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 "tree-walk.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 };
  36
  37 /*
  38  * Objects we are going to pack are colected in objects array (dynamically
  39  * expanded).  nr_objects & nr_alloc controls this array.  They are stored
  40  * in the order we see -- typically rev-list --objects order that gives us
  41  * nice "minimum seek" order.
  42  *
  43  * sorted-by-sha ans sorted-by-type are arrays of pointers that point at
  44  * elements in the objects array.  The former is used to build the pack
  45  * index (lists object names in the ascending order to help offset lookup),
  46  * and the latter is used to group similar things together by try_delta()
  47  * heuristics.
  48  */
  49
  50 static unsigned char object_list_sha1[20];
  51 static int non_empty = 0;
  52 static int no_reuse_delta = 0;
  53 static int local = 0;
  54 static int incremental = 0;
  55 static struct object_entry **sorted_by_sha, **sorted_by_type;
  56 static struct object_entry *objects = NULL;
  57 static int nr_objects = 0, nr_alloc = 0, nr_result = 0;
  58 static const char *base_name;
  59 static unsigned char pack_file_sha1[20];
  60 static int progress = 1;
  61 static volatile sig_atomic_t progress_update = 0;
  62
  63 /*
  64  * The object names in objects array are hashed with this hashtable,
  65  * to help looking up the entry by object name.  Binary search from
  66  * sorted_by_sha is also possible but this was easier to code and faster.
  67  * This hashtable is built after all the objects are seen.
  68  */
  69 static int *object_ix = NULL;
  70 static int object_ix_hashsz = 0;
  71
  72 /*
  73  * Pack index for existing packs give us easy access to the offsets into
  74  * corresponding pack file where each object's data starts, but the entries
  75  * do not store the size of the compressed representation (uncompressed
  76  * size is easily available by examining the pack entry header).  We build
  77  * a hashtable of existing packs (pack_revindex), and keep reverse index
  78  * here -- pack index file is sorted by object name mapping to offset; this
  79  * pack_revindex[].revindex array is an ordered list of offsets, so if you
  80  * know the offset of an object, next offset is where its packed
  81  * representation ends.
  82  */
  83 struct pack_revindex {
  84         struct packed_git *p;
  85         unsigned long *revindex;
  86 } *pack_revindex = NULL;
  87 static int pack_revindex_hashsz = 0;
  88
  89 /*
  90  * stats
  91  */
  92 static int written = 0;
  93 static int written_delta = 0;
  94 static int reused = 0;
  95 static int reused_delta = 0;
  96
  97 static int pack_revindex_ix(struct packed_git *p)
  98 {
  99         unsigned long ui = (unsigned long)p;
 100         int i;
 101
 102         ui = ui ^ (ui >> 16); /* defeat structure alignment */
 103         i = (int)(ui % pack_revindex_hashsz);
 104         while (pack_revindex[i].p) {
 105                 if (pack_revindex[i].p == p)
 106                         return i;
 107                 if (++i == pack_revindex_hashsz)
 108                         i = 0;
 109         }
 110         return -1 - i;
 111 }
 112
 113 static void prepare_pack_ix(void)
 114 {
 115         int num;
 116         struct packed_git *p;
 117         for (num = 0, p = packed_git; p; p = p->next)
 118                 num++;
 119         if (!num)
 120                 return;
 121         pack_revindex_hashsz = num * 11;
 122         pack_revindex = xcalloc(sizeof(*pack_revindex), pack_revindex_hashsz);
 123         for (p = packed_git; p; p = p->next) {
 124                 num = pack_revindex_ix(p);
 125                 num = - 1 - num;
 126                 pack_revindex[num].p = p;
 127         }
 128         /* revindex elements are lazily initialized */
 129 }
 130
 131 static int cmp_offset(const void *a_, const void *b_)
 132 {
 133         unsigned long a = *(unsigned long *) a_;
 134         unsigned long b = *(unsigned long *) b_;
 135         if (a < b)
 136                 return -1;
 137         else if (a == b)
 138                 return 0;
 139         else
 140                 return 1;
 141 }
 142
 143 /*
 144  * Ordered list of offsets of objects in the pack.
 145  */
 146 static void prepare_pack_revindex(struct pack_revindex *rix)
 147 {
 148         struct packed_git *p = rix->p;
 149         int num_ent = num_packed_objects(p);
 150         int i;
 151         void *index = p->index_base + 256;
 152
 153         rix->revindex = xmalloc(sizeof(unsigned long) * (num_ent + 1));
 154         for (i = 0; i < num_ent; i++) {
 155                 long hl = *((long *)(index + 24 * i));
 156                 rix->revindex[i] = ntohl(hl);
 157         }
 158         /* This knows the pack format -- the 20-byte trailer
 159          * follows immediately after the last object data.
 160          */
 161         rix->revindex[num_ent] = p->pack_size - 20;
 162         qsort(rix->revindex, num_ent, sizeof(unsigned long), cmp_offset);
 163 }
 164
 165 static unsigned long find_packed_object_size(struct packed_git *p,
 166                                              unsigned long ofs)
 167 {
 168         int num;
 169         int lo, hi;
 170         struct pack_revindex *rix;
 171         unsigned long *revindex;
 172         num = pack_revindex_ix(p);
 173         if (num < 0)
 174                 die("internal error: pack revindex uninitialized");
 175         rix = &pack_revindex[num];
 176         if (!rix->revindex)
 177                 prepare_pack_revindex(rix);
 178         revindex = rix->revindex;
 179         lo = 0;
 180         hi = num_packed_objects(p) + 1;
 181         do {
 182                 int mi = (lo + hi) / 2;
 183                 if (revindex[mi] == ofs) {
 184                         return revindex[mi+1] - ofs;
 185                 }
 186                 else if (ofs < revindex[mi])
 187                         hi = mi;
 188                 else
 189                         lo = mi + 1;
 190         } while (lo < hi);
 191         die("internal error: pack revindex corrupt");
 192 }
 193
 194 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
 195 {
 196         unsigned long othersize, delta_size;
 197         char type[10];
 198         void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
 199         void *delta_buf;
 200
 201         if (!otherbuf)
 202                 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
 203         delta_buf = diff_delta(otherbuf, othersize,
 204                                buf, size, &delta_size, 0);
 205         if (!delta_buf || delta_size != entry->delta_size)
 206                 die("delta size changed");
 207         free(buf);
 208         free(otherbuf);
 209         return delta_buf;
 210 }
 211
 212 /*
 213  * The per-object header is a pretty dense thing, which is
 214  *  - first byte: low four bits are "size", then three bits of "type",
 215  *    and the high bit is "size continues".
 216  *  - each byte afterwards: low seven bits are size continuation,
 217  *    with the high bit being "size continues"
 218  */
 219 static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
 220 {
 221         int n = 1;
 222         unsigned char c;
 223
 224         if (type < OBJ_COMMIT || type > OBJ_DELTA)
 225                 die("bad type %d", type);
 226
 227         c = (type << 4) | (size & 15);
 228         size >>= 4;
 229         while (size) {
 230                 *hdr++ = c | 0x80;
 231                 c = size & 0x7f;
 232                 size >>= 7;
 233                 n++;
 234         }
 235         *hdr = c;
 236         return n;
 237 }
 238
 239 static unsigned long write_object(struct sha1file *f,
 240                                   struct object_entry *entry)
 241 {
 242         unsigned long size;
 243         char type[10];
 244         void *buf;
 245         unsigned char header[10];
 246         unsigned hdrlen, datalen;
 247         enum object_type obj_type;
 248         int to_reuse = 0;
 249
 250         if (entry->preferred_base)
 251                 return 0;
 252
 253         obj_type = entry->type;
 254         if (! entry->in_pack)
 255                 to_reuse = 0;   /* can't reuse what we don't have */
 256         else if (obj_type == OBJ_DELTA)
 257                 to_reuse = 1;   /* check_object() decided it for us */
 258         else if (obj_type != entry->in_pack_type)
 259                 to_reuse = 0;   /* pack has delta which is unusable */
 260         else if (entry->delta)
 261                 to_reuse = 0;   /* we want to pack afresh */
 262         else
 263                 to_reuse = 1;   /* we have it in-pack undeltified,
 264                                  * and we do not need to deltify it.
 265                                  */
 266
 267         if (! to_reuse) {
 268                 buf = read_sha1_file(entry->sha1, type, &size);
 269                 if (!buf)
 270                         die("unable to read %s", sha1_to_hex(entry->sha1));
 271                 if (size != entry->size)
 272                         die("object %s size inconsistency (%lu vs %lu)",
 273                             sha1_to_hex(entry->sha1), size, entry->size);
 274                 if (entry->delta) {
 275                         buf = delta_against(buf, size, entry);
 276                         size = entry->delta_size;
 277                         obj_type = OBJ_DELTA;
 278                 }
 279                 /*
 280                  * The object header is a byte of 'type' followed by zero or
 281                  * more bytes of length.  For deltas, the 20 bytes of delta
 282                  * sha1 follows that.
 283                  */
 284                 hdrlen = encode_header(obj_type, size, header);
 285                 sha1write(f, header, hdrlen);
 286
 287                 if (entry->delta) {
 288                         sha1write(f, entry->delta, 20);
 289                         hdrlen += 20;
 290                 }
 291                 datalen = sha1write_compressed(f, buf, size);
 292                 free(buf);
 293         }
 294         else {
 295                 struct packed_git *p = entry->in_pack;
 296                 use_packed_git(p);
 297
 298                 datalen = find_packed_object_size(p, entry->in_pack_offset);
 299                 buf = p->pack_base + entry->in_pack_offset;
 300                 sha1write(f, buf, datalen);
 301                 unuse_packed_git(p);
 302                 hdrlen = 0; /* not really */
 303                 if (obj_type == OBJ_DELTA)
 304                         reused_delta++;
 305                 reused++;
 306         }
 307         if (obj_type == OBJ_DELTA)
 308                 written_delta++;
 309         written++;
 310         return hdrlen + datalen;
 311 }
 312
 313 static unsigned long write_one(struct sha1file *f,
 314                                struct object_entry *e,
 315                                unsigned long offset)
 316 {
 317         if (e->offset)
 318                 /* offset starts from header size and cannot be zero
 319                  * if it is written already.
 320                  */
 321                 return offset;
 322         e->offset = offset;
 323         offset += write_object(f, e);
 324         /* if we are deltified, write out its base object. */
 325         if (e->delta)
 326                 offset = write_one(f, e->delta, offset);
 327         return offset;
 328 }
 329
 330 static void write_pack_file(void)
 331 {
 332         int i;
 333         struct sha1file *f;
 334         unsigned long offset;
 335         struct pack_header hdr;
 336         unsigned last_percent = 999;
 337         int do_progress = 0;
 338
 339         if (!base_name)
 340                 f = sha1fd(1, "<stdout>");
 341         else {
 342                 f = sha1create("%s-%s.%s", base_name,
 343                                sha1_to_hex(object_list_sha1), "pack");
 344                 do_progress = progress;
 345         }
 346         if (do_progress)
 347                 fprintf(stderr, "Writing %d objects.\n", nr_result);
 348
 349         hdr.hdr_signature = htonl(PACK_SIGNATURE);
 350         hdr.hdr_version = htonl(PACK_VERSION);
 351         hdr.hdr_entries = htonl(nr_result);
 352         sha1write(f, &hdr, sizeof(hdr));
 353         offset = sizeof(hdr);
 354         if (!nr_result)
 355                 goto done;
 356         for (i = 0; i < nr_objects; i++) {
 357                 offset = write_one(f, objects + i, offset);
 358                 if (do_progress) {
 359                         unsigned percent = written * 100 / nr_result;
 360                         if (progress_update || percent != last_percent) {
 361                                 fprintf(stderr, "%4u%% (%u/%u) done\r",
 362                                         percent, written, nr_result);
 363                                 progress_update = 0;
 364                                 last_percent = percent;
 365                         }
 366                 }
 367         }
 368         if (do_progress)
 369                 fputc('\n', stderr);
 370  done:
 371         sha1close(f, pack_file_sha1, 1);
 372 }
 373
 374 static void write_index_file(void)
 375 {
 376         int i;
 377         struct sha1file *f = sha1create("%s-%s.%s", base_name,
 378                                         sha1_to_hex(object_list_sha1), "idx");
 379         struct object_entry **list = sorted_by_sha;
 380         struct object_entry **last = list + nr_result;
 381         unsigned int array[256];
 382
 383         /*
 384          * Write the first-level table (the list is sorted,
 385          * but we use a 256-entry lookup to be able to avoid
 386          * having to do eight extra binary search iterations).
 387          */
 388         for (i = 0; i < 256; i++) {
 389                 struct object_entry **next = list;
 390                 while (next < last) {
 391                         struct object_entry *entry = *next;
 392                         if (entry->sha1[0] != i)
 393                                 break;
 394                         next++;
 395                 }
 396                 array[i] = htonl(next - sorted_by_sha);
 397                 list = next;
 398         }
 399         sha1write(f, array, 256 * sizeof(int));
 400
 401         /*
 402          * Write the actual SHA1 entries..
 403          */
 404         list = sorted_by_sha;
 405         for (i = 0; i < nr_result; i++) {
 406                 struct object_entry *entry = *list++;
 407                 unsigned int offset = htonl(entry->offset);
 408                 sha1write(f, &offset, 4);
 409                 sha1write(f, entry->sha1, 20);
 410         }
 411         sha1write(f, pack_file_sha1, 20);
 412         sha1close(f, NULL, 1);
 413 }
 414
 415 static int locate_object_entry_hash(const unsigned char *sha1)
 416 {
 417         int i;
 418         unsigned int ui;
 419         memcpy(&ui, sha1, sizeof(unsigned int));
 420         i = ui % object_ix_hashsz;
 421         while (0 < object_ix[i]) {
 422                 if (!memcmp(sha1, objects[object_ix[i]-1].sha1, 20))
 423                         return i;
 424                 if (++i == object_ix_hashsz)
 425                         i = 0;
 426         }
 427         return -1 - i;
 428 }
 429
 430 static struct object_entry *locate_object_entry(const unsigned char *sha1)
 431 {
 432         int i;
 433
 434         if (!object_ix_hashsz)
 435                 return NULL;
 436
 437         i = locate_object_entry_hash(sha1);
 438         if (0 <= i)
 439                 return &objects[object_ix[i]-1];
 440         return NULL;
 441 }
 442
 443 static void rehash_objects(void)
 444 {
 445         int i;
 446         struct object_entry *oe;
 447
 448         object_ix_hashsz = nr_objects * 3;
 449         if (object_ix_hashsz < 1024)
 450                 object_ix_hashsz = 1024;
 451         object_ix = xrealloc(object_ix, sizeof(int) * object_ix_hashsz);
 452         object_ix = memset(object_ix, 0, sizeof(int) * object_ix_hashsz);
 453         for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
 454                 int ix = locate_object_entry_hash(oe->sha1);
 455                 if (0 <= ix)
 456                         continue;
 457                 ix = -1 - ix;
 458                 object_ix[ix] = i + 1;
 459         }
 460 }
 461
 462 struct name_path {
 463         struct name_path *up;
 464         const char *elem;
 465         int len;
 466 };
 467
 468 #define DIRBITS 12
 469
 470 static unsigned name_hash(struct name_path *path, const char *name)
 471 {
 472         struct name_path *p = path;
 473         const char *n = name + strlen(name);
 474         unsigned hash = 0, name_hash = 0, name_done = 0;
 475
 476         if (n != name && n[-1] == '\n')
 477                 n--;
 478         while (name <= --n) {
 479                 unsigned char c = *n;
 480                 if (c == '/' && !name_done) {
 481                         name_hash = hash;
 482                         name_done = 1;
 483                         hash = 0;
 484                 }
 485                 hash = hash * 11 + c;
 486         }
 487         if (!name_done) {
 488                 name_hash = hash;
 489                 hash = 0;
 490         }
 491         for (p = path; p; p = p->up) {
 492                 hash = hash * 11 + '/';
 493                 n = p->elem + p->len;
 494                 while (p->elem <= --n) {
 495                         unsigned char c = *n;
 496                         hash = hash * 11 + c;
 497                 }
 498         }
 499         /*
 500          * Make sure "Makefile" and "t/Makefile" are hashed separately
 501          * but close enough.
 502          */
 503         hash = (name_hash<<DIRBITS) | (hash & ((1U<<DIRBITS )-1));
 504
 505         if (0) { /* debug */
 506                 n = name + strlen(name);
 507                 if (n != name && n[-1] == '\n')
 508                         n--;
 509                 while (name <= --n)
 510                         fputc(*n, stderr);
 511                 for (p = path; p; p = p->up) {
 512                         fputc('/', stderr);
 513                         n = p->elem + p->len;
 514                         while (p->elem <= --n)
 515                                 fputc(*n, stderr);
 516                 }
 517                 fprintf(stderr, "\t%08x\n", hash);
 518         }
 519         return hash;
 520 }
 521
 522 static int add_object_entry(const unsigned char *sha1, unsigned hash, int exclude)
 523 {
 524         unsigned int idx = nr_objects;
 525         struct object_entry *entry;
 526         struct packed_git *p;
 527         unsigned int found_offset = 0;
 528         struct packed_git *found_pack = NULL;
 529         int ix, status = 0;
 530
 531         if (!exclude) {
 532                 for (p = packed_git; p; p = p->next) {
 533                         struct pack_entry e;
 534                         if (find_pack_entry_one(sha1, &e, p)) {
 535                                 if (incremental)
 536                                         return 0;
 537                                 if (local && !p->pack_local)
 538                                         return 0;
 539                                 if (!found_pack) {
 540                                         found_offset = e.offset;
 541                                         found_pack = e.p;
 542                                 }
 543                         }
 544                 }
 545         }
 546         if ((entry = locate_object_entry(sha1)) != NULL)
 547                 goto already_added;
 548
 549         if (idx >= nr_alloc) {
 550                 unsigned int needed = (idx + 1024) * 3 / 2;
 551                 objects = xrealloc(objects, needed * sizeof(*entry));
 552                 nr_alloc = needed;
 553         }
 554         entry = objects + idx;
 555         nr_objects = idx + 1;
 556         memset(entry, 0, sizeof(*entry));
 557         memcpy(entry->sha1, sha1, 20);
 558         entry->hash = hash;
 559
 560         if (object_ix_hashsz * 3 <= nr_objects * 4)
 561                 rehash_objects();
 562         else {
 563                 ix = locate_object_entry_hash(entry->sha1);
 564                 if (0 <= ix)
 565                         die("internal error in object hashing.");
 566                 object_ix[-1 - ix] = idx + 1;
 567         }
 568         status = 1;
 569
 570  already_added:
 571         if (progress_update) {
 572                 fprintf(stderr, "Counting objects...%d\r", nr_objects);
 573                 progress_update = 0;
 574         }
 575         if (exclude)
 576                 entry->preferred_base = 1;
 577         else {
 578                 if (found_pack) {
 579                         entry->in_pack = found_pack;
 580                         entry->in_pack_offset = found_offset;
 581                 }
 582         }
 583         return status;
 584 }
 585
 586 static void add_pbase_tree(struct tree_desc *tree, struct name_path *up)
 587 {
 588         while (tree->size) {
 589                 const unsigned char *sha1;
 590                 const char *name;
 591                 unsigned mode, hash;
 592                 unsigned long size;
 593                 char type[20];
 594
 595                 sha1 = tree_entry_extract(tree, &name, &mode);
 596                 update_tree_entry(tree);
 597                 if (!has_sha1_file(sha1))
 598                         continue;
 599                 if (sha1_object_info(sha1, type, &size))
 600                         continue;
 601
 602                 hash = name_hash(up, name);
 603                 if (!add_object_entry(sha1, hash, 1))
 604                         continue;
 605
 606                 if (!strcmp(type, "tree")) {
 607                         struct tree_desc sub;
 608                         void *elem;
 609                         struct name_path me;
 610
 611                         elem = read_sha1_file(sha1, type, &sub.size);
 612                         sub.buf = elem;
 613                         if (sub.buf) {
 614                                 me.up = up;
 615                                 me.elem = name;
 616                                 me.len = strlen(name);
 617                                 add_pbase_tree(&sub, &me);
 618                                 free(elem);
 619                         }
 620                 }
 621         }
 622 }
 623
 624 static void add_preferred_base(unsigned char *sha1)
 625 {
 626         struct tree_desc tree;
 627         void *elem;
 628
 629         elem = read_object_with_reference(sha1, "tree", &tree.size, NULL);
 630         tree.buf = elem;
 631         if (!tree.buf)
 632                 return;
 633         if (add_object_entry(sha1, name_hash(NULL, ""), 1))
 634                 add_pbase_tree(&tree, NULL);
 635         free(elem);
 636 }
 637
 638 static void check_object(struct object_entry *entry)
 639 {
 640         char type[20];
 641
 642         if (entry->in_pack && !entry->preferred_base) {
 643                 unsigned char base[20];
 644                 unsigned long size;
 645                 struct object_entry *base_entry;
 646
 647                 /* We want in_pack_type even if we do not reuse delta.
 648                  * There is no point not reusing non-delta representations.
 649                  */
 650                 check_reuse_pack_delta(entry->in_pack,
 651                                        entry->in_pack_offset,
 652                                        base, &size,
 653                                        &entry->in_pack_type);
 654
 655                 /* Check if it is delta, and the base is also an object
 656                  * we are going to pack.  If so we will reuse the existing
 657                  * delta.
 658                  */
 659                 if (!no_reuse_delta &&
 660                     entry->in_pack_type == OBJ_DELTA &&
 661                     (base_entry = locate_object_entry(base)) &&
 662                     (!base_entry->preferred_base)) {
 663
 664                         /* Depth value does not matter - find_deltas()
 665                          * will never consider reused delta as the
 666                          * base object to deltify other objects
 667                          * against, in order to avoid circular deltas.
 668                          */
 669
 670                         /* uncompressed size of the delta data */
 671                         entry->size = entry->delta_size = size;
 672                         entry->delta = base_entry;
 673                         entry->type = OBJ_DELTA;
 674
 675                         entry->delta_sibling = base_entry->delta_child;
 676                         base_entry->delta_child = entry;
 677
 678                         return;
 679                 }
 680                 /* Otherwise we would do the usual */
 681         }
 682
 683         if (sha1_object_info(entry->sha1, type, &entry->size))
 684                 die("unable to get type of object %s",
 685                     sha1_to_hex(entry->sha1));
 686
 687         if (!strcmp(type, "commit")) {
 688                 entry->type = OBJ_COMMIT;
 689         } else if (!strcmp(type, "tree")) {
 690                 entry->type = OBJ_TREE;
 691         } else if (!strcmp(type, "blob")) {
 692                 entry->type = OBJ_BLOB;
 693         } else if (!strcmp(type, "tag")) {
 694                 entry->type = OBJ_TAG;
 695         } else
 696                 die("unable to pack object %s of type %s",
 697                     sha1_to_hex(entry->sha1), type);
 698 }
 699
 700 static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
 701 {
 702         struct object_entry *child = me->delta_child;
 703         unsigned int m = n;
 704         while (child) {
 705                 unsigned int c = check_delta_limit(child, n + 1);
 706                 if (m < c)
 707                         m = c;
 708                 child = child->delta_sibling;
 709         }
 710         return m;
 711 }
 712
 713 static void get_object_details(void)
 714 {
 715         int i;
 716         struct object_entry *entry;
 717
 718         prepare_pack_ix();
 719         for (i = 0, entry = objects; i < nr_objects; i++, entry++)
 720                 check_object(entry);
 721
 722         if (nr_objects == nr_result) {
 723                 /*
 724                  * Depth of objects that depend on the entry -- this
 725                  * is subtracted from depth-max to break too deep
 726                  * delta chain because of delta data reusing.
 727                  * However, we loosen this restriction when we know we
 728                  * are creating a thin pack -- it will have to be
 729                  * expanded on the other end anyway, so do not
 730                  * artificially cut the delta chain and let it go as
 731                  * deep as it wants.
 732                  */
 733                 for (i = 0, entry = objects; i < nr_objects; i++, entry++)
 734                         if (!entry->delta && entry->delta_child)
 735                                 entry->delta_limit =
 736                                         check_delta_limit(entry, 1);
 737         }
 738 }
 739
 740 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
 741
 742 static entry_sort_t current_sort;
 743
 744 static int sort_comparator(const void *_a, const void *_b)
 745 {
 746         struct object_entry *a = *(struct object_entry **)_a;
 747         struct object_entry *b = *(struct object_entry **)_b;
 748         return current_sort(a,b);
 749 }
 750
 751 static struct object_entry **create_sorted_list(entry_sort_t sort)
 752 {
 753         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
 754         int i;
 755
 756         for (i = 0; i < nr_objects; i++)
 757                 list[i] = objects + i;
 758         current_sort = sort;
 759         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
 760         return list;
 761 }
 762
 763 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
 764 {
 765         return memcmp(a->sha1, b->sha1, 20);
 766 }
 767
 768 static struct object_entry **create_final_object_list(void)
 769 {
 770         struct object_entry **list;
 771         int i, j;
 772
 773         for (i = nr_result = 0; i < nr_objects; i++)
 774                 if (!objects[i].preferred_base)
 775                         nr_result++;
 776         list = xmalloc(nr_result * sizeof(struct object_entry *));
 777         for (i = j = 0; i < nr_objects; i++) {
 778                 if (!objects[i].preferred_base)
 779                         list[j++] = objects + i;
 780         }
 781         current_sort = sha1_sort;
 782         qsort(list, nr_result, sizeof(struct object_entry *), sort_comparator);
 783         return list;
 784 }
 785
 786 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
 787 {
 788         if (a->type < b->type)
 789                 return -1;
 790         if (a->type > b->type)
 791                 return 1;
 792         if (a->hash < b->hash)
 793                 return -1;
 794         if (a->hash > b->hash)
 795                 return 1;
 796         if (a->preferred_base < b->preferred_base)
 797                 return -1;
 798         if (a->preferred_base > b->preferred_base)
 799                 return 1;
 800         if (a->size < b->size)
 801                 return -1;
 802         if (a->size > b->size)
 803                 return 1;
 804         return a < b ? -1 : (a > b);
 805 }
 806
 807 struct unpacked {
 808         struct object_entry *entry;
 809         void *data;
 810 };
 811
 812 /*
 813  * We search for deltas _backwards_ in a list sorted by type and
 814  * by size, so that we see progressively smaller and smaller files.
 815  * That's because we prefer deltas to be from the bigger file
 816  * to the smaller - deletes are potentially cheaper, but perhaps
 817  * more importantly, the bigger file is likely the more recent
 818  * one.
 819  */
 820 static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
 821 {
 822         struct object_entry *cur_entry = cur->entry;
 823         struct object_entry *old_entry = old->entry;
 824         unsigned long size, oldsize, delta_size, sizediff;
 825         long max_size;
 826         void *delta_buf;
 827
 828         /* Don't bother doing diffs between different types */
 829         if (cur_entry->type != old_entry->type)
 830                 return -1;
 831
 832         /* We do not compute delta to *create* objects we are not
 833          * going to pack.
 834          */
 835         if (cur_entry->preferred_base)
 836                 return -1;
 837
 838         /* If the current object is at pack edge, take the depth the
 839          * objects that depend on the current object into account --
 840          * otherwise they would become too deep.
 841          */
 842         if (cur_entry->delta_child) {
 843                 if (max_depth <= cur_entry->delta_limit)
 844                         return 0;
 845                 max_depth -= cur_entry->delta_limit;
 846         }
 847
 848         size = cur_entry->size;
 849         oldsize = old_entry->size;
 850         sizediff = oldsize > size ? oldsize - size : size - oldsize;
 851
 852         if (size < 50)
 853                 return -1;
 854         if (old_entry->depth >= max_depth)
 855                 return 0;
 856
 857         /*
 858          * NOTE!
 859          *
 860          * We always delta from the bigger to the smaller, since that's
 861          * more space-efficient (deletes don't have to say _what_ they
 862          * delete).
 863          */
 864         max_size = size / 2 - 20;
 865         if (cur_entry->delta)
 866                 max_size = cur_entry->delta_size-1;
 867         if (sizediff >= max_size)
 868                 return -1;
 869         delta_buf = diff_delta(old->data, oldsize,
 870                                cur->data, size, &delta_size, max_size);
 871         if (!delta_buf)
 872                 return 0;
 873         cur_entry->delta = old_entry;
 874         cur_entry->delta_size = delta_size;
 875         cur_entry->depth = old_entry->depth + 1;
 876         free(delta_buf);
 877         return 0;
 878 }
 879
 880 static void progress_interval(int signum)
 881 {
 882         progress_update = 1;
 883 }
 884
 885 static void find_deltas(struct object_entry **list, int window, int depth)
 886 {
 887         int i, idx;
 888         unsigned int array_size = window * sizeof(struct unpacked);
 889         struct unpacked *array = xmalloc(array_size);
 890         unsigned processed = 0;
 891         unsigned last_percent = 999;
 892
 893         memset(array, 0, array_size);
 894         i = nr_objects;
 895         idx = 0;
 896         if (progress)
 897                 fprintf(stderr, "Deltifying %d objects.\n", nr_result);
 898
 899         while (--i >= 0) {
 900                 struct object_entry *entry = list[i];
 901                 struct unpacked *n = array + idx;
 902                 unsigned long size;
 903                 char type[10];
 904                 int j;
 905
 906                 if (!entry->preferred_base)
 907                         processed++;
 908
 909                 if (progress) {
 910                         unsigned percent = processed * 100 / nr_result;
 911                         if (percent != last_percent || progress_update) {
 912                                 fprintf(stderr, "%4u%% (%u/%u) done\r",
 913                                         percent, processed, nr_result);
 914                                 progress_update = 0;
 915                                 last_percent = percent;
 916                         }
 917                 }
 918
 919                 if (entry->delta)
 920                         /* This happens if we decided to reuse existing
 921                          * delta from a pack.  "!no_reuse_delta &&" is implied.
 922                          */
 923                         continue;
 924
 925                 free(n->data);
 926                 n->entry = entry;
 927                 n->data = read_sha1_file(entry->sha1, type, &size);
 928                 if (size != entry->size)
 929                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
 930
 931                 j = window;
 932                 while (--j > 0) {
 933                         unsigned int other_idx = idx + j;
 934                         struct unpacked *m;
 935                         if (other_idx >= window)
 936                                 other_idx -= window;
 937                         m = array + other_idx;
 938                         if (!m->entry)
 939                                 break;
 940                         if (try_delta(n, m, depth) < 0)
 941                                 break;
 942                 }
 943 #if 0
 944                 /* if we made n a delta, and if n is already at max
 945                  * depth, leaving it in the window is pointless.  we
 946                  * should evict it first.
 947                  * ... in theory only; somehow this makes things worse.
 948                  */
 949                 if (entry->delta && depth <= entry->depth)
 950                         continue;
 951 #endif
 952                 idx++;
 953                 if (idx >= window)
 954                         idx = 0;
 955         }
 956
 957         if (progress)
 958                 fputc('\n', stderr);
 959
 960         for (i = 0; i < window; ++i)
 961                 free(array[i].data);
 962         free(array);
 963 }
 964
 965 static void prepare_pack(int window, int depth)
 966 {
 967         get_object_details();
 968         sorted_by_type = create_sorted_list(type_size_sort);
 969         if (window && depth)
 970                 find_deltas(sorted_by_type, window+1, depth);
 971 }
 972
 973 static int reuse_cached_pack(unsigned char *sha1, int pack_to_stdout)
 974 {
 975         static const char cache[] = "pack-cache/pack-%s.%s";
 976         char *cached_pack, *cached_idx;
 977         int ifd, ofd, ifd_ix = -1;
 978
 979         cached_pack = git_path(cache, sha1_to_hex(sha1), "pack");
 980         ifd = open(cached_pack, O_RDONLY);
 981         if (ifd < 0)
 982                 return 0;
 983
 984         if (!pack_to_stdout) {
 985                 cached_idx = git_path(cache, sha1_to_hex(sha1), "idx");
 986                 ifd_ix = open(cached_idx, O_RDONLY);
 987                 if (ifd_ix < 0) {
 988                         close(ifd);
 989                         return 0;
 990                 }
 991         }
 992
 993         if (progress)
 994                 fprintf(stderr, "Reusing %d objects pack %s\n", nr_objects,
 995                         sha1_to_hex(sha1));
 996
 997         if (pack_to_stdout) {
 998                 if (copy_fd(ifd, 1))
 999                         exit(1);
1000                 close(ifd);
1001         }
1002         else {
1003                 char name[PATH_MAX];
1004                 snprintf(name, sizeof(name),
1005                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "pack");
1006                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
1007                 if (ofd < 0)
1008                         die("unable to open %s (%s)", name, strerror(errno));
1009                 if (copy_fd(ifd, ofd))
1010                         exit(1);
1011                 close(ifd);
1012
1013                 snprintf(name, sizeof(name),
1014                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "idx");
1015                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
1016                 if (ofd < 0)
1017                         die("unable to open %s (%s)", name, strerror(errno));
1018                 if (copy_fd(ifd_ix, ofd))
1019                         exit(1);
1020                 close(ifd_ix);
1021                 puts(sha1_to_hex(sha1));
1022         }
1023
1024         return 1;
1025 }
1026
1027 static void setup_progress_signal(void)
1028 {
1029         struct sigaction sa;
1030         struct itimerval v;
1031
1032         memset(&sa, 0, sizeof(sa));
1033         sa.sa_handler = progress_interval;
1034         sigemptyset(&sa.sa_mask);
1035         sa.sa_flags = SA_RESTART;
1036         sigaction(SIGALRM, &sa, NULL);
1037
1038         v.it_interval.tv_sec = 1;
1039         v.it_interval.tv_usec = 0;
1040         v.it_value = v.it_interval;
1041         setitimer(ITIMER_REAL, &v, NULL);
1042 }
1043
1044 int main(int argc, char **argv)
1045 {
1046         SHA_CTX ctx;
1047         char line[PATH_MAX + 20];
1048         int window = 10, depth = 10, pack_to_stdout = 0;
1049         struct object_entry **list;
1050         int i;
1051
1052         setup_git_directory();
1053
1054         for (i = 1; i < argc; i++) {
1055                 const char *arg = argv[i];
1056
1057                 if (*arg == '-') {
1058                         if (!strcmp("--non-empty", arg)) {
1059                                 non_empty = 1;
1060                                 continue;
1061                         }
1062                         if (!strcmp("--local", arg)) {
1063                                 local = 1;
1064                                 continue;
1065                         }
1066                         if (!strcmp("--incremental", arg)) {
1067                                 incremental = 1;
1068                                 continue;
1069                         }
1070                         if (!strncmp("--window=", arg, 9)) {
1071                                 char *end;
1072                                 window = strtoul(arg+9, &end, 0);
1073                                 if (!arg[9] || *end)
1074                                         usage(pack_usage);
1075                                 continue;
1076                         }
1077                         if (!strncmp("--depth=", arg, 8)) {
1078                                 char *end;
1079                                 depth = strtoul(arg+8, &end, 0);
1080                                 if (!arg[8] || *end)
1081                                         usage(pack_usage);
1082                                 continue;
1083                         }
1084                         if (!strcmp("-q", arg)) {
1085                                 progress = 0;
1086                                 continue;
1087                         }
1088                         if (!strcmp("--no-reuse-delta", arg)) {
1089                                 no_reuse_delta = 1;
1090                                 continue;
1091                         }
1092                         if (!strcmp("--stdout", arg)) {
1093                                 pack_to_stdout = 1;
1094                                 continue;
1095                         }
1096                         usage(pack_usage);
1097                 }
1098                 if (base_name)
1099                         usage(pack_usage);
1100                 base_name = arg;
1101         }
1102
1103         if (pack_to_stdout != !base_name)
1104                 usage(pack_usage);
1105
1106         prepare_packed_git();
1107
1108         if (progress) {
1109                 fprintf(stderr, "Generating pack...\n");
1110                 setup_progress_signal();
1111         }
1112
1113         for (;;) {
1114                 unsigned char sha1[20];
1115
1116                 if (!fgets(line, sizeof(line), stdin)) {
1117                         if (feof(stdin))
1118                                 break;
1119                         if (!ferror(stdin))
1120                                 die("fgets returned NULL, not EOF, not error!");
1121                         if (errno != EINTR)
1122                                 die("fgets: %s", strerror(errno));
1123                         clearerr(stdin);
1124                         continue;
1125                 }
1126
1127                 if (line[0] == '-') {
1128                         if (get_sha1_hex(line+1, sha1))
1129                                 die("expected edge sha1, got garbage:\n %s",
1130                                     line+1);
1131                         add_preferred_base(sha1);
1132                         continue;
1133                 }
1134                 if (get_sha1_hex(line, sha1))
1135                         die("expected sha1, got garbage:\n %s", line);
1136                 add_object_entry(sha1, name_hash(NULL, line+41), 0);
1137         }
1138         if (progress)
1139                 fprintf(stderr, "Done counting %d objects.\n", nr_objects);
1140         sorted_by_sha = create_final_object_list();
1141         if (non_empty && !nr_result)
1142                 return 0;
1143
1144         SHA1_Init(&ctx);
1145         list = sorted_by_sha;
1146         for (i = 0; i < nr_result; i++) {
1147                 struct object_entry *entry = *list++;
1148                 SHA1_Update(&ctx, entry->sha1, 20);
1149         }
1150         SHA1_Final(object_list_sha1, &ctx);
1151         if (progress && (nr_objects != nr_result))
1152                 fprintf(stderr, "Result has %d objects.\n", nr_result);
1153
1154         if (reuse_cached_pack(object_list_sha1, pack_to_stdout))
1155                 ;
1156         else {
1157                 if (nr_result)
1158                         prepare_pack(window, depth);
1159                 if (progress && pack_to_stdout) {
1160                         /* the other end usually displays progress itself */
1161                         struct itimerval v = {{0,},};
1162                         setitimer(ITIMER_REAL, &v, NULL);
1163                         signal(SIGALRM, SIG_IGN );
1164                         progress_update = 0;
1165                 }
1166                 write_pack_file();
1167                 if (!pack_to_stdout) {
1168                         write_index_file();
1169                         puts(sha1_to_hex(object_list_sha1));
1170                 }
1171         }
1172         if (progress)
1173                 fprintf(stderr, "Total %d, written %d (delta %d), reused %d (delta %d)\n",
1174                         nr_result, written, written_delta, reused, reused_delta);
1175         return 0;
1176 }