sha1_file.con commit Merge branch 'wp/doc-filter-direction' into maint (0737975)
   1/*
   2 * GIT - The information manager from hell
   3 *
   4 * Copyright (C) Linus Torvalds, 2005
   5 *
   6 * This handles basic git sha1 object files - packing, unpacking,
   7 * creation etc.
   8 */
   9#include "cache.h"
  10#include "delta.h"
  11#include "pack.h"
  12#include "blob.h"
  13#include "commit.h"
  14#include "tag.h"
  15#include "tree.h"
  16#include "refs.h"
  17#include "pack-revindex.h"
  18#include "sha1-lookup.h"
  19
  20#ifndef O_NOATIME
  21#if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
  22#define O_NOATIME 01000000
  23#else
  24#define O_NOATIME 0
  25#endif
  26#endif
  27
  28#ifdef NO_C99_FORMAT
  29#define SZ_FMT "lu"
  30static unsigned long sz_fmt(size_t s) { return (unsigned long)s; }
  31#else
  32#define SZ_FMT "zu"
  33static size_t sz_fmt(size_t s) { return s; }
  34#endif
  35
  36const unsigned char null_sha1[20];
  37
  38static inline int offset_1st_component(const char *path)
  39{
  40        if (has_dos_drive_prefix(path))
  41                return 2 + (path[2] == '/');
  42        return *path == '/';
  43}
  44
  45int safe_create_leading_directories(char *path)
  46{
  47        char *pos = path + offset_1st_component(path);
  48        struct stat st;
  49
  50        while (pos) {
  51                pos = strchr(pos, '/');
  52                if (!pos)
  53                        break;
  54                while (*++pos == '/')
  55                        ;
  56                if (!*pos)
  57                        break;
  58                *--pos = '\0';
  59                if (!stat(path, &st)) {
  60                        /* path exists */
  61                        if (!S_ISDIR(st.st_mode)) {
  62                                *pos = '/';
  63                                return -3;
  64                        }
  65                }
  66                else if (mkdir(path, 0777)) {
  67                        *pos = '/';
  68                        return -1;
  69                }
  70                else if (adjust_shared_perm(path)) {
  71                        *pos = '/';
  72                        return -2;
  73                }
  74                *pos++ = '/';
  75        }
  76        return 0;
  77}
  78
  79int safe_create_leading_directories_const(const char *path)
  80{
  81        /* path points to cache entries, so xstrdup before messing with it */
  82        char *buf = xstrdup(path);
  83        int result = safe_create_leading_directories(buf);
  84        free(buf);
  85        return result;
  86}
  87
  88static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
  89{
  90        int i;
  91        for (i = 0; i < 20; i++) {
  92                static char hex[] = "0123456789abcdef";
  93                unsigned int val = sha1[i];
  94                char *pos = pathbuf + i*2 + (i > 0);
  95                *pos++ = hex[val >> 4];
  96                *pos = hex[val & 0xf];
  97        }
  98}
  99
 100/*
 101 * NOTE! This returns a statically allocated buffer, so you have to be
 102 * careful about using it. Do an "xstrdup()" if you need to save the
 103 * filename.
 104 *
 105 * Also note that this returns the location for creating.  Reading
 106 * SHA1 file can happen from any alternate directory listed in the
 107 * DB_ENVIRONMENT environment variable if it is not found in
 108 * the primary object database.
 109 */
 110char *sha1_file_name(const unsigned char *sha1)
 111{
 112        static char *name, *base;
 113
 114        if (!base) {
 115                const char *sha1_file_directory = get_object_directory();
 116                int len = strlen(sha1_file_directory);
 117                base = xmalloc(len + 60);
 118                memcpy(base, sha1_file_directory, len);
 119                memset(base+len, 0, 60);
 120                base[len] = '/';
 121                base[len+3] = '/';
 122                name = base + len + 1;
 123        }
 124        fill_sha1_path(name, sha1);
 125        return base;
 126}
 127
 128static char *sha1_get_pack_name(const unsigned char *sha1,
 129                                char **name, char **base, const char *which)
 130{
 131        static const char hex[] = "0123456789abcdef";
 132        char *buf;
 133        int i;
 134
 135        if (!*base) {
 136                const char *sha1_file_directory = get_object_directory();
 137                int len = strlen(sha1_file_directory);
 138                *base = xmalloc(len + 60);
 139                sprintf(*base, "%s/pack/pack-1234567890123456789012345678901234567890.%s",
 140                        sha1_file_directory, which);
 141                *name = *base + len + 11;
 142        }
 143
 144        buf = *name;
 145
 146        for (i = 0; i < 20; i++) {
 147                unsigned int val = *sha1++;
 148                *buf++ = hex[val >> 4];
 149                *buf++ = hex[val & 0xf];
 150        }
 151
 152        return *base;
 153}
 154
 155char *sha1_pack_name(const unsigned char *sha1)
 156{
 157        static char *name, *base;
 158
 159        return sha1_get_pack_name(sha1, &name, &base, "pack");
 160}
 161
 162char *sha1_pack_index_name(const unsigned char *sha1)
 163{
 164        static char *name, *base;
 165
 166        return sha1_get_pack_name(sha1, &name, &base, "idx");
 167}
 168
 169struct alternate_object_database *alt_odb_list;
 170static struct alternate_object_database **alt_odb_tail;
 171
 172static void read_info_alternates(const char * alternates, int depth);
 173
 174/*
 175 * Prepare alternate object database registry.
 176 *
 177 * The variable alt_odb_list points at the list of struct
 178 * alternate_object_database.  The elements on this list come from
 179 * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
 180 * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
 181 * whose contents is similar to that environment variable but can be
 182 * LF separated.  Its base points at a statically allocated buffer that
 183 * contains "/the/directory/corresponding/to/.git/objects/...", while
 184 * its name points just after the slash at the end of ".git/objects/"
 185 * in the example above, and has enough space to hold 40-byte hex
 186 * SHA1, an extra slash for the first level indirection, and the
 187 * terminating NUL.
 188 */
 189static int link_alt_odb_entry(const char * entry, int len, const char * relative_base, int depth)
 190{
 191        const char *objdir = get_object_directory();
 192        struct alternate_object_database *ent;
 193        struct alternate_object_database *alt;
 194        /* 43 = 40-byte + 2 '/' + terminating NUL */
 195        int pfxlen = len;
 196        int entlen = pfxlen + 43;
 197        int base_len = -1;
 198
 199        if (!is_absolute_path(entry) && relative_base) {
 200                /* Relative alt-odb */
 201                if (base_len < 0)
 202                        base_len = strlen(relative_base) + 1;
 203                entlen += base_len;
 204                pfxlen += base_len;
 205        }
 206        ent = xmalloc(sizeof(*ent) + entlen);
 207
 208        if (!is_absolute_path(entry) && relative_base) {
 209                memcpy(ent->base, relative_base, base_len - 1);
 210                ent->base[base_len - 1] = '/';
 211                memcpy(ent->base + base_len, entry, len);
 212        }
 213        else
 214                memcpy(ent->base, entry, pfxlen);
 215
 216        ent->name = ent->base + pfxlen + 1;
 217        ent->base[pfxlen + 3] = '/';
 218        ent->base[pfxlen] = ent->base[entlen-1] = 0;
 219
 220        /* Detect cases where alternate disappeared */
 221        if (!is_directory(ent->base)) {
 222                error("object directory %s does not exist; "
 223                      "check .git/objects/info/alternates.",
 224                      ent->base);
 225                free(ent);
 226                return -1;
 227        }
 228
 229        /* Prevent the common mistake of listing the same
 230         * thing twice, or object directory itself.
 231         */
 232        for (alt = alt_odb_list; alt; alt = alt->next) {
 233                if (!memcmp(ent->base, alt->base, pfxlen)) {
 234                        free(ent);
 235                        return -1;
 236                }
 237        }
 238        if (!memcmp(ent->base, objdir, pfxlen)) {
 239                free(ent);
 240                return -1;
 241        }
 242
 243        /* add the alternate entry */
 244        *alt_odb_tail = ent;
 245        alt_odb_tail = &(ent->next);
 246        ent->next = NULL;
 247
 248        /* recursively add alternates */
 249        read_info_alternates(ent->base, depth + 1);
 250
 251        ent->base[pfxlen] = '/';
 252
 253        return 0;
 254}
 255
 256static void link_alt_odb_entries(const char *alt, const char *ep, int sep,
 257                                 const char *relative_base, int depth)
 258{
 259        const char *cp, *last;
 260
 261        if (depth > 5) {
 262                error("%s: ignoring alternate object stores, nesting too deep.",
 263                                relative_base);
 264                return;
 265        }
 266
 267        last = alt;
 268        while (last < ep) {
 269                cp = last;
 270                if (cp < ep && *cp == '#') {
 271                        while (cp < ep && *cp != sep)
 272                                cp++;
 273                        last = cp + 1;
 274                        continue;
 275                }
 276                while (cp < ep && *cp != sep)
 277                        cp++;
 278                if (last != cp) {
 279                        if (!is_absolute_path(last) && depth) {
 280                                error("%s: ignoring relative alternate object store %s",
 281                                                relative_base, last);
 282                        } else {
 283                                link_alt_odb_entry(last, cp - last,
 284                                                relative_base, depth);
 285                        }
 286                }
 287                while (cp < ep && *cp == sep)
 288                        cp++;
 289                last = cp;
 290        }
 291}
 292
 293static void read_info_alternates(const char * relative_base, int depth)
 294{
 295        char *map;
 296        size_t mapsz;
 297        struct stat st;
 298        const char alt_file_name[] = "info/alternates";
 299        /* Given that relative_base is no longer than PATH_MAX,
 300           ensure that "path" has enough space to append "/", the
 301           file name, "info/alternates", and a trailing NUL.  */
 302        char path[PATH_MAX + 1 + sizeof alt_file_name];
 303        int fd;
 304
 305        sprintf(path, "%s/%s", relative_base, alt_file_name);
 306        fd = open(path, O_RDONLY);
 307        if (fd < 0)
 308                return;
 309        if (fstat(fd, &st) || (st.st_size == 0)) {
 310                close(fd);
 311                return;
 312        }
 313        mapsz = xsize_t(st.st_size);
 314        map = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, fd, 0);
 315        close(fd);
 316
 317        link_alt_odb_entries(map, map + mapsz, '\n', relative_base, depth);
 318
 319        munmap(map, mapsz);
 320}
 321
 322void add_to_alternates_file(const char *reference)
 323{
 324        struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 325        int fd = hold_lock_file_for_append(lock, git_path("objects/info/alternates"), LOCK_DIE_ON_ERROR);
 326        char *alt = mkpath("%s/objects\n", reference);
 327        write_or_die(fd, alt, strlen(alt));
 328        if (commit_lock_file(lock))
 329                die("could not close alternates file");
 330        if (alt_odb_tail)
 331                link_alt_odb_entries(alt, alt + strlen(alt), '\n', NULL, 0);
 332}
 333
 334void foreach_alt_odb(alt_odb_fn fn, void *cb)
 335{
 336        struct alternate_object_database *ent;
 337
 338        prepare_alt_odb();
 339        for (ent = alt_odb_list; ent; ent = ent->next)
 340                if (fn(ent, cb))
 341                        return;
 342}
 343
 344void prepare_alt_odb(void)
 345{
 346        const char *alt;
 347
 348        if (alt_odb_tail)
 349                return;
 350
 351        alt = getenv(ALTERNATE_DB_ENVIRONMENT);
 352        if (!alt) alt = "";
 353
 354        alt_odb_tail = &alt_odb_list;
 355        link_alt_odb_entries(alt, alt + strlen(alt), PATH_SEP, NULL, 0);
 356
 357        read_info_alternates(get_object_directory(), 0);
 358}
 359
 360static int has_loose_object_local(const unsigned char *sha1)
 361{
 362        char *name = sha1_file_name(sha1);
 363        return !access(name, F_OK);
 364}
 365
 366int has_loose_object_nonlocal(const unsigned char *sha1)
 367{
 368        struct alternate_object_database *alt;
 369        prepare_alt_odb();
 370        for (alt = alt_odb_list; alt; alt = alt->next) {
 371                fill_sha1_path(alt->name, sha1);
 372                if (!access(alt->base, F_OK))
 373                        return 1;
 374        }
 375        return 0;
 376}
 377
 378static int has_loose_object(const unsigned char *sha1)
 379{
 380        return has_loose_object_local(sha1) ||
 381               has_loose_object_nonlocal(sha1);
 382}
 383
 384static unsigned int pack_used_ctr;
 385static unsigned int pack_mmap_calls;
 386static unsigned int peak_pack_open_windows;
 387static unsigned int pack_open_windows;
 388static size_t peak_pack_mapped;
 389static size_t pack_mapped;
 390struct packed_git *packed_git;
 391
 392void pack_report(void)
 393{
 394        fprintf(stderr,
 395                "pack_report: getpagesize()            = %10" SZ_FMT "\n"
 396                "pack_report: core.packedGitWindowSize = %10" SZ_FMT "\n"
 397                "pack_report: core.packedGitLimit      = %10" SZ_FMT "\n",
 398                sz_fmt(getpagesize()),
 399                sz_fmt(packed_git_window_size),
 400                sz_fmt(packed_git_limit));
 401        fprintf(stderr,
 402                "pack_report: pack_used_ctr            = %10u\n"
 403                "pack_report: pack_mmap_calls          = %10u\n"
 404                "pack_report: pack_open_windows        = %10u / %10u\n"
 405                "pack_report: pack_mapped              = "
 406                        "%10" SZ_FMT " / %10" SZ_FMT "\n",
 407                pack_used_ctr,
 408                pack_mmap_calls,
 409                pack_open_windows, peak_pack_open_windows,
 410                sz_fmt(pack_mapped), sz_fmt(peak_pack_mapped));
 411}
 412
 413static int check_packed_git_idx(const char *path,  struct packed_git *p)
 414{
 415        void *idx_map;
 416        struct pack_idx_header *hdr;
 417        size_t idx_size;
 418        uint32_t version, nr, i, *index;
 419        int fd = open(path, O_RDONLY);
 420        struct stat st;
 421
 422        if (fd < 0)
 423                return -1;
 424        if (fstat(fd, &st)) {
 425                close(fd);
 426                return -1;
 427        }
 428        idx_size = xsize_t(st.st_size);
 429        if (idx_size < 4 * 256 + 20 + 20) {
 430                close(fd);
 431                return error("index file %s is too small", path);
 432        }
 433        idx_map = xmmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
 434        close(fd);
 435
 436        hdr = idx_map;
 437        if (hdr->idx_signature == htonl(PACK_IDX_SIGNATURE)) {
 438                version = ntohl(hdr->idx_version);
 439                if (version < 2 || version > 2) {
 440                        munmap(idx_map, idx_size);
 441                        return error("index file %s is version %"PRIu32
 442                                     " and is not supported by this binary"
 443                                     " (try upgrading GIT to a newer version)",
 444                                     path, version);
 445                }
 446        } else
 447                version = 1;
 448
 449        nr = 0;
 450        index = idx_map;
 451        if (version > 1)
 452                index += 2;  /* skip index header */
 453        for (i = 0; i < 256; i++) {
 454                uint32_t n = ntohl(index[i]);
 455                if (n < nr) {
 456                        munmap(idx_map, idx_size);
 457                        return error("non-monotonic index %s", path);
 458                }
 459                nr = n;
 460        }
 461
 462        if (version == 1) {
 463                /*
 464                 * Total size:
 465                 *  - 256 index entries 4 bytes each
 466                 *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
 467                 *  - 20-byte SHA1 of the packfile
 468                 *  - 20-byte SHA1 file checksum
 469                 */
 470                if (idx_size != 4*256 + nr * 24 + 20 + 20) {
 471                        munmap(idx_map, idx_size);
 472                        return error("wrong index v1 file size in %s", path);
 473                }
 474        } else if (version == 2) {
 475                /*
 476                 * Minimum size:
 477                 *  - 8 bytes of header
 478                 *  - 256 index entries 4 bytes each
 479                 *  - 20-byte sha1 entry * nr
 480                 *  - 4-byte crc entry * nr
 481                 *  - 4-byte offset entry * nr
 482                 *  - 20-byte SHA1 of the packfile
 483                 *  - 20-byte SHA1 file checksum
 484                 * And after the 4-byte offset table might be a
 485                 * variable sized table containing 8-byte entries
 486                 * for offsets larger than 2^31.
 487                 */
 488                unsigned long min_size = 8 + 4*256 + nr*(20 + 4 + 4) + 20 + 20;
 489                unsigned long max_size = min_size;
 490                if (nr)
 491                        max_size += (nr - 1)*8;
 492                if (idx_size < min_size || idx_size > max_size) {
 493                        munmap(idx_map, idx_size);
 494                        return error("wrong index v2 file size in %s", path);
 495                }
 496                if (idx_size != min_size &&
 497                    /*
 498                     * make sure we can deal with large pack offsets.
 499                     * 31-bit signed offset won't be enough, neither
 500                     * 32-bit unsigned one will be.
 501                     */
 502                    (sizeof(off_t) <= 4)) {
 503                        munmap(idx_map, idx_size);
 504                        return error("pack too large for current definition of off_t in %s", path);
 505                }
 506        }
 507
 508        p->index_version = version;
 509        p->index_data = idx_map;
 510        p->index_size = idx_size;
 511        p->num_objects = nr;
 512        return 0;
 513}
 514
 515int open_pack_index(struct packed_git *p)
 516{
 517        char *idx_name;
 518        int ret;
 519
 520        if (p->index_data)
 521                return 0;
 522
 523        idx_name = xstrdup(p->pack_name);
 524        strcpy(idx_name + strlen(idx_name) - strlen(".pack"), ".idx");
 525        ret = check_packed_git_idx(idx_name, p);
 526        free(idx_name);
 527        return ret;
 528}
 529
 530static void scan_windows(struct packed_git *p,
 531        struct packed_git **lru_p,
 532        struct pack_window **lru_w,
 533        struct pack_window **lru_l)
 534{
 535        struct pack_window *w, *w_l;
 536
 537        for (w_l = NULL, w = p->windows; w; w = w->next) {
 538                if (!w->inuse_cnt) {
 539                        if (!*lru_w || w->last_used < (*lru_w)->last_used) {
 540                                *lru_p = p;
 541                                *lru_w = w;
 542                                *lru_l = w_l;
 543                        }
 544                }
 545                w_l = w;
 546        }
 547}
 548
 549static int unuse_one_window(struct packed_git *current, int keep_fd)
 550{
 551        struct packed_git *p, *lru_p = NULL;
 552        struct pack_window *lru_w = NULL, *lru_l = NULL;
 553
 554        if (current)
 555                scan_windows(current, &lru_p, &lru_w, &lru_l);
 556        for (p = packed_git; p; p = p->next)
 557                scan_windows(p, &lru_p, &lru_w, &lru_l);
 558        if (lru_p) {
 559                munmap(lru_w->base, lru_w->len);
 560                pack_mapped -= lru_w->len;
 561                if (lru_l)
 562                        lru_l->next = lru_w->next;
 563                else {
 564                        lru_p->windows = lru_w->next;
 565                        if (!lru_p->windows && lru_p->pack_fd != keep_fd) {
 566                                close(lru_p->pack_fd);
 567                                lru_p->pack_fd = -1;
 568                        }
 569                }
 570                free(lru_w);
 571                pack_open_windows--;
 572                return 1;
 573        }
 574        return 0;
 575}
 576
 577void release_pack_memory(size_t need, int fd)
 578{
 579        size_t cur = pack_mapped;
 580        while (need >= (cur - pack_mapped) && unuse_one_window(NULL, fd))
 581                ; /* nothing */
 582}
 583
 584void close_pack_windows(struct packed_git *p)
 585{
 586        while (p->windows) {
 587                struct pack_window *w = p->windows;
 588
 589                if (w->inuse_cnt)
 590                        die("pack '%s' still has open windows to it",
 591                            p->pack_name);
 592                munmap(w->base, w->len);
 593                pack_mapped -= w->len;
 594                pack_open_windows--;
 595                p->windows = w->next;
 596                free(w);
 597        }
 598}
 599
 600void unuse_pack(struct pack_window **w_cursor)
 601{
 602        struct pack_window *w = *w_cursor;
 603        if (w) {
 604                w->inuse_cnt--;
 605                *w_cursor = NULL;
 606        }
 607}
 608
 609/*
 610 * This is used by git-repack in case a newly created pack happens to
 611 * contain the same set of objects as an existing one.  In that case
 612 * the resulting file might be different even if its name would be the
 613 * same.  It is best to close any reference to the old pack before it is
 614 * replaced on disk.  Of course no index pointers nor windows for given pack
 615 * must subsist at this point.  If ever objects from this pack are requested
 616 * again, the new version of the pack will be reinitialized through
 617 * reprepare_packed_git().
 618 */
 619void free_pack_by_name(const char *pack_name)
 620{
 621        struct packed_git *p, **pp = &packed_git;
 622
 623        while (*pp) {
 624                p = *pp;
 625                if (strcmp(pack_name, p->pack_name) == 0) {
 626                        clear_delta_base_cache();
 627                        close_pack_windows(p);
 628                        if (p->pack_fd != -1)
 629                                close(p->pack_fd);
 630                        if (p->index_data)
 631                                munmap((void *)p->index_data, p->index_size);
 632                        free(p->bad_object_sha1);
 633                        *pp = p->next;
 634                        free(p);
 635                        return;
 636                }
 637                pp = &p->next;
 638        }
 639}
 640
 641/*
 642 * Do not call this directly as this leaks p->pack_fd on error return;
 643 * call open_packed_git() instead.
 644 */
 645static int open_packed_git_1(struct packed_git *p)
 646{
 647        struct stat st;
 648        struct pack_header hdr;
 649        unsigned char sha1[20];
 650        unsigned char *idx_sha1;
 651        long fd_flag;
 652
 653        if (!p->index_data && open_pack_index(p))
 654                return error("packfile %s index unavailable", p->pack_name);
 655
 656        p->pack_fd = open(p->pack_name, O_RDONLY);
 657        while (p->pack_fd < 0 && errno == EMFILE && unuse_one_window(p, -1))
 658                p->pack_fd = open(p->pack_name, O_RDONLY);
 659        if (p->pack_fd < 0 || fstat(p->pack_fd, &st))
 660                return -1;
 661
 662        /* If we created the struct before we had the pack we lack size. */
 663        if (!p->pack_size) {
 664                if (!S_ISREG(st.st_mode))
 665                        return error("packfile %s not a regular file", p->pack_name);
 666                p->pack_size = st.st_size;
 667        } else if (p->pack_size != st.st_size)
 668                return error("packfile %s size changed", p->pack_name);
 669
 670        /* We leave these file descriptors open with sliding mmap;
 671         * there is no point keeping them open across exec(), though.
 672         */
 673        fd_flag = fcntl(p->pack_fd, F_GETFD, 0);
 674        if (fd_flag < 0)
 675                return error("cannot determine file descriptor flags");
 676        fd_flag |= FD_CLOEXEC;
 677        if (fcntl(p->pack_fd, F_SETFD, fd_flag) == -1)
 678                return error("cannot set FD_CLOEXEC");
 679
 680        /* Verify we recognize this pack file format. */
 681        if (read_in_full(p->pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 682                return error("file %s is far too short to be a packfile", p->pack_name);
 683        if (hdr.hdr_signature != htonl(PACK_SIGNATURE))
 684                return error("file %s is not a GIT packfile", p->pack_name);
 685        if (!pack_version_ok(hdr.hdr_version))
 686                return error("packfile %s is version %"PRIu32" and not"
 687                        " supported (try upgrading GIT to a newer version)",
 688                        p->pack_name, ntohl(hdr.hdr_version));
 689
 690        /* Verify the pack matches its index. */
 691        if (p->num_objects != ntohl(hdr.hdr_entries))
 692                return error("packfile %s claims to have %"PRIu32" objects"
 693                             " while index indicates %"PRIu32" objects",
 694                             p->pack_name, ntohl(hdr.hdr_entries),
 695                             p->num_objects);
 696        if (lseek(p->pack_fd, p->pack_size - sizeof(sha1), SEEK_SET) == -1)
 697                return error("end of packfile %s is unavailable", p->pack_name);
 698        if (read_in_full(p->pack_fd, sha1, sizeof(sha1)) != sizeof(sha1))
 699                return error("packfile %s signature is unavailable", p->pack_name);
 700        idx_sha1 = ((unsigned char *)p->index_data) + p->index_size - 40;
 701        if (hashcmp(sha1, idx_sha1))
 702                return error("packfile %s does not match index", p->pack_name);
 703        return 0;
 704}
 705
 706static int open_packed_git(struct packed_git *p)
 707{
 708        if (!open_packed_git_1(p))
 709                return 0;
 710        if (p->pack_fd != -1) {
 711                close(p->pack_fd);
 712                p->pack_fd = -1;
 713        }
 714        return -1;
 715}
 716
 717static int in_window(struct pack_window *win, off_t offset)
 718{
 719        /* We must promise at least 20 bytes (one hash) after the
 720         * offset is available from this window, otherwise the offset
 721         * is not actually in this window and a different window (which
 722         * has that one hash excess) must be used.  This is to support
 723         * the object header and delta base parsing routines below.
 724         */
 725        off_t win_off = win->offset;
 726        return win_off <= offset
 727                && (offset + 20) <= (win_off + win->len);
 728}
 729
 730unsigned char *use_pack(struct packed_git *p,
 731                struct pack_window **w_cursor,
 732                off_t offset,
 733                unsigned int *left)
 734{
 735        struct pack_window *win = *w_cursor;
 736
 737        if (p->pack_fd == -1 && open_packed_git(p))
 738                die("packfile %s cannot be accessed", p->pack_name);
 739
 740        /* Since packfiles end in a hash of their content and it's
 741         * pointless to ask for an offset into the middle of that
 742         * hash, and the in_window function above wouldn't match
 743         * don't allow an offset too close to the end of the file.
 744         */
 745        if (offset > (p->pack_size - 20))
 746                die("offset beyond end of packfile (truncated pack?)");
 747
 748        if (!win || !in_window(win, offset)) {
 749                if (win)
 750                        win->inuse_cnt--;
 751                for (win = p->windows; win; win = win->next) {
 752                        if (in_window(win, offset))
 753                                break;
 754                }
 755                if (!win) {
 756                        size_t window_align = packed_git_window_size / 2;
 757                        off_t len;
 758                        win = xcalloc(1, sizeof(*win));
 759                        win->offset = (offset / window_align) * window_align;
 760                        len = p->pack_size - win->offset;
 761                        if (len > packed_git_window_size)
 762                                len = packed_git_window_size;
 763                        win->len = (size_t)len;
 764                        pack_mapped += win->len;
 765                        while (packed_git_limit < pack_mapped
 766                                && unuse_one_window(p, p->pack_fd))
 767                                ; /* nothing */
 768                        win->base = xmmap(NULL, win->len,
 769                                PROT_READ, MAP_PRIVATE,
 770                                p->pack_fd, win->offset);
 771                        if (win->base == MAP_FAILED)
 772                                die("packfile %s cannot be mapped: %s",
 773                                        p->pack_name,
 774                                        strerror(errno));
 775                        pack_mmap_calls++;
 776                        pack_open_windows++;
 777                        if (pack_mapped > peak_pack_mapped)
 778                                peak_pack_mapped = pack_mapped;
 779                        if (pack_open_windows > peak_pack_open_windows)
 780                                peak_pack_open_windows = pack_open_windows;
 781                        win->next = p->windows;
 782                        p->windows = win;
 783                }
 784        }
 785        if (win != *w_cursor) {
 786                win->last_used = pack_used_ctr++;
 787                win->inuse_cnt++;
 788                *w_cursor = win;
 789        }
 790        offset -= win->offset;
 791        if (left)
 792                *left = win->len - xsize_t(offset);
 793        return win->base + offset;
 794}
 795
 796static struct packed_git *alloc_packed_git(int extra)
 797{
 798        struct packed_git *p = xmalloc(sizeof(*p) + extra);
 799        memset(p, 0, sizeof(*p));
 800        p->pack_fd = -1;
 801        return p;
 802}
 803
 804struct packed_git *add_packed_git(const char *path, int path_len, int local)
 805{
 806        struct stat st;
 807        struct packed_git *p = alloc_packed_git(path_len + 2);
 808
 809        /*
 810         * Make sure a corresponding .pack file exists and that
 811         * the index looks sane.
 812         */
 813        path_len -= strlen(".idx");
 814        if (path_len < 1) {
 815                free(p);
 816                return NULL;
 817        }
 818        memcpy(p->pack_name, path, path_len);
 819
 820        strcpy(p->pack_name + path_len, ".keep");
 821        if (!access(p->pack_name, F_OK))
 822                p->pack_keep = 1;
 823
 824        strcpy(p->pack_name + path_len, ".pack");
 825        if (stat(p->pack_name, &st) || !S_ISREG(st.st_mode)) {
 826                free(p);
 827                return NULL;
 828        }
 829
 830        /* ok, it looks sane as far as we can check without
 831         * actually mapping the pack file.
 832         */
 833        p->pack_size = st.st_size;
 834        p->pack_local = local;
 835        p->mtime = st.st_mtime;
 836        if (path_len < 40 || get_sha1_hex(path + path_len - 40, p->sha1))
 837                hashclr(p->sha1);
 838        return p;
 839}
 840
 841struct packed_git *parse_pack_index(unsigned char *sha1)
 842{
 843        const char *idx_path = sha1_pack_index_name(sha1);
 844        const char *path = sha1_pack_name(sha1);
 845        struct packed_git *p = alloc_packed_git(strlen(path) + 1);
 846
 847        strcpy(p->pack_name, path);
 848        hashcpy(p->sha1, sha1);
 849        if (check_packed_git_idx(idx_path, p)) {
 850                free(p);
 851                return NULL;
 852        }
 853
 854        return p;
 855}
 856
 857void install_packed_git(struct packed_git *pack)
 858{
 859        pack->next = packed_git;
 860        packed_git = pack;
 861}
 862
 863static void prepare_packed_git_one(char *objdir, int local)
 864{
 865        /* Ensure that this buffer is large enough so that we can
 866           append "/pack/" without clobbering the stack even if
 867           strlen(objdir) were PATH_MAX.  */
 868        char path[PATH_MAX + 1 + 4 + 1 + 1];
 869        int len;
 870        DIR *dir;
 871        struct dirent *de;
 872
 873        sprintf(path, "%s/pack", objdir);
 874        len = strlen(path);
 875        dir = opendir(path);
 876        while (!dir && errno == EMFILE && unuse_one_window(packed_git, -1))
 877                dir = opendir(path);
 878        if (!dir) {
 879                if (errno != ENOENT)
 880                        error("unable to open object pack directory: %s: %s",
 881                              path, strerror(errno));
 882                return;
 883        }
 884        path[len++] = '/';
 885        while ((de = readdir(dir)) != NULL) {
 886                int namelen = strlen(de->d_name);
 887                struct packed_git *p;
 888
 889                if (!has_extension(de->d_name, ".idx"))
 890                        continue;
 891
 892                if (len + namelen + 1 > sizeof(path))
 893                        continue;
 894
 895                /* Don't reopen a pack we already have. */
 896                strcpy(path + len, de->d_name);
 897                for (p = packed_git; p; p = p->next) {
 898                        if (!memcmp(path, p->pack_name, len + namelen - 4))
 899                                break;
 900                }
 901                if (p)
 902                        continue;
 903                /* See if it really is a valid .idx file with corresponding
 904                 * .pack file that we can map.
 905                 */
 906                p = add_packed_git(path, len + namelen, local);
 907                if (!p)
 908                        continue;
 909                install_packed_git(p);
 910        }
 911        closedir(dir);
 912}
 913
 914static int sort_pack(const void *a_, const void *b_)
 915{
 916        struct packed_git *a = *((struct packed_git **)a_);
 917        struct packed_git *b = *((struct packed_git **)b_);
 918        int st;
 919
 920        /*
 921         * Local packs tend to contain objects specific to our
 922         * variant of the project than remote ones.  In addition,
 923         * remote ones could be on a network mounted filesystem.
 924         * Favor local ones for these reasons.
 925         */
 926        st = a->pack_local - b->pack_local;
 927        if (st)
 928                return -st;
 929
 930        /*
 931         * Younger packs tend to contain more recent objects,
 932         * and more recent objects tend to get accessed more
 933         * often.
 934         */
 935        if (a->mtime < b->mtime)
 936                return 1;
 937        else if (a->mtime == b->mtime)
 938                return 0;
 939        return -1;
 940}
 941
 942static void rearrange_packed_git(void)
 943{
 944        struct packed_git **ary, *p;
 945        int i, n;
 946
 947        for (n = 0, p = packed_git; p; p = p->next)
 948                n++;
 949        if (n < 2)
 950                return;
 951
 952        /* prepare an array of packed_git for easier sorting */
 953        ary = xcalloc(n, sizeof(struct packed_git *));
 954        for (n = 0, p = packed_git; p; p = p->next)
 955                ary[n++] = p;
 956
 957        qsort(ary, n, sizeof(struct packed_git *), sort_pack);
 958
 959        /* link them back again */
 960        for (i = 0; i < n - 1; i++)
 961                ary[i]->next = ary[i + 1];
 962        ary[n - 1]->next = NULL;
 963        packed_git = ary[0];
 964
 965        free(ary);
 966}
 967
 968static int prepare_packed_git_run_once = 0;
 969void prepare_packed_git(void)
 970{
 971        struct alternate_object_database *alt;
 972
 973        if (prepare_packed_git_run_once)
 974                return;
 975        prepare_packed_git_one(get_object_directory(), 1);
 976        prepare_alt_odb();
 977        for (alt = alt_odb_list; alt; alt = alt->next) {
 978                alt->name[-1] = 0;
 979                prepare_packed_git_one(alt->base, 0);
 980                alt->name[-1] = '/';
 981        }
 982        rearrange_packed_git();
 983        prepare_packed_git_run_once = 1;
 984}
 985
 986void reprepare_packed_git(void)
 987{
 988        discard_revindex();
 989        prepare_packed_git_run_once = 0;
 990        prepare_packed_git();
 991}
 992
 993static void mark_bad_packed_object(struct packed_git *p,
 994                                   const unsigned char *sha1)
 995{
 996        unsigned i;
 997        for (i = 0; i < p->num_bad_objects; i++)
 998                if (!hashcmp(sha1, p->bad_object_sha1 + 20 * i))
 999                        return;
1000        p->bad_object_sha1 = xrealloc(p->bad_object_sha1, 20 * (p->num_bad_objects + 1));
1001        hashcpy(p->bad_object_sha1 + 20 * p->num_bad_objects, sha1);
1002        p->num_bad_objects++;
1003}
1004
1005static int has_packed_and_bad(const unsigned char *sha1)
1006{
1007        struct packed_git *p;
1008        unsigned i;
1009
1010        for (p = packed_git; p; p = p->next)
1011                for (i = 0; i < p->num_bad_objects; i++)
1012                        if (!hashcmp(sha1, p->bad_object_sha1 + 20 * i))
1013                                return 1;
1014        return 0;
1015}
1016
1017int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
1018{
1019        unsigned char real_sha1[20];
1020        hash_sha1_file(map, size, type, real_sha1);
1021        return hashcmp(sha1, real_sha1) ? -1 : 0;
1022}
1023
1024static int git_open_noatime(const char *name)
1025{
1026        static int sha1_file_open_flag = O_NOATIME;
1027        int fd = open(name, O_RDONLY | sha1_file_open_flag);
1028
1029        /* Might the failure be due to O_NOATIME? */
1030        if (fd < 0 && errno != ENOENT && sha1_file_open_flag) {
1031                fd = open(name, O_RDONLY);
1032                if (fd >= 0)
1033                        sha1_file_open_flag = 0;
1034        }
1035        return fd;
1036}
1037
1038static int open_sha1_file(const unsigned char *sha1)
1039{
1040        int fd;
1041        char *name = sha1_file_name(sha1);
1042        struct alternate_object_database *alt;
1043
1044        fd = git_open_noatime(name);
1045        if (fd >= 0)
1046                return fd;
1047
1048        prepare_alt_odb();
1049        errno = ENOENT;
1050        for (alt = alt_odb_list; alt; alt = alt->next) {
1051                name = alt->name;
1052                fill_sha1_path(name, sha1);
1053                fd = git_open_noatime(alt->base);
1054                if (fd >= 0)
1055                        return fd;
1056        }
1057        return -1;
1058}
1059
1060static void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
1061{
1062        void *map;
1063        int fd;
1064
1065        fd = open_sha1_file(sha1);
1066        map = NULL;
1067        if (fd >= 0) {
1068                struct stat st;
1069
1070                if (!fstat(fd, &st)) {
1071                        *size = xsize_t(st.st_size);
1072                        map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
1073                }
1074                close(fd);
1075        }
1076        return map;
1077}
1078
1079static int legacy_loose_object(unsigned char *map)
1080{
1081        unsigned int word;
1082
1083        /*
1084         * Is it a zlib-compressed buffer? If so, the first byte
1085         * must be 0x78 (15-bit window size, deflated), and the
1086         * first 16-bit word is evenly divisible by 31
1087         */
1088        word = (map[0] << 8) + map[1];
1089        if (map[0] == 0x78 && !(word % 31))
1090                return 1;
1091        else
1092                return 0;
1093}
1094
1095unsigned long unpack_object_header_buffer(const unsigned char *buf,
1096                unsigned long len, enum object_type *type, unsigned long *sizep)
1097{
1098        unsigned shift;
1099        unsigned long size, c;
1100        unsigned long used = 0;
1101
1102        c = buf[used++];
1103        *type = (c >> 4) & 7;
1104        size = c & 15;
1105        shift = 4;
1106        while (c & 0x80) {
1107                if (len <= used || bitsizeof(long) <= shift) {
1108                        error("bad object header");
1109                        return 0;
1110                }
1111                c = buf[used++];
1112                size += (c & 0x7f) << shift;
1113                shift += 7;
1114        }
1115        *sizep = size;
1116        return used;
1117}
1118
1119static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
1120{
1121        unsigned long size, used;
1122        static const char valid_loose_object_type[8] = {
1123                0, /* OBJ_EXT */
1124                1, 1, 1, 1, /* "commit", "tree", "blob", "tag" */
1125                0, /* "delta" and others are invalid in a loose object */
1126        };
1127        enum object_type type;
1128
1129        /* Get the data stream */
1130        memset(stream, 0, sizeof(*stream));
1131        stream->next_in = map;
1132        stream->avail_in = mapsize;
1133        stream->next_out = buffer;
1134        stream->avail_out = bufsiz;
1135
1136        if (legacy_loose_object(map)) {
1137                git_inflate_init(stream);
1138                return git_inflate(stream, 0);
1139        }
1140
1141
1142        /*
1143         * There used to be a second loose object header format which
1144         * was meant to mimic the in-pack format, allowing for direct
1145         * copy of the object data.  This format turned up not to be
1146         * really worth it and we don't write it any longer.  But we
1147         * can still read it.
1148         */
1149        used = unpack_object_header_buffer(map, mapsize, &type, &size);
1150        if (!used || !valid_loose_object_type[type])
1151                return -1;
1152        map += used;
1153        mapsize -= used;
1154
1155        /* Set up the stream for the rest.. */
1156        stream->next_in = map;
1157        stream->avail_in = mapsize;
1158        git_inflate_init(stream);
1159
1160        /* And generate the fake traditional header */
1161        stream->total_out = 1 + snprintf(buffer, bufsiz, "%s %lu",
1162                                         typename(type), size);
1163        return 0;
1164}
1165
1166static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
1167{
1168        int bytes = strlen(buffer) + 1;
1169        unsigned char *buf = xmallocz(size);
1170        unsigned long n;
1171        int status = Z_OK;
1172
1173        n = stream->total_out - bytes;
1174        if (n > size)
1175                n = size;
1176        memcpy(buf, (char *) buffer + bytes, n);
1177        bytes = n;
1178        if (bytes <= size) {
1179                /*
1180                 * The above condition must be (bytes <= size), not
1181                 * (bytes < size).  In other words, even though we
1182                 * expect no more output and set avail_out to zer0,
1183                 * the input zlib stream may have bytes that express
1184                 * "this concludes the stream", and we *do* want to
1185                 * eat that input.
1186                 *
1187                 * Otherwise we would not be able to test that we
1188                 * consumed all the input to reach the expected size;
1189                 * we also want to check that zlib tells us that all
1190                 * went well with status == Z_STREAM_END at the end.
1191                 */
1192                stream->next_out = buf + bytes;
1193                stream->avail_out = size - bytes;
1194                while (status == Z_OK)
1195                        status = git_inflate(stream, Z_FINISH);
1196        }
1197        if (status == Z_STREAM_END && !stream->avail_in) {
1198                git_inflate_end(stream);
1199                return buf;
1200        }
1201
1202        if (status < 0)
1203                error("corrupt loose object '%s'", sha1_to_hex(sha1));
1204        else if (stream->avail_in)
1205                error("garbage at end of loose object '%s'",
1206                      sha1_to_hex(sha1));
1207        free(buf);
1208        return NULL;
1209}
1210
1211/*
1212 * We used to just use "sscanf()", but that's actually way
1213 * too permissive for what we want to check. So do an anal
1214 * object header parse by hand.
1215 */
1216static int parse_sha1_header(const char *hdr, unsigned long *sizep)
1217{
1218        char type[10];
1219        int i;
1220        unsigned long size;
1221
1222        /*
1223         * The type can be at most ten bytes (including the
1224         * terminating '\0' that we add), and is followed by
1225         * a space.
1226         */
1227        i = 0;
1228        for (;;) {
1229                char c = *hdr++;
1230                if (c == ' ')
1231                        break;
1232                type[i++] = c;
1233                if (i >= sizeof(type))
1234                        return -1;
1235        }
1236        type[i] = 0;
1237
1238        /*
1239         * The length must follow immediately, and be in canonical
1240         * decimal format (ie "010" is not valid).
1241         */
1242        size = *hdr++ - '0';
1243        if (size > 9)
1244                return -1;
1245        if (size) {
1246                for (;;) {
1247                        unsigned long c = *hdr - '0';
1248                        if (c > 9)
1249                                break;
1250                        hdr++;
1251                        size = size * 10 + c;
1252                }
1253        }
1254        *sizep = size;
1255
1256        /*
1257         * The length must be followed by a zero byte
1258         */
1259        return *hdr ? -1 : type_from_string(type);
1260}
1261
1262static void *unpack_sha1_file(void *map, unsigned long mapsize, enum object_type *type, unsigned long *size, const unsigned char *sha1)
1263{
1264        int ret;
1265        z_stream stream;
1266        char hdr[8192];
1267
1268        ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
1269        if (ret < Z_OK || (*type = parse_sha1_header(hdr, size)) < 0)
1270                return NULL;
1271
1272        return unpack_sha1_rest(&stream, hdr, *size, sha1);
1273}
1274
1275unsigned long get_size_from_delta(struct packed_git *p,
1276                                  struct pack_window **w_curs,
1277                                  off_t curpos)
1278{
1279        const unsigned char *data;
1280        unsigned char delta_head[20], *in;
1281        z_stream stream;
1282        int st;
1283
1284        memset(&stream, 0, sizeof(stream));
1285        stream.next_out = delta_head;
1286        stream.avail_out = sizeof(delta_head);
1287
1288        git_inflate_init(&stream);
1289        do {
1290                in = use_pack(p, w_curs, curpos, &stream.avail_in);
1291                stream.next_in = in;
1292                st = git_inflate(&stream, Z_FINISH);
1293                curpos += stream.next_in - in;
1294        } while ((st == Z_OK || st == Z_BUF_ERROR) &&
1295                 stream.total_out < sizeof(delta_head));
1296        git_inflate_end(&stream);
1297        if ((st != Z_STREAM_END) && stream.total_out != sizeof(delta_head)) {
1298                error("delta data unpack-initial failed");
1299                return 0;
1300        }
1301
1302        /* Examine the initial part of the delta to figure out
1303         * the result size.
1304         */
1305        data = delta_head;
1306
1307        /* ignore base size */
1308        get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
1309
1310        /* Read the result size */
1311        return get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
1312}
1313
1314static off_t get_delta_base(struct packed_git *p,
1315                                    struct pack_window **w_curs,
1316                                    off_t *curpos,
1317                                    enum object_type type,
1318                                    off_t delta_obj_offset)
1319{
1320        unsigned char *base_info = use_pack(p, w_curs, *curpos, NULL);
1321        off_t base_offset;
1322
1323        /* use_pack() assured us we have [base_info, base_info + 20)
1324         * as a range that we can look at without walking off the
1325         * end of the mapped window.  Its actually the hash size
1326         * that is assured.  An OFS_DELTA longer than the hash size
1327         * is stupid, as then a REF_DELTA would be smaller to store.
1328         */
1329        if (type == OBJ_OFS_DELTA) {
1330                unsigned used = 0;
1331                unsigned char c = base_info[used++];
1332                base_offset = c & 127;
1333                while (c & 128) {
1334                        base_offset += 1;
1335                        if (!base_offset || MSB(base_offset, 7))
1336                                return 0;  /* overflow */
1337                        c = base_info[used++];
1338                        base_offset = (base_offset << 7) + (c & 127);
1339                }
1340                base_offset = delta_obj_offset - base_offset;
1341                if (base_offset <= 0 || base_offset >= delta_obj_offset)
1342                        return 0;  /* out of bound */
1343                *curpos += used;
1344        } else if (type == OBJ_REF_DELTA) {
1345                /* The base entry _must_ be in the same pack */
1346                base_offset = find_pack_entry_one(base_info, p);
1347                *curpos += 20;
1348        } else
1349                die("I am totally screwed");
1350        return base_offset;
1351}
1352
1353/* forward declaration for a mutually recursive function */
1354static int packed_object_info(struct packed_git *p, off_t offset,
1355                              unsigned long *sizep);
1356
1357static int packed_delta_info(struct packed_git *p,
1358                             struct pack_window **w_curs,
1359                             off_t curpos,
1360                             enum object_type type,
1361                             off_t obj_offset,
1362                             unsigned long *sizep)
1363{
1364        off_t base_offset;
1365
1366        base_offset = get_delta_base(p, w_curs, &curpos, type, obj_offset);
1367        if (!base_offset)
1368                return OBJ_BAD;
1369        type = packed_object_info(p, base_offset, NULL);
1370        if (type <= OBJ_NONE) {
1371                struct revindex_entry *revidx;
1372                const unsigned char *base_sha1;
1373                revidx = find_pack_revindex(p, base_offset);
1374                if (!revidx)
1375                        return OBJ_BAD;
1376                base_sha1 = nth_packed_object_sha1(p, revidx->nr);
1377                mark_bad_packed_object(p, base_sha1);
1378                type = sha1_object_info(base_sha1, NULL);
1379                if (type <= OBJ_NONE)
1380                        return OBJ_BAD;
1381        }
1382
1383        /* We choose to only get the type of the base object and
1384         * ignore potentially corrupt pack file that expects the delta
1385         * based on a base with a wrong size.  This saves tons of
1386         * inflate() calls.
1387         */
1388        if (sizep) {
1389                *sizep = get_size_from_delta(p, w_curs, curpos);
1390                if (*sizep == 0)
1391                        type = OBJ_BAD;
1392        }
1393
1394        return type;
1395}
1396
1397static int unpack_object_header(struct packed_git *p,
1398                                struct pack_window **w_curs,
1399                                off_t *curpos,
1400                                unsigned long *sizep)
1401{
1402        unsigned char *base;
1403        unsigned int left;
1404        unsigned long used;
1405        enum object_type type;
1406
1407        /* use_pack() assures us we have [base, base + 20) available
1408         * as a range that we can look at at.  (Its actually the hash
1409         * size that is assured.)  With our object header encoding
1410         * the maximum deflated object size is 2^137, which is just
1411         * insane, so we know won't exceed what we have been given.
1412         */
1413        base = use_pack(p, w_curs, *curpos, &left);
1414        used = unpack_object_header_buffer(base, left, &type, sizep);
1415        if (!used) {
1416                type = OBJ_BAD;
1417        } else
1418                *curpos += used;
1419
1420        return type;
1421}
1422
1423const char *packed_object_info_detail(struct packed_git *p,
1424                                      off_t obj_offset,
1425                                      unsigned long *size,
1426                                      unsigned long *store_size,
1427                                      unsigned int *delta_chain_length,
1428                                      unsigned char *base_sha1)
1429{
1430        struct pack_window *w_curs = NULL;
1431        off_t curpos;
1432        unsigned long dummy;
1433        unsigned char *next_sha1;
1434        enum object_type type;
1435        struct revindex_entry *revidx;
1436
1437        *delta_chain_length = 0;
1438        curpos = obj_offset;
1439        type = unpack_object_header(p, &w_curs, &curpos, size);
1440
1441        revidx = find_pack_revindex(p, obj_offset);
1442        *store_size = revidx[1].offset - obj_offset;
1443
1444        for (;;) {
1445                switch (type) {
1446                default:
1447                        die("pack %s contains unknown object type %d",
1448                            p->pack_name, type);
1449                case OBJ_COMMIT:
1450                case OBJ_TREE:
1451                case OBJ_BLOB:
1452                case OBJ_TAG:
1453                        unuse_pack(&w_curs);
1454                        return typename(type);
1455                case OBJ_OFS_DELTA:
1456                        obj_offset = get_delta_base(p, &w_curs, &curpos, type, obj_offset);
1457                        if (!obj_offset)
1458                                die("pack %s contains bad delta base reference of type %s",
1459                                    p->pack_name, typename(type));
1460                        if (*delta_chain_length == 0) {
1461                                revidx = find_pack_revindex(p, obj_offset);
1462                                hashcpy(base_sha1, nth_packed_object_sha1(p, revidx->nr));
1463                        }
1464                        break;
1465                case OBJ_REF_DELTA:
1466                        next_sha1 = use_pack(p, &w_curs, curpos, NULL);
1467                        if (*delta_chain_length == 0)
1468                                hashcpy(base_sha1, next_sha1);
1469                        obj_offset = find_pack_entry_one(next_sha1, p);
1470                        break;
1471                }
1472                (*delta_chain_length)++;
1473                curpos = obj_offset;
1474                type = unpack_object_header(p, &w_curs, &curpos, &dummy);
1475        }
1476}
1477
1478static int packed_object_info(struct packed_git *p, off_t obj_offset,
1479                              unsigned long *sizep)
1480{
1481        struct pack_window *w_curs = NULL;
1482        unsigned long size;
1483        off_t curpos = obj_offset;
1484        enum object_type type;
1485
1486        type = unpack_object_header(p, &w_curs, &curpos, &size);
1487
1488        switch (type) {
1489        case OBJ_OFS_DELTA:
1490        case OBJ_REF_DELTA:
1491                type = packed_delta_info(p, &w_curs, curpos,
1492                                         type, obj_offset, sizep);
1493                break;
1494        case OBJ_COMMIT:
1495        case OBJ_TREE:
1496        case OBJ_BLOB:
1497        case OBJ_TAG:
1498                if (sizep)
1499                        *sizep = size;
1500                break;
1501        default:
1502                error("unknown object type %i at offset %"PRIuMAX" in %s",
1503                      type, (uintmax_t)obj_offset, p->pack_name);
1504                type = OBJ_BAD;
1505        }
1506        unuse_pack(&w_curs);
1507        return type;
1508}
1509
1510static void *unpack_compressed_entry(struct packed_git *p,
1511                                    struct pack_window **w_curs,
1512                                    off_t curpos,
1513                                    unsigned long size)
1514{
1515        int st;
1516        z_stream stream;
1517        unsigned char *buffer, *in;
1518
1519        buffer = xmallocz(size);
1520        memset(&stream, 0, sizeof(stream));
1521        stream.next_out = buffer;
1522        stream.avail_out = size + 1;
1523
1524        git_inflate_init(&stream);
1525        do {
1526                in = use_pack(p, w_curs, curpos, &stream.avail_in);
1527                stream.next_in = in;
1528                st = git_inflate(&stream, Z_FINISH);
1529                if (!stream.avail_out)
1530                        break; /* the payload is larger than it should be */
1531                curpos += stream.next_in - in;
1532        } while (st == Z_OK || st == Z_BUF_ERROR);
1533        git_inflate_end(&stream);
1534        if ((st != Z_STREAM_END) || stream.total_out != size) {
1535                free(buffer);
1536                return NULL;
1537        }
1538
1539        return buffer;
1540}
1541
1542#define MAX_DELTA_CACHE (256)
1543
1544static size_t delta_base_cached;
1545
1546static struct delta_base_cache_lru_list {
1547        struct delta_base_cache_lru_list *prev;
1548        struct delta_base_cache_lru_list *next;
1549} delta_base_cache_lru = { &delta_base_cache_lru, &delta_base_cache_lru };
1550
1551static struct delta_base_cache_entry {
1552        struct delta_base_cache_lru_list lru;
1553        void *data;
1554        struct packed_git *p;
1555        off_t base_offset;
1556        unsigned long size;
1557        enum object_type type;
1558} delta_base_cache[MAX_DELTA_CACHE];
1559
1560static unsigned long pack_entry_hash(struct packed_git *p, off_t base_offset)
1561{
1562        unsigned long hash;
1563
1564        hash = (unsigned long)p + (unsigned long)base_offset;
1565        hash += (hash >> 8) + (hash >> 16);
1566        return hash % MAX_DELTA_CACHE;
1567}
1568
1569static void *cache_or_unpack_entry(struct packed_git *p, off_t base_offset,
1570        unsigned long *base_size, enum object_type *type, int keep_cache)
1571{
1572        void *ret;
1573        unsigned long hash = pack_entry_hash(p, base_offset);
1574        struct delta_base_cache_entry *ent = delta_base_cache + hash;
1575
1576        ret = ent->data;
1577        if (!ret || ent->p != p || ent->base_offset != base_offset)
1578                return unpack_entry(p, base_offset, type, base_size);
1579
1580        if (!keep_cache) {
1581                ent->data = NULL;
1582                ent->lru.next->prev = ent->lru.prev;
1583                ent->lru.prev->next = ent->lru.next;
1584                delta_base_cached -= ent->size;
1585        } else {
1586                ret = xmemdupz(ent->data, ent->size);
1587        }
1588        *type = ent->type;
1589        *base_size = ent->size;
1590        return ret;
1591}
1592
1593static inline void release_delta_base_cache(struct delta_base_cache_entry *ent)
1594{
1595        if (ent->data) {
1596                free(ent->data);
1597                ent->data = NULL;
1598                ent->lru.next->prev = ent->lru.prev;
1599                ent->lru.prev->next = ent->lru.next;
1600                delta_base_cached -= ent->size;
1601        }
1602}
1603
1604void clear_delta_base_cache(void)
1605{
1606        unsigned long p;
1607        for (p = 0; p < MAX_DELTA_CACHE; p++)
1608                release_delta_base_cache(&delta_base_cache[p]);
1609}
1610
1611static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
1612        void *base, unsigned long base_size, enum object_type type)
1613{
1614        unsigned long hash = pack_entry_hash(p, base_offset);
1615        struct delta_base_cache_entry *ent = delta_base_cache + hash;
1616        struct delta_base_cache_lru_list *lru;
1617
1618        release_delta_base_cache(ent);
1619        delta_base_cached += base_size;
1620
1621        for (lru = delta_base_cache_lru.next;
1622             delta_base_cached > delta_base_cache_limit
1623             && lru != &delta_base_cache_lru;
1624             lru = lru->next) {
1625                struct delta_base_cache_entry *f = (void *)lru;
1626                if (f->type == OBJ_BLOB)
1627                        release_delta_base_cache(f);
1628        }
1629        for (lru = delta_base_cache_lru.next;
1630             delta_base_cached > delta_base_cache_limit
1631             && lru != &delta_base_cache_lru;
1632             lru = lru->next) {
1633                struct delta_base_cache_entry *f = (void *)lru;
1634                release_delta_base_cache(f);
1635        }
1636
1637        ent->p = p;
1638        ent->base_offset = base_offset;
1639        ent->type = type;
1640        ent->data = base;
1641        ent->size = base_size;
1642        ent->lru.next = &delta_base_cache_lru;
1643        ent->lru.prev = delta_base_cache_lru.prev;
1644        delta_base_cache_lru.prev->next = &ent->lru;
1645        delta_base_cache_lru.prev = &ent->lru;
1646}
1647
1648static void *read_object(const unsigned char *sha1, enum object_type *type,
1649                         unsigned long *size);
1650
1651static void *unpack_delta_entry(struct packed_git *p,
1652                                struct pack_window **w_curs,
1653                                off_t curpos,
1654                                unsigned long delta_size,
1655                                off_t obj_offset,
1656                                enum object_type *type,
1657                                unsigned long *sizep)
1658{
1659        void *delta_data, *result, *base;
1660        unsigned long base_size;
1661        off_t base_offset;
1662
1663        base_offset = get_delta_base(p, w_curs, &curpos, *type, obj_offset);
1664        if (!base_offset) {
1665                error("failed to validate delta base reference "
1666                      "at offset %"PRIuMAX" from %s",
1667                      (uintmax_t)curpos, p->pack_name);
1668                return NULL;
1669        }
1670        unuse_pack(w_curs);
1671        base = cache_or_unpack_entry(p, base_offset, &base_size, type, 0);
1672        if (!base) {
1673                /*
1674                 * We're probably in deep shit, but let's try to fetch
1675                 * the required base anyway from another pack or loose.
1676                 * This is costly but should happen only in the presence
1677                 * of a corrupted pack, and is better than failing outright.
1678                 */
1679                struct revindex_entry *revidx;
1680                const unsigned char *base_sha1;
1681                revidx = find_pack_revindex(p, base_offset);
1682                if (!revidx)
1683                        return NULL;
1684                base_sha1 = nth_packed_object_sha1(p, revidx->nr);
1685                error("failed to read delta base object %s"
1686                      " at offset %"PRIuMAX" from %s",
1687                      sha1_to_hex(base_sha1), (uintmax_t)base_offset,
1688                      p->pack_name);
1689                mark_bad_packed_object(p, base_sha1);
1690                base = read_object(base_sha1, type, &base_size);
1691                if (!base)
1692                        return NULL;
1693        }
1694
1695        delta_data = unpack_compressed_entry(p, w_curs, curpos, delta_size);
1696        if (!delta_data) {
1697                error("failed to unpack compressed delta "
1698                      "at offset %"PRIuMAX" from %s",
1699                      (uintmax_t)curpos, p->pack_name);
1700                free(base);
1701                return NULL;
1702        }
1703        result = patch_delta(base, base_size,
1704                             delta_data, delta_size,
1705                             sizep);
1706        if (!result)
1707                die("failed to apply delta");
1708        free(delta_data);
1709        add_delta_base_cache(p, base_offset, base, base_size, *type);
1710        return result;
1711}
1712
1713int do_check_packed_object_crc;
1714
1715void *unpack_entry(struct packed_git *p, off_t obj_offset,
1716                   enum object_type *type, unsigned long *sizep)
1717{
1718        struct pack_window *w_curs = NULL;
1719        off_t curpos = obj_offset;
1720        void *data;
1721
1722        if (do_check_packed_object_crc && p->index_version > 1) {
1723                struct revindex_entry *revidx = find_pack_revindex(p, obj_offset);
1724                unsigned long len = revidx[1].offset - obj_offset;
1725                if (check_pack_crc(p, &w_curs, obj_offset, len, revidx->nr)) {
1726                        const unsigned char *sha1 =
1727                                nth_packed_object_sha1(p, revidx->nr);
1728                        error("bad packed object CRC for %s",
1729                              sha1_to_hex(sha1));
1730                        mark_bad_packed_object(p, sha1);
1731                        unuse_pack(&w_curs);
1732                        return NULL;
1733                }
1734        }
1735
1736        *type = unpack_object_header(p, &w_curs, &curpos, sizep);
1737        switch (*type) {
1738        case OBJ_OFS_DELTA:
1739        case OBJ_REF_DELTA:
1740                data = unpack_delta_entry(p, &w_curs, curpos, *sizep,
1741                                          obj_offset, type, sizep);
1742                break;
1743        case OBJ_COMMIT:
1744        case OBJ_TREE:
1745        case OBJ_BLOB:
1746        case OBJ_TAG:
1747                data = unpack_compressed_entry(p, &w_curs, curpos, *sizep);
1748                break;
1749        default:
1750                data = NULL;
1751                error("unknown object type %i at offset %"PRIuMAX" in %s",
1752                      *type, (uintmax_t)obj_offset, p->pack_name);
1753        }
1754        unuse_pack(&w_curs);
1755        return data;
1756}
1757
1758const unsigned char *nth_packed_object_sha1(struct packed_git *p,
1759                                            uint32_t n)
1760{
1761        const unsigned char *index = p->index_data;
1762        if (!index) {
1763                if (open_pack_index(p))
1764                        return NULL;
1765                index = p->index_data;
1766        }
1767        if (n >= p->num_objects)
1768                return NULL;
1769        index += 4 * 256;
1770        if (p->index_version == 1) {
1771                return index + 24 * n + 4;
1772        } else {
1773                index += 8;
1774                return index + 20 * n;
1775        }
1776}
1777
1778off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)
1779{
1780        const unsigned char *index = p->index_data;
1781        index += 4 * 256;
1782        if (p->index_version == 1) {
1783                return ntohl(*((uint32_t *)(index + 24 * n)));
1784        } else {
1785                uint32_t off;
1786                index += 8 + p->num_objects * (20 + 4);
1787                off = ntohl(*((uint32_t *)(index + 4 * n)));
1788                if (!(off & 0x80000000))
1789                        return off;
1790                index += p->num_objects * 4 + (off & 0x7fffffff) * 8;
1791                return (((uint64_t)ntohl(*((uint32_t *)(index + 0)))) << 32) |
1792                                   ntohl(*((uint32_t *)(index + 4)));
1793        }
1794}
1795
1796off_t find_pack_entry_one(const unsigned char *sha1,
1797                                  struct packed_git *p)
1798{
1799        const uint32_t *level1_ofs = p->index_data;
1800        const unsigned char *index = p->index_data;
1801        unsigned hi, lo, stride;
1802        static int use_lookup = -1;
1803        static int debug_lookup = -1;
1804
1805        if (debug_lookup < 0)
1806                debug_lookup = !!getenv("GIT_DEBUG_LOOKUP");
1807
1808        if (!index) {
1809                if (open_pack_index(p))
1810                        return 0;
1811                level1_ofs = p->index_data;
1812                index = p->index_data;
1813        }
1814        if (p->index_version > 1) {
1815                level1_ofs += 2;
1816                index += 8;
1817        }
1818        index += 4 * 256;
1819        hi = ntohl(level1_ofs[*sha1]);
1820        lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
1821        if (p->index_version > 1) {
1822                stride = 20;
1823        } else {
1824                stride = 24;
1825                index += 4;
1826        }
1827
1828        if (debug_lookup)
1829                printf("%02x%02x%02x... lo %u hi %u nr %"PRIu32"\n",
1830                       sha1[0], sha1[1], sha1[2], lo, hi, p->num_objects);
1831
1832        if (use_lookup < 0)
1833                use_lookup = !!getenv("GIT_USE_LOOKUP");
1834        if (use_lookup) {
1835                int pos = sha1_entry_pos(index, stride, 0,
1836                                         lo, hi, p->num_objects, sha1);
1837                if (pos < 0)
1838                        return 0;
1839                return nth_packed_object_offset(p, pos);
1840        }
1841
1842        do {
1843                unsigned mi = (lo + hi) / 2;
1844                int cmp = hashcmp(index + mi * stride, sha1);
1845
1846                if (debug_lookup)
1847                        printf("lo %u hi %u rg %u mi %u\n",
1848                               lo, hi, hi - lo, mi);
1849                if (!cmp)
1850                        return nth_packed_object_offset(p, mi);
1851                if (cmp > 0)
1852                        hi = mi;
1853                else
1854                        lo = mi+1;
1855        } while (lo < hi);
1856        return 0;
1857}
1858
1859static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
1860{
1861        static struct packed_git *last_found = (void *)1;
1862        struct packed_git *p;
1863        off_t offset;
1864
1865        prepare_packed_git();
1866        if (!packed_git)
1867                return 0;
1868        p = (last_found == (void *)1) ? packed_git : last_found;
1869
1870        do {
1871                if (p->num_bad_objects) {
1872                        unsigned i;
1873                        for (i = 0; i < p->num_bad_objects; i++)
1874                                if (!hashcmp(sha1, p->bad_object_sha1 + 20 * i))
1875                                        goto next;
1876                }
1877
1878                offset = find_pack_entry_one(sha1, p);
1879                if (offset) {
1880                        /*
1881                         * We are about to tell the caller where they can
1882                         * locate the requested object.  We better make
1883                         * sure the packfile is still here and can be
1884                         * accessed before supplying that answer, as
1885                         * it may have been deleted since the index
1886                         * was loaded!
1887                         */
1888                        if (p->pack_fd == -1 && open_packed_git(p)) {
1889                                error("packfile %s cannot be accessed", p->pack_name);
1890                                goto next;
1891                        }
1892                        e->offset = offset;
1893                        e->p = p;
1894                        hashcpy(e->sha1, sha1);
1895                        last_found = p;
1896                        return 1;
1897                }
1898
1899                next:
1900                if (p == last_found)
1901                        p = packed_git;
1902                else
1903                        p = p->next;
1904                if (p == last_found)
1905                        p = p->next;
1906        } while (p);
1907        return 0;
1908}
1909
1910struct packed_git *find_sha1_pack(const unsigned char *sha1,
1911                                  struct packed_git *packs)
1912{
1913        struct packed_git *p;
1914
1915        for (p = packs; p; p = p->next) {
1916                if (find_pack_entry_one(sha1, p))
1917                        return p;
1918        }
1919        return NULL;
1920
1921}
1922
1923static int sha1_loose_object_info(const unsigned char *sha1, unsigned long *sizep)
1924{
1925        int status;
1926        unsigned long mapsize, size;
1927        void *map;
1928        z_stream stream;
1929        char hdr[32];
1930
1931        map = map_sha1_file(sha1, &mapsize);
1932        if (!map)
1933                return error("unable to find %s", sha1_to_hex(sha1));
1934        if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
1935                status = error("unable to unpack %s header",
1936                               sha1_to_hex(sha1));
1937        else if ((status = parse_sha1_header(hdr, &size)) < 0)
1938                status = error("unable to parse %s header", sha1_to_hex(sha1));
1939        else if (sizep)
1940                *sizep = size;
1941        git_inflate_end(&stream);
1942        munmap(map, mapsize);
1943        return status;
1944}
1945
1946int sha1_object_info(const unsigned char *sha1, unsigned long *sizep)
1947{
1948        struct pack_entry e;
1949        int status;
1950
1951        if (!find_pack_entry(sha1, &e)) {
1952                /* Most likely it's a loose object. */
1953                status = sha1_loose_object_info(sha1, sizep);
1954                if (status >= 0)
1955                        return status;
1956
1957                /* Not a loose object; someone else may have just packed it. */
1958                reprepare_packed_git();
1959                if (!find_pack_entry(sha1, &e))
1960                        return status;
1961        }
1962
1963        status = packed_object_info(e.p, e.offset, sizep);
1964        if (status < 0) {
1965                mark_bad_packed_object(e.p, sha1);
1966                status = sha1_object_info(sha1, sizep);
1967        }
1968
1969        return status;
1970}
1971
1972static void *read_packed_sha1(const unsigned char *sha1,
1973                              enum object_type *type, unsigned long *size)
1974{
1975        struct pack_entry e;
1976        void *data;
1977
1978        if (!find_pack_entry(sha1, &e))
1979                return NULL;
1980        data = cache_or_unpack_entry(e.p, e.offset, size, type, 1);
1981        if (!data) {
1982                /*
1983                 * We're probably in deep shit, but let's try to fetch
1984                 * the required object anyway from another pack or loose.
1985                 * This should happen only in the presence of a corrupted
1986                 * pack, and is better than failing outright.
1987                 */
1988                error("failed to read object %s at offset %"PRIuMAX" from %s",
1989                      sha1_to_hex(sha1), (uintmax_t)e.offset, e.p->pack_name);
1990                mark_bad_packed_object(e.p, sha1);
1991                data = read_object(sha1, type, size);
1992        }
1993        return data;
1994}
1995
1996/*
1997 * This is meant to hold a *small* number of objects that you would
1998 * want read_sha1_file() to be able to return, but yet you do not want
1999 * to write them into the object store (e.g. a browse-only
2000 * application).
2001 */
2002static struct cached_object {
2003        unsigned char sha1[20];
2004        enum object_type type;
2005        void *buf;
2006        unsigned long size;
2007} *cached_objects;
2008static int cached_object_nr, cached_object_alloc;
2009
2010static struct cached_object empty_tree = {
2011        EMPTY_TREE_SHA1_BIN,
2012        OBJ_TREE,
2013        "",
2014        0
2015};
2016
2017static struct cached_object *find_cached_object(const unsigned char *sha1)
2018{
2019        int i;
2020        struct cached_object *co = cached_objects;
2021
2022        for (i = 0; i < cached_object_nr; i++, co++) {
2023                if (!hashcmp(co->sha1, sha1))
2024                        return co;
2025        }
2026        if (!hashcmp(sha1, empty_tree.sha1))
2027                return &empty_tree;
2028        return NULL;
2029}
2030
2031int pretend_sha1_file(void *buf, unsigned long len, enum object_type type,
2032                      unsigned char *sha1)
2033{
2034        struct cached_object *co;
2035
2036        hash_sha1_file(buf, len, typename(type), sha1);
2037        if (has_sha1_file(sha1) || find_cached_object(sha1))
2038                return 0;
2039        if (cached_object_alloc <= cached_object_nr) {
2040                cached_object_alloc = alloc_nr(cached_object_alloc);
2041                cached_objects = xrealloc(cached_objects,
2042                                          sizeof(*cached_objects) *
2043                                          cached_object_alloc);
2044        }
2045        co = &cached_objects[cached_object_nr++];
2046        co->size = len;
2047        co->type = type;
2048        co->buf = xmalloc(len);
2049        memcpy(co->buf, buf, len);
2050        hashcpy(co->sha1, sha1);
2051        return 0;
2052}
2053
2054static void *read_object(const unsigned char *sha1, enum object_type *type,
2055                         unsigned long *size)
2056{
2057        unsigned long mapsize;
2058        void *map, *buf;
2059        struct cached_object *co;
2060
2061        co = find_cached_object(sha1);
2062        if (co) {
2063                *type = co->type;
2064                *size = co->size;
2065                return xmemdupz(co->buf, co->size);
2066        }
2067
2068        buf = read_packed_sha1(sha1, type, size);
2069        if (buf)
2070                return buf;
2071        map = map_sha1_file(sha1, &mapsize);
2072        if (map) {
2073                buf = unpack_sha1_file(map, mapsize, type, size, sha1);
2074                munmap(map, mapsize);
2075                return buf;
2076        }
2077        reprepare_packed_git();
2078        return read_packed_sha1(sha1, type, size);
2079}
2080
2081void *read_sha1_file_repl(const unsigned char *sha1,
2082                          enum object_type *type,
2083                          unsigned long *size,
2084                          const unsigned char **replacement)
2085{
2086        const unsigned char *repl = lookup_replace_object(sha1);
2087        void *data = read_object(repl, type, size);
2088
2089        /* die if we replaced an object with one that does not exist */
2090        if (!data && repl != sha1)
2091                die("replacement %s not found for %s",
2092                    sha1_to_hex(repl), sha1_to_hex(sha1));
2093
2094        /* legacy behavior is to die on corrupted objects */
2095        if (!data && (has_loose_object(repl) || has_packed_and_bad(repl)))
2096                die("object %s is corrupted", sha1_to_hex(repl));
2097
2098        if (replacement)
2099                *replacement = repl;
2100
2101        return data;
2102}
2103
2104void *read_object_with_reference(const unsigned char *sha1,
2105                                 const char *required_type_name,
2106                                 unsigned long *size,
2107                                 unsigned char *actual_sha1_return)
2108{
2109        enum object_type type, required_type;
2110        void *buffer;
2111        unsigned long isize;
2112        unsigned char actual_sha1[20];
2113
2114        required_type = type_from_string(required_type_name);
2115        hashcpy(actual_sha1, sha1);
2116        while (1) {
2117                int ref_length = -1;
2118                const char *ref_type = NULL;
2119
2120                buffer = read_sha1_file(actual_sha1, &type, &isize);
2121                if (!buffer)
2122                        return NULL;
2123                if (type == required_type) {
2124                        *size = isize;
2125                        if (actual_sha1_return)
2126                                hashcpy(actual_sha1_return, actual_sha1);
2127                        return buffer;
2128                }
2129                /* Handle references */
2130                else if (type == OBJ_COMMIT)
2131                        ref_type = "tree ";
2132                else if (type == OBJ_TAG)
2133                        ref_type = "object ";
2134                else {
2135                        free(buffer);
2136                        return NULL;
2137                }
2138                ref_length = strlen(ref_type);
2139
2140                if (ref_length + 40 > isize ||
2141                    memcmp(buffer, ref_type, ref_length) ||
2142                    get_sha1_hex((char *) buffer + ref_length, actual_sha1)) {
2143                        free(buffer);
2144                        return NULL;
2145                }
2146                free(buffer);
2147                /* Now we have the ID of the referred-to object in
2148                 * actual_sha1.  Check again. */
2149        }
2150}
2151
2152static void write_sha1_file_prepare(const void *buf, unsigned long len,
2153                                    const char *type, unsigned char *sha1,
2154                                    char *hdr, int *hdrlen)
2155{
2156        git_SHA_CTX c;
2157
2158        /* Generate the header */
2159        *hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
2160
2161        /* Sha1.. */
2162        git_SHA1_Init(&c);
2163        git_SHA1_Update(&c, hdr, *hdrlen);
2164        git_SHA1_Update(&c, buf, len);
2165        git_SHA1_Final(sha1, &c);
2166}
2167
2168/*
2169 * Move the just written object into its final resting place.
2170 * NEEDSWORK: this should be renamed to finalize_temp_file() as
2171 * "moving" is only a part of what it does, when no patch between
2172 * master to pu changes the call sites of this function.
2173 */
2174int move_temp_to_file(const char *tmpfile, const char *filename)
2175{
2176        int ret = 0;
2177
2178        if (object_creation_mode == OBJECT_CREATION_USES_RENAMES)
2179                goto try_rename;
2180        else if (link(tmpfile, filename))
2181                ret = errno;
2182
2183        /*
2184         * Coda hack - coda doesn't like cross-directory links,
2185         * so we fall back to a rename, which will mean that it
2186         * won't be able to check collisions, but that's not a
2187         * big deal.
2188         *
2189         * The same holds for FAT formatted media.
2190         *
2191         * When this succeeds, we just return.  We have nothing
2192         * left to unlink.
2193         */
2194        if (ret && ret != EEXIST) {
2195        try_rename:
2196                if (!rename(tmpfile, filename))
2197                        goto out;
2198                ret = errno;
2199        }
2200        unlink_or_warn(tmpfile);
2201        if (ret) {
2202                if (ret != EEXIST) {
2203                        return error("unable to write sha1 filename %s: %s\n", filename, strerror(ret));
2204                }
2205                /* FIXME!!! Collision check here ? */
2206        }
2207
2208out:
2209        if (adjust_shared_perm(filename))
2210                return error("unable to set permission to '%s'", filename);
2211        return 0;
2212}
2213
2214static int write_buffer(int fd, const void *buf, size_t len)
2215{
2216        if (write_in_full(fd, buf, len) < 0)
2217                return error("file write error (%s)", strerror(errno));
2218        return 0;
2219}
2220
2221int hash_sha1_file(const void *buf, unsigned long len, const char *type,
2222                   unsigned char *sha1)
2223{
2224        char hdr[32];
2225        int hdrlen;
2226        write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
2227        return 0;
2228}
2229
2230/* Finalize a file on disk, and close it. */
2231static void close_sha1_file(int fd)
2232{
2233        if (fsync_object_files)
2234                fsync_or_die(fd, "sha1 file");
2235        if (close(fd) != 0)
2236                die_errno("error when closing sha1 file");
2237}
2238
2239/* Size of directory component, including the ending '/' */
2240static inline int directory_size(const char *filename)
2241{
2242        const char *s = strrchr(filename, '/');
2243        if (!s)
2244                return 0;
2245        return s - filename + 1;
2246}
2247
2248/*
2249 * This creates a temporary file in the same directory as the final
2250 * 'filename'
2251 *
2252 * We want to avoid cross-directory filename renames, because those
2253 * can have problems on various filesystems (FAT, NFS, Coda).
2254 */
2255static int create_tmpfile(char *buffer, size_t bufsiz, const char *filename)
2256{
2257        int fd, dirlen = directory_size(filename);
2258
2259        if (dirlen + 20 > bufsiz) {
2260                errno = ENAMETOOLONG;
2261                return -1;
2262        }
2263        memcpy(buffer, filename, dirlen);
2264        strcpy(buffer + dirlen, "tmp_obj_XXXXXX");
2265        fd = git_mkstemp_mode(buffer, 0444);
2266        if (fd < 0 && dirlen && errno == ENOENT) {
2267                /* Make sure the directory exists */
2268                memcpy(buffer, filename, dirlen);
2269                buffer[dirlen-1] = 0;
2270                if (mkdir(buffer, 0777) || adjust_shared_perm(buffer))
2271                        return -1;
2272
2273                /* Try again */
2274                strcpy(buffer + dirlen - 1, "/tmp_obj_XXXXXX");
2275                fd = git_mkstemp_mode(buffer, 0444);
2276        }
2277        return fd;
2278}
2279
2280static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
2281                              void *buf, unsigned long len, time_t mtime)
2282{
2283        int fd, ret;
2284        unsigned char compressed[4096];
2285        z_stream stream;
2286        git_SHA_CTX c;
2287        unsigned char parano_sha1[20];
2288        char *filename;
2289        static char tmpfile[PATH_MAX];
2290
2291        filename = sha1_file_name(sha1);
2292        fd = create_tmpfile(tmpfile, sizeof(tmpfile), filename);
2293        while (fd < 0 && errno == EMFILE && unuse_one_window(packed_git, -1))
2294                fd = create_tmpfile(tmpfile, sizeof(tmpfile), filename);
2295        if (fd < 0) {
2296                if (errno == EACCES)
2297                        return error("insufficient permission for adding an object to repository database %s\n", get_object_directory());
2298                else
2299                        return error("unable to create temporary sha1 filename %s: %s\n", tmpfile, strerror(errno));
2300        }
2301
2302        /* Set it up */
2303        memset(&stream, 0, sizeof(stream));
2304        deflateInit(&stream, zlib_compression_level);
2305        stream.next_out = compressed;
2306        stream.avail_out = sizeof(compressed);
2307        git_SHA1_Init(&c);
2308
2309        /* First header.. */
2310        stream.next_in = (unsigned char *)hdr;
2311        stream.avail_in = hdrlen;
2312        while (deflate(&stream, 0) == Z_OK)
2313                /* nothing */;
2314        git_SHA1_Update(&c, hdr, hdrlen);
2315
2316        /* Then the data itself.. */
2317        stream.next_in = buf;
2318        stream.avail_in = len;
2319        do {
2320                unsigned char *in0 = stream.next_in;
2321                ret = deflate(&stream, Z_FINISH);
2322                git_SHA1_Update(&c, in0, stream.next_in - in0);
2323                if (write_buffer(fd, compressed, stream.next_out - compressed) < 0)
2324                        die("unable to write sha1 file");
2325                stream.next_out = compressed;
2326                stream.avail_out = sizeof(compressed);
2327        } while (ret == Z_OK);
2328
2329        if (ret != Z_STREAM_END)
2330                die("unable to deflate new object %s (%d)", sha1_to_hex(sha1), ret);
2331        ret = deflateEnd(&stream);
2332        if (ret != Z_OK)
2333                die("deflateEnd on object %s failed (%d)", sha1_to_hex(sha1), ret);
2334        git_SHA1_Final(parano_sha1, &c);
2335        if (hashcmp(sha1, parano_sha1) != 0)
2336                die("confused by unstable object source data for %s", sha1_to_hex(sha1));
2337
2338        close_sha1_file(fd);
2339
2340        if (mtime) {
2341                struct utimbuf utb;
2342                utb.actime = mtime;
2343                utb.modtime = mtime;
2344                if (utime(tmpfile, &utb) < 0)
2345                        warning("failed utime() on %s: %s",
2346                                tmpfile, strerror(errno));
2347        }
2348
2349        return move_temp_to_file(tmpfile, filename);
2350}
2351
2352int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
2353{
2354        unsigned char sha1[20];
2355        char hdr[32];
2356        int hdrlen;
2357
2358        /* Normally if we have it in the pack then we do not bother writing
2359         * it out into .git/objects/??/?{38} file.
2360         */
2361        write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
2362        if (returnsha1)
2363                hashcpy(returnsha1, sha1);
2364        if (has_sha1_file(sha1))
2365                return 0;
2366        return write_loose_object(sha1, hdr, hdrlen, buf, len, 0);
2367}
2368
2369int force_object_loose(const unsigned char *sha1, time_t mtime)
2370{
2371        void *buf;
2372        unsigned long len;
2373        enum object_type type;
2374        char hdr[32];
2375        int hdrlen;
2376        int ret;
2377
2378        if (has_loose_object(sha1))
2379                return 0;
2380        buf = read_packed_sha1(sha1, &type, &len);
2381        if (!buf)
2382                return error("cannot read sha1_file for %s", sha1_to_hex(sha1));
2383        hdrlen = sprintf(hdr, "%s %lu", typename(type), len) + 1;
2384        ret = write_loose_object(sha1, hdr, hdrlen, buf, len, mtime);
2385        free(buf);
2386
2387        return ret;
2388}
2389
2390int has_pack_index(const unsigned char *sha1)
2391{
2392        struct stat st;
2393        if (stat(sha1_pack_index_name(sha1), &st))
2394                return 0;
2395        return 1;
2396}
2397
2398int has_sha1_pack(const unsigned char *sha1)
2399{
2400        struct pack_entry e;
2401        return find_pack_entry(sha1, &e);
2402}
2403
2404int has_sha1_file(const unsigned char *sha1)
2405{
2406        struct pack_entry e;
2407
2408        if (find_pack_entry(sha1, &e))
2409                return 1;
2410        return has_loose_object(sha1);
2411}
2412
2413static int index_mem(unsigned char *sha1, void *buf, size_t size,
2414                     int write_object, enum object_type type, const char *path)
2415{
2416        int ret, re_allocated = 0;
2417
2418        if (!type)
2419                type = OBJ_BLOB;
2420
2421        /*
2422         * Convert blobs to git internal format
2423         */
2424        if ((type == OBJ_BLOB) && path) {
2425                struct strbuf nbuf = STRBUF_INIT;
2426                if (convert_to_git(path, buf, size, &nbuf,
2427                                   write_object ? safe_crlf : 0)) {
2428                        buf = strbuf_detach(&nbuf, &size);
2429                        re_allocated = 1;
2430                }
2431        }
2432
2433        if (write_object)
2434                ret = write_sha1_file(buf, size, typename(type), sha1);
2435        else
2436                ret = hash_sha1_file(buf, size, typename(type), sha1);
2437        if (re_allocated)
2438                free(buf);
2439        return ret;
2440}
2441
2442#define SMALL_FILE_SIZE (32*1024)
2443
2444int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object,
2445             enum object_type type, const char *path)
2446{
2447        int ret;
2448        size_t size = xsize_t(st->st_size);
2449
2450        if (!S_ISREG(st->st_mode)) {
2451                struct strbuf sbuf = STRBUF_INIT;
2452                if (strbuf_read(&sbuf, fd, 4096) >= 0)
2453                        ret = index_mem(sha1, sbuf.buf, sbuf.len, write_object,
2454                                        type, path);
2455                else
2456                        ret = -1;
2457                strbuf_release(&sbuf);
2458        } else if (size <= SMALL_FILE_SIZE) {
2459                char *buf = xmalloc(size);
2460                if (size == read_in_full(fd, buf, size))
2461                        ret = index_mem(sha1, buf, size, write_object, type,
2462                                        path);
2463                else
2464                        ret = error("short read %s", strerror(errno));
2465                free(buf);
2466        } else if (size) {
2467                void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
2468                ret = index_mem(sha1, buf, size, write_object, type, path);
2469                munmap(buf, size);
2470        } else
2471                ret = index_mem(sha1, NULL, size, write_object, type, path);
2472        close(fd);
2473        return ret;
2474}
2475
2476int index_path(unsigned char *sha1, const char *path, struct stat *st, int write_object)
2477{
2478        int fd;
2479        struct strbuf sb = STRBUF_INIT;
2480
2481        switch (st->st_mode & S_IFMT) {
2482        case S_IFREG:
2483                fd = open(path, O_RDONLY);
2484                if (fd < 0)
2485                        return error("open(\"%s\"): %s", path,
2486                                     strerror(errno));
2487                if (index_fd(sha1, fd, st, write_object, OBJ_BLOB, path) < 0)
2488                        return error("%s: failed to insert into database",
2489                                     path);
2490                break;
2491        case S_IFLNK:
2492                if (strbuf_readlink(&sb, path, st->st_size)) {
2493                        char *errstr = strerror(errno);
2494                        return error("readlink(\"%s\"): %s", path,
2495                                     errstr);
2496                }
2497                if (!write_object)
2498                        hash_sha1_file(sb.buf, sb.len, blob_type, sha1);
2499                else if (write_sha1_file(sb.buf, sb.len, blob_type, sha1))
2500                        return error("%s: failed to insert into database",
2501                                     path);
2502                strbuf_release(&sb);
2503                break;
2504        case S_IFDIR:
2505                return resolve_gitlink_ref(path, "HEAD", sha1);
2506        default:
2507                return error("%s: unsupported file type", path);
2508        }
2509        return 0;
2510}
2511
2512int read_pack_header(int fd, struct pack_header *header)
2513{
2514        if (read_in_full(fd, header, sizeof(*header)) < sizeof(*header))
2515                /* "eof before pack header was fully read" */
2516                return PH_ERROR_EOF;
2517
2518        if (header->hdr_signature != htonl(PACK_SIGNATURE))
2519                /* "protocol error (pack signature mismatch detected)" */
2520                return PH_ERROR_PACK_SIGNATURE;
2521        if (!pack_version_ok(header->hdr_version))
2522                /* "protocol error (pack version unsupported)" */
2523                return PH_ERROR_PROTOCOL;
2524        return 0;
2525}