(nr_objects);
143         sha1write(f, &hdr, sizeof(hdr));
144         offset = sizeof(hdr);
145         for (i = 0; i < nr_objects; i++)
146                 offset = write_one(f, objects + i, offset);
147
148         sha1close(f, pack_file_sha1, 1);
149         mb = offset >> 20;
150         offset &= 0xfffff;
151 }
152
153 static void write_index_file(void)
154 {
155         int i;
156         struct sha1file *f = sha1create("%s-%s.%s", base_name, sha1_to_hex(object_list_sha1), "idx");
157         struct object_entry **list = sorted_by_sha;
158         struct object_entry **last = list + nr_objects;
159         unsigned int array[256];
160
161         /*
162          * Write the first-level table (the list is sorted,
163          * but we use a 256-entry lookup to be able to avoid
164          * having to do eight extra binary search iterations).
165          */
166         for (i = 0; i < 256; i++) {
167                 struct object_entry **next = list;
168                 while (next < last) {
169                         struct object_entry *entry = *next;
170                         if (entry->sha1[0] != i)
171                                 break;
172                         next++;
173                 }
174                 array[i] = htonl(next - sorted_by_sha);
175                 list = next;
176         }
177         sha1write(f, array, 256 * sizeof(int));
178
179         /*
180          * Write the actual SHA1 entries..
181          */
182         list = sorted_by_sha;
183         for (i = 0; i < nr_objects; i++) {
184                 struct object_entry *entry = *list++;
185                 unsigned int offset = htonl(entry->offset);
186                 sha1write(f, &offset, 4);
187                 sha1write(f, entry->sha1, 20);
188         }
189         sha1write(f, pack_file_sha1, 20);
190         sha1close(f, NULL, 1);
191 }
192
193 static int add_object_entry(unsigned char *sha1, unsigned int hash)
194 {
195         unsigned int idx = nr_objects;
196         struct object_entry *entry;
197
198         if (incremental && has_sha1_pack(sha1))
199                 return 0;
200
201         if (idx >= nr_alloc) {
202                 unsigned int needed = (idx + 1024) * 3 / 2;
203                 objects = xrealloc(objects, needed * sizeof(*entry));
204                 nr_alloc = needed;
205         }
206         entry = objects + idx;
207         memset(entry, 0, sizeof(*entry));
208         memcpy(entry->sha1, sha1, 20);
209         entry->hash = hash;
210         nr_objects = idx+1;
211         return 1;
212 }
213
214 static void check_object(struct object_entry *entry)
215 {
216         char type[20];
217
218         if (!sha1_object_info(entry->sha1, type, &entry->size)) {
219                 if (!strcmp(type, "commit")) {
220                         entry->type = OBJ_COMMIT;
221                 } else if (!strcmp(type, "tree")) {
222                         entry->type = OBJ_TREE;
223                 } else if (!strcmp(type, "blob")) {
224                         entry->type = OBJ_BLOB;
225                 } else if (!strcmp(type, "tag")) {
226                         entry->type = OBJ_TAG;
227                 } else
228                         die("unable to pack object %s of type %s",
229                             sha1_to_hex(entry->sha1), type);
230         }
231         else
232                 die("unable to get type of object %s",
233                     sha1_to_hex(entry->sha1));
234 }
235
236 static void get_object_details(void)
237 {
238         int i;
239         struct object_entry *entry = objects;
240
241         for (i = 0; i < nr_objects; i++)
242                 check_object(entry++);
243 }
244
245 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
246
247 static entry_sort_t current_sort;
248
249 static int sort_comparator(const void *_a, const void *_b)
250 {
251         struct object_entry *a = *(struct object_entry **)_a;
252         struct object_entry *b = *(struct object_entry **)_b;
253         return current_sort(a,b);
254 }
255
256 static struct object_entry **create_sorted_list(entry_sort_t sort)
257 {
258         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
259         int i;
260
261         for (i = 0; i < nr_objects; i++)
262                 list[i] = objects + i;
263         current_sort = sort;
264         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
265         return list;
266 }
267
268 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
269 {
270         return memcmp(a->sha1, b->sha1, 20);
271 }
272
273 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
274 {
275         if (a->type < b->type)
276                 return -1;
277         if (a->type > b->type)
278                 return 1;
279         if (a->hash < b->hash)
280                 return -1;
281         if (a->hash > b->hash)
282                 return 1;
283         if (a->size < b->size)
284                 return -1;
285         if (a->size > b->size)
286                 return 1;
287         return a < b ? -1 : (a > b);
288 }
289
290 struct unpacked {
291         struct object_entry *entry;
292         void *data;
293 };
294
295 /*
296  * We search for deltas _backwards_ in a list sorted by type and
297  * by size, so that we see progressively smaller and smaller files.
298  * That's because we prefer deltas to be from the bigger file
299  * to the smaller - deletes are potentially cheaper, but perhaps
300  * more importantly, the bigger file is likely the more recent
301  * one.
302  */
303 static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
304 {
305         struct object_entry *cur_entry = cur->entry;
306         struct object_entry *old_entry = old->entry;
307         unsigned long size, oldsize, delta_size, sizediff;
308         long max_size;
309         void *delta_buf;
310
311         /* Don't bother doing diffs between different types */
312         if (cur_entry->type != old_entry->type)
313                 return -1;
314
315         size = cur_entry->size;
316         if (size < 50)
317                 return -1;
318         oldsize = old_entry->size;
319         sizediff = oldsize > size ? oldsize - size : size - oldsize;
320         if (sizediff > size / 8)
321                 return -1;
322         if (old_entry->depth >= max_depth)
323                 return 0;
324
325         /*
326          * NOTE!
327          *
328          * We always delta from the bigger to the smaller, since that's
329          * more space-efficient (deletes don't have to say _what_ they
330          * delete).
331          */
332         max_size = size / 2 - 20;
333         if (cur_entry->delta)
334                 max_size = cur_entry->delta_size-1;
335         if (sizediff >= max_size)
336                 return -1;
337         delta_buf = diff_delta(old->data, oldsize,
338                                cur->data, size, &delta_size, max_size);
339         if (!delta_buf)
340                 return 0;
341         cur_entry->delta = old_entry;
342         cur_entry->delta_size = delta_size;
343         cur_entry->depth = old_entry->depth + 1;
344         free(delta_buf);
345         return 0;
346 }
347
348 static void find_deltas(struct object_entry **list, int window, int depth)
349 {
350         int i, idx;
351         unsigned int array_size = window * sizeof(struct unpacked);
352         struct unpacked *array = xmalloc(array_size);
353
354         memset(array, 0, array_size);
355         i = nr_objects;
356         idx = 0;
357         while (--i >= 0) {
358                 struct object_entry *entry = list[i];
359                 struct unpacked *n = array + idx;
360                 unsigned long size;
361                 char type[10];
362                 int j;
363
364                 free(n->data);
365                 n->entry = entry;
366                 n->data = read_sha1_file(entry->sha1, type, &size);
367                 if (size != entry->size)
368                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
369                 j = window;
370                 while (--j > 0) {
371                         unsigned int other_idx = idx + j;
372                         struct unpacked *m;
373                         if (other_idx >= window)
374                                 other_idx -= window;
375                         m = array + other_idx;
376                         if (!m->entry)
377                                 break;
378                         if (try_delta(n, m, depth) < 0)
379                                 break;
380                 }
381                 idx++;
382                 if (idx >= window)
383                         idx = 0;
384         }
385
386         for (i = 0; i < window; ++i)
387                 free(array[i].data);
388         free(array);
389 }
390
391 int main(int argc, char **argv)
392 {
393         SHA_CTX ctx;
394         char line[PATH_MAX + 20];
395         int window = 10, depth = 10, pack_to_stdout = 0;
396         int i;
397
398         for (i = 1; i < argc; i++) {
399                 const char *arg = argv[i];
400
401                 if (*arg == '-') {
402                         if (!strcmp("--non-empty", arg)) {
403                                 non_empty = 1;
404                                 continue;
405                         }
406                         if (!strcmp("--incremental", arg)) {
407                                 incremental = 1;
408                                 continue;
409                         }
410                         if (!strncmp("--window=", arg, 9)) {
411                                 char *end;
412                                 window = strtoul(arg+9, &end, 0);
413                                 if (!arg[9] || *end)
414                                         usage(pack_usage);
415                                 continue;
416                         }
417                         if (!strncmp("--depth=", arg, 8)) {
418                                 char *end;
419                                 depth = strtoul(arg+8, &end, 0);
420                                 if (!arg[8] || *end)
421                                         usage(pack_usage);
422                                 continue;
423                         }
424                         if (!strcmp("--stdout", arg)) {
425                                 pack_to_stdout = 1;
426                                 continue;
427                         }
428                         usage(pack_usage);
429                 }
430                 if (base_name)
431                         usage(pack_usage);
432                 base_name = arg;
433         }
434
435         if (pack_to_stdout != !base_name)
436                 usage(pack_usage);
437
438         SHA1_Init(&ctx);
439         while (fgets(line, sizeof(line), stdin) != NULL) {
440                 unsigned int hash;
441                 char *p;
442                 unsigned char sha1[20];
443
444                 if (get_sha1_hex(line, sha1))
445                         die("expected sha1, got garbage");
446                 hash = 0;
447                 p = line+40;
448                 while (*p) {
449                         unsigned char c = *p++;
450                         if (isspace(c))
451                                 continue;
452                         hash = hash * 11 + c;
453                 }
454                 if (add_object_entry(sha1, hash))
455                         SHA1_Update(&ctx, sha1, 20);
456         }
457         SHA1_Final(object_list_sha1, &ctx);
458         if (non_empty && !nr_objects)
459                 return 0;
460         get_object_details();
461
462         fprintf(stderr, "Packing %d objects\n", nr_objects);
463
464         sorted_by_sha = create_sorted_list(sha1_sort);
465         sorted_by_type = create_sorted_list(type_size_sort);
466         if (window && depth)
467                 find_deltas(sorted_by_type, window+1, depth);
468
469         write_pack_file();
470         if (!pack_to_stdout) {
471                 write_index_file();
472                 puts(sha1_to_hex(object_list_sha1));
473         }
474         return 0;
475 }