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 #include <signal.h>
   9
  10 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";
  11
  12 struct object_entry {
  13         unsigned char sha1[20];
  14         unsigned long size;     /* uncompressed size */
  15         unsigned long offset;   /* offset into the final pack file;
  16                                  * nonzero if already written.
  17                                  */
  18         unsigned int depth;     /* delta depth */
  19         unsigned int delta_limit;       /* base adjustment for in-pack delta */
  20         unsigned int hash;      /* name hint hash */
  21         enum object_type type;
  22         enum object_type in_pack_type;  /* could be delta */
  23         unsigned long delta_size;       /* delta data size (uncompressed) */
  24         struct object_entry *delta;     /* delta base object */
  25         struct packed_git *in_pack;     /* already in pack */
  26         unsigned int in_pack_offset;
  27         struct object_entry *delta_child; /* delitified objects who bases me */
  28         struct object_entry *delta_sibling; /* other deltified objects who
  29                                              * uses the same base as me
  30                                              */
  31         int preferred_base;     /* we do not pack this, but is encouraged to
  32                                  * be used as the base objectto delta huge
  33                                  * objects against.
  34                                  */
  35         int based_on_preferred; /* current delta candidate is a preferred
  36                                  * one, or delta against a preferred one.
  37                                  */
  38 };
  39
  40 /*
  41  * Objects we are going to pack are colected in objects array (dynamically
  42  * expanded).  nr_objects & nr_alloc controls this array.  They are stored
  43  * in the order we see -- typically rev-list --objects order that gives us
  44  * nice "minimum seek" order.
  45  *
  46  * sorted-by-sha ans sorted-by-type are arrays of pointers that point at
  47  * elements in the objects array.  The former is used to build the pack
  48  * index (lists object names in the ascending order to help offset lookup),
  49  * and the latter is used to group similar things together by try_delta()
  50  * heuristics.
  51  */
  52
  53 static unsigned char object_list_sha1[20];
  54 static int non_empty = 0;
  55 static int no_reuse_delta = 0;
  56 static int local = 0;
  57 static int incremental = 0;
  58 static struct object_entry **sorted_by_sha, **sorted_by_type;
  59 static struct object_entry *objects = NULL;
  60 static int nr_objects = 0, nr_alloc = 0, nr_result = 0;
  61 static const char *base_name;
  62 static unsigned char pack_file_sha1[20];
  63 static int progress = 1;
  64 static volatile int progress_update = 0;
  65
  66 /*
  67  * The object names in objects array are hashed with this hashtable,
  68  * to help looking up the entry by object name.  Binary search from
  69  * sorted_by_sha is also possible but this was easier to code and faster.
  70  * This hashtable is built after all the objects are seen.
  71  */
  72 static int *object_ix = NULL;
  73 static int object_ix_hashsz = 0;
  74
  75 /*
  76  * Pack index for existing packs give us easy access to the offsets into
  77  * corresponding pack file where each object's data starts, but the entries
  78  * do not store the size of the compressed representation (uncompressed
  79  * size is easily available by examining the pack entry header).  We build
  80  * a hashtable of existing packs (pack_revindex), and keep reverse index
  81  * here -- pack index file is sorted by object name mapping to offset; this
  82  * pack_revindex[].revindex array is an ordered list of offsets, so if you
  83  * know the offset of an object, next offset is where its packed
  84  * representation ends.
  85  */
  86 struct pack_revindex {
  87         struct packed_git *p;
  88         unsigned long *revindex;
  89 } *pack_revindex = NULL;
  90 static int pack_revindex_hashsz = 0;
  91
  92 /*
  93  * stats
  94  */
  95 static int written = 0;
  96 static int written_delta = 0;
  97 static int reused = 0;
  98 static int reused_delta = 0;
  99
 100 static int pack_revindex_ix(struct packed_git *p)
 101 {
 102         unsigned int ui = (unsigned int) p;
 103         int i;
 104
 105         ui = ui ^ (ui >> 16); /* defeat structure alignment */
 106         i = (int)(ui % pack_revindex_hashsz);
 107         while (pack_revindex[i].p) {
 108                 if (pack_revindex[i].p == p)
 109                         return i;
 110                 if (++i == pack_revindex_hashsz)
 111                         i = 0;
 112         }
 113         return -1 - i;
 114 }
 115
 116 static void prepare_pack_ix(void)
 117 {
 118         int num;
 119         struct packed_git *p;
 120         for (num = 0, p = packed_git; p; p = p->next)
 121                 num++;
 122         if (!num)
 123                 return;
 124         pack_revindex_hashsz = num * 11;
 125         pack_revindex = xcalloc(sizeof(*pack_revindex), pack_revindex_hashsz);
 126         for (p = packed_git; p; p = p->next) {
 127                 num = pack_revindex_ix(p);
 128                 num = - 1 - num;
 129                 pack_revindex[num].p = p;
 130         }
 131         /* revindex elements are lazily initialized */
 132 }
 133
 134 static int cmp_offset(const void *a_, const void *b_)
 135 {
 136         unsigned long a = *(unsigned long *) a_;
 137         unsigned long b = *(unsigned long *) b_;
 138         if (a < b)
 139                 return -1;
 140         else if (a == b)
 141                 return 0;
 142         else
 143                 return 1;
 144 }
 145
 146 /*
 147  * Ordered list of offsets of objects in the pack.
 148  */
 149 static void prepare_pack_revindex(struct pack_revindex *rix)
 150 {
 151         struct packed_git *p = rix->p;
 152         int num_ent = num_packed_objects(p);
 153         int i;
 154         void *index = p->index_base + 256;
 155
 156         rix->revindex = xmalloc(sizeof(unsigned long) * (num_ent + 1));
 157         for (i = 0; i < num_ent; i++) {
 158                 long hl = *((long *)(index + 24 * i));
 159                 rix->revindex[i] = ntohl(hl);
 160         }
 161         /* This knows the pack format -- the 20-byte trailer
 162          * follows immediately after the last object data.
 163          */
 164         rix->revindex[num_ent] = p->pack_size - 20;
 165         qsort(rix->revindex, num_ent, sizeof(unsigned long), cmp_offset);
 166 }
 167
 168 static unsigned long find_packed_object_size(struct packed_git *p,
 169                                              unsigned long ofs)
 170 {
 171         int num;
 172         int lo, hi;
 173         struct pack_revindex *rix;
 174         unsigned long *revindex;
 175         num = pack_revindex_ix(p);
 176         if (num < 0)
 177                 die("internal error: pack revindex uninitialized");
 178         rix = &pack_revindex[num];
 179         if (!rix->revindex)
 180                 prepare_pack_revindex(rix);
 181         revindex = rix->revindex;
 182         lo = 0;
 183         hi = num_packed_objects(p) + 1;
 184         do {
 185                 int mi = (lo + hi) / 2;
 186                 if (revindex[mi] == ofs) {
 187                         return revindex[mi+1] - ofs;
 188                 }
 189                 else if (ofs < revindex[mi])
 190                         hi = mi;
 191                 else
 192                         lo = mi + 1;
 193         } while (lo < hi);
 194         die("internal error: pack revindex corrupt");
 195 }
 196
 197 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
 198 {
 199         unsigned long othersize, delta_size;
 200         char type[10];
 201         void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
 202         void *delta_buf;
 203
 204         if (!otherbuf)
 205                 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
 206         delta_buf = diff_delta(otherbuf, othersize,
 207                                buf, size, &delta_size, 0);
 208         if (!delta_buf || delta_size != entry->delta_size)
 209                 die("delta size changed");
 210         free(buf);
 211         free(otherbuf);
 212         return delta_buf;
 213 }
 214
 215 /*
 216  * The per-object header is a pretty dense thing, which is
 217  *  - first byte: low four bits are "size", then three bits of "type",
 218  *    and the high bit is "size continues".
 219  *  - each byte afterwards: low seven bits are size continuation,
 220  *    with the high bit being "size continues"
 221  */
 222 static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
 223 {
 224         int n = 1;
 225         unsigned char c;
 226
 227         if (type < OBJ_COMMIT || type > OBJ_DELTA)
 228                 die("bad type %d", type);
 229
 230         c = (type << 4) | (size & 15);
 231         size >>= 4;
 232         while (size) {
 233                 *hdr++ = c | 0x80;
 234                 c = size & 0x7f;
 235                 size >>= 7;
 236                 n++;
 237         }
 238         *hdr = c;
 239         return n;
 240 }
 241
 242 static unsigned long write_object(struct sha1file *f,
 243                                   struct object_entry *entry)
 244 {
 245         unsigned long size;
 246         char type[10];
 247         void *buf;
 248         unsigned char header[10];
 249         unsigned hdrlen, datalen;
 250         enum object_type obj_type;
 251         int to_reuse = 0;
 252
 253         if (entry->preferred_base)
 254                 return 0;
 255
 256         obj_type = entry->type;
 257         if (! entry->in_pack)
 258                 to_reuse = 0;   /* can't reuse what we don't have */
 259         else if (obj_type == OBJ_DELTA)
 260                 to_reuse = 1;   /* check_object() decided it for us */
 261         else if (obj_type != entry->in_pack_type)
 262                 to_reuse = 0;   /* pack has delta which is unusable */
 263         else if (entry->delta)
 264                 to_reuse = 0;   /* we want to pack afresh */
 265         else
 266                 to_reuse = 1;   /* we have it in-pack undeltified,
 267                                  * and we do not need to deltify it.
 268                                  */
 269
 270         if (! to_reuse) {
 271                 buf = read_sha1_file(entry->sha1, type, &size);
 272                 if (!buf)
 273                         die("unable to read %s", sha1_to_hex(entry->sha1));
 274                 if (size != entry->size)
 275                         die("object %s size inconsistency (%lu vs %lu)",
 276                             sha1_to_hex(entry->sha1), size, entry->size);
 277                 if (entry->delta) {
 278                         buf = delta_against(buf, size, entry);
 279                         size = entry->delta_size;
 280                         obj_type = OBJ_DELTA;
 281                 }
 282                 /*
 283                  * The object header is a byte of 'type' followed by zero or
 284                  * more bytes of length.  For deltas, the 20 bytes of delta
 285                  * sha1 follows that.
 286                  */
 287                 hdrlen = encode_header(obj_type, size, header);
 288                 sha1write(f, header, hdrlen);
 289
 290                 if (entry->delta) {
 291                         sha1write(f, entry->delta, 20);
 292                         hdrlen += 20;
 293                 }
 294                 datalen = sha1write_compressed(f, buf, size);
 295                 free(buf);
 296         }
 297         else {
 298                 struct packed_git *p = entry->in_pack;
 299                 use_packed_git(p);
 300
 301                 datalen = find_packed_object_size(p, entry->in_pack_offset);
 302                 buf = p->pack_base + entry->in_pack_offset;
 303                 sha1write(f, buf, datalen);
 304                 unuse_packed_git(p);
 305                 hdrlen = 0; /* not really */
 306                 if (obj_type == OBJ_DELTA)
 307                         reused_delta++;
 308                 reused++;
 309         }
 310         if (obj_type == OBJ_DELTA)
 311                 written_delta++;
 312         written++;
 313         return hdrlen + datalen;
 314 }
 315
 316 static unsigned long write_one(struct sha1file *f,
 317                                struct object_entry *e,
 318                                unsigned long offset)
 319 {
 320         if (e->offset)
 321                 /* offset starts from header size and cannot be zero
 322                  * if it is written already.
 323                  */
 324                 return offset;
 325         e->offset = offset;
 326         offset += write_object(f, e);
 327         /* if we are deltified, write out its base object. */
 328         if (e->delta)
 329                 offset = write_one(f, e->delta, offset);
 330         return offset;
 331 }
 332
 333 static void write_pack_file(void)
 334 {
 335         int i;
 336         struct sha1file *f;
 337         unsigned long offset;
 338         struct pack_header hdr;
 339         unsigned last_percent = 999;
 340         int do_progress = 0;
 341
 342         if (!base_name)
 343                 f = sha1fd(1, "<stdout>");
 344         else {
 345                 f = sha1create("%s-%s.%s", base_name,
 346                                sha1_to_hex(object_list_sha1), "pack");
 347                 do_progress = progress;
 348         }
 349         if (do_progress)
 350                 fprintf(stderr, "Writing %d objects.\n", nr_result);
 351
 352         hdr.hdr_signature = htonl(PACK_SIGNATURE);
 353         hdr.hdr_version = htonl(PACK_VERSION);
 354         hdr.hdr_entries = htonl(nr_result);
 355         sha1write(f, &hdr, sizeof(hdr));
 356         offset = sizeof(hdr);
 357         if (!nr_result)
 358                 goto done;
 359         for (i = 0; i < nr_objects; i++) {
 360                 offset = write_one(f, objects + i, offset);
 361                 if (do_progress) {
 362                         unsigned percent = written * 100 / nr_result;
 363                         if (progress_update || percent != last_percent) {
 364                                 fprintf(stderr, "%4u%% (%u/%u) done\r",
 365                                         percent, written, nr_result);
 366                                 progress_update = 0;
 367                                 last_percent = percent;
 368                         }
 369                 }
 370         }
 371         if (do_progress)
 372                 fputc('\n', stderr);
 373  done:
 374         sha1close(f, pack_file_sha1, 1);
 375 }
 376
 377 static void write_index_file(void)
 378 {
 379         int i;
 380         struct sha1file *f = sha1create("%s-%s.%s", base_name,
 381                                         sha1_to_hex(object_list_sha1), "idx");
 382         struct object_entry **list = sorted_by_sha;
 383         struct object_entry **last = list + nr_result;
 384         unsigned int array[256];
 385
 386         /*
 387          * Write the first-level table (the list is sorted,
 388          * but we use a 256-entry lookup to be able to avoid
 389          * having to do eight extra binary search iterations).
 390          */
 391         for (i = 0; i < 256; i++) {
 392                 struct object_entry **next = list;
 393                 while (next < last) {
 394                         struct object_entry *entry = *next;
 395                         if (entry->sha1[0] != i)
 396                                 break;
 397                         next++;
 398                 }
 399                 array[i] = htonl(next - sorted_by_sha);
 400                 list = next;
 401         }
 402         sha1write(f, array, 256 * sizeof(int));
 403
 404         /*
 405          * Write the actual SHA1 entries..
 406          */
 407         list = sorted_by_sha;
 408         for (i = 0; i < nr_result; i++) {
 409                 struct object_entry *entry = *list++;
 410                 unsigned int offset = htonl(entry->offset);
 411                 sha1write(f, &offset, 4);
 412                 sha1write(f, entry->sha1, 20);
 413         }
 414         sha1write(f, pack_file_sha1, 20);
 415         sha1close(f, NULL, 1);
 416 }
 417
 418 static int locate_object_entry_hash(const unsigned char *sha1)
 419 {
 420         int i;
 421         unsigned int ui;
 422         memcpy(&ui, sha1, sizeof(unsigned int));
 423         i = ui % object_ix_hashsz;
 424         while (0 < object_ix[i]) {
 425                 if (!memcmp(sha1, objects[object_ix[i]-1].sha1, 20))
 426                         return i;
 427                 if (++i == object_ix_hashsz)
 428                         i = 0;
 429         }
 430         return -1 - i;
 431 }
 432
 433 static struct object_entry *locate_object_entry(const unsigned char *sha1)
 434 {
 435         int i;
 436
 437         if (!object_ix_hashsz)
 438                 return NULL;
 439
 440         i = locate_object_entry_hash(sha1);
 441         if (0 <= i)
 442                 return &objects[object_ix[i]-1];
 443         return NULL;
 444 }
 445
 446 static void rehash_objects(void)
 447 {
 448         int i;
 449         struct object_entry *oe;
 450
 451         object_ix_hashsz = nr_objects * 3;
 452         if (object_ix_hashsz < 1024)
 453                 object_ix_hashsz = 1024;
 454         object_ix = xrealloc(object_ix, sizeof(int) * object_ix_hashsz);
 455         object_ix = memset(object_ix, 0, sizeof(int) * object_ix_hashsz);
 456         for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
 457                 int ix = locate_object_entry_hash(oe->sha1);
 458                 if (0 <= ix)
 459                         continue;
 460                 ix = -1 - ix;
 461                 object_ix[ix] = i + 1;
 462         }
 463 }
 464
 465 struct name_path {
 466         struct name_path *up;
 467         const char *elem;
 468         int len;
 469 };
 470
 471 #define DIRBITS 12
 472
 473 static unsigned name_hash(struct name_path *path, const char *name)
 474 {
 475         struct name_path *p = path;
 476         const char *n = name + strlen(name);
 477         unsigned hash = 0, name_hash = 0, name_done = 0;
 478
 479         if (n != name && n[-1] == '\n')
 480                 n--;
 481         while (name <= --n) {
 482                 unsigned char c = *n;
 483                 if (c == '/' && !name_done) {
 484                         name_hash = hash;
 485                         name_done = 1;
 486                         hash = 0;
 487                 }
 488                 hash = hash * 11 + c;
 489         }
 490         if (!name_done) {
 491                 name_hash = hash;
 492                 hash = 0;
 493         }
 494         for (p = path; p; p = p->up) {
 495                 hash = hash * 11 + '/';
 496                 n = p->elem + p->len;
 497                 while (p->elem <= --n) {
 498                         unsigned char c = *n;
 499                         hash = hash * 11 + c;
 500                 }
 501         }
 502         /*
 503          * Make sure "Makefile" and "t/Makefile" are hashed separately
 504          * but close enough.
 505          */
 506         hash = (name_hash<<DIRBITS) | (hash & ((1U<<DIRBITS )-1));
 507
 508         if (0) { /* debug */
 509                 n = name + strlen(name);
 510                 if (n != name && n[-1] == '\n')
 511                         n--;
 512                 while (name <= --n)
 513                         fputc(*n, stderr);
 514                 for (p = path; p; p = p->up) {
 515                         fputc('/', stderr);
 516                         n = p->elem + p->len;
 517                         while (p->elem <= --n)
 518                                 fputc(*n, stderr);
 519                 }
 520                 fprintf(stderr, "\t%08x\n", hash);
 521         }
 522         return hash;
 523 }
 524
 525 static int add_object_entry(const unsigned char *sha1, unsigned hash, int exclude)
 526 {
 527         unsigned int idx = nr_objects;
 528         struct object_entry *entry;
 529         struct packed_git *p;
 530         unsigned int found_offset = 0;
 531         struct packed_git *found_pack = NULL;
 532         int ix, status = 0;
 533
 534         if (!exclude) {
 535                 for (p = packed_git; p; p = p->next) {
 536                         struct pack_entry e;
 537                         if (find_pack_entry_one(sha1, &e, p)) {
 538                                 if (incremental)
 539                                         return 0;
 540                                 if (local && !p->pack_local)
 541                                         return 0;
 542                                 if (!found_pack) {
 543                                         found_offset = e.offset;
 544                                         found_pack = e.p;
 545                                 }
 546                         }
 547                 }
 548         }
 549         if ((entry = locate_object_entry(sha1)) != NULL)
 550                 goto already_added;
 551
 552         if (idx >= nr_alloc) {
 553                 unsigned int needed = (idx + 1024) * 3 / 2;
 554                 objects = xrealloc(objects, needed * sizeof(*entry));
 555                 nr_alloc = needed;
 556         }
 557         entry = objects + idx;
 558         nr_objects = idx + 1;
 559         memset(entry, 0, sizeof(*entry));
 560         memcpy(entry->sha1, sha1, 20);
 561         entry->hash = hash;
 562
 563         if (object_ix_hashsz * 3 <= nr_objects * 4)
 564                 rehash_objects();
 565         else {
 566                 ix = locate_object_entry_hash(entry->sha1);
 567                 if (0 <= ix)
 568                         die("internal error in object hashing.");
 569                 object_ix[-1 - ix] = idx + 1;
 570         }
 571         status = 1;
 572
 573  already_added:
 574         if (progress_update) {
 575                 fprintf(stderr, "Counting objects...%d\r", nr_objects);
 576                 progress_update = 0;
 577         }
 578         if (exclude)
 579                 entry->preferred_base = 1;
 580         else {
 581                 if (found_pack) {
 582                         entry->in_pack = found_pack;
 583                         entry->in_pack_offset = found_offset;
 584                 }
 585         }
 586         return status;
 587 }
 588
 589 static void add_pbase_tree(struct tree_desc *tree, struct name_path *up)
 590 {
 591         while (tree->size) {
 592                 const unsigned char *sha1;
 593                 const char *name;
 594                 unsigned mode, hash;
 595                 unsigned long size;
 596                 char type[20];
 597
 598                 sha1 = tree_entry_extract(tree, &name, &mode);
 599                 update_tree_entry(tree);
 600                 if (!has_sha1_file(sha1))
 601                         continue;
 602                 if (sha1_object_info(sha1, type, &size))
 603                         continue;
 604
 605                 hash = name_hash(up, name);
 606                 if (!add_object_entry(sha1, hash, 1))
 607                         continue;
 608
 609                 if (!strcmp(type, "tree")) {
 610                         struct tree_desc sub;
 611                         void *elem;
 612                         struct name_path me;
 613
 614                         elem = read_sha1_file(sha1, type, &sub.size);
 615                         sub.buf = elem;
 616                         if (sub.buf) {
 617                                 me.up = up;
 618                                 me.elem = name;
 619                                 me.len = strlen(name);
 620                                 add_pbase_tree(&sub, &me);
 621                                 free(elem);
 622                         }
 623                 }
 624         }
 625 }
 626
 627 static void add_preferred_base(unsigned char *sha1)
 628 {
 629         struct tree_desc tree;
 630         void *elem;
 631
 632         elem = read_object_with_reference(sha1, "tree", &tree.size, NULL);
 633         tree.buf = elem;
 634         if (!tree.buf)
 635                 return;
 636         if (add_object_entry(sha1, name_hash(NULL, ""), 1))
 637                 add_pbase_tree(&tree, NULL);
 638         free(elem);
 639 }
 640
 641 static void check_object(struct object_entry *entry)
 642 {
 643         char type[20];
 644
 645         if (entry->in_pack && !entry->preferred_base) {
 646                 unsigned char base[20];
 647                 unsigned long size;
 648                 struct object_entry *base_entry;
 649
 650                 /* We want in_pack_type even if we do not reuse delta.
 651                  * There is no point not reusing non-delta representations.
 652                  */
 653                 check_reuse_pack_delta(entry->in_pack,
 654                                        entry->in_pack_offset,
 655                                        base, &size,
 656                                        &entry->in_pack_type);
 657
 658                 /* Check if it is delta, and the base is also an object
 659                  * we are going to pack.  If so we will reuse the existing
 660                  * delta.
 661                  */
 662                 if (!no_reuse_delta &&
 663                     entry->in_pack_type == OBJ_DELTA &&
 664                     (base_entry = locate_object_entry(base)) &&
 665                     (!base_entry->preferred_base)) {
 666
 667                         /* Depth value does not matter - find_deltas()
 668                          * will never consider reused delta as the
 669                          * base object to deltify other objects
 670                          * against, in order to avoid circular deltas.
 671                          */
 672
 673                         /* uncompressed size of the delta data */
 674                         entry->size = entry->delta_size = size;
 675                         entry->delta = base_entry;
 676                         entry->type = OBJ_DELTA;
 677
 678                         entry->delta_sibling = base_entry->delta_child;
 679                         base_entry->delta_child = entry;
 680
 681                         return;
 682                 }
 683                 /* Otherwise we would do the usual */
 684         }
 685
 686         if (sha1_object_info(entry->sha1, type, &entry->size))
 687                 die("unable to get type of object %s",
 688                     sha1_to_hex(entry->sha1));
 689
 690         if (!strcmp(type, "commit")) {
 691                 entry->type = OBJ_COMMIT;
 692         } else if (!strcmp(type, "tree")) {
 693                 entry->type = OBJ_TREE;
 694         } else if (!strcmp(type, "blob")) {
 695                 entry->type = OBJ_BLOB;
 696         } else if (!strcmp(type, "tag")) {
 697                 entry->type = OBJ_TAG;
 698         } else
 699                 die("unable to pack object %s of type %s",
 700                     sha1_to_hex(entry->sha1), type);
 701 }
 702
 703 static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
 704 {
 705         struct object_entry *child = me->delta_child;
 706         unsigned int m = n;
 707         while (child) {
 708                 unsigned int c = check_delta_limit(child, n + 1);
 709                 if (m < c)
 710                         m = c;
 711                 child = child->delta_sibling;
 712         }
 713         return m;
 714 }
 715
 716 static void get_object_details(void)
 717 {
 718         int i;
 719         struct object_entry *entry;
 720
 721         prepare_pack_ix();
 722         for (i = 0, entry = objects; i < nr_objects; i++, entry++)
 723                 check_object(entry);
 724
 725         if (nr_objects == nr_result) {
 726                 /*
 727                  * Depth of objects that depend on the entry -- this
 728                  * is subtracted from depth-max to break too deep
 729                  * delta chain because of delta data reusing.
 730                  * However, we loosen this restriction when we know we
 731                  * are creating a thin pack -- it will have to be
 732                  * expanded on the other end anyway, so do not
 733                  * artificially cut the delta chain and let it go as
 734                  * deep as it wants.
 735                  */
 736                 for (i = 0, entry = objects; i < nr_objects; i++, entry++)
 737                         if (!entry->delta && entry->delta_child)
 738                                 entry->delta_limit =
 739                                         check_delta_limit(entry, 1);
 740         }
 741 }
 742
 743 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
 744
 745 static entry_sort_t current_sort;
 746
 747 static int sort_comparator(const void *_a, const void *_b)
 748 {
 749         struct object_entry *a = *(struct object_entry **)_a;
 750         struct object_entry *b = *(struct object_entry **)_b;
 751         return current_sort(a,b);
 752 }
 753
 754 static struct object_entry **create_sorted_list(entry_sort_t sort)
 755 {
 756         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
 757         int i;
 758
 759         for (i = 0; i < nr_objects; i++)
 760                 list[i] = objects + i;
 761         current_sort = sort;
 762         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
 763         return list;
 764 }
 765
 766 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
 767 {
 768         return memcmp(a->sha1, b->sha1, 20);
 769 }
 770
 771 static struct object_entry **create_final_object_list()
 772 {
 773         struct object_entry **list;
 774         int i, j;
 775
 776         for (i = nr_result = 0; i < nr_objects; i++)
 777                 if (!objects[i].preferred_base)
 778                         nr_result++;
 779         list = xmalloc(nr_result * sizeof(struct object_entry *));
 780         for (i = j = 0; i < nr_objects; i++) {
 781                 if (!objects[i].preferred_base)
 782                         list[j++] = objects + i;
 783         }
 784         current_sort = sha1_sort;
 785         qsort(list, nr_result, sizeof(struct object_entry *), sort_comparator);
 786         return list;
 787 }
 788
 789 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
 790 {
 791         if (a->type < b->type)
 792                 return -1;
 793         if (a->type > b->type)
 794                 return 1;
 795         if (a->hash < b->hash)
 796                 return -1;
 797         if (a->hash > b->hash)
 798                 return 1;
 799         if (a->preferred_base < b->preferred_base)
 800                 return -1;
 801         if (a->preferred_base > b->preferred_base)
 802                 return 1;
 803         if (a->size < b->size)
 804                 return -1;
 805         if (a->size > b->size)
 806                 return 1;
 807         return a < b ? -1 : (a > b);
 808 }
 809
 810 struct unpacked {
 811         struct object_entry *entry;
 812         void *data;
 813 };
 814
 815 /*
 816  * We search for deltas _backwards_ in a list sorted by type and
 817  * by size, so that we see progressively smaller and smaller files.
 818  * That's because we prefer deltas to be from the bigger file
 819  * to the smaller - deletes are potentially cheaper, but perhaps
 820  * more importantly, the bigger file is likely the more recent
 821  * one.
 822  */
 823 static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
 824 {
 825         struct object_entry *cur_entry = cur->entry;
 826         struct object_entry *old_entry = old->entry;
 827         int old_preferred = (old_entry->preferred_base ||
 828                              old_entry->based_on_preferred);
 829         unsigned long size, oldsize, delta_size, sizediff;
 830         long max_size;
 831         void *delta_buf;
 832
 833         /* Don't bother doing diffs between different types */
 834         if (cur_entry->type != old_entry->type)
 835                 return -1;
 836
 837         /* We do not compute delta to *create* objects we are not
 838          * going to pack.
 839          */
 840         if (cur_entry->preferred_base)
 841                 return -1;
 842
 843         /* If the current object is at pack edge, take the depth the
 844          * objects that depend on the current object into account --
 845          * otherwise they would become too deep.
 846          */
 847         if (cur_entry->delta_child) {
 848                 if (max_depth <= cur_entry->delta_limit)
 849                         return 0;
 850                 max_depth -= cur_entry->delta_limit;
 851         }
 852
 853         size = cur_entry->size;
 854         if (size < 50)
 855                 return -1;
 856         oldsize = old_entry->size;
 857         sizediff = oldsize > size ? oldsize - size : size - oldsize;
 858         if (sizediff > size / 8)
 859                 return -1;
 860         if (old_entry->depth >= max_depth)
 861                 return 0;
 862
 863         /*
 864          * NOTE!
 865          *
 866          * We always delta from the bigger to the smaller, since that's
 867          * more space-efficient (deletes don't have to say _what_ they
 868          * delete).
 869          */
 870         max_size = size / 2 - 20;
 871         if (cur_entry->delta) {
 872                 if (cur_entry->based_on_preferred) {
 873                         if (old_preferred)
 874                                 max_size = cur_entry->delta_size-1;
 875                         else
 876                                 /* trying with non-preferred one when we
 877                                  * already have a delta based on preferred
 878                                  * one is pointless.
 879                                  */
 880                                 return -1;
 881                 }
 882                 else if (!old_preferred)
 883                         max_size = cur_entry->delta_size-1;
 884                 else
 885                         /* otherwise...  even if delta with a
 886                          * preferred one produces a bigger result than
 887                          * what we currently have, which is based on a
 888                          * non-preferred one, it is OK.
 889                          */
 890                         ;
 891         }
 892         if (sizediff >= max_size)
 893                 return -1;
 894         delta_buf = diff_delta(old->data, oldsize,
 895                                cur->data, size, &delta_size, max_size);
 896         if (!delta_buf)
 897                 return 0;
 898         cur_entry->delta = old_entry;
 899         cur_entry->delta_size = delta_size;
 900         cur_entry->depth = old_entry->depth + 1;
 901         cur_entry->based_on_preferred = old_preferred;
 902         free(delta_buf);
 903         return 0;
 904 }
 905
 906 static void progress_interval(int signum)
 907 {
 908         signal(SIGALRM, progress_interval);
 909         progress_update = 1;
 910 }
 911
 912 static void find_deltas(struct object_entry **list, int window, int depth)
 913 {
 914         int i, idx;
 915         unsigned int array_size = window * sizeof(struct unpacked);
 916         struct unpacked *array = xmalloc(array_size);
 917         unsigned processed = 0;
 918         unsigned last_percent = 999;
 919
 920         memset(array, 0, array_size);
 921         i = nr_objects;
 922         idx = 0;
 923         if (progress)
 924                 fprintf(stderr, "Deltifying %d objects.\n", nr_result);
 925
 926         while (--i >= 0) {
 927                 struct object_entry *entry = list[i];
 928                 struct unpacked *n = array + idx;
 929                 unsigned long size;
 930                 char type[10];
 931                 int j;
 932
 933                 if (!entry->preferred_base)
 934                         processed++;
 935
 936                 if (progress) {
 937                         unsigned percent = processed * 100 / nr_result;
 938                         if (percent != last_percent || progress_update) {
 939                                 fprintf(stderr, "%4u%% (%u/%u) done\r",
 940                                         percent, processed, nr_result);
 941                                 progress_update = 0;
 942                                 last_percent = percent;
 943                         }
 944                 }
 945
 946                 if (entry->delta)
 947                         /* This happens if we decided to reuse existing
 948                          * delta from a pack.  "!no_reuse_delta &&" is implied.
 949                          */
 950                         continue;
 951
 952                 free(n->data);
 953                 n->entry = entry;
 954                 n->data = read_sha1_file(entry->sha1, type, &size);
 955                 if (size != entry->size)
 956                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
 957
 958                 j = window;
 959                 while (--j > 0) {
 960                         unsigned int other_idx = idx + j;
 961                         struct unpacked *m;
 962                         if (other_idx >= window)
 963                                 other_idx -= window;
 964                         m = array + other_idx;
 965                         if (!m->entry)
 966                                 break;
 967                         if (try_delta(n, m, depth) < 0)
 968                                 break;
 969                 }
 970                 idx++;
 971                 if (idx >= window)
 972                         idx = 0;
 973         }
 974
 975         if (progress)
 976                 fputc('\n', stderr);
 977
 978         for (i = 0; i < window; ++i)
 979                 free(array[i].data);
 980         free(array);
 981 }
 982
 983 static void prepare_pack(int window, int depth)
 984 {
 985         get_object_details();
 986         sorted_by_type = create_sorted_list(type_size_sort);
 987         if (window && depth)
 988                 find_deltas(sorted_by_type, window+1, depth);
 989 }
 990
 991 static int reuse_cached_pack(unsigned char *sha1, int pack_to_stdout)
 992 {
 993         static const char cache[] = "pack-cache/pack-%s.%s";
 994         char *cached_pack, *cached_idx;
 995         int ifd, ofd, ifd_ix = -1;
 996
 997         cached_pack = git_path(cache, sha1_to_hex(sha1), "pack");
 998         ifd = open(cached_pack, O_RDONLY);
 999         if (ifd < 0)
1000                 return 0;
1001
1002         if (!pack_to_stdout) {
1003                 cached_idx = git_path(cache, sha1_to_hex(sha1), "idx");
1004                 ifd_ix = open(cached_idx, O_RDONLY);
1005                 if (ifd_ix < 0) {
1006                         close(ifd);
1007                         return 0;
1008                 }
1009         }
1010
1011         if (progress)
1012                 fprintf(stderr, "Reusing %d objects pack %s\n", nr_objects,
1013                         sha1_to_hex(sha1));
1014
1015         if (pack_to_stdout) {
1016                 if (copy_fd(ifd, 1))
1017                         exit(1);
1018                 close(ifd);
1019         }
1020         else {
1021                 char name[PATH_MAX];
1022                 snprintf(name, sizeof(name),
1023                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "pack");
1024                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
1025                 if (ofd < 0)
1026                         die("unable to open %s (%s)", name, strerror(errno));
1027                 if (copy_fd(ifd, ofd))
1028                         exit(1);
1029                 close(ifd);
1030
1031                 snprintf(name, sizeof(name),
1032                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "idx");
1033                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
1034                 if (ofd < 0)
1035                         die("unable to open %s (%s)", name, strerror(errno));
1036                 if (copy_fd(ifd_ix, ofd))
1037                         exit(1);
1038                 close(ifd_ix);
1039                 puts(sha1_to_hex(sha1));
1040         }
1041
1042         return 1;
1043 }
1044
1045 int main(int argc, char **argv)
1046 {
1047         SHA_CTX ctx;
1048         char line[PATH_MAX + 20];
1049         int window = 10, depth = 10, pack_to_stdout = 0;
1050         struct object_entry **list;
1051         int i;
1052
1053         setup_git_directory();
1054
1055         for (i = 1; i < argc; i++) {
1056                 const char *arg = argv[i];
1057
1058                 if (*arg == '-') {
1059                         if (!strcmp("--non-empty", arg)) {
1060                                 non_empty = 1;
1061                                 continue;
1062                         }
1063                         if (!strcmp("--local", arg)) {
1064                                 local = 1;
1065                                 continue;
1066                         }
1067                         if (!strcmp("--incremental", arg)) {
1068                                 incremental = 1;
1069                                 continue;
1070                         }
1071                         if (!strncmp("--window=", arg, 9)) {
1072                                 char *end;
1073                                 window = strtoul(arg+9, &end, 0);
1074                                 if (!arg[9] || *end)
1075                                         usage(pack_usage);
1076                                 continue;
1077                         }
1078                         if (!strncmp("--depth=", arg, 8)) {
1079                                 char *end;
1080                                 depth = strtoul(arg+8, &end, 0);
1081                                 if (!arg[8] || *end)
1082                                         usage(pack_usage);
1083                                 continue;
1084                         }
1085                         if (!strcmp("-q", arg)) {
1086                                 progress = 0;
1087                                 continue;
1088                         }
1089                         if (!strcmp("--no-reuse-delta", arg)) {
1090                                 no_reuse_delta = 1;
1091                                 continue;
1092                         }
1093                         if (!strcmp("--stdout", arg)) {
1094                                 pack_to_stdout = 1;
1095                                 continue;
1096                         }
1097                         usage(pack_usage);
1098                 }
1099                 if (base_name)
1100                         usage(pack_usage);
1101                 base_name = arg;
1102         }
1103
1104         if (pack_to_stdout != !base_name)
1105                 usage(pack_usage);
1106
1107         prepare_packed_git();
1108
1109         if (progress) {
1110                 struct itimerval v;
1111                 v.it_interval.tv_sec = 1;
1112                 v.it_interval.tv_usec = 0;
1113                 v.it_value = v.it_interval;
1114                 signal(SIGALRM, progress_interval);
1115                 setitimer(ITIMER_REAL, &v, NULL);
1116                 fprintf(stderr, "Generating pack...\n");
1117         }
1118
1119         while (fgets(line, sizeof(line), stdin) != NULL) {
1120                 unsigned char sha1[20];
1121
1122                 if (line[0] == '-') {
1123                         if (get_sha1_hex(line+1, sha1))
1124                                 die("expected edge sha1, got garbage:\n %s",
1125                                     line+1);
1126                         add_preferred_base(sha1);
1127                         continue;
1128                 }
1129                 if (get_sha1_hex(line, sha1))
1130                         die("expected sha1, got garbage:\n %s", line);
1131                 add_object_entry(sha1, name_hash(NULL, line+41), 0);
1132         }
1133         if (progress)
1134                 fprintf(stderr, "Done counting %d objects.\n", nr_objects);
1135         sorted_by_sha = create_final_object_list();
1136         if (non_empty && !nr_result)
1137                 return 0;
1138
1139         SHA1_Init(&ctx);
1140         list = sorted_by_sha;
1141         for (i = 0; i < nr_result; i++) {
1142                 struct object_entry *entry = *list++;
1143                 SHA1_Update(&ctx, entry->sha1, 20);
1144         }
1145         SHA1_Final(object_list_sha1, &ctx);
1146         if (progress && (nr_objects != nr_result))
1147                 fprintf(stderr, "Result has %d objects.\n", nr_result);
1148
1149         if (reuse_cached_pack(object_list_sha1, pack_to_stdout))
1150                 ;
1151         else {
1152                 if (nr_result)
1153                         prepare_pack(window, depth);
1154                 if (progress && pack_to_stdout) {
1155                         /* the other end usually displays progress itself */
1156                         struct itimerval v = {{0,},};
1157                         setitimer(ITIMER_REAL, &v, NULL);
1158                         signal(SIGALRM, SIG_IGN );
1159                         progress_update = 0;
1160                 }
1161                 write_pack_file();
1162                 if (!pack_to_stdout) {
1163                         write_index_file();
1164                         puts(sha1_to_hex(object_list_sha1));
1165                 }
1166         }
1167         if (progress)
1168                 fprintf(stderr, "Total %d, written %d (delta %d), reused %d (delta %d)\n",
1169                         nr_result, written, written_delta, reused, reused_delta);
1170         return 0;
1171 }