pack-objects.c

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