f3920c2aefc48652e91d74fb91c32173f06db75a
   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 int get_sha1_file(const char *path, unsigned char *result)
  50{
  51        char buffer[60];
  52        int fd = open(path, O_RDONLY);
  53        int len;
  54
  55        if (fd < 0)
  56                return -1;
  57        len = read(fd, buffer, sizeof(buffer));
  58        close(fd);
  59        if (len < 40)
  60                return -1;
  61        return get_sha1_hex(buffer, result);
  62}
  63
  64static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir;
  65static void setup_git_env(void)
  66{
  67        git_dir = gitenv(GIT_DIR_ENVIRONMENT);
  68        if (!git_dir)
  69                git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
  70        git_object_dir = gitenv(DB_ENVIRONMENT);
  71        if (!git_object_dir) {
  72                git_object_dir = xmalloc(strlen(git_dir) + 9);
  73                sprintf(git_object_dir, "%s/objects", git_dir);
  74        }
  75        git_refs_dir = xmalloc(strlen(git_dir) + 6);
  76        sprintf(git_refs_dir, "%s/refs", git_dir);
  77        git_index_file = gitenv(INDEX_ENVIRONMENT);
  78        if (!git_index_file) {
  79                git_index_file = xmalloc(strlen(git_dir) + 7);
  80                sprintf(git_index_file, "%s/index", git_dir);
  81        }
  82}
  83
  84char *get_object_directory(void)
  85{
  86        if (!git_object_dir)
  87                setup_git_env();
  88        return git_object_dir;
  89}
  90
  91char *get_refs_directory(void)
  92{
  93        if (!git_refs_dir)
  94                setup_git_env();
  95        return git_refs_dir;
  96}
  97
  98char *get_index_file(void)
  99{
 100        if (!git_index_file)
 101                setup_git_env();
 102        return git_index_file;
 103}
 104
 105int get_sha1(const char *str, unsigned char *sha1)
 106{
 107        static char pathname[PATH_MAX];
 108        static const char *prefix[] = {
 109                "",
 110                "refs",
 111                "refs/tags",
 112                "refs/heads",
 113                "refs/snap",
 114                NULL
 115        };
 116        const char **p;
 117
 118        if (!get_sha1_hex(str, sha1))
 119                return 0;
 120
 121        if (!git_dir)
 122                setup_git_env();
 123        for (p = prefix; *p; p++) {
 124                snprintf(pathname, sizeof(pathname), "%s/%s/%s",
 125                         git_dir, *p, str);
 126                if (!get_sha1_file(pathname, sha1))
 127                        return 0;
 128        }
 129
 130        return -1;
 131}
 132
 133char * sha1_to_hex(const unsigned char *sha1)
 134{
 135        static char buffer[50];
 136        static const char hex[] = "0123456789abcdef";
 137        char *buf = buffer;
 138        int i;
 139
 140        for (i = 0; i < 20; i++) {
 141                unsigned int val = *sha1++;
 142                *buf++ = hex[val >> 4];
 143                *buf++ = hex[val & 0xf];
 144        }
 145        return buffer;
 146}
 147
 148static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 149{
 150        int i;
 151        for (i = 0; i < 20; i++) {
 152                static char hex[] = "0123456789abcdef";
 153                unsigned int val = sha1[i];
 154                char *pos = pathbuf + i*2 + (i > 0);
 155                *pos++ = hex[val >> 4];
 156                *pos = hex[val & 0xf];
 157        }
 158}
 159
 160/*
 161 * NOTE! This returns a statically allocated buffer, so you have to be
 162 * careful about using it. Do a "strdup()" if you need to save the
 163 * filename.
 164 *
 165 * Also note that this returns the location for creating.  Reading
 166 * SHA1 file can happen from any alternate directory listed in the
 167 * DB_ENVIRONMENT environment variable if it is not found in
 168 * the primary object database.
 169 */
 170char *sha1_file_name(const unsigned char *sha1)
 171{
 172        static char *name, *base;
 173
 174        if (!base) {
 175                const char *sha1_file_directory = get_object_directory();
 176                int len = strlen(sha1_file_directory);
 177                base = xmalloc(len + 60);
 178                memcpy(base, sha1_file_directory, len);
 179                memset(base+len, 0, 60);
 180                base[len] = '/';
 181                base[len+3] = '/';
 182                name = base + len + 1;
 183        }
 184        fill_sha1_path(name, sha1);
 185        return base;
 186}
 187
 188struct alternate_object_database *alt_odb;
 189
 190/*
 191 * Prepare alternate object database registry.
 192 * alt_odb points at an array of struct alternate_object_database.
 193 * This array is terminated with an element that has both its base
 194 * and name set to NULL.  alt_odb[n] comes from n'th non-empty
 195 * element from colon separated ALTERNATE_DB_ENVIRONMENT environment
 196 * variable, and its base points at a statically allocated buffer
 197 * that contains "/the/directory/corresponding/to/.git/objects/...",
 198 * while its name points just after the slash at the end of
 199 * ".git/objects/" in the example above, and has enough space to hold
 200 * 40-byte hex SHA1, an extra slash for the first level indirection,
 201 * and the terminating NUL.
 202 * This function allocates the alt_odb array and all the strings
 203 * pointed by base fields of the array elements with one xmalloc();
 204 * the string pool immediately follows the array.
 205 */
 206void prepare_alt_odb(void)
 207{
 208        int pass, totlen, i;
 209        const char *cp, *last;
 210        char *op = NULL;
 211        const char *alt = gitenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
 212
 213        if (alt_odb)
 214                return;
 215        /* The first pass counts how large an area to allocate to
 216         * hold the entire alt_odb structure, including array of
 217         * structs and path buffers for them.  The second pass fills
 218         * the structure and prepares the path buffers for use by
 219         * fill_sha1_path().
 220         */
 221        for (totlen = pass = 0; pass < 2; pass++) {
 222                last = alt;
 223                i = 0;
 224                do {
 225                        cp = strchr(last, ':') ? : last + strlen(last);
 226                        if (last != cp) {
 227                                /* 43 = 40-byte + 2 '/' + terminating NUL */
 228                                int pfxlen = cp - last;
 229                                int entlen = pfxlen + 43;
 230                                if (pass == 0)
 231                                        totlen += entlen;
 232                                else {
 233                                        alt_odb[i].base = op;
 234                                        alt_odb[i].name = op + pfxlen + 1;
 235                                        memcpy(op, last, pfxlen);
 236                                        op[pfxlen] = op[pfxlen + 3] = '/';
 237                                        op[entlen-1] = 0;
 238                                        op += entlen;
 239                                }
 240                                i++;
 241                        }
 242                        while (*cp && *cp == ':')
 243                                cp++;
 244                        last = cp;
 245                } while (*cp);
 246                if (pass)
 247                        break;
 248                alt_odb = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
 249                alt_odb[i].base = alt_odb[i].name = NULL;
 250                op = (char*)(&alt_odb[i+1]);
 251        }
 252}
 253
 254static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 255{
 256        int i;
 257        char *name = sha1_file_name(sha1);
 258
 259        if (!stat(name, st))
 260                return name;
 261        prepare_alt_odb();
 262        for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
 263                fill_sha1_path(name, sha1);
 264                if (!stat(alt_odb[i].base, st))
 265                        return alt_odb[i].base;
 266        }
 267        return NULL;
 268}
 269
 270#define PACK_MAX_SZ (1<<26)
 271static int pack_used_ctr;
 272static unsigned long pack_mapped;
 273struct packed_git *packed_git;
 274
 275static int check_packed_git_idx(const char *path, unsigned long *idx_size_,
 276                                void **idx_map_)
 277{
 278        void *idx_map;
 279        unsigned int *index;
 280        unsigned long idx_size;
 281        int nr, i;
 282        int fd = open(path, O_RDONLY);
 283        struct stat st;
 284        if (fd < 0)
 285                return -1;
 286        if (fstat(fd, &st)) {
 287                close(fd);
 288                return -1;
 289        }
 290        idx_size = st.st_size;
 291        idx_map = mmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
 292        close(fd);
 293        if (idx_map == MAP_FAILED)
 294                return -1;
 295
 296        index = idx_map;
 297
 298        /* check index map */
 299        if (idx_size < 4*256 + 20 + 20)
 300                return error("index file too small");
 301        nr = 0;
 302        for (i = 0; i < 256; i++) {
 303                unsigned int n = ntohl(index[i]);
 304                if (n < nr)
 305                        return error("non-monotonic index");
 306                nr = n;
 307        }
 308
 309        /*
 310         * Total size:
 311         *  - 256 index entries 4 bytes each
 312         *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
 313         *  - 20-byte SHA1 of the packfile
 314         *  - 20-byte SHA1 file checksum
 315         */
 316        if (idx_size != 4*256 + nr * 24 + 20 + 20)
 317                return error("wrong index file size");
 318
 319        *idx_map_ = idx_map;
 320        *idx_size_ = idx_size;
 321        return 0;
 322}
 323
 324static int unuse_one_packed_git(void)
 325{
 326        struct packed_git *p, *lru = NULL;
 327
 328        for (p = packed_git; p; p = p->next) {
 329                if (p->pack_use_cnt || !p->pack_base)
 330                        continue;
 331                if (!lru || p->pack_last_used < lru->pack_last_used)
 332                        lru = p;
 333        }
 334        if (!lru)
 335                return 0;
 336        munmap(lru->pack_base, lru->pack_size);
 337        lru->pack_base = NULL;
 338        return 1;
 339}
 340
 341void unuse_packed_git(struct packed_git *p)
 342{
 343        p->pack_use_cnt--;
 344}
 345
 346int use_packed_git(struct packed_git *p)
 347{
 348        if (!p->pack_base) {
 349                int fd;
 350                struct stat st;
 351                void *map;
 352
 353                pack_mapped += p->pack_size;
 354                while (PACK_MAX_SZ < pack_mapped && unuse_one_packed_git())
 355                        ; /* nothing */
 356                fd = open(p->pack_name, O_RDONLY);
 357                if (fd < 0)
 358                        die("packfile %s cannot be opened", p->pack_name);
 359                if (fstat(fd, &st)) {
 360                        close(fd);
 361                        die("packfile %s cannot be opened", p->pack_name);
 362                }
 363                if (st.st_size != p->pack_size)
 364                        die("packfile %s size mismatch.", p->pack_name);
 365                map = mmap(NULL, p->pack_size, PROT_READ, MAP_PRIVATE, fd, 0);
 366                close(fd);
 367                if (map == MAP_FAILED)
 368                        die("packfile %s cannot be mapped.", p->pack_name);
 369                p->pack_base = map;
 370
 371                /* Check if the pack file matches with the index file.
 372                 * this is cheap.
 373                 */
 374                if (memcmp((char*)(p->index_base) + p->index_size - 40,
 375                           p->pack_base + p->pack_size - 20, 20))
 376                        die("packfile %s does not match index.", p->pack_name);
 377        }
 378        p->pack_last_used = pack_used_ctr++;
 379        p->pack_use_cnt++;
 380        return 0;
 381}
 382
 383struct packed_git *add_packed_git(char *path, int path_len)
 384{
 385        struct stat st;
 386        struct packed_git *p;
 387        unsigned long idx_size;
 388        void *idx_map;
 389
 390        if (check_packed_git_idx(path, &idx_size, &idx_map))
 391                return NULL;
 392
 393        /* do we have a corresponding .pack file? */
 394        strcpy(path + path_len - 4, ".pack");
 395        if (stat(path, &st) || !S_ISREG(st.st_mode)) {
 396                munmap(idx_map, idx_size);
 397                return NULL;
 398        }
 399        /* ok, it looks sane as far as we can check without
 400         * actually mapping the pack file.
 401         */
 402        p = xmalloc(sizeof(*p) + path_len + 2);
 403        strcpy(p->pack_name, path);
 404        p->index_size = idx_size;
 405        p->pack_size = st.st_size;
 406        p->index_base = idx_map;
 407        p->next = NULL;
 408        p->pack_base = NULL;
 409        p->pack_last_used = 0;
 410        p->pack_use_cnt = 0;
 411        return p;
 412}
 413
 414static void prepare_packed_git_one(char *objdir)
 415{
 416        char path[PATH_MAX];
 417        int len;
 418        DIR *dir;
 419        struct dirent *de;
 420
 421        sprintf(path, "%s/pack", objdir);
 422        len = strlen(path);
 423        dir = opendir(path);
 424        if (!dir)
 425                return;
 426        path[len++] = '/';
 427        while ((de = readdir(dir)) != NULL) {
 428                int namelen = strlen(de->d_name);
 429                struct packed_git *p;
 430
 431                if (strcmp(de->d_name + namelen - 4, ".idx"))
 432                        continue;
 433
 434                /* we have .idx.  Is it a file we can map? */
 435                strcpy(path + len, de->d_name);
 436                p = add_packed_git(path, len + namelen);
 437                if (!p)
 438                        continue;
 439                p->next = packed_git;
 440                packed_git = p;
 441        }
 442}
 443
 444void prepare_packed_git(void)
 445{
 446        int i;
 447        static int run_once = 0;
 448
 449        if (run_once++)
 450                return;
 451
 452        prepare_packed_git_one(get_object_directory());
 453        prepare_alt_odb();
 454        for (i = 0; alt_odb[i].base != NULL; i++) {
 455                alt_odb[i].name[0] = 0;
 456                prepare_packed_git_one(alt_odb[i].base);
 457        }
 458}
 459
 460int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
 461{
 462        char header[100];
 463        unsigned char real_sha1[20];
 464        SHA_CTX c;
 465
 466        SHA1_Init(&c);
 467        SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 468        SHA1_Update(&c, map, size);
 469        SHA1_Final(real_sha1, &c);
 470        return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 471}
 472
 473static void *map_sha1_file_internal(const unsigned char *sha1,
 474                                    unsigned long *size,
 475                                    int say_error)
 476{
 477        struct stat st;
 478        void *map;
 479        int fd;
 480        char *filename = find_sha1_file(sha1, &st);
 481
 482        if (!filename) {
 483                if (say_error)
 484                        error("cannot map sha1 file %s", sha1_to_hex(sha1));
 485                return NULL;
 486        }
 487
 488        fd = open(filename, O_RDONLY | sha1_file_open_flag);
 489        if (fd < 0) {
 490                /* See if it works without O_NOATIME */
 491                switch (sha1_file_open_flag) {
 492                default:
 493                        fd = open(filename, O_RDONLY);
 494                        if (fd >= 0)
 495                                break;
 496                /* Fallthrough */
 497                case 0:
 498                        if (say_error)
 499                                perror(filename);
 500                        return NULL;
 501                }
 502
 503                /* If it failed once, it will probably fail again.
 504                 * Stop using O_NOATIME
 505                 */
 506                sha1_file_open_flag = 0;
 507        }
 508        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 509        close(fd);
 510        if (-1 == (int)(long)map)
 511                return NULL;
 512        *size = st.st_size;
 513        return map;
 514}
 515
 516void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 517{
 518        return map_sha1_file_internal(sha1, size, 1);
 519}
 520
 521int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size)
 522{
 523        /* Get the data stream */
 524        memset(stream, 0, sizeof(*stream));
 525        stream->next_in = map;
 526        stream->avail_in = mapsize;
 527        stream->next_out = buffer;
 528        stream->avail_out = size;
 529
 530        inflateInit(stream);
 531        return inflate(stream, 0);
 532}
 533
 534void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
 535{
 536        int bytes = strlen(buffer) + 1;
 537        unsigned char *buf = xmalloc(1+size);
 538
 539        memcpy(buf, buffer + bytes, stream->total_out - bytes);
 540        bytes = stream->total_out - bytes;
 541        if (bytes < size) {
 542                stream->next_out = buf + bytes;
 543                stream->avail_out = size - bytes;
 544                while (inflate(stream, Z_FINISH) == Z_OK)
 545                        /* nothing */;
 546        }
 547        buf[size] = 0;
 548        inflateEnd(stream);
 549        return buf;
 550}
 551
 552/*
 553 * We used to just use "sscanf()", but that's actually way
 554 * too permissive for what we want to check. So do an anal
 555 * object header parse by hand.
 556 */
 557int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
 558{
 559        int i;
 560        unsigned long size;
 561
 562        /*
 563         * The type can be at most ten bytes (including the 
 564         * terminating '\0' that we add), and is followed by
 565         * a space. 
 566         */
 567        i = 10;
 568        for (;;) {
 569                char c = *hdr++;
 570                if (c == ' ')
 571                        break;
 572                if (!--i)
 573                        return -1;
 574                *type++ = c;
 575        }
 576        *type = 0;
 577
 578        /*
 579         * The length must follow immediately, and be in canonical
 580         * decimal format (ie "010" is not valid).
 581         */
 582        size = *hdr++ - '0';
 583        if (size > 9)
 584                return -1;
 585        if (size) {
 586                for (;;) {
 587                        unsigned long c = *hdr - '0';
 588                        if (c > 9)
 589                                break;
 590                        hdr++;
 591                        size = size * 10 + c;
 592                }
 593        }
 594        *sizep = size;
 595
 596        /*
 597         * The length must be followed by a zero byte
 598         */
 599        return *hdr ? -1 : 0;
 600}
 601
 602void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 603{
 604        int ret;
 605        z_stream stream;
 606        char hdr[8192];
 607
 608        ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 609        if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
 610                return NULL;
 611
 612        return unpack_sha1_rest(&stream, hdr, *size);
 613}
 614
 615/* forward declaration for a mutually recursive function */
 616static int packed_object_info(struct pack_entry *entry,
 617                              char *type, unsigned long *sizep);
 618
 619static int packed_delta_info(unsigned char *base_sha1,
 620                             unsigned long delta_size,
 621                             unsigned long left,
 622                             char *type,
 623                             unsigned long *sizep,
 624                             struct packed_git *p)
 625{
 626        struct pack_entry base_ent;
 627
 628        if (left < 20)
 629                die("truncated pack file");
 630
 631        /* The base entry _must_ be in the same pack */
 632        if (!find_pack_entry_one(base_sha1, &base_ent, p))
 633                die("failed to find delta-pack base object %s",
 634                    sha1_to_hex(base_sha1));
 635
 636        /* We choose to only get the type of the base object and
 637         * ignore potentially corrupt pack file that expects the delta
 638         * based on a base with a wrong size.  This saves tons of
 639         * inflate() calls.
 640         */
 641
 642        if (packed_object_info(&base_ent, type, NULL))
 643                die("cannot get info for delta-pack base");
 644
 645        if (sizep) {
 646                const unsigned char *data;
 647                unsigned char delta_head[64];
 648                unsigned long result_size;
 649                z_stream stream;
 650                int st;
 651
 652                memset(&stream, 0, sizeof(stream));
 653
 654                data = stream.next_in = base_sha1 + 20;
 655                stream.avail_in = left - 20;
 656                stream.next_out = delta_head;
 657                stream.avail_out = sizeof(delta_head);
 658
 659                inflateInit(&stream);
 660                st = inflate(&stream, Z_FINISH);
 661                inflateEnd(&stream);
 662                if ((st != Z_STREAM_END) &&
 663                    stream.total_out != sizeof(delta_head))
 664                        die("delta data unpack-initial failed");
 665
 666                /* Examine the initial part of the delta to figure out
 667                 * the result size.
 668                 */
 669                data = delta_head;
 670                get_delta_hdr_size(&data); /* ignore base size */
 671
 672                /* Read the result size */
 673                result_size = get_delta_hdr_size(&data);
 674                *sizep = result_size;
 675        }
 676        return 0;
 677}
 678
 679static unsigned long unpack_object_header(struct packed_git *p, unsigned long offset,
 680        enum object_type *type, unsigned long *sizep)
 681{
 682        unsigned shift;
 683        unsigned char *pack, c;
 684        unsigned long size;
 685
 686        if (offset >= p->pack_size)
 687                die("object offset outside of pack file");
 688
 689        pack =  p->pack_base + offset;
 690        c = *pack++;
 691        offset++;
 692        *type = (c >> 4) & 7;
 693        size = c & 15;
 694        shift = 4;
 695        while (c & 0x80) {
 696                if (offset >= p->pack_size)
 697                        die("object offset outside of pack file");
 698                c = *pack++;
 699                offset++;
 700                size += (c & 0x7f) << shift;
 701                shift += 7;
 702        }
 703        *sizep = size;
 704        return offset;
 705}
 706
 707static int packed_object_info(struct pack_entry *entry,
 708                              char *type, unsigned long *sizep)
 709{
 710        struct packed_git *p = entry->p;
 711        unsigned long offset, size, left;
 712        unsigned char *pack;
 713        enum object_type kind;
 714        int retval;
 715
 716        if (use_packed_git(p))
 717                die("cannot map packed file");
 718
 719        offset = unpack_object_header(p, entry->offset, &kind, &size);
 720        pack = p->pack_base + offset;
 721        left = p->pack_size - offset;
 722
 723        switch (kind) {
 724        case OBJ_DELTA:
 725                retval = packed_delta_info(pack, size, left, type, sizep, p);
 726                unuse_packed_git(p);
 727                return retval;
 728        case OBJ_COMMIT:
 729                strcpy(type, "commit");
 730                break;
 731        case OBJ_TREE:
 732                strcpy(type, "tree");
 733                break;
 734        case OBJ_BLOB:
 735                strcpy(type, "blob");
 736                break;
 737        case OBJ_TAG:
 738                strcpy(type, "tag");
 739                break;
 740        default:
 741                die("corrupted pack file");
 742        }
 743        if (sizep)
 744                *sizep = size;
 745        unuse_packed_git(p);
 746        return 0;
 747}
 748
 749/* forward declaration for a mutually recursive function */
 750static void *unpack_entry(struct pack_entry *, char *, unsigned long *);
 751
 752static void *unpack_delta_entry(unsigned char *base_sha1,
 753                                unsigned long delta_size,
 754                                unsigned long left,
 755                                char *type,
 756                                unsigned long *sizep,
 757                                struct packed_git *p)
 758{
 759        struct pack_entry base_ent;
 760        void *data, *delta_data, *result, *base;
 761        unsigned long data_size, result_size, base_size;
 762        z_stream stream;
 763        int st;
 764
 765        if (left < 20)
 766                die("truncated pack file");
 767        data = base_sha1 + 20;
 768        data_size = left - 20;
 769        delta_data = xmalloc(delta_size);
 770
 771        memset(&stream, 0, sizeof(stream));
 772
 773        stream.next_in = data;
 774        stream.avail_in = data_size;
 775        stream.next_out = delta_data;
 776        stream.avail_out = delta_size;
 777
 778        inflateInit(&stream);
 779        st = inflate(&stream, Z_FINISH);
 780        inflateEnd(&stream);
 781        if ((st != Z_STREAM_END) || stream.total_out != delta_size)
 782                die("delta data unpack failed");
 783
 784        /* The base entry _must_ be in the same pack */
 785        if (!find_pack_entry_one(base_sha1, &base_ent, p))
 786                die("failed to find delta-pack base object %s",
 787                    sha1_to_hex(base_sha1));
 788        base = unpack_entry_gently(&base_ent, type, &base_size);
 789        if (!base)
 790                die("failed to read delta-pack base object %s",
 791                    sha1_to_hex(base_sha1));
 792        result = patch_delta(base, base_size,
 793                             delta_data, delta_size,
 794                             &result_size);
 795        if (!result)
 796                die("failed to apply delta");
 797        free(delta_data);
 798        free(base);
 799        *sizep = result_size;
 800        return result;
 801}
 802
 803static void *unpack_non_delta_entry(unsigned char *data,
 804                                    unsigned long size,
 805                                    unsigned long left)
 806{
 807        int st;
 808        z_stream stream;
 809        char *buffer;
 810
 811        buffer = xmalloc(size + 1);
 812        buffer[size] = 0;
 813        memset(&stream, 0, sizeof(stream));
 814        stream.next_in = data;
 815        stream.avail_in = left;
 816        stream.next_out = buffer;
 817        stream.avail_out = size;
 818
 819        inflateInit(&stream);
 820        st = inflate(&stream, Z_FINISH);
 821        inflateEnd(&stream);
 822        if ((st != Z_STREAM_END) || stream.total_out != size) {
 823                free(buffer);
 824                return NULL;
 825        }
 826
 827        return buffer;
 828}
 829
 830static void *unpack_entry(struct pack_entry *entry,
 831                          char *type, unsigned long *sizep)
 832{
 833        struct packed_git *p = entry->p;
 834        void *retval;
 835
 836        if (use_packed_git(p))
 837                die("cannot map packed file");
 838        retval = unpack_entry_gently(entry, type, sizep);
 839        unuse_packed_git(p);
 840        if (!retval)
 841                die("corrupted pack file");
 842        return retval;
 843}
 844
 845/* The caller is responsible for use_packed_git()/unuse_packed_git() pair */
 846void *unpack_entry_gently(struct pack_entry *entry,
 847                          char *type, unsigned long *sizep)
 848{
 849        struct packed_git *p = entry->p;
 850        unsigned long offset, size, left;
 851        unsigned char *pack;
 852        enum object_type kind;
 853        void *retval;
 854
 855        offset = unpack_object_header(p, entry->offset, &kind, &size);
 856        pack = p->pack_base + offset;
 857        left = p->pack_size - offset;
 858        switch (kind) {
 859        case OBJ_DELTA:
 860                retval = unpack_delta_entry(pack, size, left, type, sizep, p);
 861                return retval;
 862        case OBJ_COMMIT:
 863                strcpy(type, "commit");
 864                break;
 865        case OBJ_TREE:
 866                strcpy(type, "tree");
 867                break;
 868        case OBJ_BLOB:
 869                strcpy(type, "blob");
 870                break;
 871        case OBJ_TAG:
 872                strcpy(type, "tag");
 873                break;
 874        default:
 875                return NULL;
 876        }
 877        *sizep = size;
 878        retval = unpack_non_delta_entry(pack, size, left);
 879        return retval;
 880}
 881
 882int num_packed_objects(const struct packed_git *p)
 883{
 884        /* See check_packed_git_idx() */
 885        return (p->index_size - 20 - 20 - 4*256) / 24;
 886}
 887
 888int nth_packed_object_sha1(const struct packed_git *p, int n,
 889                           unsigned char* sha1)
 890{
 891        void *index = p->index_base + 256;
 892        if (n < 0 || num_packed_objects(p) <= n)
 893                return -1;
 894        memcpy(sha1, (index + 24 * n + 4), 20);
 895        return 0;
 896}
 897
 898int find_pack_entry_one(const unsigned char *sha1,
 899                        struct pack_entry *e, struct packed_git *p)
 900{
 901        int *level1_ofs = p->index_base;
 902        int hi = ntohl(level1_ofs[*sha1]);
 903        int lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
 904        void *index = p->index_base + 256;
 905
 906        do {
 907                int mi = (lo + hi) / 2;
 908                int cmp = memcmp(index + 24 * mi + 4, sha1, 20);
 909                if (!cmp) {
 910                        e->offset = ntohl(*((int*)(index + 24 * mi)));
 911                        memcpy(e->sha1, sha1, 20);
 912                        e->p = p;
 913                        return 1;
 914                }
 915                if (cmp > 0)
 916                        hi = mi;
 917                else
 918                        lo = mi+1;
 919        } while (lo < hi);
 920        return 0;
 921}
 922
 923static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
 924{
 925        struct packed_git *p;
 926        prepare_packed_git();
 927
 928        for (p = packed_git; p; p = p->next) {
 929                if (find_pack_entry_one(sha1, e, p))
 930                        return 1;
 931        }
 932        return 0;
 933}
 934
 935int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
 936{
 937        int status;
 938        unsigned long mapsize, size;
 939        void *map;
 940        z_stream stream;
 941        char hdr[128];
 942
 943        map = map_sha1_file_internal(sha1, &mapsize, 0);
 944        if (!map) {
 945                struct pack_entry e;
 946
 947                if (!find_pack_entry(sha1, &e))
 948                        return error("unable to find %s", sha1_to_hex(sha1));
 949                return packed_object_info(&e, type, sizep);
 950        }
 951        if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
 952                status = error("unable to unpack %s header",
 953                               sha1_to_hex(sha1));
 954        if (parse_sha1_header(hdr, type, &size) < 0)
 955                status = error("unable to parse %s header", sha1_to_hex(sha1));
 956        else {
 957                status = 0;
 958                if (sizep)
 959                        *sizep = size;
 960        }
 961        inflateEnd(&stream);
 962        munmap(map, mapsize);
 963        return status;
 964}
 965
 966static void *read_packed_sha1(const unsigned char *sha1, char *type, unsigned long *size)
 967{
 968        struct pack_entry e;
 969
 970        if (!find_pack_entry(sha1, &e)) {
 971                error("cannot read sha1_file for %s", sha1_to_hex(sha1));
 972                return NULL;
 973        }
 974        return unpack_entry(&e, type, size);
 975}
 976
 977void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 978{
 979        unsigned long mapsize;
 980        void *map, *buf;
 981
 982        map = map_sha1_file_internal(sha1, &mapsize, 0);
 983        if (map) {
 984                buf = unpack_sha1_file(map, mapsize, type, size);
 985                munmap(map, mapsize);
 986                return buf;
 987        }
 988        return read_packed_sha1(sha1, type, size);
 989}
 990
 991void *read_object_with_reference(const unsigned char *sha1,
 992                                 const char *required_type,
 993                                 unsigned long *size,
 994                                 unsigned char *actual_sha1_return)
 995{
 996        char type[20];
 997        void *buffer;
 998        unsigned long isize;
 999        unsigned char actual_sha1[20];
1000
1001        memcpy(actual_sha1, sha1, 20);
1002        while (1) {
1003                int ref_length = -1;
1004                const char *ref_type = NULL;
1005
1006                buffer = read_sha1_file(actual_sha1, type, &isize);
1007                if (!buffer)
1008                        return NULL;
1009                if (!strcmp(type, required_type)) {
1010                        *size = isize;
1011                        if (actual_sha1_return)
1012                                memcpy(actual_sha1_return, actual_sha1, 20);
1013                        return buffer;
1014                }
1015                /* Handle references */
1016                else if (!strcmp(type, "commit"))
1017                        ref_type = "tree ";
1018                else if (!strcmp(type, "tag"))
1019                        ref_type = "object ";
1020                else {
1021                        free(buffer);
1022                        return NULL;
1023                }
1024                ref_length = strlen(ref_type);
1025
1026                if (memcmp(buffer, ref_type, ref_length) ||
1027                    get_sha1_hex(buffer + ref_length, actual_sha1)) {
1028                        free(buffer);
1029                        return NULL;
1030                }
1031                /* Now we have the ID of the referred-to object in
1032                 * actual_sha1.  Check again. */
1033        }
1034}
1035
1036static char *write_sha1_file_prepare(void *buf,
1037                                     unsigned long len,
1038                                     const char *type,
1039                                     unsigned char *sha1,
1040                                     unsigned char *hdr,
1041                                     int *hdrlen)
1042{
1043        SHA_CTX c;
1044
1045        /* Generate the header */
1046        *hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
1047
1048        /* Sha1.. */
1049        SHA1_Init(&c);
1050        SHA1_Update(&c, hdr, *hdrlen);
1051        SHA1_Update(&c, buf, len);
1052        SHA1_Final(sha1, &c);
1053
1054        return sha1_file_name(sha1);
1055}
1056
1057int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
1058{
1059        int size;
1060        unsigned char *compressed;
1061        z_stream stream;
1062        unsigned char sha1[20];
1063        char *filename;
1064        static char tmpfile[PATH_MAX];
1065        unsigned char hdr[50];
1066        int fd, hdrlen, ret;
1067
1068        /* Normally if we have it in the pack then we do not bother writing
1069         * it out into .git/objects/??/?{38} file.
1070         */
1071        filename = write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
1072        if (returnsha1)
1073                memcpy(returnsha1, sha1, 20);
1074        if (has_sha1_file(sha1))
1075                return 0;
1076        fd = open(filename, O_RDONLY);
1077        if (fd >= 0) {
1078                /*
1079                 * FIXME!!! We might do collision checking here, but we'd
1080                 * need to uncompress the old file and check it. Later.
1081                 */
1082                close(fd);
1083                return 0;
1084        }
1085
1086        if (errno != ENOENT) {
1087                fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
1088                return -1;
1089        }
1090
1091        snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
1092
1093        fd = mkstemp(tmpfile);
1094        if (fd < 0) {
1095                fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
1096                return -1;
1097        }
1098
1099        /* Set it up */
1100        memset(&stream, 0, sizeof(stream));
1101        deflateInit(&stream, Z_BEST_COMPRESSION);
1102        size = deflateBound(&stream, len+hdrlen);
1103        compressed = xmalloc(size);
1104
1105        /* Compress it */
1106        stream.next_out = compressed;
1107        stream.avail_out = size;
1108
1109        /* First header.. */
1110        stream.next_in = hdr;
1111        stream.avail_in = hdrlen;
1112        while (deflate(&stream, 0) == Z_OK)
1113                /* nothing */;
1114
1115        /* Then the data itself.. */
1116        stream.next_in = buf;
1117        stream.avail_in = len;
1118        while (deflate(&stream, Z_FINISH) == Z_OK)
1119                /* nothing */;
1120        deflateEnd(&stream);
1121        size = stream.total_out;
1122
1123        if (write(fd, compressed, size) != size)
1124                die("unable to write file");
1125        fchmod(fd, 0444);
1126        close(fd);
1127        free(compressed);
1128
1129        ret = link(tmpfile, filename);
1130        if (ret < 0) {
1131                ret = errno;
1132
1133                /*
1134                 * Coda hack - coda doesn't like cross-directory links,
1135                 * so we fall back to a rename, which will mean that it
1136                 * won't be able to check collisions, but that's not a
1137                 * big deal.
1138                 *
1139                 * When this succeeds, we just return 0. We have nothing
1140                 * left to unlink.
1141                 */
1142                if (ret == EXDEV && !rename(tmpfile, filename))
1143                        return 0;
1144        }
1145        unlink(tmpfile);
1146        if (ret) {
1147                if (ret != EEXIST) {
1148                        fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
1149                        return -1;
1150                }
1151                /* FIXME!!! Collision check here ? */
1152        }
1153
1154        return 0;
1155}
1156
1157int write_sha1_from_fd(const unsigned char *sha1, int fd)
1158{
1159        char *filename = sha1_file_name(sha1);
1160
1161        int local;
1162        z_stream stream;
1163        unsigned char real_sha1[20];
1164        unsigned char buf[4096];
1165        unsigned char discard[4096];
1166        int ret;
1167        SHA_CTX c;
1168
1169        local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
1170
1171        if (local < 0)
1172                return error("Couldn't open %s\n", filename);
1173
1174        memset(&stream, 0, sizeof(stream));
1175
1176        inflateInit(&stream);
1177
1178        SHA1_Init(&c);
1179
1180        do {
1181                ssize_t size;
1182                size = read(fd, buf, 4096);
1183                if (size <= 0) {
1184                        close(local);
1185                        unlink(filename);
1186                        if (!size)
1187                                return error("Connection closed?");
1188                        perror("Reading from connection");
1189                        return -1;
1190                }
1191                write(local, buf, size);
1192                stream.avail_in = size;
1193                stream.next_in = buf;
1194                do {
1195                        stream.next_out = discard;
1196                        stream.avail_out = sizeof(discard);
1197                        ret = inflate(&stream, Z_SYNC_FLUSH);
1198                        SHA1_Update(&c, discard, sizeof(discard) -
1199                                    stream.avail_out);
1200                } while (stream.avail_in && ret == Z_OK);
1201                
1202        } while (ret == Z_OK);
1203        inflateEnd(&stream);
1204
1205        close(local);
1206        SHA1_Final(real_sha1, &c);
1207        if (ret != Z_STREAM_END) {
1208                unlink(filename);
1209                return error("File %s corrupted", sha1_to_hex(sha1));
1210        }
1211        if (memcmp(sha1, real_sha1, 20)) {
1212                unlink(filename);
1213                return error("File %s has bad hash\n", sha1_to_hex(sha1));
1214        }
1215        
1216        return 0;
1217}
1218
1219int has_sha1_file(const unsigned char *sha1)
1220{
1221        struct stat st;
1222        struct pack_entry e;
1223
1224        if (find_sha1_file(sha1, &st))
1225                return 1;
1226        return find_pack_entry(sha1, &e);
1227}
1228
1229int index_fd(unsigned char *sha1, int fd, struct stat *st)
1230{
1231        unsigned long size = st->st_size;
1232        void *buf;
1233        int ret;
1234
1235        buf = "";
1236        if (size)
1237                buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
1238        close(fd);
1239        if ((int)(long)buf == -1)
1240                return -1;
1241
1242        ret = write_sha1_file(buf, size, "blob", sha1);
1243        if (size)
1244                munmap(buf, size);
1245        return ret;
1246}