pack-objects: hash basename and direname a bit differently.
[git] / pack-objects.c
1 #include "cache.h"
2 #include "object.h"
3 #include "delta.h"
4 #include "pack.h"
5 #include "csum-file.h"
6 #include "diff.h"
7 #include <sys/time.h>
8
9 static const char pack_usage[] = "git-pack-objects [-q] [--no-reuse-delta] [--non-empty] [--local] [--incremental] [--window=N] [--depth=N] {--stdout | base-name} < object-list";
10
11 struct object_entry {
12         unsigned char sha1[20];
13         unsigned long size;     /* uncompressed size */
14         unsigned long offset;   /* offset into the final pack file;
15                                  * nonzero if already written.
16                                  */
17         unsigned int depth;     /* delta depth */
18         unsigned int delta_limit;       /* base adjustment for in-pack delta */
19         unsigned int hash;      /* name hint hash */
20         enum object_type type;
21         enum object_type in_pack_type;  /* could be delta */
22         unsigned long delta_size;       /* delta data size (uncompressed) */
23         struct object_entry *delta;     /* delta base object */
24         struct packed_git *in_pack;     /* already in pack */
25         unsigned int in_pack_offset;
26         struct object_entry *delta_child; /* delitified objects who bases me */
27         struct object_entry *delta_sibling; /* other deltified objects who
28                                              * uses the same base as me
29                                              */
30         int preferred_base;     /* we do not pack this, but is encouraged to
31                                  * be used as the base objectto delta huge
32                                  * objects against.
33                                  */
34         int based_on_preferred; /* current delta candidate is a preferred
35                                  * one, or delta against a preferred one.
36                                  */
37 };
38
39 /*
40  * Objects we are going to pack are colected in objects array (dynamically
41  * expanded).  nr_objects & nr_alloc controls this array.  They are stored
42  * in the order we see -- typically rev-list --objects order that gives us
43  * nice "minimum seek" order.
44  *
45  * sorted-by-sha ans sorted-by-type are arrays of pointers that point at
46  * elements in the objects array.  The former is used to build the pack
47  * index (lists object names in the ascending order to help offset lookup),
48  * and the latter is used to group similar things together by try_delta()
49  * heuristics.
50  */
51
52 static unsigned char object_list_sha1[20];
53 static int non_empty = 0;
54 static int no_reuse_delta = 0;
55 static int local = 0;
56 static int incremental = 0;
57 static struct object_entry **sorted_by_sha, **sorted_by_type;
58 static struct object_entry *objects = NULL;
59 static int nr_objects = 0, nr_alloc = 0, nr_result = 0;
60 static const char *base_name;
61 static unsigned char pack_file_sha1[20];
62 static int progress = 1;
63
64 /*
65  * The object names in objects array are hashed with this hashtable,
66  * to help looking up the entry by object name.  Binary search from
67  * sorted_by_sha is also possible but this was easier to code and faster.
68  * This hashtable is built after all the objects are seen.
69  */
70 static int *object_ix = NULL;
71 static int object_ix_hashsz = 0;
72
73 /*
74  * Pack index for existing packs give us easy access to the offsets into
75  * corresponding pack file where each object's data starts, but the entries
76  * do not store the size of the compressed representation (uncompressed
77  * size is easily available by examining the pack entry header).  We build
78  * a hashtable of existing packs (pack_revindex), and keep reverse index
79  * here -- pack index file is sorted by object name mapping to offset; this
80  * pack_revindex[].revindex array is an ordered list of offsets, so if you
81  * know the offset of an object, next offset is where its packed
82  * representation ends.
83  */
84 struct pack_revindex {
85         struct packed_git *p;
86         unsigned long *revindex;
87 } *pack_revindex = NULL;
88 static int pack_revindex_hashsz = 0;
89
90 /*
91  * stats
92  */
93 static int written = 0;
94 static int written_delta = 0;
95 static int reused = 0;
96 static int reused_delta = 0;
97
98 static int pack_revindex_ix(struct packed_git *p)
99 {
100         unsigned int ui = (unsigned int) p;
101         int i;
102
103         ui = ui ^ (ui >> 16); /* defeat structure alignment */
104         i = (int)(ui % pack_revindex_hashsz);
105         while (pack_revindex[i].p) {
106                 if (pack_revindex[i].p == p)
107                         return i;
108                 if (++i == pack_revindex_hashsz)
109                         i = 0;
110         }
111         return -1 - i;
112 }
113
114 static void prepare_pack_ix(void)
115 {
116         int num;
117         struct packed_git *p;
118         for (num = 0, p = packed_git; p; p = p->next)
119                 num++;
120         if (!num)
121                 return;
122         pack_revindex_hashsz = num * 11;
123         pack_revindex = xcalloc(sizeof(*pack_revindex), pack_revindex_hashsz);
124         for (p = packed_git; p; p = p->next) {
125                 num = pack_revindex_ix(p);
126                 num = - 1 - num;
127                 pack_revindex[num].p = p;
128         }
129         /* revindex elements are lazily initialized */
130 }
131
132 static int cmp_offset(const void *a_, const void *b_)
133 {
134         unsigned long a = *(unsigned long *) a_;
135         unsigned long b = *(unsigned long *) b_;
136         if (a < b)
137                 return -1;
138         else if (a == b)
139                 return 0;
140         else
141                 return 1;
142 }
143
144 /*
145  * Ordered list of offsets of objects in the pack.
146  */
147 static void prepare_pack_revindex(struct pack_revindex *rix)
148 {
149         struct packed_git *p = rix->p;
150         int num_ent = num_packed_objects(p);
151         int i;
152         void *index = p->index_base + 256;
153
154         rix->revindex = xmalloc(sizeof(unsigned long) * (num_ent + 1));
155         for (i = 0; i < num_ent; i++) {
156                 long hl = *((long *)(index + 24 * i));
157                 rix->revindex[i] = ntohl(hl);
158         }
159         /* This knows the pack format -- the 20-byte trailer
160          * follows immediately after the last object data.
161          */
162         rix->revindex[num_ent] = p->pack_size - 20;
163         qsort(rix->revindex, num_ent, sizeof(unsigned long), cmp_offset);
164 }
165
166 static unsigned long find_packed_object_size(struct packed_git *p,
167                                              unsigned long ofs)
168 {
169         int num;
170         int lo, hi;
171         struct pack_revindex *rix;
172         unsigned long *revindex;
173         num = pack_revindex_ix(p);
174         if (num < 0)
175                 die("internal error: pack revindex uninitialized");
176         rix = &pack_revindex[num];
177         if (!rix->revindex)
178                 prepare_pack_revindex(rix);
179         revindex = rix->revindex;
180         lo = 0;
181         hi = num_packed_objects(p) + 1;
182         do {
183                 int mi = (lo + hi) / 2;
184                 if (revindex[mi] == ofs) {
185                         return revindex[mi+1] - ofs;
186                 }
187                 else if (ofs < revindex[mi])
188                         hi = mi;
189                 else
190                         lo = mi + 1;
191         } while (lo < hi);
192         die("internal error: pack revindex corrupt");
193 }
194
195 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
196 {
197         unsigned long othersize, delta_size;
198         char type[10];
199         void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
200         void *delta_buf;
201
202         if (!otherbuf)
203                 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
204         delta_buf = diff_delta(otherbuf, othersize,
205                                buf, size, &delta_size, 0);
206         if (!delta_buf || delta_size != entry->delta_size)
207                 die("delta size changed");
208         free(buf);
209         free(otherbuf);
210         return delta_buf;
211 }
212
213 /*
214  * The per-object header is a pretty dense thing, which is
215  *  - first byte: low four bits are "size", then three bits of "type",
216  *    and the high bit is "size continues".
217  *  - each byte afterwards: low seven bits are size continuation,
218  *    with the high bit being "size continues"
219  */
220 static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
221 {
222         int n = 1;
223         unsigned char c;
224
225         if (type < OBJ_COMMIT || type > OBJ_DELTA)
226                 die("bad type %d", type);
227
228         c = (type << 4) | (size & 15);
229         size >>= 4;
230         while (size) {
231                 *hdr++ = c | 0x80;
232                 c = size & 0x7f;
233                 size >>= 7;
234                 n++;
235         }
236         *hdr = c;
237         return n;
238 }
239
240 static unsigned long write_object(struct sha1file *f,
241                                   struct object_entry *entry)
242 {
243         unsigned long size;
244         char type[10];
245         void *buf;
246         unsigned char header[10];
247         unsigned hdrlen, datalen;
248         enum object_type obj_type;
249         int to_reuse = 0;
250
251         if (entry->preferred_base)
252                 return 0;
253
254         obj_type = entry->type;
255         if (! entry->in_pack)
256                 to_reuse = 0;   /* can't reuse what we don't have */
257         else if (obj_type == OBJ_DELTA)
258                 to_reuse = 1;   /* check_object() decided it for us */
259         else if (obj_type != entry->in_pack_type)
260                 to_reuse = 0;   /* pack has delta which is unusable */
261         else if (entry->delta)
262                 to_reuse = 0;   /* we want to pack afresh */
263         else
264                 to_reuse = 1;   /* we have it in-pack undeltified,
265                                  * and we do not need to deltify it.
266                                  */
267
268         if (! to_reuse) {
269                 buf = read_sha1_file(entry->sha1, type, &size);
270                 if (!buf)
271                         die("unable to read %s", sha1_to_hex(entry->sha1));
272                 if (size != entry->size)
273                         die("object %s size inconsistency (%lu vs %lu)",
274                             sha1_to_hex(entry->sha1), size, entry->size);
275                 if (entry->delta) {
276                         buf = delta_against(buf, size, entry);
277                         size = entry->delta_size;
278                         obj_type = OBJ_DELTA;
279                 }
280                 /*
281                  * The object header is a byte of 'type' followed by zero or
282                  * more bytes of length.  For deltas, the 20 bytes of delta
283                  * sha1 follows that.
284                  */
285                 hdrlen = encode_header(obj_type, size, header);
286                 sha1write(f, header, hdrlen);
287
288                 if (entry->delta) {
289                         sha1write(f, entry->delta, 20);
290                         hdrlen += 20;
291                 }
292                 datalen = sha1write_compressed(f, buf, size);
293                 free(buf);
294         }
295         else {
296                 struct packed_git *p = entry->in_pack;
297                 use_packed_git(p);
298
299                 datalen = find_packed_object_size(p, entry->in_pack_offset);
300                 buf = p->pack_base + entry->in_pack_offset;
301                 sha1write(f, buf, datalen);
302                 unuse_packed_git(p);
303                 hdrlen = 0; /* not really */
304                 if (obj_type == OBJ_DELTA)
305                         reused_delta++;
306                 reused++;
307         }
308         if (obj_type == OBJ_DELTA)
309                 written_delta++;
310         written++;
311         return hdrlen + datalen;
312 }
313
314 static unsigned long write_one(struct sha1file *f,
315                                struct object_entry *e,
316                                unsigned long offset)
317 {
318         if (e->offset)
319                 /* offset starts from header size and cannot be zero
320                  * if it is written already.
321                  */
322                 return offset;
323         e->offset = offset;
324         offset += write_object(f, e);
325         /* if we are deltified, write out its base object. */
326         if (e->delta)
327                 offset = write_one(f, e->delta, offset);
328         return offset;
329 }
330
331 static void write_pack_file(void)
332 {
333         int i;
334         struct sha1file *f;
335         unsigned long offset;
336         struct pack_header hdr;
337
338         if (!base_name)
339                 f = sha1fd(1, "<stdout>");
340         else
341                 f = sha1create("%s-%s.%s", base_name,
342                                sha1_to_hex(object_list_sha1), "pack");
343         hdr.hdr_signature = htonl(PACK_SIGNATURE);
344         hdr.hdr_version = htonl(PACK_VERSION);
345         hdr.hdr_entries = htonl(nr_result);
346         sha1write(f, &hdr, sizeof(hdr));
347         offset = sizeof(hdr);
348         for (i = 0; i < nr_objects; i++)
349                 offset = write_one(f, objects + i, offset);
350
351         sha1close(f, pack_file_sha1, 1);
352 }
353
354 static void write_index_file(void)
355 {
356         int i;
357         struct sha1file *f = sha1create("%s-%s.%s", base_name,
358                                         sha1_to_hex(object_list_sha1), "idx");
359         struct object_entry **list = sorted_by_sha;
360         struct object_entry **last = list + nr_result;
361         unsigned int array[256];
362
363         /*
364          * Write the first-level table (the list is sorted,
365          * but we use a 256-entry lookup to be able to avoid
366          * having to do eight extra binary search iterations).
367          */
368         for (i = 0; i < 256; i++) {
369                 struct object_entry **next = list;
370                 while (next < last) {
371                         struct object_entry *entry = *next;
372                         if (entry->sha1[0] != i)
373                                 break;
374                         next++;
375                 }
376                 array[i] = htonl(next - sorted_by_sha);
377                 list = next;
378         }
379         sha1write(f, array, 256 * sizeof(int));
380
381         /*
382          * Write the actual SHA1 entries..
383          */
384         list = sorted_by_sha;
385         for (i = 0; i < nr_result; i++) {
386                 struct object_entry *entry = *list++;
387                 unsigned int offset = htonl(entry->offset);
388                 sha1write(f, &offset, 4);
389                 sha1write(f, entry->sha1, 20);
390         }
391         sha1write(f, pack_file_sha1, 20);
392         sha1close(f, NULL, 1);
393 }
394
395 static int locate_object_entry_hash(const unsigned char *sha1)
396 {
397         int i;
398         unsigned int ui;
399         memcpy(&ui, sha1, sizeof(unsigned int));
400         i = ui % object_ix_hashsz;
401         while (0 < object_ix[i]) {
402                 if (!memcmp(sha1, objects[object_ix[i]-1].sha1, 20))
403                         return i;
404                 if (++i == object_ix_hashsz)
405                         i = 0;
406         }
407         return -1 - i;
408 }
409
410 static struct object_entry *locate_object_entry(const unsigned char *sha1)
411 {
412         int i;
413
414         if (!object_ix_hashsz)
415                 return NULL;
416
417         i = locate_object_entry_hash(sha1);
418         if (0 <= i)
419                 return &objects[object_ix[i]-1];
420         return NULL;
421 }
422
423 static void rehash_objects(void)
424 {
425         int i;
426         struct object_entry *oe;
427
428         object_ix_hashsz = nr_objects * 3;
429         if (object_ix_hashsz < 1024)
430                 object_ix_hashsz = 1024;
431         object_ix = xrealloc(object_ix, sizeof(int) * object_ix_hashsz);
432         object_ix = memset(object_ix, 0, sizeof(int) * object_ix_hashsz);
433         for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
434                 int ix = locate_object_entry_hash(oe->sha1);
435                 if (0 <= ix)
436                         continue;
437                 ix = -1 - ix;
438                 object_ix[ix] = i + 1;
439         }
440 }
441
442 struct name_path {
443         struct name_path *up;
444         const char *elem;
445         int len;
446 };
447
448 #define DIRBITS 12
449
450 static unsigned name_hash(struct name_path *path, const char *name)
451 {
452         struct name_path *p = path;
453         const char *n = name + strlen(name);
454         unsigned hash = 0, name_hash = 0, name_done = 0;
455
456         if (n != name && n[-1] == '\n')
457                 n--;
458         while (name <= --n) {
459                 unsigned char c = *n;
460                 if (c == '/' && !name_done) {
461                         name_hash = hash;
462                         name_done = 1;
463                         hash = 0;
464                 }
465                 hash = hash * 11 + c;
466         }
467         if (!name_done) {
468                 name_hash = hash;
469                 hash = 0;
470         }
471         for (p = path; p; p = p->up) {
472                 hash = hash * 11 + '/';
473                 n = p->elem + p->len;
474                 while (p->elem <= --n) {
475                         unsigned char c = *n;
476                         hash = hash * 11 + c;
477                 }
478         }
479         /*
480          * Make sure "Makefile" and "t/Makefile" are hashed separately
481          * but close enough.
482          */
483         hash = (name_hash<<DIRBITS) | (hash & ((1U<<DIRBITS )-1));
484
485         if (0) { /* debug */
486                 n = name + strlen(name);
487                 if (n != name && n[-1] == '\n')
488                         n--;
489                 while (name <= --n)
490                         fputc(*n, stderr);
491                 for (p = path; p; p = p->up) {
492                         fputc('/', stderr);
493                         n = p->elem + p->len;
494                         while (p->elem <= --n)
495                                 fputc(*n, stderr);
496                 }
497                 fprintf(stderr, "\t%08x\n", hash);
498         }
499         return hash;
500 }
501
502 static int add_object_entry(const unsigned char *sha1, unsigned hash, int exclude)
503 {
504         unsigned int idx = nr_objects;
505         struct object_entry *entry;
506         struct packed_git *p;
507         unsigned int found_offset = 0;
508         struct packed_git *found_pack = NULL;
509         int ix, status = 0;
510
511         if (!exclude) {
512                 for (p = packed_git; p; p = p->next) {
513                         struct pack_entry e;
514                         if (find_pack_entry_one(sha1, &e, p)) {
515                                 if (incremental)
516                                         return 0;
517                                 if (local && !p->pack_local)
518                                         return 0;
519                                 if (!found_pack) {
520                                         found_offset = e.offset;
521                                         found_pack = e.p;
522                                 }
523                         }
524                 }
525         }
526         if ((entry = locate_object_entry(sha1)) != NULL)
527                 goto already_added;
528
529         if (idx >= nr_alloc) {
530                 unsigned int needed = (idx + 1024) * 3 / 2;
531                 objects = xrealloc(objects, needed * sizeof(*entry));
532                 nr_alloc = needed;
533         }
534         entry = objects + idx;
535         nr_objects = idx + 1;
536         memset(entry, 0, sizeof(*entry));
537         memcpy(entry->sha1, sha1, 20);
538         entry->hash = hash;
539
540         if (object_ix_hashsz * 3 <= nr_objects * 4)
541                 rehash_objects();
542         else {
543                 ix = locate_object_entry_hash(entry->sha1);
544                 if (0 <= ix)
545                         die("internal error in object hashing.");
546                 object_ix[-1 - ix] = idx + 1;
547         }
548         status = 1;
549
550  already_added:
551         if (exclude)
552                 entry->preferred_base = 1;
553         else {
554                 if (found_pack) {
555                         entry->in_pack = found_pack;
556                         entry->in_pack_offset = found_offset;
557                 }
558         }
559         return status;
560 }
561
562 static void add_pbase_tree(struct tree_desc *tree, struct name_path *up)
563 {
564         while (tree->size) {
565                 const unsigned char *sha1;
566                 const char *name;
567                 unsigned mode, hash;
568                 unsigned long size;
569                 char type[20];
570
571                 sha1 = tree_entry_extract(tree, &name, &mode);
572                 update_tree_entry(tree);
573                 if (!has_sha1_file(sha1))
574                         continue;
575                 if (sha1_object_info(sha1, type, &size))
576                         continue;
577
578                 hash = name_hash(up, name);
579                 if (!add_object_entry(sha1, hash, 1))
580                         continue;
581
582                 if (!strcmp(type, "tree")) {
583                         struct tree_desc sub;
584                         void *elem;
585                         struct name_path me;
586
587                         elem = read_sha1_file(sha1, type, &sub.size);
588                         sub.buf = elem;
589                         if (sub.buf) {
590                                 me.up = up;
591                                 me.elem = name;
592                                 me.len = strlen(name);
593                                 add_pbase_tree(&sub, &me);
594                                 free(elem);
595                         }
596                 }
597         }
598 }
599
600 static void add_preferred_base(unsigned char *sha1)
601 {
602         struct tree_desc tree;
603         void *elem;
604
605         elem = read_object_with_reference(sha1, "tree", &tree.size, NULL);
606         tree.buf = elem;
607         if (!tree.buf)
608                 return;
609         if (add_object_entry(sha1, name_hash(NULL, ""), 1))
610                 add_pbase_tree(&tree, NULL);
611         free(elem);
612 }
613
614 static void check_object(struct object_entry *entry)
615 {
616         char type[20];
617
618         if (entry->in_pack && !entry->preferred_base) {
619                 unsigned char base[20];
620                 unsigned long size;
621                 struct object_entry *base_entry;
622
623                 /* We want in_pack_type even if we do not reuse delta.
624                  * There is no point not reusing non-delta representations.
625                  */
626                 check_reuse_pack_delta(entry->in_pack,
627                                        entry->in_pack_offset,
628                                        base, &size,
629                                        &entry->in_pack_type);
630
631                 /* Check if it is delta, and the base is also an object
632                  * we are going to pack.  If so we will reuse the existing
633                  * delta.
634                  */
635                 if (!no_reuse_delta &&
636                     entry->in_pack_type == OBJ_DELTA &&
637                     (base_entry = locate_object_entry(base)) &&
638                     (!base_entry->preferred_base)) {
639
640                         /* Depth value does not matter - find_deltas()
641                          * will never consider reused delta as the
642                          * base object to deltify other objects
643                          * against, in order to avoid circular deltas.
644                          */
645
646                         /* uncompressed size of the delta data */
647                         entry->size = entry->delta_size = size;
648                         entry->delta = base_entry;
649                         entry->type = OBJ_DELTA;
650
651                         entry->delta_sibling = base_entry->delta_child;
652                         base_entry->delta_child = entry;
653
654                         return;
655                 }
656                 /* Otherwise we would do the usual */
657         }
658
659         if (sha1_object_info(entry->sha1, type, &entry->size))
660                 die("unable to get type of object %s",
661                     sha1_to_hex(entry->sha1));
662
663         if (!strcmp(type, "commit")) {
664                 entry->type = OBJ_COMMIT;
665         } else if (!strcmp(type, "tree")) {
666                 entry->type = OBJ_TREE;
667         } else if (!strcmp(type, "blob")) {
668                 entry->type = OBJ_BLOB;
669         } else if (!strcmp(type, "tag")) {
670                 entry->type = OBJ_TAG;
671         } else
672                 die("unable to pack object %s of type %s",
673                     sha1_to_hex(entry->sha1), type);
674 }
675
676 static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
677 {
678         struct object_entry *child = me->delta_child;
679         unsigned int m = n;
680         while (child) {
681                 unsigned int c = check_delta_limit(child, n + 1);
682                 if (m < c)
683                         m = c;
684                 child = child->delta_sibling;
685         }
686         return m;
687 }
688
689 static void get_object_details(void)
690 {
691         int i;
692         struct object_entry *entry;
693
694         prepare_pack_ix();
695         for (i = 0, entry = objects; i < nr_objects; i++, entry++)
696                 check_object(entry);
697
698         if (nr_objects == nr_result) {
699                 /*
700                  * Depth of objects that depend on the entry -- this
701                  * is subtracted from depth-max to break too deep
702                  * delta chain because of delta data reusing.
703                  * However, we loosen this restriction when we know we
704                  * are creating a thin pack -- it will have to be
705                  * expanded on the other end anyway, so do not
706                  * artificially cut the delta chain and let it go as
707                  * deep as it wants.
708                  */
709                 for (i = 0, entry = objects; i < nr_objects; i++, entry++)
710                         if (!entry->delta && entry->delta_child)
711                                 entry->delta_limit =
712                                         check_delta_limit(entry, 1);
713         }
714 }
715
716 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
717
718 static entry_sort_t current_sort;
719
720 static int sort_comparator(const void *_a, const void *_b)
721 {
722         struct object_entry *a = *(struct object_entry **)_a;
723         struct object_entry *b = *(struct object_entry **)_b;
724         return current_sort(a,b);
725 }
726
727 static struct object_entry **create_sorted_list(entry_sort_t sort)
728 {
729         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
730         int i;
731
732         for (i = 0; i < nr_objects; i++)
733                 list[i] = objects + i;
734         current_sort = sort;
735         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
736         return list;
737 }
738
739 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
740 {
741         return memcmp(a->sha1, b->sha1, 20);
742 }
743
744 static struct object_entry **create_final_object_list()
745 {
746         struct object_entry **list;
747         int i, j;
748
749         for (i = nr_result = 0; i < nr_objects; i++)
750                 if (!objects[i].preferred_base)
751                         nr_result++;
752         list = xmalloc(nr_result * sizeof(struct object_entry *));
753         for (i = j = 0; i < nr_objects; i++) {
754                 if (!objects[i].preferred_base)
755                         list[j++] = objects + i;
756         }
757         current_sort = sha1_sort;
758         qsort(list, nr_result, sizeof(struct object_entry *), sort_comparator);
759         return list;
760 }
761
762 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
763 {
764         if (a->type < b->type)
765                 return -1;
766         if (a->type > b->type)
767                 return 1;
768         if (a->hash < b->hash)
769                 return -1;
770         if (a->hash > b->hash)
771                 return 1;
772         if (a->preferred_base < b->preferred_base)
773                 return -1;
774         if (a->preferred_base > b->preferred_base)
775                 return 1;
776         if (a->size < b->size)
777                 return -1;
778         if (a->size > b->size)
779                 return 1;
780         return a < b ? -1 : (a > b);
781 }
782
783 struct unpacked {
784         struct object_entry *entry;
785         void *data;
786 };
787
788 /*
789  * We search for deltas _backwards_ in a list sorted by type and
790  * by size, so that we see progressively smaller and smaller files.
791  * That's because we prefer deltas to be from the bigger file
792  * to the smaller - deletes are potentially cheaper, but perhaps
793  * more importantly, the bigger file is likely the more recent
794  * one.
795  */
796 static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
797 {
798         struct object_entry *cur_entry = cur->entry;
799         struct object_entry *old_entry = old->entry;
800         int old_preferred = (old_entry->preferred_base ||
801                              old_entry->based_on_preferred);
802         unsigned long size, oldsize, delta_size, sizediff;
803         long max_size;
804         void *delta_buf;
805
806         /* Don't bother doing diffs between different types */
807         if (cur_entry->type != old_entry->type)
808                 return -1;
809
810         /* We do not compute delta to *create* objects we are not
811          * going to pack.
812          */
813         if (cur_entry->preferred_base)
814                 return -1;
815
816         /* If the current object is at pack edge, take the depth the
817          * objects that depend on the current object into account --
818          * otherwise they would become too deep.
819          */
820         if (cur_entry->delta_child) {
821                 if (max_depth <= cur_entry->delta_limit)
822                         return 0;
823                 max_depth -= cur_entry->delta_limit;
824         }
825
826         size = cur_entry->size;
827         if (size < 50)
828                 return -1;
829         oldsize = old_entry->size;
830         sizediff = oldsize > size ? oldsize - size : size - oldsize;
831         if (sizediff > size / 8)
832                 return -1;
833         if (old_entry->depth >= max_depth)
834                 return 0;
835
836         /*
837          * NOTE!
838          *
839          * We always delta from the bigger to the smaller, since that's
840          * more space-efficient (deletes don't have to say _what_ they
841          * delete).
842          */
843         max_size = size / 2 - 20;
844         if (cur_entry->delta) {
845                 if (cur_entry->based_on_preferred) {
846                         if (old_preferred)
847                                 max_size = cur_entry->delta_size-1;
848                         else
849                                 /* trying with non-preferred one when we
850                                  * already have a delta based on preferred
851                                  * one is pointless.
852                                  */
853                                 return -1;
854                 }
855                 else if (!old_preferred)
856                         max_size = cur_entry->delta_size-1;
857                 else
858                         /* otherwise...  even if delta with a
859                          * preferred one produces a bigger result than
860                          * what we currently have, which is based on a
861                          * non-preferred one, it is OK.
862                          */
863                         ;
864         }
865         if (sizediff >= max_size)
866                 return -1;
867         delta_buf = diff_delta(old->data, oldsize,
868                                cur->data, size, &delta_size, max_size);
869         if (!delta_buf)
870                 return 0;
871         cur_entry->delta = old_entry;
872         cur_entry->delta_size = delta_size;
873         cur_entry->depth = old_entry->depth + 1;
874         cur_entry->based_on_preferred = old_preferred;
875         free(delta_buf);
876         return 0;
877 }
878
879 static void find_deltas(struct object_entry **list, int window, int depth)
880 {
881         int i, idx;
882         unsigned int array_size = window * sizeof(struct unpacked);
883         struct unpacked *array = xmalloc(array_size);
884         int eye_candy;
885
886         memset(array, 0, array_size);
887         i = nr_objects;
888         idx = 0;
889         eye_candy = i - (nr_objects / 20);
890
891         while (--i >= 0) {
892                 struct object_entry *entry = list[i];
893                 struct unpacked *n = array + idx;
894                 unsigned long size;
895                 char type[10];
896                 int j;
897
898                 if (progress && i <= eye_candy) {
899                         eye_candy -= nr_objects / 20;
900                         fputc('.', stderr);
901                 }
902
903                 if (entry->delta)
904                         /* This happens if we decided to reuse existing
905                          * delta from a pack.  "!no_reuse_delta &&" is implied.
906                          */
907                         continue;
908
909                 free(n->data);
910                 n->entry = entry;
911                 n->data = read_sha1_file(entry->sha1, type, &size);
912                 if (size != entry->size)
913                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
914
915                 j = window;
916                 while (--j > 0) {
917                         unsigned int other_idx = idx + j;
918                         struct unpacked *m;
919                         if (other_idx >= window)
920                                 other_idx -= window;
921                         m = array + other_idx;
922                         if (!m->entry)
923                                 break;
924                         if (try_delta(n, m, depth) < 0)
925                                 break;
926                 }
927                 idx++;
928                 if (idx >= window)
929                         idx = 0;
930         }
931
932         for (i = 0; i < window; ++i)
933                 free(array[i].data);
934         free(array);
935 }
936
937 static void prepare_pack(int window, int depth)
938 {
939         if (progress)
940                 fprintf(stderr, "Packing %d objects", nr_result);
941         get_object_details();
942         if (progress)
943                 fputc('.', stderr);
944
945         sorted_by_type = create_sorted_list(type_size_sort);
946         if (window && depth)
947                 find_deltas(sorted_by_type, window+1, depth);
948         if (progress)
949                 fputc('\n', stderr);
950         write_pack_file();
951 }
952
953 static int reuse_cached_pack(unsigned char *sha1, int pack_to_stdout)
954 {
955         static const char cache[] = "pack-cache/pack-%s.%s";
956         char *cached_pack, *cached_idx;
957         int ifd, ofd, ifd_ix = -1;
958
959         cached_pack = git_path(cache, sha1_to_hex(sha1), "pack");
960         ifd = open(cached_pack, O_RDONLY);
961         if (ifd < 0)
962                 return 0;
963
964         if (!pack_to_stdout) {
965                 cached_idx = git_path(cache, sha1_to_hex(sha1), "idx");
966                 ifd_ix = open(cached_idx, O_RDONLY);
967                 if (ifd_ix < 0) {
968                         close(ifd);
969                         return 0;
970                 }
971         }
972
973         if (progress)
974                 fprintf(stderr, "Reusing %d objects pack %s\n", nr_objects,
975                         sha1_to_hex(sha1));
976
977         if (pack_to_stdout) {
978                 if (copy_fd(ifd, 1))
979                         exit(1);
980                 close(ifd);
981         }
982         else {
983                 char name[PATH_MAX];
984                 snprintf(name, sizeof(name),
985                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "pack");
986                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
987                 if (ofd < 0)
988                         die("unable to open %s (%s)", name, strerror(errno));
989                 if (copy_fd(ifd, ofd))
990                         exit(1);
991                 close(ifd);
992
993                 snprintf(name, sizeof(name),
994                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "idx");
995                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
996                 if (ofd < 0)
997                         die("unable to open %s (%s)", name, strerror(errno));
998                 if (copy_fd(ifd_ix, ofd))
999                         exit(1);
1000                 close(ifd_ix);
1001                 puts(sha1_to_hex(sha1));
1002         }
1003
1004         return 1;
1005 }
1006
1007 int main(int argc, char **argv)
1008 {
1009         SHA_CTX ctx;
1010         char line[PATH_MAX + 20];
1011         int window = 10, depth = 10, pack_to_stdout = 0;
1012         struct object_entry **list;
1013         int i;
1014         struct timeval prev_tv;
1015         int eye_candy = 0;
1016         int eye_candy_incr = 500;
1017
1018
1019         setup_git_directory();
1020
1021         for (i = 1; i < argc; i++) {
1022                 const char *arg = argv[i];
1023
1024                 if (*arg == '-') {
1025                         if (!strcmp("--non-empty", arg)) {
1026                                 non_empty = 1;
1027                                 continue;
1028                         }
1029                         if (!strcmp("--local", arg)) {
1030                                 local = 1;
1031                                 continue;
1032                         }
1033                         if (!strcmp("--incremental", arg)) {
1034                                 incremental = 1;
1035                                 continue;
1036                         }
1037                         if (!strncmp("--window=", arg, 9)) {
1038                                 char *end;
1039                                 window = strtoul(arg+9, &end, 0);
1040                                 if (!arg[9] || *end)
1041                                         usage(pack_usage);
1042                                 continue;
1043                         }
1044                         if (!strncmp("--depth=", arg, 8)) {
1045                                 char *end;
1046                                 depth = strtoul(arg+8, &end, 0);
1047                                 if (!arg[8] || *end)
1048                                         usage(pack_usage);
1049                                 continue;
1050                         }
1051                         if (!strcmp("-q", arg)) {
1052                                 progress = 0;
1053                                 continue;
1054                         }
1055                         if (!strcmp("--no-reuse-delta", arg)) {
1056                                 no_reuse_delta = 1;
1057                                 continue;
1058                         }
1059                         if (!strcmp("--stdout", arg)) {
1060                                 pack_to_stdout = 1;
1061                                 continue;
1062                         }
1063                         usage(pack_usage);
1064                 }
1065                 if (base_name)
1066                         usage(pack_usage);
1067                 base_name = arg;
1068         }
1069
1070         if (pack_to_stdout != !base_name)
1071                 usage(pack_usage);
1072
1073         prepare_packed_git();
1074         if (progress) {
1075                 fprintf(stderr, "Generating pack...\n");
1076                 gettimeofday(&prev_tv, NULL);
1077         }
1078         while (fgets(line, sizeof(line), stdin) != NULL) {
1079                 unsigned char sha1[20];
1080
1081                 if (progress && (eye_candy <= nr_objects)) {
1082                         fprintf(stderr, "Counting objects...%d\r", nr_objects);
1083                         if (eye_candy && (50 <= eye_candy_incr)) {
1084                                 struct timeval tv;
1085                                 int time_diff;
1086                                 gettimeofday(&tv, NULL);
1087                                 time_diff = (tv.tv_sec - prev_tv.tv_sec);
1088                                 time_diff <<= 10;
1089                                 time_diff += (tv.tv_usec - prev_tv.tv_usec);
1090                                 if ((1 << 9) < time_diff)
1091                                         eye_candy_incr += 50;
1092                                 else if (50 < eye_candy_incr)
1093                                         eye_candy_incr -= 50;
1094                         }
1095                         eye_candy += eye_candy_incr;
1096                 }
1097                 if (line[0] == '-') {
1098                         if (get_sha1_hex(line+1, sha1))
1099                                 die("expected edge sha1, got garbage:\n %s",
1100                                     line+1);
1101                         add_preferred_base(sha1);
1102                         continue;
1103                 }
1104                 if (get_sha1_hex(line, sha1))
1105                         die("expected sha1, got garbage:\n %s", line);
1106                 add_object_entry(sha1, name_hash(NULL, line+41), 0);
1107         }
1108         if (progress)
1109                 fprintf(stderr, "Done counting %d objects.\n", nr_objects);
1110         if (non_empty && !nr_objects)
1111                 return 0;
1112
1113         sorted_by_sha = create_final_object_list();
1114         SHA1_Init(&ctx);
1115         list = sorted_by_sha;
1116         for (i = 0; i < nr_result; i++) {
1117                 struct object_entry *entry = *list++;
1118                 SHA1_Update(&ctx, entry->sha1, 20);
1119         }
1120         SHA1_Final(object_list_sha1, &ctx);
1121         if (progress && (nr_objects != nr_result))
1122                 fprintf(stderr, "Result has %d objects.\n", nr_result);
1123
1124         if (reuse_cached_pack(object_list_sha1, pack_to_stdout))
1125                 ;
1126         else {
1127                 prepare_pack(window, depth);
1128                 if (!pack_to_stdout) {
1129                         write_index_file();
1130                         puts(sha1_to_hex(object_list_sha1));
1131                 }
1132         }
1133         if (progress)
1134                 fprintf(stderr, "Total %d, written %d (delta %d), reused %d (delta %d)\n",
1135                         nr_result, written, written_delta, reused, reused_delta);
1136         return 0;
1137 }