Andrew's git / gitweb.git / sha1_file.c
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sha1_file.con commit Move signal setting into service_loop() (9220282)
   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 <sys/types.h>
  10#include <dirent.h>
  11#include "cache.h"
  12#include "delta.h"
  13#include "pack.h"
  14
  15#ifndef O_NOATIME
  16#if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
  17#define O_NOATIME 01000000
  18#else
  19#define O_NOATIME 0
  20#endif
  21#endif
  22
  23static unsigned int sha1_file_open_flag = O_NOATIME;
  24
  25static unsigned hexval(char c)
  26{
  27        if (c >= '0' && c <= '9')
  28                return c - '0';
  29        if (c >= 'a' && c <= 'f')
  30                return c - 'a' + 10;
  31        if (c >= 'A' && c <= 'F')
  32                return c - 'A' + 10;
  33        return ~0;
  34}
  35
  36int get_sha1_hex(const char *hex, unsigned char *sha1)
  37{
  38        int i;
  39        for (i = 0; i < 20; i++) {
  40                unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  41                if (val & ~0xff)
  42                        return -1;
  43                *sha1++ = val;
  44                hex += 2;
  45        }
  46        return 0;
  47}
  48
  49static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir,
  50        *git_graft_file;
  51static void setup_git_env(void)
  52{
  53        git_dir = getenv(GIT_DIR_ENVIRONMENT);
  54        if (!git_dir)
  55                git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
  56        git_object_dir = getenv(DB_ENVIRONMENT);
  57        if (!git_object_dir) {
  58                git_object_dir = xmalloc(strlen(git_dir) + 9);
  59                sprintf(git_object_dir, "%s/objects", git_dir);
  60        }
  61        git_refs_dir = xmalloc(strlen(git_dir) + 6);
  62        sprintf(git_refs_dir, "%s/refs", git_dir);
  63        git_index_file = getenv(INDEX_ENVIRONMENT);
  64        if (!git_index_file) {
  65                git_index_file = xmalloc(strlen(git_dir) + 7);
  66                sprintf(git_index_file, "%s/index", git_dir);
  67        }
  68        git_graft_file = getenv(GRAFT_ENVIRONMENT);
  69        if (!git_graft_file)
  70                git_graft_file = strdup(git_path("info/grafts"));
  71}
  72
  73char *get_git_dir(void)
  74{
  75        if (!git_dir)
  76                setup_git_env();
  77        return git_dir;
  78}
  79
  80char *get_object_directory(void)
  81{
  82        if (!git_object_dir)
  83                setup_git_env();
  84        return git_object_dir;
  85}
  86
  87char *get_refs_directory(void)
  88{
  89        if (!git_refs_dir)
  90                setup_git_env();
  91        return git_refs_dir;
  92}
  93
  94char *get_index_file(void)
  95{
  96        if (!git_index_file)
  97                setup_git_env();
  98        return git_index_file;
  99}
 100
 101char *get_graft_file(void)
 102{
 103        if (!git_graft_file)
 104                setup_git_env();
 105        return git_graft_file;
 106}
 107
 108int safe_create_leading_directories(char *path)
 109{
 110        char *pos = path;
 111
 112        while (pos) {
 113                pos = strchr(pos, '/');
 114                if (!pos)
 115                        break;
 116                *pos = 0;
 117                if (mkdir(path, 0777) < 0)
 118                        if (errno != EEXIST) {
 119                                *pos = '/';
 120                                return -1;
 121                        }
 122                *pos++ = '/';
 123        }
 124        return 0;
 125}
 126
 127char * sha1_to_hex(const unsigned char *sha1)
 128{
 129        static char buffer[50];
 130        static const char hex[] = "0123456789abcdef";
 131        char *buf = buffer;
 132        int i;
 133
 134        for (i = 0; i < 20; i++) {
 135                unsigned int val = *sha1++;
 136                *buf++ = hex[val >> 4];
 137                *buf++ = hex[val & 0xf];
 138        }
 139        return buffer;
 140}
 141
 142static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 143{
 144        int i;
 145        for (i = 0; i < 20; i++) {
 146                static char hex[] = "0123456789abcdef";
 147                unsigned int val = sha1[i];
 148                char *pos = pathbuf + i*2 + (i > 0);
 149                *pos++ = hex[val >> 4];
 150                *pos = hex[val & 0xf];
 151        }
 152}
 153
 154/*
 155 * NOTE! This returns a statically allocated buffer, so you have to be
 156 * careful about using it. Do a "strdup()" if you need to save the
 157 * filename.
 158 *
 159 * Also note that this returns the location for creating.  Reading
 160 * SHA1 file can happen from any alternate directory listed in the
 161 * DB_ENVIRONMENT environment variable if it is not found in
 162 * the primary object database.
 163 */
 164char *sha1_file_name(const unsigned char *sha1)
 165{
 166        static char *name, *base;
 167
 168        if (!base) {
 169                const char *sha1_file_directory = get_object_directory();
 170                int len = strlen(sha1_file_directory);
 171                base = xmalloc(len + 60);
 172                memcpy(base, sha1_file_directory, len);
 173                memset(base+len, 0, 60);
 174                base[len] = '/';
 175                base[len+3] = '/';
 176                name = base + len + 1;
 177        }
 178        fill_sha1_path(name, sha1);
 179        return base;
 180}
 181
 182char *sha1_pack_name(const unsigned char *sha1)
 183{
 184        static const char hex[] = "0123456789abcdef";
 185        static char *name, *base, *buf;
 186        int i;
 187
 188        if (!base) {
 189                const char *sha1_file_directory = get_object_directory();
 190                int len = strlen(sha1_file_directory);
 191                base = xmalloc(len + 60);
 192                sprintf(base, "%s/pack/pack-1234567890123456789012345678901234567890.pack", sha1_file_directory);
 193                name = base + len + 11;
 194        }
 195
 196        buf = name;
 197
 198        for (i = 0; i < 20; i++) {
 199                unsigned int val = *sha1++;
 200                *buf++ = hex[val >> 4];
 201                *buf++ = hex[val & 0xf];
 202        }
 203        
 204        return base;
 205}
 206
 207char *sha1_pack_index_name(const unsigned char *sha1)
 208{
 209        static const char hex[] = "0123456789abcdef";
 210        static char *name, *base, *buf;
 211        int i;
 212
 213        if (!base) {
 214                const char *sha1_file_directory = get_object_directory();
 215                int len = strlen(sha1_file_directory);
 216                base = xmalloc(len + 60);
 217                sprintf(base, "%s/pack/pack-1234567890123456789012345678901234567890.idx", sha1_file_directory);
 218                name = base + len + 11;
 219        }
 220
 221        buf = name;
 222
 223        for (i = 0; i < 20; i++) {
 224                unsigned int val = *sha1++;
 225                *buf++ = hex[val >> 4];
 226                *buf++ = hex[val & 0xf];
 227        }
 228        
 229        return base;
 230}
 231
 232struct alternate_object_database *alt_odb_list;
 233static struct alternate_object_database **alt_odb_tail;
 234
 235/*
 236 * Prepare alternate object database registry.
 237 *
 238 * The variable alt_odb_list points at the list of struct
 239 * alternate_object_database.  The elements on this list come from
 240 * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
 241 * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
 242 * whose contents is exactly in the same format as that environment
 243 * variable.  Its base points at a statically allocated buffer that
 244 * contains "/the/directory/corresponding/to/.git/objects/...", while
 245 * its name points just after the slash at the end of ".git/objects/"
 246 * in the example above, and has enough space to hold 40-byte hex
 247 * SHA1, an extra slash for the first level indirection, and the
 248 * terminating NUL.
 249 */
 250static void link_alt_odb_entries(const char *alt, const char *ep, int sep,
 251                                 const char *relative_base)
 252{
 253        const char *cp, *last;
 254        struct alternate_object_database *ent;
 255        int base_len = -1;
 256
 257        last = alt;
 258        while (last < ep) {
 259                cp = last;
 260                if (cp < ep && *cp == '#') {
 261                        while (cp < ep && *cp != sep)
 262                                cp++;
 263                        last = cp + 1;
 264                        continue;
 265                }
 266                for ( ; cp < ep && *cp != sep; cp++)
 267                        ;
 268                if (last != cp) {
 269                        /* 43 = 40-byte + 2 '/' + terminating NUL */
 270                        int pfxlen = cp - last;
 271                        int entlen = pfxlen + 43;
 272
 273                        if (*last != '/' && relative_base) {
 274                                /* Relative alt-odb */
 275                                if (base_len < 0)
 276                                        base_len = strlen(relative_base) + 1;
 277                                entlen += base_len;
 278                                pfxlen += base_len;
 279                        }
 280                        ent = xmalloc(sizeof(*ent) + entlen);
 281                        *alt_odb_tail = ent;
 282                        alt_odb_tail = &(ent->next);
 283                        ent->next = NULL;
 284                        if (*last != '/' && relative_base) {
 285                                memcpy(ent->base, relative_base, base_len - 1);
 286                                ent->base[base_len - 1] = '/';
 287                                memcpy(ent->base + base_len,
 288                                       last, cp - last);
 289                        }
 290                        else
 291                                memcpy(ent->base, last, pfxlen);
 292                        ent->name = ent->base + pfxlen + 1;
 293                        ent->base[pfxlen] = ent->base[pfxlen + 3] = '/';
 294                        ent->base[entlen-1] = 0;
 295                }
 296                while (cp < ep && *cp == sep)
 297                        cp++;
 298                last = cp;
 299        }
 300}
 301
 302void prepare_alt_odb(void)
 303{
 304        char path[PATH_MAX];
 305        char *map;
 306        int fd;
 307        struct stat st;
 308        char *alt;
 309
 310        alt = getenv(ALTERNATE_DB_ENVIRONMENT);
 311        if (!alt) alt = "";
 312
 313        if (alt_odb_tail)
 314                return;
 315        alt_odb_tail = &alt_odb_list;
 316        link_alt_odb_entries(alt, alt + strlen(alt), ':', NULL);
 317
 318        sprintf(path, "%s/info/alternates", get_object_directory());
 319        fd = open(path, O_RDONLY);
 320        if (fd < 0)
 321                return;
 322        if (fstat(fd, &st) || (st.st_size == 0)) {
 323                close(fd);
 324                return;
 325        }
 326        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 327        close(fd);
 328        if (map == MAP_FAILED)
 329                return;
 330
 331        link_alt_odb_entries(map, map + st.st_size, '\n',
 332                             get_object_directory());
 333        munmap(map, st.st_size);
 334}
 335
 336static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 337{
 338        char *name = sha1_file_name(sha1);
 339        struct alternate_object_database *alt;
 340
 341        if (!stat(name, st))
 342                return name;
 343        prepare_alt_odb();
 344        for (alt = alt_odb_list; alt; alt = alt->next) {
 345                name = alt->name;
 346                fill_sha1_path(name, sha1);
 347                if (!stat(alt->base, st))
 348                        return alt->base;
 349        }
 350        return NULL;
 351}
 352
 353#define PACK_MAX_SZ (1<<26)
 354static int pack_used_ctr;
 355static unsigned long pack_mapped;
 356struct packed_git *packed_git;
 357
 358static int check_packed_git_idx(const char *path, unsigned long *idx_size_,
 359                                void **idx_map_)
 360{
 361        void *idx_map;
 362        unsigned int *index;
 363        unsigned long idx_size;
 364        int nr, i;
 365        int fd = open(path, O_RDONLY);
 366        struct stat st;
 367        if (fd < 0)
 368                return -1;
 369        if (fstat(fd, &st)) {
 370                close(fd);
 371                return -1;
 372        }
 373        idx_size = st.st_size;
 374        idx_map = mmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
 375        close(fd);
 376        if (idx_map == MAP_FAILED)
 377                return -1;
 378
 379        index = idx_map;
 380        *idx_map_ = idx_map;
 381        *idx_size_ = idx_size;
 382
 383        /* check index map */
 384        if (idx_size < 4*256 + 20 + 20)
 385                return error("index file too small");
 386        nr = 0;
 387        for (i = 0; i < 256; i++) {
 388                unsigned int n = ntohl(index[i]);
 389                if (n < nr)
 390                        return error("non-monotonic index");
 391                nr = n;
 392        }
 393
 394        /*
 395         * Total size:
 396         *  - 256 index entries 4 bytes each
 397         *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
 398         *  - 20-byte SHA1 of the packfile
 399         *  - 20-byte SHA1 file checksum
 400         */
 401        if (idx_size != 4*256 + nr * 24 + 20 + 20)
 402                return error("wrong index file size");
 403
 404        return 0;
 405}
 406
 407static int unuse_one_packed_git(void)
 408{
 409        struct packed_git *p, *lru = NULL;
 410
 411        for (p = packed_git; p; p = p->next) {
 412                if (p->pack_use_cnt || !p->pack_base)
 413                        continue;
 414                if (!lru || p->pack_last_used < lru->pack_last_used)
 415                        lru = p;
 416        }
 417        if (!lru)
 418                return 0;
 419        munmap(lru->pack_base, lru->pack_size);
 420        lru->pack_base = NULL;
 421        return 1;
 422}
 423
 424void unuse_packed_git(struct packed_git *p)
 425{
 426        p->pack_use_cnt--;
 427}
 428
 429int use_packed_git(struct packed_git *p)
 430{
 431        if (!p->pack_size) {
 432                struct stat st;
 433                // We created the struct before we had the pack
 434                stat(p->pack_name, &st);
 435                if (!S_ISREG(st.st_mode))
 436                        die("packfile %s not a regular file", p->pack_name);
 437                p->pack_size = st.st_size;
 438        }
 439        if (!p->pack_base) {
 440                int fd;
 441                struct stat st;
 442                void *map;
 443
 444                pack_mapped += p->pack_size;
 445                while (PACK_MAX_SZ < pack_mapped && unuse_one_packed_git())
 446                        ; /* nothing */
 447                fd = open(p->pack_name, O_RDONLY);
 448                if (fd < 0)
 449                        die("packfile %s cannot be opened", p->pack_name);
 450                if (fstat(fd, &st)) {
 451                        close(fd);
 452                        die("packfile %s cannot be opened", p->pack_name);
 453                }
 454                if (st.st_size != p->pack_size)
 455                        die("packfile %s size mismatch.", p->pack_name);
 456                map = mmap(NULL, p->pack_size, PROT_READ, MAP_PRIVATE, fd, 0);
 457                close(fd);
 458                if (map == MAP_FAILED)
 459                        die("packfile %s cannot be mapped.", p->pack_name);
 460                p->pack_base = map;
 461
 462                /* Check if the pack file matches with the index file.
 463                 * this is cheap.
 464                 */
 465                if (memcmp((char*)(p->index_base) + p->index_size - 40,
 466                           p->pack_base + p->pack_size - 20, 20)) {
 467                              
 468                        die("packfile %s does not match index.", p->pack_name);
 469                }
 470        }
 471        p->pack_last_used = pack_used_ctr++;
 472        p->pack_use_cnt++;
 473        return 0;
 474}
 475
 476struct packed_git *add_packed_git(char *path, int path_len)
 477{
 478        struct stat st;
 479        struct packed_git *p;
 480        unsigned long idx_size;
 481        void *idx_map;
 482
 483        if (check_packed_git_idx(path, &idx_size, &idx_map))
 484                return NULL;
 485
 486        /* do we have a corresponding .pack file? */
 487        strcpy(path + path_len - 4, ".pack");
 488        if (stat(path, &st) || !S_ISREG(st.st_mode)) {
 489                munmap(idx_map, idx_size);
 490                return NULL;
 491        }
 492        /* ok, it looks sane as far as we can check without
 493         * actually mapping the pack file.
 494         */
 495        p = xmalloc(sizeof(*p) + path_len + 2);
 496        strcpy(p->pack_name, path);
 497        p->index_size = idx_size;
 498        p->pack_size = st.st_size;
 499        p->index_base = idx_map;
 500        p->next = NULL;
 501        p->pack_base = NULL;
 502        p->pack_last_used = 0;
 503        p->pack_use_cnt = 0;
 504        return p;
 505}
 506
 507struct packed_git *parse_pack_index(unsigned char *sha1)
 508{
 509        char *path = sha1_pack_index_name(sha1);
 510        return parse_pack_index_file(sha1, path);
 511}
 512
 513struct packed_git *parse_pack_index_file(const unsigned char *sha1, char *idx_path)
 514{
 515        struct packed_git *p;
 516        unsigned long idx_size;
 517        void *idx_map;
 518        char *path;
 519
 520        if (check_packed_git_idx(idx_path, &idx_size, &idx_map))
 521                return NULL;
 522
 523        path = sha1_pack_name(sha1);
 524
 525        p = xmalloc(sizeof(*p) + strlen(path) + 2);
 526        strcpy(p->pack_name, path);
 527        p->index_size = idx_size;
 528        p->pack_size = 0;
 529        p->index_base = idx_map;
 530        p->next = NULL;
 531        p->pack_base = NULL;
 532        p->pack_last_used = 0;
 533        p->pack_use_cnt = 0;
 534        memcpy(p->sha1, sha1, 20);
 535        return p;
 536}
 537
 538void install_packed_git(struct packed_git *pack)
 539{
 540        pack->next = packed_git;
 541        packed_git = pack;
 542}
 543
 544static void prepare_packed_git_one(char *objdir)
 545{
 546        char path[PATH_MAX];
 547        int len;
 548        DIR *dir;
 549        struct dirent *de;
 550
 551        sprintf(path, "%s/pack", objdir);
 552        len = strlen(path);
 553        dir = opendir(path);
 554        if (!dir)
 555                return;
 556        path[len++] = '/';
 557        while ((de = readdir(dir)) != NULL) {
 558                int namelen = strlen(de->d_name);
 559                struct packed_git *p;
 560
 561                if (strcmp(de->d_name + namelen - 4, ".idx"))
 562                        continue;
 563
 564                /* we have .idx.  Is it a file we can map? */
 565                strcpy(path + len, de->d_name);
 566                p = add_packed_git(path, len + namelen);
 567                if (!p)
 568                        continue;
 569                p->next = packed_git;
 570                packed_git = p;
 571        }
 572        closedir(dir);
 573}
 574
 575void prepare_packed_git(void)
 576{
 577        static int run_once = 0;
 578        struct alternate_object_database *alt;
 579
 580        if (run_once)
 581                return;
 582        prepare_packed_git_one(get_object_directory());
 583        prepare_alt_odb();
 584        for (alt = alt_odb_list; alt; alt = alt->next) {
 585                alt->name[0] = 0;
 586                prepare_packed_git_one(alt->base);
 587        }
 588        run_once = 1;
 589}
 590
 591int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
 592{
 593        char header[100];
 594        unsigned char real_sha1[20];
 595        SHA_CTX c;
 596
 597        SHA1_Init(&c);
 598        SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 599        SHA1_Update(&c, map, size);
 600        SHA1_Final(real_sha1, &c);
 601        return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 602}
 603
 604static void *map_sha1_file_internal(const unsigned char *sha1,
 605                                    unsigned long *size)
 606{
 607        struct stat st;
 608        void *map;
 609        int fd;
 610        char *filename = find_sha1_file(sha1, &st);
 611
 612        if (!filename) {
 613                return NULL;
 614        }
 615
 616        fd = open(filename, O_RDONLY | sha1_file_open_flag);
 617        if (fd < 0) {
 618                /* See if it works without O_NOATIME */
 619                switch (sha1_file_open_flag) {
 620                default:
 621                        fd = open(filename, O_RDONLY);
 622                        if (fd >= 0)
 623                                break;
 624                /* Fallthrough */
 625                case 0:
 626                        return NULL;
 627                }
 628
 629                /* If it failed once, it will probably fail again.
 630                 * Stop using O_NOATIME
 631                 */
 632                sha1_file_open_flag = 0;
 633        }
 634        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 635        close(fd);
 636        if (map == MAP_FAILED)
 637                return NULL;
 638        *size = st.st_size;
 639        return map;
 640}
 641
 642int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size)
 643{
 644        /* Get the data stream */
 645        memset(stream, 0, sizeof(*stream));
 646        stream->next_in = map;
 647        stream->avail_in = mapsize;
 648        stream->next_out = buffer;
 649        stream->avail_out = size;
 650
 651        inflateInit(stream);
 652        return inflate(stream, 0);
 653}
 654
 655static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
 656{
 657        int bytes = strlen(buffer) + 1;
 658        unsigned char *buf = xmalloc(1+size);
 659
 660        memcpy(buf, buffer + bytes, stream->total_out - bytes);
 661        bytes = stream->total_out - bytes;
 662        if (bytes < size) {
 663                stream->next_out = buf + bytes;
 664                stream->avail_out = size - bytes;
 665                while (inflate(stream, Z_FINISH) == Z_OK)
 666                        /* nothing */;
 667        }
 668        buf[size] = 0;
 669        inflateEnd(stream);
 670        return buf;
 671}
 672
 673/*
 674 * We used to just use "sscanf()", but that's actually way
 675 * too permissive for what we want to check. So do an anal
 676 * object header parse by hand.
 677 */
 678int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
 679{
 680        int i;
 681        unsigned long size;
 682
 683        /*
 684         * The type can be at most ten bytes (including the 
 685         * terminating '\0' that we add), and is followed by
 686         * a space. 
 687         */
 688        i = 10;
 689        for (;;) {
 690                char c = *hdr++;
 691                if (c == ' ')
 692                        break;
 693                if (!--i)
 694                        return -1;
 695                *type++ = c;
 696        }
 697        *type = 0;
 698
 699        /*
 700         * The length must follow immediately, and be in canonical
 701         * decimal format (ie "010" is not valid).
 702         */
 703        size = *hdr++ - '0';
 704        if (size > 9)
 705                return -1;
 706        if (size) {
 707                for (;;) {
 708                        unsigned long c = *hdr - '0';
 709                        if (c > 9)
 710                                break;
 711                        hdr++;
 712                        size = size * 10 + c;
 713                }
 714        }
 715        *sizep = size;
 716
 717        /*
 718         * The length must be followed by a zero byte
 719         */
 720        return *hdr ? -1 : 0;
 721}
 722
 723void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 724{
 725        int ret;
 726        z_stream stream;
 727        char hdr[8192];
 728
 729        ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 730        if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
 731                return NULL;
 732
 733        return unpack_sha1_rest(&stream, hdr, *size);
 734}
 735
 736/* forward declaration for a mutually recursive function */
 737static int packed_object_info(struct pack_entry *entry,
 738                              char *type, unsigned long *sizep);
 739
 740static int packed_delta_info(unsigned char *base_sha1,
 741                             unsigned long delta_size,
 742                             unsigned long left,
 743                             char *type,
 744                             unsigned long *sizep,
 745                             struct packed_git *p)
 746{
 747        struct pack_entry base_ent;
 748
 749        if (left < 20)
 750                die("truncated pack file");
 751
 752        /* The base entry _must_ be in the same pack */
 753        if (!find_pack_entry_one(base_sha1, &base_ent, p))
 754                die("failed to find delta-pack base object %s",
 755                    sha1_to_hex(base_sha1));
 756
 757        /* We choose to only get the type of the base object and
 758         * ignore potentially corrupt pack file that expects the delta
 759         * based on a base with a wrong size.  This saves tons of
 760         * inflate() calls.
 761         */
 762
 763        if (packed_object_info(&base_ent, type, NULL))
 764                die("cannot get info for delta-pack base");
 765
 766        if (sizep) {
 767                const unsigned char *data;
 768                unsigned char delta_head[64];
 769                unsigned long result_size;
 770                z_stream stream;
 771                int st;
 772
 773                memset(&stream, 0, sizeof(stream));
 774
 775                data = stream.next_in = base_sha1 + 20;
 776                stream.avail_in = left - 20;
 777                stream.next_out = delta_head;
 778                stream.avail_out = sizeof(delta_head);
 779
 780                inflateInit(&stream);
 781                st = inflate(&stream, Z_FINISH);
 782                inflateEnd(&stream);
 783                if ((st != Z_STREAM_END) &&
 784                    stream.total_out != sizeof(delta_head))
 785                        die("delta data unpack-initial failed");
 786
 787                /* Examine the initial part of the delta to figure out
 788                 * the result size.
 789                 */
 790                data = delta_head;
 791                get_delta_hdr_size(&data); /* ignore base size */
 792
 793                /* Read the result size */
 794                result_size = get_delta_hdr_size(&data);
 795                *sizep = result_size;
 796        }
 797        return 0;
 798}
 799
 800static unsigned long unpack_object_header(struct packed_git *p, unsigned long offset,
 801        enum object_type *type, unsigned long *sizep)
 802{
 803        unsigned shift;
 804        unsigned char *pack, c;
 805        unsigned long size;
 806
 807        if (offset >= p->pack_size)
 808                die("object offset outside of pack file");
 809
 810        pack =  p->pack_base + offset;
 811        c = *pack++;
 812        offset++;
 813        *type = (c >> 4) & 7;
 814        size = c & 15;
 815        shift = 4;
 816        while (c & 0x80) {
 817                if (offset >= p->pack_size)
 818                        die("object offset outside of pack file");
 819                c = *pack++;
 820                offset++;
 821                size += (c & 0x7f) << shift;
 822                shift += 7;
 823        }
 824        *sizep = size;
 825        return offset;
 826}
 827
 828void packed_object_info_detail(struct pack_entry *e,
 829                               char *type,
 830                               unsigned long *size,
 831                               unsigned long *store_size,
 832                               int *delta_chain_length,
 833                               unsigned char *base_sha1)
 834{
 835        struct packed_git *p = e->p;
 836        unsigned long offset, left;
 837        unsigned char *pack;
 838        enum object_type kind;
 839
 840        offset = unpack_object_header(p, e->offset, &kind, size);
 841        pack = p->pack_base + offset;
 842        left = p->pack_size - offset;
 843        if (kind != OBJ_DELTA)
 844                *delta_chain_length = 0;
 845        else {
 846                int chain_length = 0;
 847                memcpy(base_sha1, pack, 20);
 848                do {
 849                        struct pack_entry base_ent;
 850                        unsigned long junk;
 851
 852                        find_pack_entry_one(pack, &base_ent, p);
 853                        offset = unpack_object_header(p, base_ent.offset,
 854                                                      &kind, &junk);
 855                        pack = p->pack_base + offset;
 856                        chain_length++;
 857                } while (kind == OBJ_DELTA);
 858                *delta_chain_length = chain_length;
 859        }
 860        switch (kind) {
 861        case OBJ_COMMIT:
 862                strcpy(type, "commit");
 863                break;
 864        case OBJ_TREE:
 865                strcpy(type, "tree");
 866                break;
 867        case OBJ_BLOB:
 868                strcpy(type, "blob");
 869                break;
 870        case OBJ_TAG:
 871                strcpy(type, "tag");
 872                break;
 873        default:
 874                die("corrupted pack file %s containing object of kind %d",
 875                    p->pack_name, kind);
 876        }
 877        *store_size = 0; /* notyet */
 878}
 879
 880static int packed_object_info(struct pack_entry *entry,
 881                              char *type, unsigned long *sizep)
 882{
 883        struct packed_git *p = entry->p;
 884        unsigned long offset, size, left;
 885        unsigned char *pack;
 886        enum object_type kind;
 887        int retval;
 888
 889        if (use_packed_git(p))
 890                die("cannot map packed file");
 891
 892        offset = unpack_object_header(p, entry->offset, &kind, &size);
 893        pack = p->pack_base + offset;
 894        left = p->pack_size - offset;
 895
 896        switch (kind) {
 897        case OBJ_DELTA:
 898                retval = packed_delta_info(pack, size, left, type, sizep, p);
 899                unuse_packed_git(p);
 900                return retval;
 901        case OBJ_COMMIT:
 902                strcpy(type, "commit");
 903                break;
 904        case OBJ_TREE:
 905                strcpy(type, "tree");
 906                break;
 907        case OBJ_BLOB:
 908                strcpy(type, "blob");
 909                break;
 910        case OBJ_TAG:
 911                strcpy(type, "tag");
 912                break;
 913        default:
 914                die("corrupted pack file %s containing object of kind %d",
 915                    p->pack_name, kind);
 916        }
 917        if (sizep)
 918                *sizep = size;
 919        unuse_packed_git(p);
 920        return 0;
 921}
 922
 923/* forward declaration for a mutually recursive function */
 924static void *unpack_entry(struct pack_entry *, char *, unsigned long *);
 925
 926static void *unpack_delta_entry(unsigned char *base_sha1,
 927                                unsigned long delta_size,
 928                                unsigned long left,
 929                                char *type,
 930                                unsigned long *sizep,
 931                                struct packed_git *p)
 932{
 933        struct pack_entry base_ent;
 934        void *data, *delta_data, *result, *base;
 935        unsigned long data_size, result_size, base_size;
 936        z_stream stream;
 937        int st;
 938
 939        if (left < 20)
 940                die("truncated pack file");
 941        data = base_sha1 + 20;
 942        data_size = left - 20;
 943        delta_data = xmalloc(delta_size);
 944
 945        memset(&stream, 0, sizeof(stream));
 946
 947        stream.next_in = data;
 948        stream.avail_in = data_size;
 949        stream.next_out = delta_data;
 950        stream.avail_out = delta_size;
 951
 952        inflateInit(&stream);
 953        st = inflate(&stream, Z_FINISH);
 954        inflateEnd(&stream);
 955        if ((st != Z_STREAM_END) || stream.total_out != delta_size)
 956                die("delta data unpack failed");
 957
 958        /* The base entry _must_ be in the same pack */
 959        if (!find_pack_entry_one(base_sha1, &base_ent, p))
 960                die("failed to find delta-pack base object %s",
 961                    sha1_to_hex(base_sha1));
 962        base = unpack_entry_gently(&base_ent, type, &base_size);
 963        if (!base)
 964                die("failed to read delta-pack base object %s",
 965                    sha1_to_hex(base_sha1));
 966        result = patch_delta(base, base_size,
 967                             delta_data, delta_size,
 968                             &result_size);
 969        if (!result)
 970                die("failed to apply delta");
 971        free(delta_data);
 972        free(base);
 973        *sizep = result_size;
 974        return result;
 975}
 976
 977static void *unpack_non_delta_entry(unsigned char *data,
 978                                    unsigned long size,
 979                                    unsigned long left)
 980{
 981        int st;
 982        z_stream stream;
 983        unsigned char *buffer;
 984
 985        buffer = xmalloc(size + 1);
 986        buffer[size] = 0;
 987        memset(&stream, 0, sizeof(stream));
 988        stream.next_in = data;
 989        stream.avail_in = left;
 990        stream.next_out = buffer;
 991        stream.avail_out = size;
 992
 993        inflateInit(&stream);
 994        st = inflate(&stream, Z_FINISH);
 995        inflateEnd(&stream);
 996        if ((st != Z_STREAM_END) || stream.total_out != size) {
 997                free(buffer);
 998                return NULL;
 999        }
1000
1001        return buffer;
1002}
1003
1004static void *unpack_entry(struct pack_entry *entry,
1005                          char *type, unsigned long *sizep)
1006{
1007        struct packed_git *p = entry->p;
1008        void *retval;
1009
1010        if (use_packed_git(p))
1011                die("cannot map packed file");
1012        retval = unpack_entry_gently(entry, type, sizep);
1013        unuse_packed_git(p);
1014        if (!retval)
1015                die("corrupted pack file %s", p->pack_name);
1016        return retval;
1017}
1018
1019/* The caller is responsible for use_packed_git()/unuse_packed_git() pair */
1020void *unpack_entry_gently(struct pack_entry *entry,
1021                          char *type, unsigned long *sizep)
1022{
1023        struct packed_git *p = entry->p;
1024        unsigned long offset, size, left;
1025        unsigned char *pack;
1026        enum object_type kind;
1027        void *retval;
1028
1029        offset = unpack_object_header(p, entry->offset, &kind, &size);
1030        pack = p->pack_base + offset;
1031        left = p->pack_size - offset;
1032        switch (kind) {
1033        case OBJ_DELTA:
1034                retval = unpack_delta_entry(pack, size, left, type, sizep, p);
1035                return retval;
1036        case OBJ_COMMIT:
1037                strcpy(type, "commit");
1038                break;
1039        case OBJ_TREE:
1040                strcpy(type, "tree");
1041                break;
1042        case OBJ_BLOB:
1043                strcpy(type, "blob");
1044                break;
1045        case OBJ_TAG:
1046                strcpy(type, "tag");
1047                break;
1048        default:
1049                return NULL;
1050        }
1051        *sizep = size;
1052        retval = unpack_non_delta_entry(pack, size, left);
1053        return retval;
1054}
1055
1056int num_packed_objects(const struct packed_git *p)
1057{
1058        /* See check_packed_git_idx() */
1059        return (p->index_size - 20 - 20 - 4*256) / 24;
1060}
1061
1062int nth_packed_object_sha1(const struct packed_git *p, int n,
1063                           unsigned char* sha1)
1064{
1065        void *index = p->index_base + 256;
1066        if (n < 0 || num_packed_objects(p) <= n)
1067                return -1;
1068        memcpy(sha1, (index + 24 * n + 4), 20);
1069        return 0;
1070}
1071
1072int find_pack_entry_one(const unsigned char *sha1,
1073                        struct pack_entry *e, struct packed_git *p)
1074{
1075        unsigned int *level1_ofs = p->index_base;
1076        int hi = ntohl(level1_ofs[*sha1]);
1077        int lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
1078        void *index = p->index_base + 256;
1079
1080        do {
1081                int mi = (lo + hi) / 2;
1082                int cmp = memcmp(index + 24 * mi + 4, sha1, 20);
1083                if (!cmp) {
1084                        e->offset = ntohl(*((int*)(index + 24 * mi)));
1085                        memcpy(e->sha1, sha1, 20);
1086                        e->p = p;
1087                        return 1;
1088                }
1089                if (cmp > 0)
1090                        hi = mi;
1091                else
1092                        lo = mi+1;
1093        } while (lo < hi);
1094        return 0;
1095}
1096
1097static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
1098{
1099        struct packed_git *p;
1100        prepare_packed_git();
1101
1102        for (p = packed_git; p; p = p->next) {
1103                if (find_pack_entry_one(sha1, e, p))
1104                        return 1;
1105        }
1106        return 0;
1107}
1108
1109struct packed_git *find_sha1_pack(const unsigned char *sha1, 
1110                                  struct packed_git *packs)
1111{
1112        struct packed_git *p;
1113        struct pack_entry e;
1114
1115        for (p = packs; p; p = p->next) {
1116                if (find_pack_entry_one(sha1, &e, p))
1117                        return p;
1118        }
1119        return NULL;
1120        
1121}
1122
1123int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
1124{
1125        int status;
1126        unsigned long mapsize, size;
1127        void *map;
1128        z_stream stream;
1129        char hdr[128];
1130
1131        map = map_sha1_file_internal(sha1, &mapsize);
1132        if (!map) {
1133                struct pack_entry e;
1134
1135                if (!find_pack_entry(sha1, &e))
1136                        return error("unable to find %s", sha1_to_hex(sha1));
1137                return packed_object_info(&e, type, sizep);
1138        }
1139        if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
1140                status = error("unable to unpack %s header",
1141                               sha1_to_hex(sha1));
1142        if (parse_sha1_header(hdr, type, &size) < 0)
1143                status = error("unable to parse %s header", sha1_to_hex(sha1));
1144        else {
1145                status = 0;
1146                if (sizep)
1147                        *sizep = size;
1148        }
1149        inflateEnd(&stream);
1150        munmap(map, mapsize);
1151        return status;
1152}
1153
1154static void *read_packed_sha1(const unsigned char *sha1, char *type, unsigned long *size)
1155{
1156        struct pack_entry e;
1157
1158        if (!find_pack_entry(sha1, &e)) {
1159                error("cannot read sha1_file for %s", sha1_to_hex(sha1));
1160                return NULL;
1161        }
1162        return unpack_entry(&e, type, size);
1163}
1164
1165void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
1166{
1167        unsigned long mapsize;
1168        void *map, *buf;
1169        struct pack_entry e;
1170
1171        if (find_pack_entry(sha1, &e))
1172                return read_packed_sha1(sha1, type, size);
1173        map = map_sha1_file_internal(sha1, &mapsize);
1174        if (map) {
1175                buf = unpack_sha1_file(map, mapsize, type, size);
1176                munmap(map, mapsize);
1177                return buf;
1178        }
1179        return NULL;
1180}
1181
1182void *read_object_with_reference(const unsigned char *sha1,
1183                                 const char *required_type,
1184                                 unsigned long *size,
1185                                 unsigned char *actual_sha1_return)
1186{
1187        char type[20];
1188        void *buffer;
1189        unsigned long isize;
1190        unsigned char actual_sha1[20];
1191
1192        memcpy(actual_sha1, sha1, 20);
1193        while (1) {
1194                int ref_length = -1;
1195                const char *ref_type = NULL;
1196
1197                buffer = read_sha1_file(actual_sha1, type, &isize);
1198                if (!buffer)
1199                        return NULL;
1200                if (!strcmp(type, required_type)) {
1201                        *size = isize;
1202                        if (actual_sha1_return)
1203                                memcpy(actual_sha1_return, actual_sha1, 20);
1204                        return buffer;
1205                }
1206                /* Handle references */
1207                else if (!strcmp(type, "commit"))
1208                        ref_type = "tree ";
1209                else if (!strcmp(type, "tag"))
1210                        ref_type = "object ";
1211                else {
1212                        free(buffer);
1213                        return NULL;
1214                }
1215                ref_length = strlen(ref_type);
1216
1217                if (memcmp(buffer, ref_type, ref_length) ||
1218                    get_sha1_hex(buffer + ref_length, actual_sha1)) {
1219                        free(buffer);
1220                        return NULL;
1221                }
1222                free(buffer);
1223                /* Now we have the ID of the referred-to object in
1224                 * actual_sha1.  Check again. */
1225        }
1226}
1227
1228char *write_sha1_file_prepare(void *buf,
1229                              unsigned long len,
1230                              const char *type,
1231                              unsigned char *sha1,
1232                              unsigned char *hdr,
1233                              int *hdrlen)
1234{
1235        SHA_CTX c;
1236
1237        /* Generate the header */
1238        *hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
1239
1240        /* Sha1.. */
1241        SHA1_Init(&c);
1242        SHA1_Update(&c, hdr, *hdrlen);
1243        SHA1_Update(&c, buf, len);
1244        SHA1_Final(sha1, &c);
1245
1246        return sha1_file_name(sha1);
1247}
1248
1249int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
1250{
1251        int size;
1252        unsigned char *compressed;
1253        z_stream stream;
1254        unsigned char sha1[20];
1255        char *filename;
1256        static char tmpfile[PATH_MAX];
1257        unsigned char hdr[50];
1258        int fd, hdrlen, ret;
1259
1260        /* Normally if we have it in the pack then we do not bother writing
1261         * it out into .git/objects/??/?{38} file.
1262         */
1263        filename = write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
1264        if (returnsha1)
1265                memcpy(returnsha1, sha1, 20);
1266        if (has_sha1_file(sha1))
1267                return 0;
1268        fd = open(filename, O_RDONLY);
1269        if (fd >= 0) {
1270                /*
1271                 * FIXME!!! We might do collision checking here, but we'd
1272                 * need to uncompress the old file and check it. Later.
1273                 */
1274                close(fd);
1275                return 0;
1276        }
1277
1278        if (errno != ENOENT) {
1279                fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
1280                return -1;
1281        }
1282
1283        snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
1284
1285        fd = mkstemp(tmpfile);
1286        if (fd < 0) {
1287                fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
1288                return -1;
1289        }
1290
1291        /* Set it up */
1292        memset(&stream, 0, sizeof(stream));
1293        deflateInit(&stream, Z_BEST_COMPRESSION);
1294        size = deflateBound(&stream, len+hdrlen);
1295        compressed = xmalloc(size);
1296
1297        /* Compress it */
1298        stream.next_out = compressed;
1299        stream.avail_out = size;
1300
1301        /* First header.. */
1302        stream.next_in = hdr;
1303        stream.avail_in = hdrlen;
1304        while (deflate(&stream, 0) == Z_OK)
1305                /* nothing */;
1306
1307        /* Then the data itself.. */
1308        stream.next_in = buf;
1309        stream.avail_in = len;
1310        while (deflate(&stream, Z_FINISH) == Z_OK)
1311                /* nothing */;
1312        deflateEnd(&stream);
1313        size = stream.total_out;
1314
1315        if (write(fd, compressed, size) != size)
1316                die("unable to write file");
1317        fchmod(fd, 0444);
1318        close(fd);
1319        free(compressed);
1320
1321        ret = link(tmpfile, filename);
1322        if (ret < 0) {
1323                ret = errno;
1324
1325                /*
1326                 * Coda hack - coda doesn't like cross-directory links,
1327                 * so we fall back to a rename, which will mean that it
1328                 * won't be able to check collisions, but that's not a
1329                 * big deal.
1330                 *
1331                 * When this succeeds, we just return 0. We have nothing
1332                 * left to unlink.
1333                 */
1334                if (ret == EXDEV && !rename(tmpfile, filename))
1335                        return 0;
1336        }
1337        unlink(tmpfile);
1338        if (ret) {
1339                if (ret != EEXIST) {
1340                        fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
1341                        return -1;
1342                }
1343                /* FIXME!!! Collision check here ? */
1344        }
1345
1346        return 0;
1347}
1348
1349int write_sha1_to_fd(int fd, const unsigned char *sha1)
1350{
1351        ssize_t size;
1352        unsigned long objsize;
1353        int posn = 0;
1354        void *map = map_sha1_file_internal(sha1, &objsize);
1355        void *buf = map;
1356        void *temp_obj = NULL;
1357        z_stream stream;
1358
1359        if (!buf) {
1360                unsigned char *unpacked;
1361                unsigned long len;
1362                char type[20];
1363                char hdr[50];
1364                int hdrlen;
1365                // need to unpack and recompress it by itself
1366                unpacked = read_packed_sha1(sha1, type, &len);
1367
1368                hdrlen = sprintf(hdr, "%s %lu", type, len) + 1;
1369
1370                /* Set it up */
1371                memset(&stream, 0, sizeof(stream));
1372                deflateInit(&stream, Z_BEST_COMPRESSION);
1373                size = deflateBound(&stream, len + hdrlen);
1374                temp_obj = buf = xmalloc(size);
1375
1376                /* Compress it */
1377                stream.next_out = buf;
1378                stream.avail_out = size;
1379                
1380                /* First header.. */
1381                stream.next_in = (void *)hdr;
1382                stream.avail_in = hdrlen;
1383                while (deflate(&stream, 0) == Z_OK)
1384                        /* nothing */;
1385
1386                /* Then the data itself.. */
1387                stream.next_in = unpacked;
1388                stream.avail_in = len;
1389                while (deflate(&stream, Z_FINISH) == Z_OK)
1390                        /* nothing */;
1391                deflateEnd(&stream);
1392                free(unpacked);
1393                
1394                objsize = stream.total_out;
1395        }
1396
1397        do {
1398                size = write(fd, buf + posn, objsize - posn);
1399                if (size <= 0) {
1400                        if (!size) {
1401                                fprintf(stderr, "write closed");
1402                        } else {
1403                                perror("write ");
1404                        }
1405                        return -1;
1406                }
1407                posn += size;
1408        } while (posn < objsize);
1409
1410        if (map)
1411                munmap(map, objsize);
1412        if (temp_obj)
1413                free(temp_obj);
1414
1415        return 0;
1416}
1417
1418int write_sha1_from_fd(const unsigned char *sha1, int fd, char *buffer,
1419                       size_t bufsize, size_t *bufposn)
1420{
1421        char *filename = sha1_file_name(sha1);
1422
1423        int local;
1424        z_stream stream;
1425        unsigned char real_sha1[20];
1426        unsigned char discard[4096];
1427        int ret;
1428        SHA_CTX c;
1429
1430        local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
1431
1432        if (local < 0)
1433                return error("Couldn't open %s\n", filename);
1434
1435        memset(&stream, 0, sizeof(stream));
1436
1437        inflateInit(&stream);
1438
1439        SHA1_Init(&c);
1440
1441        do {
1442                ssize_t size;
1443                if (*bufposn) {
1444                        stream.avail_in = *bufposn;
1445                        stream.next_in = (unsigned char *) buffer;
1446                        do {
1447                                stream.next_out = discard;
1448                                stream.avail_out = sizeof(discard);
1449                                ret = inflate(&stream, Z_SYNC_FLUSH);
1450                                SHA1_Update(&c, discard, sizeof(discard) -
1451                                            stream.avail_out);
1452                        } while (stream.avail_in && ret == Z_OK);
1453                        write(local, buffer, *bufposn - stream.avail_in);
1454                        memmove(buffer, buffer + *bufposn - stream.avail_in,
1455                                stream.avail_in);
1456                        *bufposn = stream.avail_in;
1457                        if (ret != Z_OK)
1458                                break;
1459                }
1460                size = read(fd, buffer + *bufposn, bufsize - *bufposn);
1461                if (size <= 0) {
1462                        close(local);
1463                        unlink(filename);
1464                        if (!size)
1465                                return error("Connection closed?");
1466                        perror("Reading from connection");
1467                        return -1;
1468                }
1469                *bufposn += size;
1470        } while (1);
1471        inflateEnd(&stream);
1472
1473        close(local);
1474        SHA1_Final(real_sha1, &c);
1475        if (ret != Z_STREAM_END) {
1476                unlink(filename);
1477                return error("File %s corrupted", sha1_to_hex(sha1));
1478        }
1479        if (memcmp(sha1, real_sha1, 20)) {
1480                unlink(filename);
1481                return error("File %s has bad hash\n", sha1_to_hex(sha1));
1482        }
1483        
1484        return 0;
1485}
1486
1487int has_pack_index(const unsigned char *sha1)
1488{
1489        struct stat st;
1490        if (stat(sha1_pack_index_name(sha1), &st))
1491                return 0;
1492        return 1;
1493}
1494
1495int has_pack_file(const unsigned char *sha1)
1496{
1497        struct stat st;
1498        if (stat(sha1_pack_name(sha1), &st))
1499                return 0;
1500        return 1;
1501}
1502
1503int has_sha1_pack(const unsigned char *sha1)
1504{
1505        struct pack_entry e;
1506        return find_pack_entry(sha1, &e);
1507}
1508
1509int has_sha1_file(const unsigned char *sha1)
1510{
1511        struct stat st;
1512        struct pack_entry e;
1513
1514        if (find_pack_entry(sha1, &e))
1515                return 1;
1516        return find_sha1_file(sha1, &st) ? 1 : 0;
1517}
1518
1519int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object, const char *type)
1520{
1521        unsigned long size = st->st_size;
1522        void *buf;
1523        int ret;
1524        unsigned char hdr[50];
1525        int hdrlen;
1526
1527        buf = "";
1528        if (size)
1529                buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
1530        close(fd);
1531        if (buf == MAP_FAILED)
1532                return -1;
1533
1534        if (!type)
1535                type = "blob";
1536        if (write_object)
1537                ret = write_sha1_file(buf, size, type, sha1);
1538        else {
1539                write_sha1_file_prepare(buf, size, type, sha1, hdr, &hdrlen);
1540                ret = 0;
1541        }
1542        if (size)
1543                munmap(buf, size);
1544        return ret;
1545}