Andrew's git / gitweb.git / sha1_file.c
?
sha1_file.con commit Merge branch 'fixes' (d53174d)
   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
  23const unsigned char null_sha1[20] = { 0, };
  24
  25static unsigned int sha1_file_open_flag = O_NOATIME;
  26
  27static unsigned hexval(char c)
  28{
  29        if (c >= '0' && c <= '9')
  30                return c - '0';
  31        if (c >= 'a' && c <= 'f')
  32                return c - 'a' + 10;
  33        if (c >= 'A' && c <= 'F')
  34                return c - 'A' + 10;
  35        return ~0;
  36}
  37
  38int get_sha1_hex(const char *hex, unsigned char *sha1)
  39{
  40        int i;
  41        for (i = 0; i < 20; i++) {
  42                unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  43                if (val & ~0xff)
  44                        return -1;
  45                *sha1++ = val;
  46                hex += 2;
  47        }
  48        return 0;
  49}
  50
  51static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir,
  52        *git_graft_file;
  53static void setup_git_env(void)
  54{
  55        git_dir = getenv(GIT_DIR_ENVIRONMENT);
  56        if (!git_dir)
  57                git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
  58        git_object_dir = getenv(DB_ENVIRONMENT);
  59        if (!git_object_dir) {
  60                git_object_dir = xmalloc(strlen(git_dir) + 9);
  61                sprintf(git_object_dir, "%s/objects", git_dir);
  62        }
  63        git_refs_dir = xmalloc(strlen(git_dir) + 6);
  64        sprintf(git_refs_dir, "%s/refs", git_dir);
  65        git_index_file = getenv(INDEX_ENVIRONMENT);
  66        if (!git_index_file) {
  67                git_index_file = xmalloc(strlen(git_dir) + 7);
  68                sprintf(git_index_file, "%s/index", git_dir);
  69        }
  70        git_graft_file = getenv(GRAFT_ENVIRONMENT);
  71        if (!git_graft_file)
  72                git_graft_file = strdup(git_path("info/grafts"));
  73}
  74
  75char *get_git_dir(void)
  76{
  77        if (!git_dir)
  78                setup_git_env();
  79        return git_dir;
  80}
  81
  82char *get_object_directory(void)
  83{
  84        if (!git_object_dir)
  85                setup_git_env();
  86        return git_object_dir;
  87}
  88
  89char *get_refs_directory(void)
  90{
  91        if (!git_refs_dir)
  92                setup_git_env();
  93        return git_refs_dir;
  94}
  95
  96char *get_index_file(void)
  97{
  98        if (!git_index_file)
  99                setup_git_env();
 100        return git_index_file;
 101}
 102
 103char *get_graft_file(void)
 104{
 105        if (!git_graft_file)
 106                setup_git_env();
 107        return git_graft_file;
 108}
 109
 110int safe_create_leading_directories(char *path)
 111{
 112        char *pos = path;
 113
 114        while (pos) {
 115                pos = strchr(pos, '/');
 116                if (!pos)
 117                        break;
 118                *pos = 0;
 119                if (mkdir(path, 0777) < 0)
 120                        if (errno != EEXIST) {
 121                                *pos = '/';
 122                                return -1;
 123                        }
 124                *pos++ = '/';
 125        }
 126        return 0;
 127}
 128
 129char * sha1_to_hex(const unsigned char *sha1)
 130{
 131        static char buffer[50];
 132        static const char hex[] = "0123456789abcdef";
 133        char *buf = buffer;
 134        int i;
 135
 136        for (i = 0; i < 20; i++) {
 137                unsigned int val = *sha1++;
 138                *buf++ = hex[val >> 4];
 139                *buf++ = hex[val & 0xf];
 140        }
 141        return buffer;
 142}
 143
 144static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 145{
 146        int i;
 147        for (i = 0; i < 20; i++) {
 148                static char hex[] = "0123456789abcdef";
 149                unsigned int val = sha1[i];
 150                char *pos = pathbuf + i*2 + (i > 0);
 151                *pos++ = hex[val >> 4];
 152                *pos = hex[val & 0xf];
 153        }
 154}
 155
 156/*
 157 * NOTE! This returns a statically allocated buffer, so you have to be
 158 * careful about using it. Do a "strdup()" if you need to save the
 159 * filename.
 160 *
 161 * Also note that this returns the location for creating.  Reading
 162 * SHA1 file can happen from any alternate directory listed in the
 163 * DB_ENVIRONMENT environment variable if it is not found in
 164 * the primary object database.
 165 */
 166char *sha1_file_name(const unsigned char *sha1)
 167{
 168        static char *name, *base;
 169
 170        if (!base) {
 171                const char *sha1_file_directory = get_object_directory();
 172                int len = strlen(sha1_file_directory);
 173                base = xmalloc(len + 60);
 174                memcpy(base, sha1_file_directory, len);
 175                memset(base+len, 0, 60);
 176                base[len] = '/';
 177                base[len+3] = '/';
 178                name = base + len + 1;
 179        }
 180        fill_sha1_path(name, sha1);
 181        return base;
 182}
 183
 184char *sha1_pack_name(const unsigned char *sha1)
 185{
 186        static const char hex[] = "0123456789abcdef";
 187        static char *name, *base, *buf;
 188        int i;
 189
 190        if (!base) {
 191                const char *sha1_file_directory = get_object_directory();
 192                int len = strlen(sha1_file_directory);
 193                base = xmalloc(len + 60);
 194                sprintf(base, "%s/pack/pack-1234567890123456789012345678901234567890.pack", sha1_file_directory);
 195                name = base + len + 11;
 196        }
 197
 198        buf = name;
 199
 200        for (i = 0; i < 20; i++) {
 201                unsigned int val = *sha1++;
 202                *buf++ = hex[val >> 4];
 203                *buf++ = hex[val & 0xf];
 204        }
 205        
 206        return base;
 207}
 208
 209char *sha1_pack_index_name(const unsigned char *sha1)
 210{
 211        static const char hex[] = "0123456789abcdef";
 212        static char *name, *base, *buf;
 213        int i;
 214
 215        if (!base) {
 216                const char *sha1_file_directory = get_object_directory();
 217                int len = strlen(sha1_file_directory);
 218                base = xmalloc(len + 60);
 219                sprintf(base, "%s/pack/pack-1234567890123456789012345678901234567890.idx", sha1_file_directory);
 220                name = base + len + 11;
 221        }
 222
 223        buf = name;
 224
 225        for (i = 0; i < 20; i++) {
 226                unsigned int val = *sha1++;
 227                *buf++ = hex[val >> 4];
 228                *buf++ = hex[val & 0xf];
 229        }
 230        
 231        return base;
 232}
 233
 234struct alternate_object_database *alt_odb_list;
 235static struct alternate_object_database **alt_odb_tail;
 236
 237/*
 238 * Prepare alternate object database registry.
 239 *
 240 * The variable alt_odb_list points at the list of struct
 241 * alternate_object_database.  The elements on this list come from
 242 * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
 243 * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
 244 * whose contents is exactly in the same format as that environment
 245 * variable.  Its base points at a statically allocated buffer that
 246 * contains "/the/directory/corresponding/to/.git/objects/...", while
 247 * its name points just after the slash at the end of ".git/objects/"
 248 * in the example above, and has enough space to hold 40-byte hex
 249 * SHA1, an extra slash for the first level indirection, and the
 250 * terminating NUL.
 251 */
 252static void link_alt_odb_entries(const char *alt, const char *ep, int sep,
 253                                 const char *relative_base)
 254{
 255        const char *cp, *last;
 256        struct alternate_object_database *ent;
 257        int base_len = -1;
 258
 259        last = alt;
 260        while (last < ep) {
 261                cp = last;
 262                if (cp < ep && *cp == '#') {
 263                        while (cp < ep && *cp != sep)
 264                                cp++;
 265                        last = cp + 1;
 266                        continue;
 267                }
 268                for ( ; cp < ep && *cp != sep; cp++)
 269                        ;
 270                if (last != cp) {
 271                        /* 43 = 40-byte + 2 '/' + terminating NUL */
 272                        int pfxlen = cp - last;
 273                        int entlen = pfxlen + 43;
 274
 275                        if (*last != '/' && relative_base) {
 276                                /* Relative alt-odb */
 277                                if (base_len < 0)
 278                                        base_len = strlen(relative_base) + 1;
 279                                entlen += base_len;
 280                                pfxlen += base_len;
 281                        }
 282                        ent = xmalloc(sizeof(*ent) + entlen);
 283                        *alt_odb_tail = ent;
 284                        alt_odb_tail = &(ent->next);
 285                        ent->next = NULL;
 286                        if (*last != '/' && relative_base) {
 287                                memcpy(ent->base, relative_base, base_len - 1);
 288                                ent->base[base_len - 1] = '/';
 289                                memcpy(ent->base + base_len,
 290                                       last, cp - last);
 291                        }
 292                        else
 293                                memcpy(ent->base, last, pfxlen);
 294                        ent->name = ent->base + pfxlen + 1;
 295                        ent->base[pfxlen] = ent->base[pfxlen + 3] = '/';
 296                        ent->base[entlen-1] = 0;
 297                }
 298                while (cp < ep && *cp == sep)
 299                        cp++;
 300                last = cp;
 301        }
 302}
 303
 304void prepare_alt_odb(void)
 305{
 306        char path[PATH_MAX];
 307        char *map;
 308        int fd;
 309        struct stat st;
 310        char *alt;
 311
 312        alt = getenv(ALTERNATE_DB_ENVIRONMENT);
 313        if (!alt) alt = "";
 314
 315        if (alt_odb_tail)
 316                return;
 317        alt_odb_tail = &alt_odb_list;
 318        link_alt_odb_entries(alt, alt + strlen(alt), ':', NULL);
 319
 320        sprintf(path, "%s/info/alternates", get_object_directory());
 321        fd = open(path, O_RDONLY);
 322        if (fd < 0)
 323                return;
 324        if (fstat(fd, &st) || (st.st_size == 0)) {
 325                close(fd);
 326                return;
 327        }
 328        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 329        close(fd);
 330        if (map == MAP_FAILED)
 331                return;
 332
 333        link_alt_odb_entries(map, map + st.st_size, '\n',
 334                             get_object_directory());
 335        munmap(map, st.st_size);
 336}
 337
 338static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 339{
 340        char *name = sha1_file_name(sha1);
 341        struct alternate_object_database *alt;
 342
 343        if (!stat(name, st))
 344                return name;
 345        prepare_alt_odb();
 346        for (alt = alt_odb_list; alt; alt = alt->next) {
 347                name = alt->name;
 348                fill_sha1_path(name, sha1);
 349                if (!stat(alt->base, st))
 350                        return alt->base;
 351        }
 352        return NULL;
 353}
 354
 355#define PACK_MAX_SZ (1<<26)
 356static int pack_used_ctr;
 357static unsigned long pack_mapped;
 358struct packed_git *packed_git;
 359
 360static int check_packed_git_idx(const char *path, unsigned long *idx_size_,
 361                                void **idx_map_)
 362{
 363        void *idx_map;
 364        unsigned int *index;
 365        unsigned long idx_size;
 366        int nr, i;
 367        int fd = open(path, O_RDONLY);
 368        struct stat st;
 369        if (fd < 0)
 370                return -1;
 371        if (fstat(fd, &st)) {
 372                close(fd);
 373                return -1;
 374        }
 375        idx_size = st.st_size;
 376        idx_map = mmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
 377        close(fd);
 378        if (idx_map == MAP_FAILED)
 379                return -1;
 380
 381        index = idx_map;
 382        *idx_map_ = idx_map;
 383        *idx_size_ = idx_size;
 384
 385        /* check index map */
 386        if (idx_size < 4*256 + 20 + 20)
 387                return error("index file too small");
 388        nr = 0;
 389        for (i = 0; i < 256; i++) {
 390                unsigned int n = ntohl(index[i]);
 391                if (n < nr)
 392                        return error("non-monotonic index");
 393                nr = n;
 394        }
 395
 396        /*
 397         * Total size:
 398         *  - 256 index entries 4 bytes each
 399         *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
 400         *  - 20-byte SHA1 of the packfile
 401         *  - 20-byte SHA1 file checksum
 402         */
 403        if (idx_size != 4*256 + nr * 24 + 20 + 20)
 404                return error("wrong index file size");
 405
 406        return 0;
 407}
 408
 409static int unuse_one_packed_git(void)
 410{
 411        struct packed_git *p, *lru = NULL;
 412
 413        for (p = packed_git; p; p = p->next) {
 414                if (p->pack_use_cnt || !p->pack_base)
 415                        continue;
 416                if (!lru || p->pack_last_used < lru->pack_last_used)
 417                        lru = p;
 418        }
 419        if (!lru)
 420                return 0;
 421        munmap(lru->pack_base, lru->pack_size);
 422        lru->pack_base = NULL;
 423        return 1;
 424}
 425
 426void unuse_packed_git(struct packed_git *p)
 427{
 428        p->pack_use_cnt--;
 429}
 430
 431int use_packed_git(struct packed_git *p)
 432{
 433        if (!p->pack_size) {
 434                struct stat st;
 435                // We created the struct before we had the pack
 436                stat(p->pack_name, &st);
 437                if (!S_ISREG(st.st_mode))
 438                        die("packfile %s not a regular file", p->pack_name);
 439                p->pack_size = st.st_size;
 440        }
 441        if (!p->pack_base) {
 442                int fd;
 443                struct stat st;
 444                void *map;
 445
 446                pack_mapped += p->pack_size;
 447                while (PACK_MAX_SZ < pack_mapped && unuse_one_packed_git())
 448                        ; /* nothing */
 449                fd = open(p->pack_name, O_RDONLY);
 450                if (fd < 0)
 451                        die("packfile %s cannot be opened", p->pack_name);
 452                if (fstat(fd, &st)) {
 453                        close(fd);
 454                        die("packfile %s cannot be opened", p->pack_name);
 455                }
 456                if (st.st_size != p->pack_size)
 457                        die("packfile %s size mismatch.", p->pack_name);
 458                map = mmap(NULL, p->pack_size, PROT_READ, MAP_PRIVATE, fd, 0);
 459                close(fd);
 460                if (map == MAP_FAILED)
 461                        die("packfile %s cannot be mapped.", p->pack_name);
 462                p->pack_base = map;
 463
 464                /* Check if the pack file matches with the index file.
 465                 * this is cheap.
 466                 */
 467                if (memcmp((char*)(p->index_base) + p->index_size - 40,
 468                           p->pack_base + p->pack_size - 20, 20)) {
 469                              
 470                        die("packfile %s does not match index.", p->pack_name);
 471                }
 472        }
 473        p->pack_last_used = pack_used_ctr++;
 474        p->pack_use_cnt++;
 475        return 0;
 476}
 477
 478struct packed_git *add_packed_git(char *path, int path_len)
 479{
 480        struct stat st;
 481        struct packed_git *p;
 482        unsigned long idx_size;
 483        void *idx_map;
 484
 485        if (check_packed_git_idx(path, &idx_size, &idx_map))
 486                return NULL;
 487
 488        /* do we have a corresponding .pack file? */
 489        strcpy(path + path_len - 4, ".pack");
 490        if (stat(path, &st) || !S_ISREG(st.st_mode)) {
 491                munmap(idx_map, idx_size);
 492                return NULL;
 493        }
 494        /* ok, it looks sane as far as we can check without
 495         * actually mapping the pack file.
 496         */
 497        p = xmalloc(sizeof(*p) + path_len + 2);
 498        strcpy(p->pack_name, path);
 499        p->index_size = idx_size;
 500        p->pack_size = st.st_size;
 501        p->index_base = idx_map;
 502        p->next = NULL;
 503        p->pack_base = NULL;
 504        p->pack_last_used = 0;
 505        p->pack_use_cnt = 0;
 506        return p;
 507}
 508
 509struct packed_git *parse_pack_index(unsigned char *sha1)
 510{
 511        char *path = sha1_pack_index_name(sha1);
 512        return parse_pack_index_file(sha1, path);
 513}
 514
 515struct packed_git *parse_pack_index_file(const unsigned char *sha1, char *idx_path)
 516{
 517        struct packed_git *p;
 518        unsigned long idx_size;
 519        void *idx_map;
 520        char *path;
 521
 522        if (check_packed_git_idx(idx_path, &idx_size, &idx_map))
 523                return NULL;
 524
 525        path = sha1_pack_name(sha1);
 526
 527        p = xmalloc(sizeof(*p) + strlen(path) + 2);
 528        strcpy(p->pack_name, path);
 529        p->index_size = idx_size;
 530        p->pack_size = 0;
 531        p->index_base = idx_map;
 532        p->next = NULL;
 533        p->pack_base = NULL;
 534        p->pack_last_used = 0;
 535        p->pack_use_cnt = 0;
 536        memcpy(p->sha1, sha1, 20);
 537        return p;
 538}
 539
 540void install_packed_git(struct packed_git *pack)
 541{
 542        pack->next = packed_git;
 543        packed_git = pack;
 544}
 545
 546static void prepare_packed_git_one(char *objdir)
 547{
 548        char path[PATH_MAX];
 549        int len;
 550        DIR *dir;
 551        struct dirent *de;
 552
 553        sprintf(path, "%s/pack", objdir);
 554        len = strlen(path);
 555        dir = opendir(path);
 556        if (!dir)
 557                return;
 558        path[len++] = '/';
 559        while ((de = readdir(dir)) != NULL) {
 560                int namelen = strlen(de->d_name);
 561                struct packed_git *p;
 562
 563                if (strcmp(de->d_name + namelen - 4, ".idx"))
 564                        continue;
 565
 566                /* we have .idx.  Is it a file we can map? */
 567                strcpy(path + len, de->d_name);
 568                p = add_packed_git(path, len + namelen);
 569                if (!p)
 570                        continue;
 571                p->next = packed_git;
 572                packed_git = p;
 573        }
 574        closedir(dir);
 575}
 576
 577void prepare_packed_git(void)
 578{
 579        static int run_once = 0;
 580        struct alternate_object_database *alt;
 581
 582        if (run_once)
 583                return;
 584        prepare_packed_git_one(get_object_directory());
 585        prepare_alt_odb();
 586        for (alt = alt_odb_list; alt; alt = alt->next) {
 587                alt->name[0] = 0;
 588                prepare_packed_git_one(alt->base);
 589        }
 590        run_once = 1;
 591}
 592
 593int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
 594{
 595        char header[100];
 596        unsigned char real_sha1[20];
 597        SHA_CTX c;
 598
 599        SHA1_Init(&c);
 600        SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 601        SHA1_Update(&c, map, size);
 602        SHA1_Final(real_sha1, &c);
 603        return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 604}
 605
 606static void *map_sha1_file_internal(const unsigned char *sha1,
 607                                    unsigned long *size)
 608{
 609        struct stat st;
 610        void *map;
 611        int fd;
 612        char *filename = find_sha1_file(sha1, &st);
 613
 614        if (!filename) {
 615                return NULL;
 616        }
 617
 618        fd = open(filename, O_RDONLY | sha1_file_open_flag);
 619        if (fd < 0) {
 620                /* See if it works without O_NOATIME */
 621                switch (sha1_file_open_flag) {
 622                default:
 623                        fd = open(filename, O_RDONLY);
 624                        if (fd >= 0)
 625                                break;
 626                /* Fallthrough */
 627                case 0:
 628                        return NULL;
 629                }
 630
 631                /* If it failed once, it will probably fail again.
 632                 * Stop using O_NOATIME
 633                 */
 634                sha1_file_open_flag = 0;
 635        }
 636        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 637        close(fd);
 638        if (map == MAP_FAILED)
 639                return NULL;
 640        *size = st.st_size;
 641        return map;
 642}
 643
 644int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size)
 645{
 646        /* Get the data stream */
 647        memset(stream, 0, sizeof(*stream));
 648        stream->next_in = map;
 649        stream->avail_in = mapsize;
 650        stream->next_out = buffer;
 651        stream->avail_out = size;
 652
 653        inflateInit(stream);
 654        return inflate(stream, 0);
 655}
 656
 657static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
 658{
 659        int bytes = strlen(buffer) + 1;
 660        unsigned char *buf = xmalloc(1+size);
 661
 662        memcpy(buf, buffer + bytes, stream->total_out - bytes);
 663        bytes = stream->total_out - bytes;
 664        if (bytes < size) {
 665                stream->next_out = buf + bytes;
 666                stream->avail_out = size - bytes;
 667                while (inflate(stream, Z_FINISH) == Z_OK)
 668                        /* nothing */;
 669        }
 670        buf[size] = 0;
 671        inflateEnd(stream);
 672        return buf;
 673}
 674
 675/*
 676 * We used to just use "sscanf()", but that's actually way
 677 * too permissive for what we want to check. So do an anal
 678 * object header parse by hand.
 679 */
 680int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
 681{
 682        int i;
 683        unsigned long size;
 684
 685        /*
 686         * The type can be at most ten bytes (including the 
 687         * terminating '\0' that we add), and is followed by
 688         * a space. 
 689         */
 690        i = 10;
 691        for (;;) {
 692                char c = *hdr++;
 693                if (c == ' ')
 694                        break;
 695                if (!--i)
 696                        return -1;
 697                *type++ = c;
 698        }
 699        *type = 0;
 700
 701        /*
 702         * The length must follow immediately, and be in canonical
 703         * decimal format (ie "010" is not valid).
 704         */
 705        size = *hdr++ - '0';
 706        if (size > 9)
 707                return -1;
 708        if (size) {
 709                for (;;) {
 710                        unsigned long c = *hdr - '0';
 711                        if (c > 9)
 712                                break;
 713                        hdr++;
 714                        size = size * 10 + c;
 715                }
 716        }
 717        *sizep = size;
 718
 719        /*
 720         * The length must be followed by a zero byte
 721         */
 722        return *hdr ? -1 : 0;
 723}
 724
 725void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 726{
 727        int ret;
 728        z_stream stream;
 729        char hdr[8192];
 730
 731        ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 732        if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
 733                return NULL;
 734
 735        return unpack_sha1_rest(&stream, hdr, *size);
 736}
 737
 738/* forward declaration for a mutually recursive function */
 739static int packed_object_info(struct pack_entry *entry,
 740                              char *type, unsigned long *sizep);
 741
 742static int packed_delta_info(unsigned char *base_sha1,
 743                             unsigned long delta_size,
 744                             unsigned long left,
 745                             char *type,
 746                             unsigned long *sizep,
 747                             struct packed_git *p)
 748{
 749        struct pack_entry base_ent;
 750
 751        if (left < 20)
 752                die("truncated pack file");
 753
 754        /* The base entry _must_ be in the same pack */
 755        if (!find_pack_entry_one(base_sha1, &base_ent, p))
 756                die("failed to find delta-pack base object %s",
 757                    sha1_to_hex(base_sha1));
 758
 759        /* We choose to only get the type of the base object and
 760         * ignore potentially corrupt pack file that expects the delta
 761         * based on a base with a wrong size.  This saves tons of
 762         * inflate() calls.
 763         */
 764
 765        if (packed_object_info(&base_ent, type, NULL))
 766                die("cannot get info for delta-pack base");
 767
 768        if (sizep) {
 769                const unsigned char *data;
 770                unsigned char delta_head[64];
 771                unsigned long result_size;
 772                z_stream stream;
 773                int st;
 774
 775                memset(&stream, 0, sizeof(stream));
 776
 777                data = stream.next_in = base_sha1 + 20;
 778                stream.avail_in = left - 20;
 779                stream.next_out = delta_head;
 780                stream.avail_out = sizeof(delta_head);
 781
 782                inflateInit(&stream);
 783                st = inflate(&stream, Z_FINISH);
 784                inflateEnd(&stream);
 785                if ((st != Z_STREAM_END) &&
 786                    stream.total_out != sizeof(delta_head))
 787                        die("delta data unpack-initial failed");
 788
 789                /* Examine the initial part of the delta to figure out
 790                 * the result size.
 791                 */
 792                data = delta_head;
 793                get_delta_hdr_size(&data); /* ignore base size */
 794
 795                /* Read the result size */
 796                result_size = get_delta_hdr_size(&data);
 797                *sizep = result_size;
 798        }
 799        return 0;
 800}
 801
 802static unsigned long unpack_object_header(struct packed_git *p, unsigned long offset,
 803        enum object_type *type, unsigned long *sizep)
 804{
 805        unsigned shift;
 806        unsigned char *pack, c;
 807        unsigned long size;
 808
 809        if (offset >= p->pack_size)
 810                die("object offset outside of pack file");
 811
 812        pack =  p->pack_base + offset;
 813        c = *pack++;
 814        offset++;
 815        *type = (c >> 4) & 7;
 816        size = c & 15;
 817        shift = 4;
 818        while (c & 0x80) {
 819                if (offset >= p->pack_size)
 820                        die("object offset outside of pack file");
 821                c = *pack++;
 822                offset++;
 823                size += (c & 0x7f) << shift;
 824                shift += 7;
 825        }
 826        *sizep = size;
 827        return offset;
 828}
 829
 830void packed_object_info_detail(struct pack_entry *e,
 831                               char *type,
 832                               unsigned long *size,
 833                               unsigned long *store_size,
 834                               int *delta_chain_length,
 835                               unsigned char *base_sha1)
 836{
 837        struct packed_git *p = e->p;
 838        unsigned long offset, left;
 839        unsigned char *pack;
 840        enum object_type kind;
 841
 842        offset = unpack_object_header(p, e->offset, &kind, size);
 843        pack = p->pack_base + offset;
 844        left = p->pack_size - offset;
 845        if (kind != OBJ_DELTA)
 846                *delta_chain_length = 0;
 847        else {
 848                int chain_length = 0;
 849                memcpy(base_sha1, pack, 20);
 850                do {
 851                        struct pack_entry base_ent;
 852                        unsigned long junk;
 853
 854                        find_pack_entry_one(pack, &base_ent, p);
 855                        offset = unpack_object_header(p, base_ent.offset,
 856                                                      &kind, &junk);
 857                        pack = p->pack_base + offset;
 858                        chain_length++;
 859                } while (kind == OBJ_DELTA);
 860                *delta_chain_length = chain_length;
 861        }
 862        switch (kind) {
 863        case OBJ_COMMIT:
 864                strcpy(type, "commit");
 865                break;
 866        case OBJ_TREE:
 867                strcpy(type, "tree");
 868                break;
 869        case OBJ_BLOB:
 870                strcpy(type, "blob");
 871                break;
 872        case OBJ_TAG:
 873                strcpy(type, "tag");
 874                break;
 875        default:
 876                die("corrupted pack file %s containing object of kind %d",
 877                    p->pack_name, kind);
 878        }
 879        *store_size = 0; /* notyet */
 880}
 881
 882static int packed_object_info(struct pack_entry *entry,
 883                              char *type, unsigned long *sizep)
 884{
 885        struct packed_git *p = entry->p;
 886        unsigned long offset, size, left;
 887        unsigned char *pack;
 888        enum object_type kind;
 889        int retval;
 890
 891        if (use_packed_git(p))
 892                die("cannot map packed file");
 893
 894        offset = unpack_object_header(p, entry->offset, &kind, &size);
 895        pack = p->pack_base + offset;
 896        left = p->pack_size - offset;
 897
 898        switch (kind) {
 899        case OBJ_DELTA:
 900                retval = packed_delta_info(pack, size, left, type, sizep, p);
 901                unuse_packed_git(p);
 902                return retval;
 903        case OBJ_COMMIT:
 904                strcpy(type, "commit");
 905                break;
 906        case OBJ_TREE:
 907                strcpy(type, "tree");
 908                break;
 909        case OBJ_BLOB:
 910                strcpy(type, "blob");
 911                break;
 912        case OBJ_TAG:
 913                strcpy(type, "tag");
 914                break;
 915        default:
 916                die("corrupted pack file %s containing object of kind %d",
 917                    p->pack_name, kind);
 918        }
 919        if (sizep)
 920                *sizep = size;
 921        unuse_packed_git(p);
 922        return 0;
 923}
 924
 925/* forward declaration for a mutually recursive function */
 926static void *unpack_entry(struct pack_entry *, char *, unsigned long *);
 927
 928static void *unpack_delta_entry(unsigned char *base_sha1,
 929                                unsigned long delta_size,
 930                                unsigned long left,
 931                                char *type,
 932                                unsigned long *sizep,
 933                                struct packed_git *p)
 934{
 935        struct pack_entry base_ent;
 936        void *data, *delta_data, *result, *base;
 937        unsigned long data_size, result_size, base_size;
 938        z_stream stream;
 939        int st;
 940
 941        if (left < 20)
 942                die("truncated pack file");
 943        data = base_sha1 + 20;
 944        data_size = left - 20;
 945        delta_data = xmalloc(delta_size);
 946
 947        memset(&stream, 0, sizeof(stream));
 948
 949        stream.next_in = data;
 950        stream.avail_in = data_size;
 951        stream.next_out = delta_data;
 952        stream.avail_out = delta_size;
 953
 954        inflateInit(&stream);
 955        st = inflate(&stream, Z_FINISH);
 956        inflateEnd(&stream);
 957        if ((st != Z_STREAM_END) || stream.total_out != delta_size)
 958                die("delta data unpack failed");
 959
 960        /* The base entry _must_ be in the same pack */
 961        if (!find_pack_entry_one(base_sha1, &base_ent, p))
 962                die("failed to find delta-pack base object %s",
 963                    sha1_to_hex(base_sha1));
 964        base = unpack_entry_gently(&base_ent, type, &base_size);
 965        if (!base)
 966                die("failed to read delta-pack base object %s",
 967                    sha1_to_hex(base_sha1));
 968        result = patch_delta(base, base_size,
 969                             delta_data, delta_size,
 970                             &result_size);
 971        if (!result)
 972                die("failed to apply delta");
 973        free(delta_data);
 974        free(base);
 975        *sizep = result_size;
 976        return result;
 977}
 978
 979static void *unpack_non_delta_entry(unsigned char *data,
 980                                    unsigned long size,
 981                                    unsigned long left)
 982{
 983        int st;
 984        z_stream stream;
 985        unsigned char *buffer;
 986
 987        buffer = xmalloc(size + 1);
 988        buffer[size] = 0;
 989        memset(&stream, 0, sizeof(stream));
 990        stream.next_in = data;
 991        stream.avail_in = left;
 992        stream.next_out = buffer;
 993        stream.avail_out = size;
 994
 995        inflateInit(&stream);
 996        st = inflate(&stream, Z_FINISH);
 997        inflateEnd(&stream);
 998        if ((st != Z_STREAM_END) || stream.total_out != size) {
 999                free(buffer);
1000                return NULL;
1001        }
1002
1003        return buffer;
1004}
1005
1006static void *unpack_entry(struct pack_entry *entry,
1007                          char *type, unsigned long *sizep)
1008{
1009        struct packed_git *p = entry->p;
1010        void *retval;
1011
1012        if (use_packed_git(p))
1013                die("cannot map packed file");
1014        retval = unpack_entry_gently(entry, type, sizep);
1015        unuse_packed_git(p);
1016        if (!retval)
1017                die("corrupted pack file %s", p->pack_name);
1018        return retval;
1019}
1020
1021/* The caller is responsible for use_packed_git()/unuse_packed_git() pair */
1022void *unpack_entry_gently(struct pack_entry *entry,
1023                          char *type, unsigned long *sizep)
1024{
1025        struct packed_git *p = entry->p;
1026        unsigned long offset, size, left;
1027        unsigned char *pack;
1028        enum object_type kind;
1029        void *retval;
1030
1031        offset = unpack_object_header(p, entry->offset, &kind, &size);
1032        pack = p->pack_base + offset;
1033        left = p->pack_size - offset;
1034        switch (kind) {
1035        case OBJ_DELTA:
1036                retval = unpack_delta_entry(pack, size, left, type, sizep, p);
1037                return retval;
1038        case OBJ_COMMIT:
1039                strcpy(type, "commit");
1040                break;
1041        case OBJ_TREE:
1042                strcpy(type, "tree");
1043                break;
1044        case OBJ_BLOB:
1045                strcpy(type, "blob");
1046                break;
1047        case OBJ_TAG:
1048                strcpy(type, "tag");
1049                break;
1050        default:
1051                return NULL;
1052        }
1053        *sizep = size;
1054        retval = unpack_non_delta_entry(pack, size, left);
1055        return retval;
1056}
1057
1058int num_packed_objects(const struct packed_git *p)
1059{
1060        /* See check_packed_git_idx() */
1061        return (p->index_size - 20 - 20 - 4*256) / 24;
1062}
1063
1064int nth_packed_object_sha1(const struct packed_git *p, int n,
1065                           unsigned char* sha1)
1066{
1067        void *index = p->index_base + 256;
1068        if (n < 0 || num_packed_objects(p) <= n)
1069                return -1;
1070        memcpy(sha1, (index + 24 * n + 4), 20);
1071        return 0;
1072}
1073
1074int find_pack_entry_one(const unsigned char *sha1,
1075                        struct pack_entry *e, struct packed_git *p)
1076{
1077        unsigned int *level1_ofs = p->index_base;
1078        int hi = ntohl(level1_ofs[*sha1]);
1079        int lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
1080        void *index = p->index_base + 256;
1081
1082        do {
1083                int mi = (lo + hi) / 2;
1084                int cmp = memcmp(index + 24 * mi + 4, sha1, 20);
1085                if (!cmp) {
1086                        e->offset = ntohl(*((int*)(index + 24 * mi)));
1087                        memcpy(e->sha1, sha1, 20);
1088                        e->p = p;
1089                        return 1;
1090                }
1091                if (cmp > 0)
1092                        hi = mi;
1093                else
1094                        lo = mi+1;
1095        } while (lo < hi);
1096        return 0;
1097}
1098
1099static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
1100{
1101        struct packed_git *p;
1102        prepare_packed_git();
1103
1104        for (p = packed_git; p; p = p->next) {
1105                if (find_pack_entry_one(sha1, e, p))
1106                        return 1;
1107        }
1108        return 0;
1109}
1110
1111struct packed_git *find_sha1_pack(const unsigned char *sha1, 
1112                                  struct packed_git *packs)
1113{
1114        struct packed_git *p;
1115        struct pack_entry e;
1116
1117        for (p = packs; p; p = p->next) {
1118                if (find_pack_entry_one(sha1, &e, p))
1119                        return p;
1120        }
1121        return NULL;
1122        
1123}
1124
1125int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
1126{
1127        int status;
1128        unsigned long mapsize, size;
1129        void *map;
1130        z_stream stream;
1131        char hdr[128];
1132
1133        map = map_sha1_file_internal(sha1, &mapsize);
1134        if (!map) {
1135                struct pack_entry e;
1136
1137                if (!find_pack_entry(sha1, &e))
1138                        return error("unable to find %s", sha1_to_hex(sha1));
1139                return packed_object_info(&e, type, sizep);
1140        }
1141        if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
1142                status = error("unable to unpack %s header",
1143                               sha1_to_hex(sha1));
1144        if (parse_sha1_header(hdr, type, &size) < 0)
1145                status = error("unable to parse %s header", sha1_to_hex(sha1));
1146        else {
1147                status = 0;
1148                if (sizep)
1149                        *sizep = size;
1150        }
1151        inflateEnd(&stream);
1152        munmap(map, mapsize);
1153        return status;
1154}
1155
1156static void *read_packed_sha1(const unsigned char *sha1, char *type, unsigned long *size)
1157{
1158        struct pack_entry e;
1159
1160        if (!find_pack_entry(sha1, &e)) {
1161                error("cannot read sha1_file for %s", sha1_to_hex(sha1));
1162                return NULL;
1163        }
1164        return unpack_entry(&e, type, size);
1165}
1166
1167void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
1168{
1169        unsigned long mapsize;
1170        void *map, *buf;
1171        struct pack_entry e;
1172
1173        if (find_pack_entry(sha1, &e))
1174                return read_packed_sha1(sha1, type, size);
1175        map = map_sha1_file_internal(sha1, &mapsize);
1176        if (map) {
1177                buf = unpack_sha1_file(map, mapsize, type, size);
1178                munmap(map, mapsize);
1179                return buf;
1180        }
1181        return NULL;
1182}
1183
1184void *read_object_with_reference(const unsigned char *sha1,
1185                                 const char *required_type,
1186                                 unsigned long *size,
1187                                 unsigned char *actual_sha1_return)
1188{
1189        char type[20];
1190        void *buffer;
1191        unsigned long isize;
1192        unsigned char actual_sha1[20];
1193
1194        memcpy(actual_sha1, sha1, 20);
1195        while (1) {
1196                int ref_length = -1;
1197                const char *ref_type = NULL;
1198
1199                buffer = read_sha1_file(actual_sha1, type, &isize);
1200                if (!buffer)
1201                        return NULL;
1202                if (!strcmp(type, required_type)) {
1203                        *size = isize;
1204                        if (actual_sha1_return)
1205                                memcpy(actual_sha1_return, actual_sha1, 20);
1206                        return buffer;
1207                }
1208                /* Handle references */
1209                else if (!strcmp(type, "commit"))
1210                        ref_type = "tree ";
1211                else if (!strcmp(type, "tag"))
1212                        ref_type = "object ";
1213                else {
1214                        free(buffer);
1215                        return NULL;
1216                }
1217                ref_length = strlen(ref_type);
1218
1219                if (memcmp(buffer, ref_type, ref_length) ||
1220                    get_sha1_hex(buffer + ref_length, actual_sha1)) {
1221                        free(buffer);
1222                        return NULL;
1223                }
1224                free(buffer);
1225                /* Now we have the ID of the referred-to object in
1226                 * actual_sha1.  Check again. */
1227        }
1228}
1229
1230char *write_sha1_file_prepare(void *buf,
1231                              unsigned long len,
1232                              const char *type,
1233                              unsigned char *sha1,
1234                              unsigned char *hdr,
1235                              int *hdrlen)
1236{
1237        SHA_CTX c;
1238
1239        /* Generate the header */
1240        *hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
1241
1242        /* Sha1.. */
1243        SHA1_Init(&c);
1244        SHA1_Update(&c, hdr, *hdrlen);
1245        SHA1_Update(&c, buf, len);
1246        SHA1_Final(sha1, &c);
1247
1248        return sha1_file_name(sha1);
1249}
1250
1251int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
1252{
1253        int size;
1254        unsigned char *compressed;
1255        z_stream stream;
1256        unsigned char sha1[20];
1257        char *filename;
1258        static char tmpfile[PATH_MAX];
1259        unsigned char hdr[50];
1260        int fd, hdrlen, ret;
1261
1262        /* Normally if we have it in the pack then we do not bother writing
1263         * it out into .git/objects/??/?{38} file.
1264         */
1265        filename = write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
1266        if (returnsha1)
1267                memcpy(returnsha1, sha1, 20);
1268        if (has_sha1_file(sha1))
1269                return 0;
1270        fd = open(filename, O_RDONLY);
1271        if (fd >= 0) {
1272                /*
1273                 * FIXME!!! We might do collision checking here, but we'd
1274                 * need to uncompress the old file and check it. Later.
1275                 */
1276                close(fd);
1277                return 0;
1278        }
1279
1280        if (errno != ENOENT) {
1281                fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
1282                return -1;
1283        }
1284
1285        snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
1286
1287        fd = mkstemp(tmpfile);
1288        if (fd < 0) {
1289                fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
1290                return -1;
1291        }
1292
1293        /* Set it up */
1294        memset(&stream, 0, sizeof(stream));
1295        deflateInit(&stream, Z_BEST_COMPRESSION);
1296        size = deflateBound(&stream, len+hdrlen);
1297        compressed = xmalloc(size);
1298
1299        /* Compress it */
1300        stream.next_out = compressed;
1301        stream.avail_out = size;
1302
1303        /* First header.. */
1304        stream.next_in = hdr;
1305        stream.avail_in = hdrlen;
1306        while (deflate(&stream, 0) == Z_OK)
1307                /* nothing */;
1308
1309        /* Then the data itself.. */
1310        stream.next_in = buf;
1311        stream.avail_in = len;
1312        while (deflate(&stream, Z_FINISH) == Z_OK)
1313                /* nothing */;
1314        deflateEnd(&stream);
1315        size = stream.total_out;
1316
1317        if (write(fd, compressed, size) != size)
1318                die("unable to write file");
1319        fchmod(fd, 0444);
1320        close(fd);
1321        free(compressed);
1322
1323        ret = link(tmpfile, filename);
1324        if (ret < 0) {
1325                ret = errno;
1326
1327                /*
1328                 * Coda hack - coda doesn't like cross-directory links,
1329                 * so we fall back to a rename, which will mean that it
1330                 * won't be able to check collisions, but that's not a
1331                 * big deal.
1332                 *
1333                 * When this succeeds, we just return 0. We have nothing
1334                 * left to unlink.
1335                 */
1336                if (ret == EXDEV && !rename(tmpfile, filename))
1337                        return 0;
1338        }
1339        unlink(tmpfile);
1340        if (ret) {
1341                if (ret != EEXIST) {
1342                        fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
1343                        return -1;
1344                }
1345                /* FIXME!!! Collision check here ? */
1346        }
1347
1348        return 0;
1349}
1350
1351int write_sha1_to_fd(int fd, const unsigned char *sha1)
1352{
1353        ssize_t size;
1354        unsigned long objsize;
1355        int posn = 0;
1356        void *map = map_sha1_file_internal(sha1, &objsize);
1357        void *buf = map;
1358        void *temp_obj = NULL;
1359        z_stream stream;
1360
1361        if (!buf) {
1362                unsigned char *unpacked;
1363                unsigned long len;
1364                char type[20];
1365                char hdr[50];
1366                int hdrlen;
1367                // need to unpack and recompress it by itself
1368                unpacked = read_packed_sha1(sha1, type, &len);
1369
1370                hdrlen = sprintf(hdr, "%s %lu", type, len) + 1;
1371
1372                /* Set it up */
1373                memset(&stream, 0, sizeof(stream));
1374                deflateInit(&stream, Z_BEST_COMPRESSION);
1375                size = deflateBound(&stream, len + hdrlen);
1376                temp_obj = buf = xmalloc(size);
1377
1378                /* Compress it */
1379                stream.next_out = buf;
1380                stream.avail_out = size;
1381                
1382                /* First header.. */
1383                stream.next_in = (void *)hdr;
1384                stream.avail_in = hdrlen;
1385                while (deflate(&stream, 0) == Z_OK)
1386                        /* nothing */;
1387
1388                /* Then the data itself.. */
1389                stream.next_in = unpacked;
1390                stream.avail_in = len;
1391                while (deflate(&stream, Z_FINISH) == Z_OK)
1392                        /* nothing */;
1393                deflateEnd(&stream);
1394                free(unpacked);
1395                
1396                objsize = stream.total_out;
1397        }
1398
1399        do {
1400                size = write(fd, buf + posn, objsize - posn);
1401                if (size <= 0) {
1402                        if (!size) {
1403                                fprintf(stderr, "write closed");
1404                        } else {
1405                                perror("write ");
1406                        }
1407                        return -1;
1408                }
1409                posn += size;
1410        } while (posn < objsize);
1411
1412        if (map)
1413                munmap(map, objsize);
1414        if (temp_obj)
1415                free(temp_obj);
1416
1417        return 0;
1418}
1419
1420int write_sha1_from_fd(const unsigned char *sha1, int fd, char *buffer,
1421                       size_t bufsize, size_t *bufposn)
1422{
1423        char *filename = sha1_file_name(sha1);
1424
1425        int local;
1426        z_stream stream;
1427        unsigned char real_sha1[20];
1428        unsigned char discard[4096];
1429        int ret;
1430        SHA_CTX c;
1431
1432        local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
1433
1434        if (local < 0)
1435                return error("Couldn't open %s\n", filename);
1436
1437        memset(&stream, 0, sizeof(stream));
1438
1439        inflateInit(&stream);
1440
1441        SHA1_Init(&c);
1442
1443        do {
1444                ssize_t size;
1445                if (*bufposn) {
1446                        stream.avail_in = *bufposn;
1447                        stream.next_in = (unsigned char *) buffer;
1448                        do {
1449                                stream.next_out = discard;
1450                                stream.avail_out = sizeof(discard);
1451                                ret = inflate(&stream, Z_SYNC_FLUSH);
1452                                SHA1_Update(&c, discard, sizeof(discard) -
1453                                            stream.avail_out);
1454                        } while (stream.avail_in && ret == Z_OK);
1455                        write(local, buffer, *bufposn - stream.avail_in);
1456                        memmove(buffer, buffer + *bufposn - stream.avail_in,
1457                                stream.avail_in);
1458                        *bufposn = stream.avail_in;
1459                        if (ret != Z_OK)
1460                                break;
1461                }
1462                size = read(fd, buffer + *bufposn, bufsize - *bufposn);
1463                if (size <= 0) {
1464                        close(local);
1465                        unlink(filename);
1466                        if (!size)
1467                                return error("Connection closed?");
1468                        perror("Reading from connection");
1469                        return -1;
1470                }
1471                *bufposn += size;
1472        } while (1);
1473        inflateEnd(&stream);
1474
1475        close(local);
1476        SHA1_Final(real_sha1, &c);
1477        if (ret != Z_STREAM_END) {
1478                unlink(filename);
1479                return error("File %s corrupted", sha1_to_hex(sha1));
1480        }
1481        if (memcmp(sha1, real_sha1, 20)) {
1482                unlink(filename);
1483                return error("File %s has bad hash\n", sha1_to_hex(sha1));
1484        }
1485        
1486        return 0;
1487}
1488
1489int has_pack_index(const unsigned char *sha1)
1490{
1491        struct stat st;
1492        if (stat(sha1_pack_index_name(sha1), &st))
1493                return 0;
1494        return 1;
1495}
1496
1497int has_pack_file(const unsigned char *sha1)
1498{
1499        struct stat st;
1500        if (stat(sha1_pack_name(sha1), &st))
1501                return 0;
1502        return 1;
1503}
1504
1505int has_sha1_pack(const unsigned char *sha1)
1506{
1507        struct pack_entry e;
1508        return find_pack_entry(sha1, &e);
1509}
1510
1511int has_sha1_file(const unsigned char *sha1)
1512{
1513        struct stat st;
1514        struct pack_entry e;
1515
1516        if (find_pack_entry(sha1, &e))
1517                return 1;
1518        return find_sha1_file(sha1, &st) ? 1 : 0;
1519}
1520
1521int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object, const char *type)
1522{
1523        unsigned long size = st->st_size;
1524        void *buf;
1525        int ret;
1526        unsigned char hdr[50];
1527        int hdrlen;
1528
1529        buf = "";
1530        if (size)
1531                buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
1532        close(fd);
1533        if (buf == MAP_FAILED)
1534                return -1;
1535
1536        if (!type)
1537                type = "blob";
1538        if (write_object)
1539                ret = write_sha1_file(buf, size, type, sha1);
1540        else {
1541                write_sha1_file_prepare(buf, size, type, sha1, hdr, &hdrlen);
1542                ret = 0;
1543        }
1544        if (size)
1545                munmap(buf, size);
1546        return ret;
1547}