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