sha1_file.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  *
   6  * This handles basic git sha1 object files - packing, unpacking,
   7  * creation etc.
   8  */
   9 #include "cache.h"
  10 #include "delta.h"
  11
  12 #ifndef O_NOATIME
  13 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
  14 #define O_NOATIME 01000000
  15 #else
  16 #define O_NOATIME 0
  17 #endif
  18 #endif
  19
  20 static unsigned int sha1_file_open_flag = O_NOATIME;
  21
  22 static unsigned hexval(char c)
  23 {
  24         if (c >= '0' && c <= '9')
  25                 return c - '0';
  26         if (c >= 'a' && c <= 'f')
  27                 return c - 'a' + 10;
  28         if (c >= 'A' && c <= 'F')
  29                 return c - 'A' + 10;
  30         return ~0;
  31 }
  32
  33 int get_sha1_hex(const char *hex, unsigned char *sha1)
  34 {
  35         int i;
  36         for (i = 0; i < 20; i++) {
  37                 unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  38                 if (val & ~0xff)
  39                         return -1;
  40                 *sha1++ = val;
  41                 hex += 2;
  42         }
  43         return 0;
  44 }
  45
  46 static int get_sha1_file(const char *path, unsigned char *result)
  47 {
  48         char buffer[60];
  49         int fd = open(path, O_RDONLY);
  50         int len;
  51
  52         if (fd < 0)
  53                 return -1;
  54         len = read(fd, buffer, sizeof(buffer));
  55         close(fd);
  56         if (len < 40)
  57                 return -1;
  58         return get_sha1_hex(buffer, result);
  59 }
  60
  61 static char *git_dir, *git_object_dir, *git_index_file;
  62 static void setup_git_env(void)
  63 {
  64         git_dir = gitenv(GIT_DIR_ENVIRONMENT);
  65         if (!git_dir)
  66                 git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
  67         git_object_dir = gitenv(DB_ENVIRONMENT);
  68         if (!git_object_dir) {
  69                 git_object_dir = xmalloc(strlen(git_dir) + 9);
  70                 sprintf(git_object_dir, "%s/objects", git_dir);
  71         }
  72         git_index_file = gitenv(INDEX_ENVIRONMENT);
  73         if (!git_index_file) {
  74                 git_index_file = xmalloc(strlen(git_dir) + 7);
  75                 sprintf(git_index_file, "%s/index", git_dir);
  76         }
  77 }
  78
  79 char *get_object_directory(void)
  80 {
  81         if (!git_object_dir)
  82                 setup_git_env();
  83         return git_object_dir;
  84 }
  85
  86 char *get_index_file(void)
  87 {
  88         if (!git_index_file)
  89                 setup_git_env();
  90         return git_index_file;
  91 }
  92
  93 int get_sha1(const char *str, unsigned char *sha1)
  94 {
  95         static char pathname[PATH_MAX];
  96         static const char *prefix[] = {
  97                 "",
  98                 "refs",
  99                 "refs/tags",
 100                 "refs/heads",
 101                 "refs/snap",
 102                 NULL
 103         };
 104         const char **p;
 105
 106         if (!get_sha1_hex(str, sha1))
 107                 return 0;
 108
 109         if (!git_dir)
 110                 setup_git_env();
 111         for (p = prefix; *p; p++) {
 112                 snprintf(pathname, sizeof(pathname), "%s/%s/%s",
 113                          git_dir, *p, str);
 114                 if (!get_sha1_file(pathname, sha1))
 115                         return 0;
 116         }
 117
 118         return -1;
 119 }
 120
 121 char * sha1_to_hex(const unsigned char *sha1)
 122 {
 123         static char buffer[50];
 124         static const char hex[] = "0123456789abcdef";
 125         char *buf = buffer;
 126         int i;
 127
 128         for (i = 0; i < 20; i++) {
 129                 unsigned int val = *sha1++;
 130                 *buf++ = hex[val >> 4];
 131                 *buf++ = hex[val & 0xf];
 132         }
 133         return buffer;
 134 }
 135
 136 static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 137 {
 138         int i;
 139         for (i = 0; i < 20; i++) {
 140                 static char hex[] = "0123456789abcdef";
 141                 unsigned int val = sha1[i];
 142                 char *pos = pathbuf + i*2 + (i > 0);
 143                 *pos++ = hex[val >> 4];
 144                 *pos = hex[val & 0xf];
 145         }
 146 }
 147
 148 /*
 149  * NOTE! This returns a statically allocated buffer, so you have to be
 150  * careful about using it. Do a "strdup()" if you need to save the
 151  * filename.
 152  *
 153  * Also note that this returns the location for creating.  Reading
 154  * SHA1 file can happen from any alternate directory listed in the
 155  * DB_ENVIRONMENT environment variable if it is not found in
 156  * the primary object database.
 157  */
 158 char *sha1_file_name(const unsigned char *sha1)
 159 {
 160         static char *name, *base;
 161
 162         if (!base) {
 163                 const char *sha1_file_directory = get_object_directory();
 164                 int len = strlen(sha1_file_directory);
 165                 base = xmalloc(len + 60);
 166                 memcpy(base, sha1_file_directory, len);
 167                 memset(base+len, 0, 60);
 168                 base[len] = '/';
 169                 base[len+3] = '/';
 170                 name = base + len + 1;
 171         }
 172         fill_sha1_path(name, sha1);
 173         return base;
 174 }
 175
 176 static struct alternate_object_database {
 177         char *base;
 178         char *name;
 179 } *alt_odb;
 180
 181 /*
 182  * Prepare alternate object database registry.
 183  * alt_odb points at an array of struct alternate_object_database.
 184  * This array is terminated with an element that has both its base
 185  * and name set to NULL.  alt_odb[n] comes from n'th non-empty
 186  * element from colon separated ALTERNATE_DB_ENVIRONMENT environment
 187  * variable, and its base points at a statically allocated buffer
 188  * that contains "/the/directory/corresponding/to/.git/objects/...",
 189  * while its name points just after the slash at the end of
 190  * ".git/objects/" in the example above, and has enough space to hold
 191  * 40-byte hex SHA1, an extra slash for the first level indirection,
 192  * and the terminating NUL.
 193  * This function allocates the alt_odb array and all the strings
 194  * pointed by base fields of the array elements with one xmalloc();
 195  * the string pool immediately follows the array.
 196  */
 197 static void prepare_alt_odb(void)
 198 {
 199         int pass, totlen, i;
 200         const char *cp, *last;
 201         char *op = NULL;
 202         const char *alt = gitenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
 203
 204         /* The first pass counts how large an area to allocate to
 205          * hold the entire alt_odb structure, including array of
 206          * structs and path buffers for them.  The second pass fills
 207          * the structure and prepares the path buffers for use by
 208          * fill_sha1_path().
 209          */
 210         for (totlen = pass = 0; pass < 2; pass++) {
 211                 last = alt;
 212                 i = 0;
 213                 do {
 214                         cp = strchr(last, ':') ? : last + strlen(last);
 215                         if (last != cp) {
 216                                 /* 43 = 40-byte + 2 '/' + terminating NUL */
 217                                 int pfxlen = cp - last;
 218                                 int entlen = pfxlen + 43;
 219                                 if (pass == 0)
 220                                         totlen += entlen;
 221                                 else {
 222                                         alt_odb[i].base = op;
 223                                         alt_odb[i].name = op + pfxlen + 1;
 224                                         memcpy(op, last, pfxlen);
 225                                         op[pfxlen] = op[pfxlen + 3] = '/';
 226                                         op[entlen-1] = 0;
 227                                         op += entlen;
 228                                 }
 229                                 i++;
 230                         }
 231                         while (*cp && *cp == ':')
 232                                 cp++;
 233                         last = cp;
 234                 } while (*cp);
 235                 if (pass)
 236                         break;
 237                 alt_odb = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
 238                 alt_odb[i].base = alt_odb[i].name = NULL;
 239                 op = (char*)(&alt_odb[i+1]);
 240         }
 241 }
 242
 243 static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 244 {
 245         int i;
 246         char *name = sha1_file_name(sha1);
 247
 248         if (!stat(name, st))
 249                 return name;
 250         if (!alt_odb)
 251                 prepare_alt_odb();
 252         for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
 253                 fill_sha1_path(name, sha1);
 254                 if (!stat(alt_odb[i].base, st))
 255                         return alt_odb[i].base;
 256         }
 257         return NULL;
 258 }
 259
 260 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
 261 {
 262         char header[100];
 263         unsigned char real_sha1[20];
 264         SHA_CTX c;
 265
 266         SHA1_Init(&c);
 267         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 268         SHA1_Update(&c, map, size);
 269         SHA1_Final(real_sha1, &c);
 270         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 271 }
 272
 273 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 274 {
 275         struct stat st;
 276         void *map;
 277         int fd;
 278         char *filename = find_sha1_file(sha1, &st);
 279
 280         if (!filename) {
 281                 error("cannot map sha1 file %s", sha1_to_hex(sha1));
 282                 return NULL;
 283         }
 284
 285         fd = open(filename, O_RDONLY | sha1_file_open_flag);
 286         if (fd < 0) {
 287                 /* See if it works without O_NOATIME */
 288                 switch (sha1_file_open_flag) {
 289                 default:
 290                         fd = open(filename, O_RDONLY);
 291                         if (fd >= 0)
 292                                 break;
 293                 /* Fallthrough */
 294                 case 0:
 295                         perror(filename);
 296                         return NULL;
 297                 }
 298
 299                 /* If it failed once, it will probably fail again. Stop using O_NOATIME */
 300                 sha1_file_open_flag = 0;
 301         }
 302         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 303         close(fd);
 304         if (-1 == (int)(long)map)
 305                 return NULL;
 306         *size = st.st_size;
 307         return map;
 308 }
 309
 310 int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size)
 311 {
 312         /* Get the data stream */
 313         memset(stream, 0, sizeof(*stream));
 314         stream->next_in = map;
 315         stream->avail_in = mapsize;
 316         stream->next_out = buffer;
 317         stream->avail_out = size;
 318
 319         inflateInit(stream);
 320         return inflate(stream, 0);
 321 }
 322
 323 void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
 324 {
 325         int bytes = strlen(buffer) + 1;
 326         char *buf = xmalloc(1+size);
 327
 328         memcpy(buf, buffer + bytes, stream->total_out - bytes);
 329         bytes = stream->total_out - bytes;
 330         if (bytes < size) {
 331                 stream->next_out = buf + bytes;
 332                 stream->avail_out = size - bytes;
 333                 while (inflate(stream, Z_FINISH) == Z_OK)
 334                         /* nothing */;
 335         }
 336         buf[size] = 0;
 337         inflateEnd(stream);
 338         return buf;
 339 }
 340
 341 /*
 342  * We used to just use "sscanf()", but that's actually way
 343  * too permissive for what we want to check. So do an anal
 344  * object header parse by hand.
 345  */
 346 int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
 347 {
 348         int i;
 349         unsigned long size;
 350
 351         /*
 352          * The type can be at most ten bytes (including the
 353          * terminating '\0' that we add), and is followed by
 354          * a space.
 355          */
 356         i = 10;
 357         for (;;) {
 358                 char c = *hdr++;
 359                 if (c == ' ')
 360                         break;
 361                 if (!--i)
 362                         return -1;
 363                 *type++ = c;
 364         }
 365         *type = 0;
 366
 367         /*
 368          * The length must follow immediately, and be in canonical
 369          * decimal format (ie "010" is not valid).
 370          */
 371         size = *hdr++ - '0';
 372         if (size > 9)
 373                 return -1;
 374         if (size) {
 375                 for (;;) {
 376                         unsigned long c = *hdr - '0';
 377                         if (c > 9)
 378                                 break;
 379                         hdr++;
 380                         size = size * 10 + c;
 381                 }
 382         }
 383         *sizep = size;
 384
 385         /*
 386          * The length must be followed by a zero byte
 387          */
 388         return *hdr ? -1 : 0;
 389 }
 390
 391 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 392 {
 393         int ret;
 394         z_stream stream;
 395         char hdr[8192];
 396
 397         ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 398         if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
 399                 return NULL;
 400
 401         return unpack_sha1_rest(&stream, hdr, *size);
 402 }
 403
 404 int sha1_delta_base(const unsigned char *sha1, unsigned char *base_sha1)
 405 {
 406         int ret;
 407         unsigned long mapsize, size;
 408         void *map;
 409         z_stream stream;
 410         char hdr[64], type[20];
 411         void *delta_data_head;
 412
 413         map = map_sha1_file(sha1, &mapsize);
 414         if (!map)
 415                 return -1;
 416         ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 417         if (ret < Z_OK || parse_sha1_header(hdr, type, &size) < 0) {
 418                 ret = -1;
 419                 goto out;
 420         }
 421         if (strcmp(type, "delta")) {
 422                 ret = 0;
 423                 goto out;
 424         }
 425
 426         delta_data_head = hdr + strlen(hdr) + 1;
 427         ret = 1;
 428         memcpy(base_sha1, delta_data_head, 20);
 429  out:
 430         inflateEnd(&stream);
 431         munmap(map, mapsize);
 432         return ret;
 433 }
 434
 435 int sha1_file_size(const unsigned char *sha1, unsigned long *sizep)
 436 {
 437         int ret, status;
 438         unsigned long mapsize, size;
 439         void *map;
 440         z_stream stream;
 441         char hdr[64], type[20];
 442         const unsigned char *data;
 443         unsigned char cmd;
 444         int i;
 445
 446         map = map_sha1_file(sha1, &mapsize);
 447         if (!map)
 448                 return -1;
 449         ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 450         status = -1;
 451         if (ret < Z_OK || parse_sha1_header(hdr, type, &size) < 0)
 452                 goto out;
 453         if (strcmp(type, "delta")) {
 454                 *sizep = size;
 455                 status = 0;
 456                 goto out;
 457         }
 458
 459         /* We are dealing with a delta object.  Inflated, the first
 460          * 20 bytes hold the base object SHA1, and delta data follows
 461          * immediately after it.
 462          *
 463          * The initial part of the delta starts at delta_data_head +
 464          * 20.  Borrow code from patch-delta to read the result size.
 465          */
 466         data = hdr + strlen(hdr) + 1 + 20;
 467
 468         /* Skip over the source size; we are not interested in
 469          * it and we cannot verify it because we do not want
 470          * to read the base object.
 471          */
 472         cmd = *data++;
 473         while (cmd) {
 474                 if (cmd & 1)
 475                         data++;
 476                 cmd >>= 1;
 477         }
 478         /* Read the result size */
 479         size = i = 0;
 480         cmd = *data++;
 481         while (cmd) {
 482                 if (cmd & 1)
 483                         size |= *data++ << i;
 484                 i += 8;
 485                 cmd >>= 1;
 486         }
 487         *sizep = size;
 488         status = 0;
 489  out:
 490         inflateEnd(&stream);
 491         munmap(map, mapsize);
 492         return status;
 493 }
 494
 495 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 496 {
 497         unsigned long mapsize;
 498         void *map, *buf;
 499
 500         map = map_sha1_file(sha1, &mapsize);
 501         if (map) {
 502                 buf = unpack_sha1_file(map, mapsize, type, size);
 503                 munmap(map, mapsize);
 504                 if (buf && !strcmp(type, "delta")) {
 505                         void *ref = NULL, *delta = buf;
 506                         unsigned long ref_size, delta_size = *size;
 507                         buf = NULL;
 508                         if (delta_size > 20)
 509                                 ref = read_sha1_file(delta, type, &ref_size);
 510                         if (ref)
 511                                 buf = patch_delta(ref, ref_size,
 512                                                   delta+20, delta_size-20,
 513                                                   size);
 514                         free(delta);
 515                         free(ref);
 516                 }
 517                 return buf;
 518         }
 519         return NULL;
 520 }
 521
 522 void *read_object_with_reference(const unsigned char *sha1,
 523                                  const char *required_type,
 524                                  unsigned long *size,
 525                                  unsigned char *actual_sha1_return)
 526 {
 527         char type[20];
 528         void *buffer;
 529         unsigned long isize;
 530         unsigned char actual_sha1[20];
 531
 532         memcpy(actual_sha1, sha1, 20);
 533         while (1) {
 534                 int ref_length = -1;
 535                 const char *ref_type = NULL;
 536
 537                 buffer = read_sha1_file(actual_sha1, type, &isize);
 538                 if (!buffer)
 539                         return NULL;
 540                 if (!strcmp(type, required_type)) {
 541                         *size = isize;
 542                         if (actual_sha1_return)
 543                                 memcpy(actual_sha1_return, actual_sha1, 20);
 544                         return buffer;
 545                 }
 546                 /* Handle references */
 547                 else if (!strcmp(type, "commit"))
 548                         ref_type = "tree ";
 549                 else if (!strcmp(type, "tag"))
 550                         ref_type = "object ";
 551                 else {
 552                         free(buffer);
 553                         return NULL;
 554                 }
 555                 ref_length = strlen(ref_type);
 556
 557                 if (memcmp(buffer, ref_type, ref_length) ||
 558                     get_sha1_hex(buffer + ref_length, actual_sha1)) {
 559                         free(buffer);
 560                         return NULL;
 561                 }
 562                 /* Now we have the ID of the referred-to object in
 563                  * actual_sha1.  Check again. */
 564         }
 565 }
 566
 567 int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 568 {
 569         int size;
 570         unsigned char *compressed;
 571         z_stream stream;
 572         unsigned char sha1[20];
 573         SHA_CTX c;
 574         char *filename;
 575         static char tmpfile[PATH_MAX];
 576         unsigned char hdr[50];
 577         int fd, hdrlen, ret;
 578
 579         /* Generate the header */
 580         hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
 581
 582         /* Sha1.. */
 583         SHA1_Init(&c);
 584         SHA1_Update(&c, hdr, hdrlen);
 585         SHA1_Update(&c, buf, len);
 586         SHA1_Final(sha1, &c);
 587
 588         if (returnsha1)
 589                 memcpy(returnsha1, sha1, 20);
 590
 591         filename = sha1_file_name(sha1);
 592         fd = open(filename, O_RDONLY);
 593         if (fd >= 0) {
 594                 /*
 595                  * FIXME!!! We might do collision checking here, but we'd
 596                  * need to uncompress the old file and check it. Later.
 597                  */
 598                 close(fd);
 599                 return 0;
 600         }
 601
 602         if (errno != ENOENT) {
 603                 fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
 604                 return -1;
 605         }
 606
 607         snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
 608
 609         fd = mkstemp(tmpfile);
 610         if (fd < 0) {
 611                 fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
 612                 return -1;
 613         }
 614
 615         /* Set it up */
 616         memset(&stream, 0, sizeof(stream));
 617         deflateInit(&stream, Z_BEST_COMPRESSION);
 618         size = deflateBound(&stream, len+hdrlen);
 619         compressed = xmalloc(size);
 620
 621         /* Compress it */
 622         stream.next_out = compressed;
 623         stream.avail_out = size;
 624
 625         /* First header.. */
 626         stream.next_in = hdr;
 627         stream.avail_in = hdrlen;
 628         while (deflate(&stream, 0) == Z_OK)
 629                 /* nothing */;
 630
 631         /* Then the data itself.. */
 632         stream.next_in = buf;
 633         stream.avail_in = len;
 634         while (deflate(&stream, Z_FINISH) == Z_OK)
 635                 /* nothing */;
 636         deflateEnd(&stream);
 637         size = stream.total_out;
 638
 639         if (write(fd, compressed, size) != size)
 640                 die("unable to write file");
 641         fchmod(fd, 0444);
 642         close(fd);
 643         free(compressed);
 644
 645         ret = link(tmpfile, filename);
 646         if (ret < 0) {
 647                 ret = errno;
 648
 649                 /*
 650                  * Coda hack - coda doesn't like cross-directory links,
 651                  * so we fall back to a rename, which will mean that it
 652                  * won't be able to check collisions, but that's not a
 653                  * big deal.
 654                  *
 655                  * When this succeeds, we just return 0. We have nothing
 656                  * left to unlink.
 657                  */
 658                 if (ret == EXDEV && !rename(tmpfile, filename))
 659                         return 0;
 660         }
 661         unlink(tmpfile);
 662         if (ret) {
 663                 if (ret != EEXIST) {
 664                         fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
 665                         return -1;
 666                 }
 667                 /* FIXME!!! Collision check here ? */
 668         }
 669
 670         return 0;
 671 }
 672
 673 int write_sha1_from_fd(const unsigned char *sha1, int fd)
 674 {
 675         char *filename = sha1_file_name(sha1);
 676
 677         int local;
 678         z_stream stream;
 679         unsigned char real_sha1[20];
 680         unsigned char buf[4096];
 681         unsigned char discard[4096];
 682         int ret;
 683         SHA_CTX c;
 684
 685         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 686
 687         if (local < 0)
 688                 return error("Couldn't open %s\n", filename);
 689
 690         memset(&stream, 0, sizeof(stream));
 691
 692         inflateInit(&stream);
 693
 694         SHA1_Init(&c);
 695
 696         do {
 697                 ssize_t size;
 698                 size = read(fd, buf, 4096);
 699                 if (size <= 0) {
 700                         close(local);
 701                         unlink(filename);
 702                         if (!size)
 703                                 return error("Connection closed?");
 704                         perror("Reading from connection");
 705                         return -1;
 706                 }
 707                 write(local, buf, size);
 708                 stream.avail_in = size;
 709                 stream.next_in = buf;
 710                 do {
 711                         stream.next_out = discard;
 712                         stream.avail_out = sizeof(discard);
 713                         ret = inflate(&stream, Z_SYNC_FLUSH);
 714                         SHA1_Update(&c, discard, sizeof(discard) -
 715                                     stream.avail_out);
 716                 } while (stream.avail_in && ret == Z_OK);
 717
 718         } while (ret == Z_OK);
 719         inflateEnd(&stream);
 720
 721         close(local);
 722         SHA1_Final(real_sha1, &c);
 723         if (ret != Z_STREAM_END) {
 724                 unlink(filename);
 725                 return error("File %s corrupted", sha1_to_hex(sha1));
 726         }
 727         if (memcmp(sha1, real_sha1, 20)) {
 728                 unlink(filename);
 729                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
 730         }
 731
 732         return 0;
 733 }
 734
 735 int has_sha1_file(const unsigned char *sha1)
 736 {
 737         struct stat st;
 738         return !!find_sha1_file(sha1, &st);
 739 }
 740
 741 int index_fd(unsigned char *sha1, int fd, struct stat *st)
 742 {
 743         unsigned long size = st->st_size;
 744         void *buf;
 745         int ret;
 746
 747         buf = "";
 748         if (size)
 749                 buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 750         close(fd);
 751         if ((int)(long)buf == -1)
 752                 return -1;
 753
 754         ret = write_sha1_file(buf, size, "blob", sha1);
 755         if (size)
 756                 munmap(buf, size);
 757         return ret;
 758 }