pack-objects.c

   1 #include "cache.h"
   2 #include "object.h"
   3 #include "blob.h"
   4 #include "commit.h"
   5 #include "tag.h"
   6 #include "tree.h"
   7 #include "delta.h"
   8 #include "pack.h"
   9 #include "csum-file.h"
  10 #include "tree-walk.h"
  11 #include <sys/time.h>
  12 #include <signal.h>
  13
  14 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";
  15
  16 struct object_entry {
  17         unsigned char sha1[20];
  18         unsigned long size;     /* uncompressed size */
  19         unsigned long offset;   /* offset into the final pack file;
  20                                  * nonzero if already written.
  21                                  */
  22         unsigned int depth;     /* delta depth */
  23         unsigned int delta_limit;       /* base adjustment for in-pack delta */
  24         unsigned int hash;      /* name hint hash */
  25         enum object_type type;
  26         enum object_type in_pack_type;  /* could be delta */
  27         unsigned long delta_size;       /* delta data size (uncompressed) */
  28         struct object_entry *delta;     /* delta base object */
  29         struct packed_git *in_pack;     /* already in pack */
  30         unsigned int in_pack_offset;
  31         struct object_entry *delta_child; /* delitified objects who bases me */
  32         struct object_entry *delta_sibling; /* other deltified objects who
  33                                              * uses the same base as me
  34                                              */
  35         int preferred_base;     /* we do not pack this, but is encouraged to
  36                                  * be used as the base objectto delta huge
  37                                  * objects against.
  38                                  */
  39 };
  40
  41 /*
  42  * Objects we are going to pack are colected in objects array (dynamically
  43  * expanded).  nr_objects & nr_alloc controls this array.  They are stored
  44  * in the order we see -- typically rev-list --objects order that gives us
  45  * nice "minimum seek" order.
  46  *
  47  * sorted-by-sha ans sorted-by-type are arrays of pointers that point at
  48  * elements in the objects array.  The former is used to build the pack
  49  * index (lists object names in the ascending order to help offset lookup),
  50  * and the latter is used to group similar things together by try_delta()
  51  * heuristics.
  52  */
  53
  54 static unsigned char object_list_sha1[20];
  55 static int non_empty = 0;
  56 static int no_reuse_delta = 0;
  57 static int local = 0;
  58 static int incremental = 0;
  59 static struct object_entry **sorted_by_sha, **sorted_by_type;
  60 static struct object_entry *objects = NULL;
  61 static int nr_objects = 0, nr_alloc = 0, nr_result = 0;
  62 static const char *base_name;
  63 static unsigned char pack_file_sha1[20];
  64 static int progress = 1;
  65 static volatile sig_atomic_t progress_update = 0;
  66
  67 /*
  68  * The object names in objects array are hashed with this hashtable,
  69  * to help looking up the entry by object name.  Binary search from
  70  * sorted_by_sha is also possible but this was easier to code and faster.
  71  * This hashtable is built after all the objects are seen.
  72  */
  73 static int *object_ix = NULL;
  74 static int object_ix_hashsz = 0;
  75
  76 /*
  77  * Pack index for existing packs give us easy access to the offsets into
  78  * corresponding pack file where each object's data starts, but the entries
  79  * do not store the size of the compressed representation (uncompressed
  80  * size is easily available by examining the pack entry header).  We build
  81  * a hashtable of existing packs (pack_revindex), and keep reverse index
  82  * here -- pack index file is sorted by object name mapping to offset; this
  83  * pack_revindex[].revindex array is an ordered list of offsets, so if you
  84  * know the offset of an object, next offset is where its packed
  85  * representation ends.
  86  */
  87 struct pack_revindex {
  88         struct packed_git *p;
  89         unsigned long *revindex;
  90 } *pack_revindex = NULL;
  91 static int pack_revindex_hashsz = 0;
  92
  93 /*
  94  * stats
  95  */
  96 static int written = 0;
  97 static int written_delta = 0;
  98 static int reused = 0;
  99 static int reused_delta = 0;
 100
 101 static int pack_revindex_ix(struct packed_git *p)
 102 {
 103         unsigned long ui = (unsigned long)p;
 104         int i;
 105
 106         ui = ui ^ (ui >> 16); /* defeat structure alignment */
 107         i = (int)(ui % pack_revindex_hashsz);
 108         while (pack_revindex[i].p) {
 109                 if (pack_revindex[i].p == p)
 110                         return i;
 111                 if (++i == pack_revindex_hashsz)
 112                         i = 0;
 113         }
 114         return -1 - i;
 115 }
 116
 117 static void prepare_pack_ix(void)
 118 {
 119         int num;
 120         struct packed_git *p;
 121         for (num = 0, p = packed_git; p; p = p->next)
 122                 num++;
 123         if (!num)
 124                 return;
 125         pack_revindex_hashsz = num * 11;
 126         pack_revindex = xcalloc(sizeof(*pack_revindex), pack_revindex_hashsz);
 127         for (p = packed_git; p; p = p->next) {
 128                 num = pack_revindex_ix(p);
 129                 num = - 1 - num;
 130                 pack_revindex[num].p = p;
 131         }
 132         /* revindex elements are lazily initialized */
 133 }
 134
 135 static int cmp_offset(const void *a_, const void *b_)
 136 {
 137         unsigned long a = *(unsigned long *) a_;
 138         unsigned long b = *(unsigned long *) b_;
 139         if (a < b)
 140                 return -1;
 141         else if (a == b)
 142                 return 0;
 143         else
 144                 return 1;
 145 }
 146
 147 /*
 148  * Ordered list of offsets of objects in the pack.
 149  */
 150 static void prepare_pack_revindex(struct pack_revindex *rix)
 151 {
 152         struct packed_git *p = rix->p;
 153         int num_ent = num_packed_objects(p);
 154         int i;
 155         void *index = p->index_base + 256;
 156
 157         rix->revindex = xmalloc(sizeof(unsigned long) * (num_ent + 1));
 158         for (i = 0; i < num_ent; i++) {
 159                 long hl = *((long *)(index + 24 * i));
 160                 rix->revindex[i] = ntohl(hl);
 161         }
 162         /* This knows the pack format -- the 20-byte trailer
 163          * follows immediately after the last object data.
 164          */
 165         rix->revindex[num_ent] = p->pack_size - 20;
 166         qsort(rix->revindex, num_ent, sizeof(unsigned long), cmp_offset);
 167 }
 168
 169 static unsigned long find_packed_object_size(struct packed_git *p,
 170                                              unsigned long ofs)
 171 {
 172         int num;
 173         int lo, hi;
 174         struct pack_revindex *rix;
 175         unsigned long *revindex;
 176         num = pack_revindex_ix(p);
 177         if (num < 0)
 178                 die("internal error: pack revindex uninitialized");
 179         rix = &pack_revindex[num];
 180         if (!rix->revindex)
 181                 prepare_pack_revindex(rix);
 182         revindex = rix->revindex;
 183         lo = 0;
 184         hi = num_packed_objects(p) + 1;
 185         do {
 186                 int mi = (lo + hi) / 2;
 187                 if (revindex[mi] == ofs) {
 188                         return revindex[mi+1] - ofs;
 189                 }
 190                 else if (ofs < revindex[mi])
 191                         hi = mi;
 192                 else
 193                         lo = mi + 1;
 194         } while (lo < hi);
 195         die("internal error: pack revindex corrupt");
 196 }
 197
 198 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
 199 {
 200         unsigned long othersize, delta_size;
 201         char type[10];
 202         void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
 203         void *delta_buf;
 204
 205         if (!otherbuf)
 206                 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
 207         delta_buf = diff_delta(otherbuf, othersize,
 208                                buf, size, &delta_size, 0);
 209         if (!delta_buf || delta_size != entry->delta_size)
 210                 die("delta size changed");
 211         free(buf);
 212         free(otherbuf);
 213         return delta_buf;
 214 }
 215
 216 /*
 217  * The per-object header is a pretty dense thing, which is
 218  *  - first byte: low four bits are "size", then three bits of "type",
 219  *    and the high bit is "size continues".
 220  *  - each byte afterwards: low seven bits are size continuation,
 221  *    with the high bit being "size continues"
 222  */
 223 static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
 224 {
 225         int n = 1;
 226         unsigned char c;
 227
 228         if (type < OBJ_COMMIT || type > OBJ_DELTA)
 229                 die("bad type %d", type);
 230
 231         c = (type << 4) | (size & 15);
 232         size >>= 4;
 233         while (size) {
 234                 *hdr++ = c | 0x80;
 235                 c = size & 0x7f;
 236                 size >>= 7;
 237                 n++;
 238         }
 239         *hdr = c;
 240         return n;
 241 }
 242
 243 static unsigned long write_object(struct sha1file *f,
 244                                   struct object_entry *entry)
 245 {
 246         unsigned long size;
 247         char type[10];
 248         void *buf;
 249         unsigned char header[10];
 250         unsigned hdrlen, datalen;
 251         enum object_type obj_type;
 252         int to_reuse = 0;
 253
 254         if (entry->preferred_base)
 255                 return 0;
 256
 257         obj_type = entry->type;
 258         if (! entry->in_pack)
 259                 to_reuse = 0;   /* can't reuse what we don't have */
 260         else if (obj_type == OBJ_DELTA)
 261                 to_reuse = 1;   /* check_object() decided it for us */
 262         else if (obj_type != entry->in_pack_type)
 263                 to_reuse = 0;   /* pack has delta which is unusable */
 264         else if (entry->delta)
 265                 to_reuse = 0;   /* we want to pack afresh */
 266         else
 267                 to_reuse = 1;   /* we have it in-pack undeltified,
 268                                  * and we do not need to deltify it.
 269                                  */
 270
 271         if (! to_reuse) {
 272                 buf = read_sha1_file(entry->sha1, type, &size);
 273                 if (!buf)
 274                         die("unable to read %s", sha1_to_hex(entry->sha1));
 275                 if (size != entry->size)
 276                         die("object %s size inconsistency (%lu vs %lu)",
 277                             sha1_to_hex(entry->sha1), size, entry->size);
 278                 if (entry->delta) {
 279                         buf = delta_against(buf, size, entry);
 280                         size = entry->delta_size;
 281                         obj_type = OBJ_DELTA;
 282                 }
 283                 /*
 284                  * The object header is a byte of 'type' followed by zero or
 285                  * more bytes of length.  For deltas, the 20 bytes of delta
 286                  * sha1 follows that.
 287                  */
 288                 hdrlen = encode_header(obj_type, size, header);
 289                 sha1write(f, header, hdrlen);
 290
 291                 if (entry->delta) {
 292                         sha1write(f, entry->delta, 20);
 293                         hdrlen += 20;
 294                 }
 295                 datalen = sha1write_compressed(f, buf, size);
 296                 free(buf);
 297         }
 298         else {
 299                 struct packed_git *p = entry->in_pack;
 300                 use_packed_git(p);
 301
 302                 datalen = find_packed_object_size(p, entry->in_pack_offset);
 303                 buf = p->pack_base + entry->in_pack_offset;
 304                 sha1write(f, buf, datalen);
 305                 unuse_packed_git(p);
 306                 hdrlen = 0; /* not really */
 307                 if (obj_type == OBJ_DELTA)
 308                         reused_delta++;
 309                 reused++;
 310         }
 311         if (obj_type == OBJ_DELTA)
 312                 written_delta++;
 313         written++;
 314         return hdrlen + datalen;
 315 }
 316
 317 static unsigned long write_one(struct sha1file *f,
 318                                struct object_entry *e,
 319                                unsigned long offset)
 320 {
 321         if (e->offset)
 322                 /* offset starts from header size and cannot be zero
 323                  * if it is written already.
 324                  */
 325                 return offset;
 326         e->offset = offset;
 327         offset += write_object(f, e);
 328         /* if we are deltified, write out its base object. */
 329         if (e->delta)
 330                 offset = write_one(f, e->delta, offset);
 331         return offset;
 332 }
 333
 334 static void write_pack_file(void)
 335 {
 336         int i;
 337         struct sha1file *f;
 338         unsigned long offset;
 339         struct pack_header hdr;
 340         unsigned last_percent = 999;
 341         int do_progress = 0;
 342
 343         if (!base_name)
 344                 f = sha1fd(1, "<stdout>");
 345         else {
 346                 f = sha1create("%s-%s.%s", base_name,
 347                                sha1_to_hex(object_list_sha1), "pack");
 348                 do_progress = progress;
 349         }
 350         if (do_progress)
 351                 fprintf(stderr, "Writing %d objects.\n", nr_result);
 352
 353         hdr.hdr_signature = htonl(PACK_SIGNATURE);
 354         hdr.hdr_version = htonl(PACK_VERSION);
 355         hdr.hdr_entries = htonl(nr_result);
 356         sha1write(f, &hdr, sizeof(hdr));
 357         offset = sizeof(hdr);
 358         if (!nr_result)
 359                 goto done;
 360         for (i = 0; i < nr_objects; i++) {
 361                 offset = write_one(f, objects + i, offset);
 362                 if (do_progress) {
 363                         unsigned percent = written * 100 / nr_result;
 364                         if (progress_update || percent != last_percent) {
 365                                 fprintf(stderr, "%4u%% (%u/%u) done\r",
 366                                         percent, written, nr_result);
 367                                 progress_update = 0;
 368                                 last_percent = percent;
 369                         }
 370                 }
 371         }
 372         if (do_progress)
 373                 fputc('\n', stderr);
 374  done:
 375         sha1close(f, pack_file_sha1, 1);
 376 }
 377
 378 static void write_index_file(void)
 379 {
 380         int i;
 381         struct sha1file *f = sha1create("%s-%s.%s", base_name,
 382                                         sha1_to_hex(object_list_sha1), "idx");
 383         struct object_entry **list = sorted_by_sha;
 384         struct object_entry **last = list + nr_result;
 385         unsigned int array[256];
 386
 387         /*
 388          * Write the first-level table (the list is sorted,
 389          * but we use a 256-entry lookup to be able to avoid
 390          * having to do eight extra binary search iterations).
 391          */
 392         for (i = 0; i < 256; i++) {
 393                 struct object_entry **next = list;
 394                 while (next < last) {
 395                         struct object_entry *entry = *next;
 396                         if (entry->sha1[0] != i)
 397                                 break;
 398                         next++;
 399                 }
 400                 array[i] = htonl(next - sorted_by_sha);
 401                 list = next;
 402         }
 403         sha1write(f, array, 256 * sizeof(int));
 404
 405         /*
 406          * Write the actual SHA1 entries..
 407          */
 408         list = sorted_by_sha;
 409         for (i = 0; i < nr_result; i++) {
 410                 struct object_entry *entry = *list++;
 411                 unsigned int offset = htonl(entry->offset);
 412                 sha1write(f, &offset, 4);
 413                 sha1write(f, entry->sha1, 20);
 414         }
 415         sha1write(f, pack_file_sha1, 20);
 416         sha1close(f, NULL, 1);
 417 }
 418
 419 static int locate_object_entry_hash(const unsigned char *sha1)
 420 {
 421         int i;
 422         unsigned int ui;
 423         memcpy(&ui, sha1, sizeof(unsigned int));
 424         i = ui % object_ix_hashsz;
 425         while (0 < object_ix[i]) {
 426                 if (!memcmp(sha1, objects[object_ix[i]-1].sha1, 20))
 427                         return i;
 428                 if (++i == object_ix_hashsz)
 429                         i = 0;
 430         }
 431         return -1 - i;
 432 }
 433
 434 static struct object_entry *locate_object_entry(const unsigned char *sha1)
 435 {
 436         int i;
 437
 438         if (!object_ix_hashsz)
 439                 return NULL;
 440
 441         i = locate_object_entry_hash(sha1);
 442         if (0 <= i)
 443                 return &objects[object_ix[i]-1];
 444         return NULL;
 445 }
 446
 447 static void rehash_objects(void)
 448 {
 449         int i;
 450         struct object_entry *oe;
 451
 452         object_ix_hashsz = nr_objects * 3;
 453         if (object_ix_hashsz < 1024)
 454                 object_ix_hashsz = 1024;
 455         object_ix = xrealloc(object_ix, sizeof(int) * object_ix_hashsz);
 456         memset(object_ix, 0, sizeof(int) * object_ix_hashsz);
 457         for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
 458                 int ix = locate_object_entry_hash(oe->sha1);
 459                 if (0 <= ix)
 460                         continue;
 461                 ix = -1 - ix;
 462                 object_ix[ix] = i + 1;
 463         }
 464 }
 465
 466 struct name_path {
 467         struct name_path *up;
 468         const char *elem;
 469         int len;
 470 };
 471
 472 #define DIRBITS 12
 473
 474 static unsigned name_hash(struct name_path *path, const char *name)
 475 {
 476         struct name_path *p = path;
 477         const char *n = name + strlen(name);
 478         unsigned hash = 0, name_hash = 0, name_done = 0;
 479
 480         if (n != name && n[-1] == '\n')
 481                 n--;
 482         while (name <= --n) {
 483                 unsigned char c = *n;
 484                 if (c == '/' && !name_done) {
 485                         name_hash = hash;
 486                         name_done = 1;
 487                         hash = 0;
 488                 }
 489                 hash = hash * 11 + c;
 490         }
 491         if (!name_done) {
 492                 name_hash = hash;
 493                 hash = 0;
 494         }
 495         for (p = path; p; p = p->up) {
 496                 hash = hash * 11 + '/';
 497                 n = p->elem + p->len;
 498                 while (p->elem <= --n) {
 499                         unsigned char c = *n;
 500                         hash = hash * 11 + c;
 501                 }
 502         }
 503         /*
 504          * Make sure "Makefile" and "t/Makefile" are hashed separately
 505          * but close enough.
 506          */
 507         hash = (name_hash<<DIRBITS) | (hash & ((1U<<DIRBITS )-1));
 508         return hash;
 509 }
 510
 511 static int add_object_entry(const unsigned char *sha1, unsigned hash, int exclude)
 512 {
 513         unsigned int idx = nr_objects;
 514         struct object_entry *entry;
 515         struct packed_git *p;
 516         unsigned int found_offset = 0;
 517         struct packed_git *found_pack = NULL;
 518         int ix, status = 0;
 519
 520         if (!exclude) {
 521                 for (p = packed_git; p; p = p->next) {
 522                         struct pack_entry e;
 523                         if (find_pack_entry_one(sha1, &e, p)) {
 524                                 if (incremental)
 525                                         return 0;
 526                                 if (local && !p->pack_local)
 527                                         return 0;
 528                                 if (!found_pack) {
 529                                         found_offset = e.offset;
 530                                         found_pack = e.p;
 531                                 }
 532                         }
 533                 }
 534         }
 535         if ((entry = locate_object_entry(sha1)) != NULL)
 536                 goto already_added;
 537
 538         if (idx >= nr_alloc) {
 539                 unsigned int needed = (idx + 1024) * 3 / 2;
 540                 objects = xrealloc(objects, needed * sizeof(*entry));
 541                 nr_alloc = needed;
 542         }
 543         entry = objects + idx;
 544         nr_objects = idx + 1;
 545         memset(entry, 0, sizeof(*entry));
 546         memcpy(entry->sha1, sha1, 20);
 547         entry->hash = hash;
 548
 549         if (object_ix_hashsz * 3 <= nr_objects * 4)
 550                 rehash_objects();
 551         else {
 552                 ix = locate_object_entry_hash(entry->sha1);
 553                 if (0 <= ix)
 554                         die("internal error in object hashing.");
 555                 object_ix[-1 - ix] = idx + 1;
 556         }
 557         status = 1;
 558
 559  already_added:
 560         if (progress_update) {
 561                 fprintf(stderr, "Counting objects...%d\r", nr_objects);
 562                 progress_update = 0;
 563         }
 564         if (exclude)
 565                 entry->preferred_base = 1;
 566         else {
 567                 if (found_pack) {
 568                         entry->in_pack = found_pack;
 569                         entry->in_pack_offset = found_offset;
 570                 }
 571         }
 572         return status;
 573 }
 574
 575 struct pbase_tree_cache {
 576         unsigned char sha1[20];
 577         int ref;
 578         int temporary;
 579         void *tree_data;
 580         unsigned long tree_size;
 581 };
 582
 583 static struct pbase_tree_cache *(pbase_tree_cache[256]);
 584 static int pbase_tree_cache_ix(const unsigned char *sha1)
 585 {
 586         return sha1[0] % ARRAY_SIZE(pbase_tree_cache);
 587 }
 588 static int pbase_tree_cache_ix_incr(int ix)
 589 {
 590         return (ix+1) % ARRAY_SIZE(pbase_tree_cache);
 591 }
 592
 593 static struct pbase_tree {
 594         struct pbase_tree *next;
 595         /* This is a phony "cache" entry; we are not
 596          * going to evict it nor find it through _get()
 597          * mechanism -- this is for the toplevel node that
 598          * would almost always change with any commit.
 599          */
 600         struct pbase_tree_cache pcache;
 601 } *pbase_tree;
 602
 603 static struct pbase_tree_cache *pbase_tree_get(const unsigned char *sha1)
 604 {
 605         struct pbase_tree_cache *ent, *nent;
 606         void *data;
 607         unsigned long size;
 608         char type[20];
 609         int neigh;
 610         int my_ix = pbase_tree_cache_ix(sha1);
 611         int available_ix = -1;
 612
 613         /* pbase-tree-cache acts as a limited hashtable.
 614          * your object will be found at your index or within a few
 615          * slots after that slot if it is cached.
 616          */
 617         for (neigh = 0; neigh < 8; neigh++) {
 618                 ent = pbase_tree_cache[my_ix];
 619                 if (ent && !memcmp(ent->sha1, sha1, 20)) {
 620                         ent->ref++;
 621                         return ent;
 622                 }
 623                 else if (((available_ix < 0) && (!ent || !ent->ref)) ||
 624                          ((0 <= available_ix) &&
 625                           (!ent && pbase_tree_cache[available_ix])))
 626                         available_ix = my_ix;
 627                 if (!ent)
 628                         break;
 629                 my_ix = pbase_tree_cache_ix_incr(my_ix);
 630         }
 631
 632         /* Did not find one.  Either we got a bogus request or
 633          * we need to read and perhaps cache.
 634          */
 635         data = read_sha1_file(sha1, type, &size);
 636         if (!data)
 637                 return NULL;
 638         if (strcmp(type, tree_type)) {
 639                 free(data);
 640                 return NULL;
 641         }
 642
 643         /* We need to either cache or return a throwaway copy */
 644
 645         if (available_ix < 0)
 646                 ent = NULL;
 647         else {
 648                 ent = pbase_tree_cache[available_ix];
 649                 my_ix = available_ix;
 650         }
 651
 652         if (!ent) {
 653                 nent = xmalloc(sizeof(*nent));
 654                 nent->temporary = (available_ix < 0);
 655         }
 656         else {
 657                 /* evict and reuse */
 658                 free(ent->tree_data);
 659                 nent = ent;
 660         }
 661         memcpy(nent->sha1, sha1, 20);
 662         nent->tree_data = data;
 663         nent->tree_size = size;
 664         nent->ref = 1;
 665         if (!nent->temporary)
 666                 pbase_tree_cache[my_ix] = nent;
 667         return nent;
 668 }
 669
 670 static void pbase_tree_put(struct pbase_tree_cache *cache)
 671 {
 672         if (!cache->temporary) {
 673                 cache->ref--;
 674                 return;
 675         }
 676         free(cache->tree_data);
 677         free(cache);
 678 }
 679
 680 static int name_cmp_len(const char *name)
 681 {
 682         int i;
 683         for (i = 0; name[i] && name[i] != '\n' && name[i] != '/'; i++)
 684                 ;
 685         return i;
 686 }
 687
 688 static void add_pbase_object(struct tree_desc *tree,
 689                              struct name_path *up,
 690                              const char *name,
 691                              int cmplen)
 692 {
 693         while (tree->size) {
 694                 const unsigned char *sha1;
 695                 const char *entry_name;
 696                 int entry_len;
 697                 unsigned mode;
 698                 unsigned long size;
 699                 char type[20];
 700
 701                 sha1 = tree_entry_extract(tree, &entry_name, &mode);
 702                 update_tree_entry(tree);
 703                 entry_len = strlen(entry_name);
 704                 if (entry_len != cmplen ||
 705                     memcmp(entry_name, name, cmplen) ||
 706                     !has_sha1_file(sha1) ||
 707                     sha1_object_info(sha1, type, &size))
 708                         continue;
 709                 if (name[cmplen] != '/') {
 710                         unsigned hash = name_hash(up, name);
 711                         add_object_entry(sha1, hash, 1);
 712                         return;
 713                 }
 714                 if (!strcmp(type, tree_type)) {
 715                         struct tree_desc sub;
 716                         struct name_path me;
 717                         struct pbase_tree_cache *tree;
 718                         const char *down = name+cmplen+1;
 719                         int downlen = name_cmp_len(down);
 720
 721                         tree = pbase_tree_get(sha1);
 722                         if (!tree)
 723                                 return;
 724                         sub.buf = tree->tree_data;
 725                         sub.size = tree->tree_size;
 726
 727                         me.up = up;
 728                         me.elem = entry_name;
 729                         me.len = entry_len;
 730                         add_pbase_object(&sub, &me, down, downlen);
 731                         pbase_tree_put(tree);
 732                 }
 733         }
 734 }
 735
 736 static unsigned *done_pbase_paths;
 737 static int done_pbase_paths_num;
 738 static int done_pbase_paths_alloc;
 739 static int done_pbase_path_pos(unsigned hash)
 740 {
 741         int lo = 0;
 742         int hi = done_pbase_paths_num;
 743         while (lo < hi) {
 744                 int mi = (hi + lo) / 2;
 745                 if (done_pbase_paths[mi] == hash)
 746                         return mi;
 747                 if (done_pbase_paths[mi] < hash)
 748                         hi = mi;
 749                 else
 750                         lo = mi + 1;
 751         }
 752         return -lo-1;
 753 }
 754
 755 static int check_pbase_path(unsigned hash)
 756 {
 757         int pos = (!done_pbase_paths) ? -1 : done_pbase_path_pos(hash);
 758         if (0 <= pos)
 759                 return 1;
 760         pos = -pos - 1;
 761         if (done_pbase_paths_alloc <= done_pbase_paths_num) {
 762                 done_pbase_paths_alloc = alloc_nr(done_pbase_paths_alloc);
 763                 done_pbase_paths = xrealloc(done_pbase_paths,
 764                                             done_pbase_paths_alloc *
 765                                             sizeof(unsigned));
 766         }
 767         done_pbase_paths_num++;
 768         if (pos < done_pbase_paths_num)
 769                 memmove(done_pbase_paths + pos + 1,
 770                         done_pbase_paths + pos,
 771                         (done_pbase_paths_num - pos - 1) * sizeof(unsigned));
 772         done_pbase_paths[pos] = hash;
 773         return 0;
 774 }
 775
 776 static void add_preferred_base_object(char *name, unsigned hash)
 777 {
 778         struct pbase_tree *it;
 779         int cmplen = name_cmp_len(name);
 780
 781         if (check_pbase_path(hash))
 782                 return;
 783
 784         for (it = pbase_tree; it; it = it->next) {
 785                 if (cmplen == 0) {
 786                         hash = name_hash(NULL, "");
 787                         add_object_entry(it->pcache.sha1, hash, 1);
 788                 }
 789                 else {
 790                         struct tree_desc tree;
 791                         tree.buf = it->pcache.tree_data;
 792                         tree.size = it->pcache.tree_size;
 793                         add_pbase_object(&tree, NULL, name, cmplen);
 794                 }
 795         }
 796 }
 797
 798 static void add_preferred_base(unsigned char *sha1)
 799 {
 800         struct pbase_tree *it;
 801         void *data;
 802         unsigned long size;
 803         unsigned char tree_sha1[20];
 804
 805         data = read_object_with_reference(sha1, tree_type, &size, tree_sha1);
 806         if (!data)
 807                 return;
 808
 809         for (it = pbase_tree; it; it = it->next) {
 810                 if (!memcmp(it->pcache.sha1, tree_sha1, 20)) {
 811                         free(data);
 812                         return;
 813                 }
 814         }
 815
 816         it = xcalloc(1, sizeof(*it));
 817         it->next = pbase_tree;
 818         pbase_tree = it;
 819
 820         memcpy(it->pcache.sha1, tree_sha1, 20);
 821         it->pcache.tree_data = data;
 822         it->pcache.tree_size = size;
 823 }
 824
 825 static void check_object(struct object_entry *entry)
 826 {
 827         char type[20];
 828
 829         if (entry->in_pack && !entry->preferred_base) {
 830                 unsigned char base[20];
 831                 unsigned long size;
 832                 struct object_entry *base_entry;
 833
 834                 /* We want in_pack_type even if we do not reuse delta.
 835                  * There is no point not reusing non-delta representations.
 836                  */
 837                 check_reuse_pack_delta(entry->in_pack,
 838                                        entry->in_pack_offset,
 839                                        base, &size,
 840                                        &entry->in_pack_type);
 841
 842                 /* Check if it is delta, and the base is also an object
 843                  * we are going to pack.  If so we will reuse the existing
 844                  * delta.
 845                  */
 846                 if (!no_reuse_delta &&
 847                     entry->in_pack_type == OBJ_DELTA &&
 848                     (base_entry = locate_object_entry(base)) &&
 849                     (!base_entry->preferred_base)) {
 850
 851                         /* Depth value does not matter - find_deltas()
 852                          * will never consider reused delta as the
 853                          * base object to deltify other objects
 854                          * against, in order to avoid circular deltas.
 855                          */
 856
 857                         /* uncompressed size of the delta data */
 858                         entry->size = entry->delta_size = size;
 859                         entry->delta = base_entry;
 860                         entry->type = OBJ_DELTA;
 861
 862                         entry->delta_sibling = base_entry->delta_child;
 863                         base_entry->delta_child = entry;
 864
 865                         return;
 866                 }
 867                 /* Otherwise we would do the usual */
 868         }
 869
 870         if (sha1_object_info(entry->sha1, type, &entry->size))
 871                 die("unable to get type of object %s",
 872                     sha1_to_hex(entry->sha1));
 873
 874         if (!strcmp(type, commit_type)) {
 875                 entry->type = OBJ_COMMIT;
 876         } else if (!strcmp(type, tree_type)) {
 877                 entry->type = OBJ_TREE;
 878         } else if (!strcmp(type, blob_type)) {
 879                 entry->type = OBJ_BLOB;
 880         } else if (!strcmp(type, tag_type)) {
 881                 entry->type = OBJ_TAG;
 882         } else
 883                 die("unable to pack object %s of type %s",
 884                     sha1_to_hex(entry->sha1), type);
 885 }
 886
 887 static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
 888 {
 889         struct object_entry *child = me->delta_child;
 890         unsigned int m = n;
 891         while (child) {
 892                 unsigned int c = check_delta_limit(child, n + 1);
 893                 if (m < c)
 894                         m = c;
 895                 child = child->delta_sibling;
 896         }
 897         return m;
 898 }
 899
 900 static void get_object_details(void)
 901 {
 902         int i;
 903         struct object_entry *entry;
 904
 905         prepare_pack_ix();
 906         for (i = 0, entry = objects; i < nr_objects; i++, entry++)
 907                 check_object(entry);
 908
 909         if (nr_objects == nr_result) {
 910                 /*
 911                  * Depth of objects that depend on the entry -- this
 912                  * is subtracted from depth-max to break too deep
 913                  * delta chain because of delta data reusing.
 914                  * However, we loosen this restriction when we know we
 915                  * are creating a thin pack -- it will have to be
 916                  * expanded on the other end anyway, so do not
 917                  * artificially cut the delta chain and let it go as
 918                  * deep as it wants.
 919                  */
 920                 for (i = 0, entry = objects; i < nr_objects; i++, entry++)
 921                         if (!entry->delta && entry->delta_child)
 922                                 entry->delta_limit =
 923                                         check_delta_limit(entry, 1);
 924         }
 925 }
 926
 927 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
 928
 929 static entry_sort_t current_sort;
 930
 931 static int sort_comparator(const void *_a, const void *_b)
 932 {
 933         struct object_entry *a = *(struct object_entry **)_a;
 934         struct object_entry *b = *(struct object_entry **)_b;
 935         return current_sort(a,b);
 936 }
 937
 938 static struct object_entry **create_sorted_list(entry_sort_t sort)
 939 {
 940         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
 941         int i;
 942
 943         for (i = 0; i < nr_objects; i++)
 944                 list[i] = objects + i;
 945         current_sort = sort;
 946         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
 947         return list;
 948 }
 949
 950 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
 951 {
 952         return memcmp(a->sha1, b->sha1, 20);
 953 }
 954
 955 static struct object_entry **create_final_object_list(void)
 956 {
 957         struct object_entry **list;
 958         int i, j;
 959
 960         for (i = nr_result = 0; i < nr_objects; i++)
 961                 if (!objects[i].preferred_base)
 962                         nr_result++;
 963         list = xmalloc(nr_result * sizeof(struct object_entry *));
 964         for (i = j = 0; i < nr_objects; i++) {
 965                 if (!objects[i].preferred_base)
 966                         list[j++] = objects + i;
 967         }
 968         current_sort = sha1_sort;
 969         qsort(list, nr_result, sizeof(struct object_entry *), sort_comparator);
 970         return list;
 971 }
 972
 973 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
 974 {
 975         if (a->type < b->type)
 976                 return -1;
 977         if (a->type > b->type)
 978                 return 1;
 979         if (a->hash < b->hash)
 980                 return -1;
 981         if (a->hash > b->hash)
 982                 return 1;
 983         if (a->preferred_base < b->preferred_base)
 984                 return -1;
 985         if (a->preferred_base > b->preferred_base)
 986                 return 1;
 987         if (a->size < b->size)
 988                 return -1;
 989         if (a->size > b->size)
 990                 return 1;
 991         return a < b ? -1 : (a > b);
 992 }
 993
 994 struct unpacked {
 995         struct object_entry *entry;
 996         void *data;
 997 };
 998
 999 /*
1000  * We search for deltas _backwards_ in a list sorted by type and
1001  * by size, so that we see progressively smaller and smaller files.
1002  * That's because we prefer deltas to be from the bigger file
1003  * to the smaller - deletes are potentially cheaper, but perhaps
1004  * more importantly, the bigger file is likely the more recent
1005  * one.
1006  */
1007 static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
1008 {
1009         struct object_entry *cur_entry = cur->entry;
1010         struct object_entry *old_entry = old->entry;
1011         unsigned long size, oldsize, delta_size, sizediff;
1012         long max_size;
1013         void *delta_buf;
1014
1015         /* Don't bother doing diffs between different types */
1016         if (cur_entry->type != old_entry->type)
1017                 return -1;
1018
1019         /* We do not compute delta to *create* objects we are not
1020          * going to pack.
1021          */
1022         if (cur_entry->preferred_base)
1023                 return -1;
1024
1025         /* If the current object is at pack edge, take the depth the
1026          * objects that depend on the current object into account --
1027          * otherwise they would become too deep.
1028          */
1029         if (cur_entry->delta_child) {
1030                 if (max_depth <= cur_entry->delta_limit)
1031                         return 0;
1032                 max_depth -= cur_entry->delta_limit;
1033         }
1034
1035         size = cur_entry->size;
1036         oldsize = old_entry->size;
1037         sizediff = oldsize > size ? oldsize - size : size - oldsize;
1038
1039         if (size < 50)
1040                 return -1;
1041         if (old_entry->depth >= max_depth)
1042                 return 0;
1043
1044         /*
1045          * NOTE!
1046          *
1047          * We always delta from the bigger to the smaller, since that's
1048          * more space-efficient (deletes don't have to say _what_ they
1049          * delete).
1050          */
1051         max_size = size / 2 - 20;
1052         if (cur_entry->delta)
1053                 max_size = cur_entry->delta_size-1;
1054         if (sizediff >= max_size)
1055                 return 0;
1056         delta_buf = diff_delta(old->data, oldsize,
1057                                cur->data, size, &delta_size, max_size);
1058         if (!delta_buf)
1059                 return 0;
1060         cur_entry->delta = old_entry;
1061         cur_entry->delta_size = delta_size;
1062         cur_entry->depth = old_entry->depth + 1;
1063         free(delta_buf);
1064         return 0;
1065 }
1066
1067 static void progress_interval(int signum)
1068 {
1069         progress_update = 1;
1070 }
1071
1072 static void find_deltas(struct object_entry **list, int window, int depth)
1073 {
1074         int i, idx;
1075         unsigned int array_size = window * sizeof(struct unpacked);
1076         struct unpacked *array = xmalloc(array_size);
1077         unsigned processed = 0;
1078         unsigned last_percent = 999;
1079
1080         memset(array, 0, array_size);
1081         i = nr_objects;
1082         idx = 0;
1083         if (progress)
1084                 fprintf(stderr, "Deltifying %d objects.\n", nr_result);
1085
1086         while (--i >= 0) {
1087                 struct object_entry *entry = list[i];
1088                 struct unpacked *n = array + idx;
1089                 unsigned long size;
1090                 char type[10];
1091                 int j;
1092
1093                 if (!entry->preferred_base)
1094                         processed++;
1095
1096                 if (progress) {
1097                         unsigned percent = processed * 100 / nr_result;
1098                         if (percent != last_percent || progress_update) {
1099                                 fprintf(stderr, "%4u%% (%u/%u) done\r",
1100                                         percent, processed, nr_result);
1101                                 progress_update = 0;
1102                                 last_percent = percent;
1103                         }
1104                 }
1105
1106                 if (entry->delta)
1107                         /* This happens if we decided to reuse existing
1108                          * delta from a pack.  "!no_reuse_delta &&" is implied.
1109                          */
1110                         continue;
1111
1112                 free(n->data);
1113                 n->entry = entry;
1114                 n->data = read_sha1_file(entry->sha1, type, &size);
1115                 if (size != entry->size)
1116                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
1117
1118                 j = window;
1119                 while (--j > 0) {
1120                         unsigned int other_idx = idx + j;
1121                         struct unpacked *m;
1122                         if (other_idx >= window)
1123                                 other_idx -= window;
1124                         m = array + other_idx;
1125                         if (!m->entry)
1126                                 break;
1127                         if (try_delta(n, m, depth) < 0)
1128                                 break;
1129                 }
1130 #if 0
1131                 /* if we made n a delta, and if n is already at max
1132                  * depth, leaving it in the window is pointless.  we
1133                  * should evict it first.
1134                  * ... in theory only; somehow this makes things worse.
1135                  */
1136                 if (entry->delta && depth <= entry->depth)
1137                         continue;
1138 #endif
1139                 idx++;
1140                 if (idx >= window)
1141                         idx = 0;
1142         }
1143
1144         if (progress)
1145                 fputc('\n', stderr);
1146
1147         for (i = 0; i < window; ++i)
1148                 free(array[i].data);
1149         free(array);
1150 }
1151
1152 static void prepare_pack(int window, int depth)
1153 {
1154         get_object_details();
1155         sorted_by_type = create_sorted_list(type_size_sort);
1156         if (window && depth)
1157                 find_deltas(sorted_by_type, window+1, depth);
1158 }
1159
1160 static int reuse_cached_pack(unsigned char *sha1, int pack_to_stdout)
1161 {
1162         static const char cache[] = "pack-cache/pack-%s.%s";
1163         char *cached_pack, *cached_idx;
1164         int ifd, ofd, ifd_ix = -1;
1165
1166         cached_pack = git_path(cache, sha1_to_hex(sha1), "pack");
1167         ifd = open(cached_pack, O_RDONLY);
1168         if (ifd < 0)
1169                 return 0;
1170
1171         if (!pack_to_stdout) {
1172                 cached_idx = git_path(cache, sha1_to_hex(sha1), "idx");
1173                 ifd_ix = open(cached_idx, O_RDONLY);
1174                 if (ifd_ix < 0) {
1175                         close(ifd);
1176                         return 0;
1177                 }
1178         }
1179
1180         if (progress)
1181                 fprintf(stderr, "Reusing %d objects pack %s\n", nr_objects,
1182                         sha1_to_hex(sha1));
1183
1184         if (pack_to_stdout) {
1185                 if (copy_fd(ifd, 1))
1186                         exit(1);
1187                 close(ifd);
1188         }
1189         else {
1190                 char name[PATH_MAX];
1191                 snprintf(name, sizeof(name),
1192                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "pack");
1193                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
1194                 if (ofd < 0)
1195                         die("unable to open %s (%s)", name, strerror(errno));
1196                 if (copy_fd(ifd, ofd))
1197                         exit(1);
1198                 close(ifd);
1199
1200                 snprintf(name, sizeof(name),
1201                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "idx");
1202                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
1203                 if (ofd < 0)
1204                         die("unable to open %s (%s)", name, strerror(errno));
1205                 if (copy_fd(ifd_ix, ofd))
1206                         exit(1);
1207                 close(ifd_ix);
1208                 puts(sha1_to_hex(sha1));
1209         }
1210
1211         return 1;
1212 }
1213
1214 static void setup_progress_signal(void)
1215 {
1216         struct sigaction sa;
1217         struct itimerval v;
1218
1219         memset(&sa, 0, sizeof(sa));
1220         sa.sa_handler = progress_interval;
1221         sigemptyset(&sa.sa_mask);
1222         sa.sa_flags = SA_RESTART;
1223         sigaction(SIGALRM, &sa, NULL);
1224
1225         v.it_interval.tv_sec = 1;
1226         v.it_interval.tv_usec = 0;
1227         v.it_value = v.it_interval;
1228         setitimer(ITIMER_REAL, &v, NULL);
1229 }
1230
1231 int main(int argc, char **argv)
1232 {
1233         SHA_CTX ctx;
1234         char line[40 + 1 + PATH_MAX + 2];
1235         int window = 10, depth = 10, pack_to_stdout = 0;
1236         struct object_entry **list;
1237         int num_preferred_base = 0;
1238         int i;
1239
1240         setup_git_directory();
1241
1242         for (i = 1; i < argc; i++) {
1243                 const char *arg = argv[i];
1244
1245                 if (*arg == '-') {
1246                         if (!strcmp("--non-empty", arg)) {
1247                                 non_empty = 1;
1248                                 continue;
1249                         }
1250                         if (!strcmp("--local", arg)) {
1251                                 local = 1;
1252                                 continue;
1253                         }
1254                         if (!strcmp("--incremental", arg)) {
1255                                 incremental = 1;
1256                                 continue;
1257                         }
1258                         if (!strncmp("--window=", arg, 9)) {
1259                                 char *end;
1260                                 window = strtoul(arg+9, &end, 0);
1261                                 if (!arg[9] || *end)
1262                                         usage(pack_usage);
1263                                 continue;
1264                         }
1265                         if (!strncmp("--depth=", arg, 8)) {
1266                                 char *end;
1267                                 depth = strtoul(arg+8, &end, 0);
1268                                 if (!arg[8] || *end)
1269                                         usage(pack_usage);
1270                                 continue;
1271                         }
1272                         if (!strcmp("-q", arg)) {
1273                                 progress = 0;
1274                                 continue;
1275                         }
1276                         if (!strcmp("--no-reuse-delta", arg)) {
1277                                 no_reuse_delta = 1;
1278                                 continue;
1279                         }
1280                         if (!strcmp("--stdout", arg)) {
1281                                 pack_to_stdout = 1;
1282                                 continue;
1283                         }
1284                         usage(pack_usage);
1285                 }
1286                 if (base_name)
1287                         usage(pack_usage);
1288                 base_name = arg;
1289         }
1290
1291         if (pack_to_stdout != !base_name)
1292                 usage(pack_usage);
1293
1294         prepare_packed_git();
1295
1296         if (progress) {
1297                 fprintf(stderr, "Generating pack...\n");
1298                 setup_progress_signal();
1299         }
1300
1301         for (;;) {
1302                 unsigned char sha1[20];
1303                 unsigned hash;
1304
1305                 if (!fgets(line, sizeof(line), stdin)) {
1306                         if (feof(stdin))
1307                                 break;
1308                         if (!ferror(stdin))
1309                                 die("fgets returned NULL, not EOF, not error!");
1310                         if (errno != EINTR)
1311                                 die("fgets: %s", strerror(errno));
1312                         clearerr(stdin);
1313                         continue;
1314                 }
1315
1316                 if (line[0] == '-') {
1317                         if (get_sha1_hex(line+1, sha1))
1318                                 die("expected edge sha1, got garbage:\n %s",
1319                                     line+1);
1320                         if (num_preferred_base++ < window)
1321                                 add_preferred_base(sha1);
1322                         continue;
1323                 }
1324                 if (get_sha1_hex(line, sha1))
1325                         die("expected sha1, got garbage:\n %s", line);
1326                 hash = name_hash(NULL, line+41);
1327                 add_preferred_base_object(line+41, hash);
1328                 add_object_entry(sha1, hash, 0);
1329         }
1330         if (progress)
1331                 fprintf(stderr, "Done counting %d objects.\n", nr_objects);
1332         sorted_by_sha = create_final_object_list();
1333         if (non_empty && !nr_result)
1334                 return 0;
1335
1336         SHA1_Init(&ctx);
1337         list = sorted_by_sha;
1338         for (i = 0; i < nr_result; i++) {
1339                 struct object_entry *entry = *list++;
1340                 SHA1_Update(&ctx, entry->sha1, 20);
1341         }
1342         SHA1_Final(object_list_sha1, &ctx);
1343         if (progress && (nr_objects != nr_result))
1344                 fprintf(stderr, "Result has %d objects.\n", nr_result);
1345
1346         if (reuse_cached_pack(object_list_sha1, pack_to_stdout))
1347                 ;
1348         else {
1349                 if (nr_result)
1350                         prepare_pack(window, depth);
1351                 if (progress && pack_to_stdout) {
1352                         /* the other end usually displays progress itself */
1353                         struct itimerval v = {{0,},};
1354                         setitimer(ITIMER_REAL, &v, NULL);
1355                         signal(SIGALRM, SIG_IGN );
1356                         progress_update = 0;
1357                 }
1358                 write_pack_file();
1359                 if (!pack_to_stdout) {
1360                         write_index_file();
1361                         puts(sha1_to_hex(object_list_sha1));
1362                 }
1363         }
1364         if (progress)
1365                 fprintf(stderr, "Total %d, written %d (delta %d), reused %d (delta %d)\n",
1366                         nr_result, written, written_delta, reused, reused_delta);
1367         return 0;
1368 }