sha1_file.con commit git-svn: reintroduce using a single get_log() to fetch (fbcc173)
   1/*
   2 * GIT - The information manager from hell
   3 *
   4 * Copyright (C) Linus Torvalds, 2005
   5 *
   6 * This handles basic git sha1 object files - packing, unpacking,
   7 * creation etc.
   8 */
   9#include "cache.h"
  10#include "delta.h"
  11#include "pack.h"
  12#include "blob.h"
  13#include "commit.h"
  14#include "tag.h"
  15#include "tree.h"
  16
  17#ifndef O_NOATIME
  18#if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
  19#define O_NOATIME 01000000
  20#else
  21#define O_NOATIME 0
  22#endif
  23#endif
  24
  25#ifdef NO_C99_FORMAT
  26#define SZ_FMT "lu"
  27#else
  28#define SZ_FMT "zu"
  29#endif
  30
  31const unsigned char null_sha1[20];
  32
  33static unsigned int sha1_file_open_flag = O_NOATIME;
  34
  35signed char hexval_table[256] = {
  36         -1, -1, -1, -1, -1, -1, -1, -1,                /* 00-07 */
  37         -1, -1, -1, -1, -1, -1, -1, -1,                /* 08-0f */
  38         -1, -1, -1, -1, -1, -1, -1, -1,                /* 10-17 */
  39         -1, -1, -1, -1, -1, -1, -1, -1,                /* 18-1f */
  40         -1, -1, -1, -1, -1, -1, -1, -1,                /* 20-27 */
  41         -1, -1, -1, -1, -1, -1, -1, -1,                /* 28-2f */
  42          0,  1,  2,  3,  4,  5,  6,  7,                /* 30-37 */
  43          8,  9, -1, -1, -1, -1, -1, -1,                /* 38-3f */
  44         -1, 10, 11, 12, 13, 14, 15, -1,                /* 40-47 */
  45         -1, -1, -1, -1, -1, -1, -1, -1,                /* 48-4f */
  46         -1, -1, -1, -1, -1, -1, -1, -1,                /* 50-57 */
  47         -1, -1, -1, -1, -1, -1, -1, -1,                /* 58-5f */
  48         -1, 10, 11, 12, 13, 14, 15, -1,                /* 60-67 */
  49         -1, -1, -1, -1, -1, -1, -1, -1,                /* 68-67 */
  50         -1, -1, -1, -1, -1, -1, -1, -1,                /* 70-77 */
  51         -1, -1, -1, -1, -1, -1, -1, -1,                /* 78-7f */
  52         -1, -1, -1, -1, -1, -1, -1, -1,                /* 80-87 */
  53         -1, -1, -1, -1, -1, -1, -1, -1,                /* 88-8f */
  54         -1, -1, -1, -1, -1, -1, -1, -1,                /* 90-97 */
  55         -1, -1, -1, -1, -1, -1, -1, -1,                /* 98-9f */
  56         -1, -1, -1, -1, -1, -1, -1, -1,                /* a0-a7 */
  57         -1, -1, -1, -1, -1, -1, -1, -1,                /* a8-af */
  58         -1, -1, -1, -1, -1, -1, -1, -1,                /* b0-b7 */
  59         -1, -1, -1, -1, -1, -1, -1, -1,                /* b8-bf */
  60         -1, -1, -1, -1, -1, -1, -1, -1,                /* c0-c7 */
  61         -1, -1, -1, -1, -1, -1, -1, -1,                /* c8-cf */
  62         -1, -1, -1, -1, -1, -1, -1, -1,                /* d0-d7 */
  63         -1, -1, -1, -1, -1, -1, -1, -1,                /* d8-df */
  64         -1, -1, -1, -1, -1, -1, -1, -1,                /* e0-e7 */
  65         -1, -1, -1, -1, -1, -1, -1, -1,                /* e8-ef */
  66         -1, -1, -1, -1, -1, -1, -1, -1,                /* f0-f7 */
  67         -1, -1, -1, -1, -1, -1, -1, -1,                /* f8-ff */
  68};
  69
  70int get_sha1_hex(const char *hex, unsigned char *sha1)
  71{
  72        int i;
  73        for (i = 0; i < 20; i++) {
  74                unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  75                if (val & ~0xff)
  76                        return -1;
  77                *sha1++ = val;
  78                hex += 2;
  79        }
  80        return 0;
  81}
  82
  83int safe_create_leading_directories(char *path)
  84{
  85        char *pos = path;
  86        struct stat st;
  87
  88        if (*pos == '/')
  89                pos++;
  90
  91        while (pos) {
  92                pos = strchr(pos, '/');
  93                if (!pos)
  94                        break;
  95                *pos = 0;
  96                if (!stat(path, &st)) {
  97                        /* path exists */
  98                        if (!S_ISDIR(st.st_mode)) {
  99                                *pos = '/';
 100                                return -3;
 101                        }
 102                }
 103                else if (mkdir(path, 0777)) {
 104                        *pos = '/';
 105                        return -1;
 106                }
 107                else if (adjust_shared_perm(path)) {
 108                        *pos = '/';
 109                        return -2;
 110                }
 111                *pos++ = '/';
 112        }
 113        return 0;
 114}
 115
 116char * sha1_to_hex(const unsigned char *sha1)
 117{
 118        static int bufno;
 119        static char hexbuffer[4][50];
 120        static const char hex[] = "0123456789abcdef";
 121        char *buffer = hexbuffer[3 & ++bufno], *buf = buffer;
 122        int i;
 123
 124        for (i = 0; i < 20; i++) {
 125                unsigned int val = *sha1++;
 126                *buf++ = hex[val >> 4];
 127                *buf++ = hex[val & 0xf];
 128        }
 129        *buf = '\0';
 130
 131        return buffer;
 132}
 133
 134static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 135{
 136        int i;
 137        for (i = 0; i < 20; i++) {
 138                static char hex[] = "0123456789abcdef";
 139                unsigned int val = sha1[i];
 140                char *pos = pathbuf + i*2 + (i > 0);
 141                *pos++ = hex[val >> 4];
 142                *pos = hex[val & 0xf];
 143        }
 144}
 145
 146/*
 147 * NOTE! This returns a statically allocated buffer, so you have to be
 148 * careful about using it. Do a "xstrdup()" if you need to save the
 149 * filename.
 150 *
 151 * Also note that this returns the location for creating.  Reading
 152 * SHA1 file can happen from any alternate directory listed in the
 153 * DB_ENVIRONMENT environment variable if it is not found in
 154 * the primary object database.
 155 */
 156char *sha1_file_name(const unsigned char *sha1)
 157{
 158        static char *name, *base;
 159
 160        if (!base) {
 161                const char *sha1_file_directory = get_object_directory();
 162                int len = strlen(sha1_file_directory);
 163                base = xmalloc(len + 60);
 164                memcpy(base, sha1_file_directory, len);
 165                memset(base+len, 0, 60);
 166                base[len] = '/';
 167                base[len+3] = '/';
 168                name = base + len + 1;
 169        }
 170        fill_sha1_path(name, sha1);
 171        return base;
 172}
 173
 174char *sha1_pack_name(const unsigned char *sha1)
 175{
 176        static const char hex[] = "0123456789abcdef";
 177        static char *name, *base, *buf;
 178        int i;
 179
 180        if (!base) {
 181                const char *sha1_file_directory = get_object_directory();
 182                int len = strlen(sha1_file_directory);
 183                base = xmalloc(len + 60);
 184                sprintf(base, "%s/pack/pack-1234567890123456789012345678901234567890.pack", sha1_file_directory);
 185                name = base + len + 11;
 186        }
 187
 188        buf = name;
 189
 190        for (i = 0; i < 20; i++) {
 191                unsigned int val = *sha1++;
 192                *buf++ = hex[val >> 4];
 193                *buf++ = hex[val & 0xf];
 194        }
 195        
 196        return base;
 197}
 198
 199char *sha1_pack_index_name(const unsigned char *sha1)
 200{
 201        static const char hex[] = "0123456789abcdef";
 202        static char *name, *base, *buf;
 203        int i;
 204
 205        if (!base) {
 206                const char *sha1_file_directory = get_object_directory();
 207                int len = strlen(sha1_file_directory);
 208                base = xmalloc(len + 60);
 209                sprintf(base, "%s/pack/pack-1234567890123456789012345678901234567890.idx", sha1_file_directory);
 210                name = base + len + 11;
 211        }
 212
 213        buf = name;
 214
 215        for (i = 0; i < 20; i++) {
 216                unsigned int val = *sha1++;
 217                *buf++ = hex[val >> 4];
 218                *buf++ = hex[val & 0xf];
 219        }
 220        
 221        return base;
 222}
 223
 224struct alternate_object_database *alt_odb_list;
 225static struct alternate_object_database **alt_odb_tail;
 226
 227static void read_info_alternates(const char * alternates, int depth);
 228
 229/*
 230 * Prepare alternate object database registry.
 231 *
 232 * The variable alt_odb_list points at the list of struct
 233 * alternate_object_database.  The elements on this list come from
 234 * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
 235 * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
 236 * whose contents is similar to that environment variable but can be
 237 * LF separated.  Its base points at a statically allocated buffer that
 238 * contains "/the/directory/corresponding/to/.git/objects/...", while
 239 * its name points just after the slash at the end of ".git/objects/"
 240 * in the example above, and has enough space to hold 40-byte hex
 241 * SHA1, an extra slash for the first level indirection, and the
 242 * terminating NUL.
 243 */
 244static int link_alt_odb_entry(const char * entry, int len, const char * relative_base, int depth)
 245{
 246        struct stat st;
 247        const char *objdir = get_object_directory();
 248        struct alternate_object_database *ent;
 249        struct alternate_object_database *alt;
 250        /* 43 = 40-byte + 2 '/' + terminating NUL */
 251        int pfxlen = len;
 252        int entlen = pfxlen + 43;
 253        int base_len = -1;
 254
 255        if (*entry != '/' && relative_base) {
 256                /* Relative alt-odb */
 257                if (base_len < 0)
 258                        base_len = strlen(relative_base) + 1;
 259                entlen += base_len;
 260                pfxlen += base_len;
 261        }
 262        ent = xmalloc(sizeof(*ent) + entlen);
 263
 264        if (*entry != '/' && relative_base) {
 265                memcpy(ent->base, relative_base, base_len - 1);
 266                ent->base[base_len - 1] = '/';
 267                memcpy(ent->base + base_len, entry, len);
 268        }
 269        else
 270                memcpy(ent->base, entry, pfxlen);
 271
 272        ent->name = ent->base + pfxlen + 1;
 273        ent->base[pfxlen + 3] = '/';
 274        ent->base[pfxlen] = ent->base[entlen-1] = 0;
 275
 276        /* Detect cases where alternate disappeared */
 277        if (stat(ent->base, &st) || !S_ISDIR(st.st_mode)) {
 278                error("object directory %s does not exist; "
 279                      "check .git/objects/info/alternates.",
 280                      ent->base);
 281                free(ent);
 282                return -1;
 283        }
 284
 285        /* Prevent the common mistake of listing the same
 286         * thing twice, or object directory itself.
 287         */
 288        for (alt = alt_odb_list; alt; alt = alt->next) {
 289                if (!memcmp(ent->base, alt->base, pfxlen)) {
 290                        free(ent);
 291                        return -1;
 292                }
 293        }
 294        if (!memcmp(ent->base, objdir, pfxlen)) {
 295                free(ent);
 296                return -1;
 297        }
 298
 299        /* add the alternate entry */
 300        *alt_odb_tail = ent;
 301        alt_odb_tail = &(ent->next);
 302        ent->next = NULL;
 303
 304        /* recursively add alternates */
 305        read_info_alternates(ent->base, depth + 1);
 306
 307        ent->base[pfxlen] = '/';
 308
 309        return 0;
 310}
 311
 312static void link_alt_odb_entries(const char *alt, const char *ep, int sep,
 313                                 const char *relative_base, int depth)
 314{
 315        const char *cp, *last;
 316
 317        if (depth > 5) {
 318                error("%s: ignoring alternate object stores, nesting too deep.",
 319                                relative_base);
 320                return;
 321        }
 322
 323        last = alt;
 324        while (last < ep) {
 325                cp = last;
 326                if (cp < ep && *cp == '#') {
 327                        while (cp < ep && *cp != sep)
 328                                cp++;
 329                        last = cp + 1;
 330                        continue;
 331                }
 332                while (cp < ep && *cp != sep)
 333                        cp++;
 334                if (last != cp) {
 335                        if ((*last != '/') && depth) {
 336                                error("%s: ignoring relative alternate object store %s",
 337                                                relative_base, last);
 338                        } else {
 339                                link_alt_odb_entry(last, cp - last,
 340                                                relative_base, depth);
 341                        }
 342                }
 343                while (cp < ep && *cp == sep)
 344                        cp++;
 345                last = cp;
 346        }
 347}
 348
 349static void read_info_alternates(const char * relative_base, int depth)
 350{
 351        char *map;
 352        struct stat st;
 353        char path[PATH_MAX];
 354        int fd;
 355
 356        sprintf(path, "%s/info/alternates", relative_base);
 357        fd = open(path, O_RDONLY);
 358        if (fd < 0)
 359                return;
 360        if (fstat(fd, &st) || (st.st_size == 0)) {
 361                close(fd);
 362                return;
 363        }
 364        map = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 365        close(fd);
 366
 367        link_alt_odb_entries(map, map + st.st_size, '\n', relative_base, depth);
 368
 369        munmap(map, st.st_size);
 370}
 371
 372void prepare_alt_odb(void)
 373{
 374        const char *alt;
 375
 376        alt = getenv(ALTERNATE_DB_ENVIRONMENT);
 377        if (!alt) alt = "";
 378
 379        if (alt_odb_tail)
 380                return;
 381        alt_odb_tail = &alt_odb_list;
 382        link_alt_odb_entries(alt, alt + strlen(alt), ':', NULL, 0);
 383
 384        read_info_alternates(get_object_directory(), 0);
 385}
 386
 387static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 388{
 389        char *name = sha1_file_name(sha1);
 390        struct alternate_object_database *alt;
 391
 392        if (!stat(name, st))
 393                return name;
 394        prepare_alt_odb();
 395        for (alt = alt_odb_list; alt; alt = alt->next) {
 396                name = alt->name;
 397                fill_sha1_path(name, sha1);
 398                if (!stat(alt->base, st))
 399                        return alt->base;
 400        }
 401        return NULL;
 402}
 403
 404static unsigned int pack_used_ctr;
 405static unsigned int pack_mmap_calls;
 406static unsigned int peak_pack_open_windows;
 407static unsigned int pack_open_windows;
 408static size_t peak_pack_mapped;
 409static size_t pack_mapped;
 410struct packed_git *packed_git;
 411
 412void pack_report()
 413{
 414        fprintf(stderr,
 415                "pack_report: getpagesize()            = %10" SZ_FMT "\n"
 416                "pack_report: core.packedGitWindowSize = %10" SZ_FMT "\n"
 417                "pack_report: core.packedGitLimit      = %10" SZ_FMT "\n",
 418                (size_t) getpagesize(),
 419                packed_git_window_size,
 420                packed_git_limit);
 421        fprintf(stderr,
 422                "pack_report: pack_used_ctr            = %10u\n"
 423                "pack_report: pack_mmap_calls          = %10u\n"
 424                "pack_report: pack_open_windows        = %10u / %10u\n"
 425                "pack_report: pack_mapped              = "
 426                        "%10" SZ_FMT " / %10" SZ_FMT "\n",
 427                pack_used_ctr,
 428                pack_mmap_calls,
 429                pack_open_windows, peak_pack_open_windows,
 430                pack_mapped, peak_pack_mapped);
 431}
 432
 433static int check_packed_git_idx(const char *path, unsigned long *idx_size_,
 434                                void **idx_map_)
 435{
 436        void *idx_map;
 437        uint32_t *index;
 438        unsigned long idx_size;
 439        int nr, i;
 440        int fd = open(path, O_RDONLY);
 441        struct stat st;
 442        if (fd < 0)
 443                return -1;
 444        if (fstat(fd, &st)) {
 445                close(fd);
 446                return -1;
 447        }
 448        idx_size = st.st_size;
 449        idx_map = xmmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
 450        close(fd);
 451
 452        index = idx_map;
 453        *idx_map_ = idx_map;
 454        *idx_size_ = idx_size;
 455
 456        /* check index map */
 457        if (idx_size < 4*256 + 20 + 20)
 458                return error("index file %s is too small", path);
 459
 460        /* a future index format would start with this, as older git
 461         * binaries would fail the non-monotonic index check below.
 462         * give a nicer warning to the user if we can.
 463         */
 464        if (index[0] == htonl(PACK_IDX_SIGNATURE))
 465                return error("index file %s is a newer version"
 466                        " and is not supported by this binary"
 467                        " (try upgrading GIT to a newer version)",
 468                        path);
 469
 470        nr = 0;
 471        for (i = 0; i < 256; i++) {
 472                unsigned int n = ntohl(index[i]);
 473                if (n < nr)
 474                        return error("non-monotonic index %s", path);
 475                nr = n;
 476        }
 477
 478        /*
 479         * Total size:
 480         *  - 256 index entries 4 bytes each
 481         *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
 482         *  - 20-byte SHA1 of the packfile
 483         *  - 20-byte SHA1 file checksum
 484         */
 485        if (idx_size != 4*256 + nr * 24 + 20 + 20)
 486                return error("wrong index file size in %s", path);
 487
 488        return 0;
 489}
 490
 491static void scan_windows(struct packed_git *p,
 492        struct packed_git **lru_p,
 493        struct pack_window **lru_w,
 494        struct pack_window **lru_l)
 495{
 496        struct pack_window *w, *w_l;
 497
 498        for (w_l = NULL, w = p->windows; w; w = w->next) {
 499                if (!w->inuse_cnt) {
 500                        if (!*lru_w || w->last_used < (*lru_w)->last_used) {
 501                                *lru_p = p;
 502                                *lru_w = w;
 503                                *lru_l = w_l;
 504                        }
 505                }
 506                w_l = w;
 507        }
 508}
 509
 510static int unuse_one_window(struct packed_git *current)
 511{
 512        struct packed_git *p, *lru_p = NULL;
 513        struct pack_window *lru_w = NULL, *lru_l = NULL;
 514
 515        if (current)
 516                scan_windows(current, &lru_p, &lru_w, &lru_l);
 517        for (p = packed_git; p; p = p->next)
 518                scan_windows(p, &lru_p, &lru_w, &lru_l);
 519        if (lru_p) {
 520                munmap(lru_w->base, lru_w->len);
 521                pack_mapped -= lru_w->len;
 522                if (lru_l)
 523                        lru_l->next = lru_w->next;
 524                else {
 525                        lru_p->windows = lru_w->next;
 526                        if (!lru_p->windows && lru_p != current) {
 527                                close(lru_p->pack_fd);
 528                                lru_p->pack_fd = -1;
 529                        }
 530                }
 531                free(lru_w);
 532                pack_open_windows--;
 533                return 1;
 534        }
 535        return 0;
 536}
 537
 538void release_pack_memory(size_t need)
 539{
 540        size_t cur = pack_mapped;
 541        while (need >= (cur - pack_mapped) && unuse_one_window(NULL))
 542                ; /* nothing */
 543}
 544
 545void unuse_pack(struct pack_window **w_cursor)
 546{
 547        struct pack_window *w = *w_cursor;
 548        if (w) {
 549                w->inuse_cnt--;
 550                *w_cursor = NULL;
 551        }
 552}
 553
 554/*
 555 * Do not call this directly as this leaks p->pack_fd on error return;
 556 * call open_packed_git() instead.
 557 */
 558static int open_packed_git_1(struct packed_git *p)
 559{
 560        struct stat st;
 561        struct pack_header hdr;
 562        unsigned char sha1[20];
 563        unsigned char *idx_sha1;
 564        long fd_flag;
 565
 566        p->pack_fd = open(p->pack_name, O_RDONLY);
 567        if (p->pack_fd < 0 || fstat(p->pack_fd, &st))
 568                return -1;
 569
 570        /* If we created the struct before we had the pack we lack size. */
 571        if (!p->pack_size) {
 572                if (!S_ISREG(st.st_mode))
 573                        return error("packfile %s not a regular file", p->pack_name);
 574                p->pack_size = st.st_size;
 575        } else if (p->pack_size != st.st_size)
 576                return error("packfile %s size changed", p->pack_name);
 577
 578        /* We leave these file descriptors open with sliding mmap;
 579         * there is no point keeping them open across exec(), though.
 580         */
 581        fd_flag = fcntl(p->pack_fd, F_GETFD, 0);
 582        if (fd_flag < 0)
 583                return error("cannot determine file descriptor flags");
 584        fd_flag |= FD_CLOEXEC;
 585        if (fcntl(p->pack_fd, F_SETFD, fd_flag) == -1)
 586                return error("cannot set FD_CLOEXEC");
 587
 588        /* Verify we recognize this pack file format. */
 589        if (read_in_full(p->pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 590                return error("file %s is far too short to be a packfile", p->pack_name);
 591        if (hdr.hdr_signature != htonl(PACK_SIGNATURE))
 592                return error("file %s is not a GIT packfile", p->pack_name);
 593        if (!pack_version_ok(hdr.hdr_version))
 594                return error("packfile %s is version %u and not supported"
 595                        " (try upgrading GIT to a newer version)",
 596                        p->pack_name, ntohl(hdr.hdr_version));
 597
 598        /* Verify the pack matches its index. */
 599        if (num_packed_objects(p) != ntohl(hdr.hdr_entries))
 600                return error("packfile %s claims to have %u objects"
 601                        " while index size indicates %u objects",
 602                        p->pack_name, ntohl(hdr.hdr_entries),
 603                        num_packed_objects(p));
 604        if (lseek(p->pack_fd, p->pack_size - sizeof(sha1), SEEK_SET) == -1)
 605                return error("end of packfile %s is unavailable", p->pack_name);
 606        if (read_in_full(p->pack_fd, sha1, sizeof(sha1)) != sizeof(sha1))
 607                return error("packfile %s signature is unavailable", p->pack_name);
 608        idx_sha1 = ((unsigned char *)p->index_base) + p->index_size - 40;
 609        if (hashcmp(sha1, idx_sha1))
 610                return error("packfile %s does not match index", p->pack_name);
 611        return 0;
 612}
 613
 614static int open_packed_git(struct packed_git *p)
 615{
 616        if (!open_packed_git_1(p))
 617                return 0;
 618        if (p->pack_fd != -1) {
 619                close(p->pack_fd);
 620                p->pack_fd = -1;
 621        }
 622        return -1;
 623}
 624
 625static int in_window(struct pack_window *win, unsigned long offset)
 626{
 627        /* We must promise at least 20 bytes (one hash) after the
 628         * offset is available from this window, otherwise the offset
 629         * is not actually in this window and a different window (which
 630         * has that one hash excess) must be used.  This is to support
 631         * the object header and delta base parsing routines below.
 632         */
 633        off_t win_off = win->offset;
 634        return win_off <= offset
 635                && (offset + 20) <= (win_off + win->len);
 636}
 637
 638unsigned char* use_pack(struct packed_git *p,
 639                struct pack_window **w_cursor,
 640                unsigned long offset,
 641                unsigned int *left)
 642{
 643        struct pack_window *win = *w_cursor;
 644
 645        if (p->pack_fd == -1 && open_packed_git(p))
 646                die("packfile %s cannot be accessed", p->pack_name);
 647
 648        /* Since packfiles end in a hash of their content and its
 649         * pointless to ask for an offset into the middle of that
 650         * hash, and the in_window function above wouldn't match
 651         * don't allow an offset too close to the end of the file.
 652         */
 653        if (offset > (p->pack_size - 20))
 654                die("offset beyond end of packfile (truncated pack?)");
 655
 656        if (!win || !in_window(win, offset)) {
 657                if (win)
 658                        win->inuse_cnt--;
 659                for (win = p->windows; win; win = win->next) {
 660                        if (in_window(win, offset))
 661                                break;
 662                }
 663                if (!win) {
 664                        size_t window_align = packed_git_window_size / 2;
 665                        win = xcalloc(1, sizeof(*win));
 666                        win->offset = (offset / window_align) * window_align;
 667                        win->len = p->pack_size - win->offset;
 668                        if (win->len > packed_git_window_size)
 669                                win->len = packed_git_window_size;
 670                        pack_mapped += win->len;
 671                        while (packed_git_limit < pack_mapped
 672                                && unuse_one_window(p))
 673                                ; /* nothing */
 674                        win->base = xmmap(NULL, win->len,
 675                                PROT_READ, MAP_PRIVATE,
 676                                p->pack_fd, win->offset);
 677                        if (win->base == MAP_FAILED)
 678                                die("packfile %s cannot be mapped: %s",
 679                                        p->pack_name,
 680                                        strerror(errno));
 681                        pack_mmap_calls++;
 682                        pack_open_windows++;
 683                        if (pack_mapped > peak_pack_mapped)
 684                                peak_pack_mapped = pack_mapped;
 685                        if (pack_open_windows > peak_pack_open_windows)
 686                                peak_pack_open_windows = pack_open_windows;
 687                        win->next = p->windows;
 688                        p->windows = win;
 689                }
 690        }
 691        if (win != *w_cursor) {
 692                win->last_used = pack_used_ctr++;
 693                win->inuse_cnt++;
 694                *w_cursor = win;
 695        }
 696        offset -= win->offset;
 697        if (left)
 698                *left = win->len - offset;
 699        return win->base + offset;
 700}
 701
 702struct packed_git *add_packed_git(char *path, int path_len, int local)
 703{
 704        struct stat st;
 705        struct packed_git *p;
 706        unsigned long idx_size;
 707        void *idx_map;
 708        unsigned char sha1[20];
 709
 710        if (check_packed_git_idx(path, &idx_size, &idx_map))
 711                return NULL;
 712
 713        /* do we have a corresponding .pack file? */
 714        strcpy(path + path_len - 4, ".pack");
 715        if (stat(path, &st) || !S_ISREG(st.st_mode)) {
 716                munmap(idx_map, idx_size);
 717                return NULL;
 718        }
 719        /* ok, it looks sane as far as we can check without
 720         * actually mapping the pack file.
 721         */
 722        p = xmalloc(sizeof(*p) + path_len + 2);
 723        strcpy(p->pack_name, path);
 724        p->index_size = idx_size;
 725        p->pack_size = st.st_size;
 726        p->index_base = idx_map;
 727        p->next = NULL;
 728        p->windows = NULL;
 729        p->pack_fd = -1;
 730        p->pack_local = local;
 731        if ((path_len > 44) && !get_sha1_hex(path + path_len - 44, sha1))
 732                hashcpy(p->sha1, sha1);
 733        return p;
 734}
 735
 736struct packed_git *parse_pack_index(unsigned char *sha1)
 737{
 738        char *path = sha1_pack_index_name(sha1);
 739        return parse_pack_index_file(sha1, path);
 740}
 741
 742struct packed_git *parse_pack_index_file(const unsigned char *sha1, char *idx_path)
 743{
 744        struct packed_git *p;
 745        unsigned long idx_size;
 746        void *idx_map;
 747        char *path;
 748
 749        if (check_packed_git_idx(idx_path, &idx_size, &idx_map))
 750                return NULL;
 751
 752        path = sha1_pack_name(sha1);
 753
 754        p = xmalloc(sizeof(*p) + strlen(path) + 2);
 755        strcpy(p->pack_name, path);
 756        p->index_size = idx_size;
 757        p->pack_size = 0;
 758        p->index_base = idx_map;
 759        p->next = NULL;
 760        p->windows = NULL;
 761        p->pack_fd = -1;
 762        hashcpy(p->sha1, sha1);
 763        return p;
 764}
 765
 766void install_packed_git(struct packed_git *pack)
 767{
 768        pack->next = packed_git;
 769        packed_git = pack;
 770}
 771
 772static void prepare_packed_git_one(char *objdir, int local)
 773{
 774        char path[PATH_MAX];
 775        int len;
 776        DIR *dir;
 777        struct dirent *de;
 778
 779        sprintf(path, "%s/pack", objdir);
 780        len = strlen(path);
 781        dir = opendir(path);
 782        if (!dir) {
 783                if (errno != ENOENT)
 784                        error("unable to open object pack directory: %s: %s",
 785                              path, strerror(errno));
 786                return;
 787        }
 788        path[len++] = '/';
 789        while ((de = readdir(dir)) != NULL) {
 790                int namelen = strlen(de->d_name);
 791                struct packed_git *p;
 792
 793                if (!has_extension(de->d_name, ".idx"))
 794                        continue;
 795
 796                /* Don't reopen a pack we already have. */
 797                strcpy(path + len, de->d_name);
 798                for (p = packed_git; p; p = p->next) {
 799                        if (!memcmp(path, p->pack_name, len + namelen - 4))
 800                                break;
 801                }
 802                if (p)
 803                        continue;
 804                /* See if it really is a valid .idx file with corresponding
 805                 * .pack file that we can map.
 806                 */
 807                p = add_packed_git(path, len + namelen, local);
 808                if (!p)
 809                        continue;
 810                install_packed_git(p);
 811        }
 812        closedir(dir);
 813}
 814
 815static int prepare_packed_git_run_once = 0;
 816void prepare_packed_git(void)
 817{
 818        struct alternate_object_database *alt;
 819
 820        if (prepare_packed_git_run_once)
 821                return;
 822        prepare_packed_git_one(get_object_directory(), 1);
 823        prepare_alt_odb();
 824        for (alt = alt_odb_list; alt; alt = alt->next) {
 825                alt->name[-1] = 0;
 826                prepare_packed_git_one(alt->base, 0);
 827                alt->name[-1] = '/';
 828        }
 829        prepare_packed_git_run_once = 1;
 830}
 831
 832void reprepare_packed_git(void)
 833{
 834        prepare_packed_git_run_once = 0;
 835        prepare_packed_git();
 836}
 837
 838int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
 839{
 840        unsigned char real_sha1[20];
 841        hash_sha1_file(map, size, type, real_sha1);
 842        return hashcmp(sha1, real_sha1) ? -1 : 0;
 843}
 844
 845void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 846{
 847        struct stat st;
 848        void *map;
 849        int fd;
 850        char *filename = find_sha1_file(sha1, &st);
 851
 852        if (!filename) {
 853                return NULL;
 854        }
 855
 856        fd = open(filename, O_RDONLY | sha1_file_open_flag);
 857        if (fd < 0) {
 858                /* See if it works without O_NOATIME */
 859                switch (sha1_file_open_flag) {
 860                default:
 861                        fd = open(filename, O_RDONLY);
 862                        if (fd >= 0)
 863                                break;
 864                /* Fallthrough */
 865                case 0:
 866                        return NULL;
 867                }
 868
 869                /* If it failed once, it will probably fail again.
 870                 * Stop using O_NOATIME
 871                 */
 872                sha1_file_open_flag = 0;
 873        }
 874        map = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 875        close(fd);
 876        *size = st.st_size;
 877        return map;
 878}
 879
 880int legacy_loose_object(unsigned char *map)
 881{
 882        unsigned int word;
 883
 884        /*
 885         * Is it a zlib-compressed buffer? If so, the first byte
 886         * must be 0x78 (15-bit window size, deflated), and the
 887         * first 16-bit word is evenly divisible by 31
 888         */
 889        word = (map[0] << 8) + map[1];
 890        if (map[0] == 0x78 && !(word % 31))
 891                return 1;
 892        else
 893                return 0;
 894}
 895
 896unsigned long unpack_object_header_gently(const unsigned char *buf, unsigned long len, enum object_type *type, unsigned long *sizep)
 897{
 898        unsigned shift;
 899        unsigned char c;
 900        unsigned long size;
 901        unsigned long used = 0;
 902
 903        c = buf[used++];
 904        *type = (c >> 4) & 7;
 905        size = c & 15;
 906        shift = 4;
 907        while (c & 0x80) {
 908                if (len <= used)
 909                        return 0;
 910                if (sizeof(long) * 8 <= shift)
 911                        return 0;
 912                c = buf[used++];
 913                size += (c & 0x7f) << shift;
 914                shift += 7;
 915        }
 916        *sizep = size;
 917        return used;
 918}
 919
 920static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
 921{
 922        unsigned long size, used;
 923        static const char valid_loose_object_type[8] = {
 924                0, /* OBJ_EXT */
 925                1, 1, 1, 1, /* "commit", "tree", "blob", "tag" */
 926                0, /* "delta" and others are invalid in a loose object */
 927        };
 928        enum object_type type;
 929
 930        /* Get the data stream */
 931        memset(stream, 0, sizeof(*stream));
 932        stream->next_in = map;
 933        stream->avail_in = mapsize;
 934        stream->next_out = buffer;
 935        stream->avail_out = bufsiz;
 936
 937        if (legacy_loose_object(map)) {
 938                inflateInit(stream);
 939                return inflate(stream, 0);
 940        }
 941
 942        used = unpack_object_header_gently(map, mapsize, &type, &size);
 943        if (!used || !valid_loose_object_type[type])
 944                return -1;
 945        map += used;
 946        mapsize -= used;
 947
 948        /* Set up the stream for the rest.. */
 949        stream->next_in = map;
 950        stream->avail_in = mapsize;
 951        inflateInit(stream);
 952
 953        /* And generate the fake traditional header */
 954        stream->total_out = 1 + snprintf(buffer, bufsiz, "%s %lu",
 955                                         type_names[type], size);
 956        return 0;
 957}
 958
 959static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
 960{
 961        int bytes = strlen(buffer) + 1;
 962        unsigned char *buf = xmalloc(1+size);
 963        unsigned long n;
 964
 965        n = stream->total_out - bytes;
 966        if (n > size)
 967                n = size;
 968        memcpy(buf, (char *) buffer + bytes, n);
 969        bytes = n;
 970        if (bytes < size) {
 971                stream->next_out = buf + bytes;
 972                stream->avail_out = size - bytes;
 973                while (inflate(stream, Z_FINISH) == Z_OK)
 974                        /* nothing */;
 975        }
 976        buf[size] = 0;
 977        inflateEnd(stream);
 978        return buf;
 979}
 980
 981/*
 982 * We used to just use "sscanf()", but that's actually way
 983 * too permissive for what we want to check. So do an anal
 984 * object header parse by hand.
 985 */
 986static int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
 987{
 988        int i;
 989        unsigned long size;
 990
 991        /*
 992         * The type can be at most ten bytes (including the 
 993         * terminating '\0' that we add), and is followed by
 994         * a space. 
 995         */
 996        i = 10;
 997        for (;;) {
 998                char c = *hdr++;
 999                if (c == ' ')
1000                        break;
1001                if (!--i)
1002                        return -1;
1003                *type++ = c;
1004        }
1005        *type = 0;
1006
1007        /*
1008         * The length must follow immediately, and be in canonical
1009         * decimal format (ie "010" is not valid).
1010         */
1011        size = *hdr++ - '0';
1012        if (size > 9)
1013                return -1;
1014        if (size) {
1015                for (;;) {
1016                        unsigned long c = *hdr - '0';
1017                        if (c > 9)
1018                                break;
1019                        hdr++;
1020                        size = size * 10 + c;
1021                }
1022        }
1023        *sizep = size;
1024
1025        /*
1026         * The length must be followed by a zero byte
1027         */
1028        return *hdr ? -1 : 0;
1029}
1030
1031void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
1032{
1033        int ret;
1034        z_stream stream;
1035        char hdr[8192];
1036
1037        ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
1038        if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
1039                return NULL;
1040
1041        return unpack_sha1_rest(&stream, hdr, *size);
1042}
1043
1044static unsigned long get_delta_base(struct packed_git *p,
1045                                    struct pack_window **w_curs,
1046                                    unsigned long offset,
1047                                    enum object_type kind,
1048                                    unsigned long delta_obj_offset,
1049                                    unsigned long *base_obj_offset)
1050{
1051        unsigned char *base_info = use_pack(p, w_curs, offset, NULL);
1052        unsigned long base_offset;
1053
1054        /* use_pack() assured us we have [base_info, base_info + 20)
1055         * as a range that we can look at without walking off the
1056         * end of the mapped window.  Its actually the hash size
1057         * that is assured.  An OFS_DELTA longer than the hash size
1058         * is stupid, as then a REF_DELTA would be smaller to store.
1059         */
1060        if (kind == OBJ_OFS_DELTA) {
1061                unsigned used = 0;
1062                unsigned char c = base_info[used++];
1063                base_offset = c & 127;
1064                while (c & 128) {
1065                        base_offset += 1;
1066                        if (!base_offset || base_offset & ~(~0UL >> 7))
1067                                die("offset value overflow for delta base object");
1068                        c = base_info[used++];
1069                        base_offset = (base_offset << 7) + (c & 127);
1070                }
1071                base_offset = delta_obj_offset - base_offset;
1072                if (base_offset >= delta_obj_offset)
1073                        die("delta base offset out of bound");
1074                offset += used;
1075        } else if (kind == OBJ_REF_DELTA) {
1076                /* The base entry _must_ be in the same pack */
1077                base_offset = find_pack_entry_one(base_info, p);
1078                if (!base_offset)
1079                        die("failed to find delta-pack base object %s",
1080                                sha1_to_hex(base_info));
1081                offset += 20;
1082        } else
1083                die("I am totally screwed");
1084        *base_obj_offset = base_offset;
1085        return offset;
1086}
1087
1088/* forward declaration for a mutually recursive function */
1089static int packed_object_info(struct packed_git *p, unsigned long offset,
1090                              char *type, unsigned long *sizep);
1091
1092static int packed_delta_info(struct packed_git *p,
1093                             struct pack_window **w_curs,
1094                             unsigned long offset,
1095                             enum object_type kind,
1096                             unsigned long obj_offset,
1097                             char *type,
1098                             unsigned long *sizep)
1099{
1100        unsigned long base_offset;
1101
1102        offset = get_delta_base(p, w_curs, offset, kind,
1103                obj_offset, &base_offset);
1104
1105        /* We choose to only get the type of the base object and
1106         * ignore potentially corrupt pack file that expects the delta
1107         * based on a base with a wrong size.  This saves tons of
1108         * inflate() calls.
1109         */
1110        if (packed_object_info(p, base_offset, type, NULL))
1111                die("cannot get info for delta-pack base");
1112
1113        if (sizep) {
1114                const unsigned char *data;
1115                unsigned char delta_head[20], *in;
1116                unsigned long result_size;
1117                z_stream stream;
1118                int st;
1119
1120                memset(&stream, 0, sizeof(stream));
1121                stream.next_out = delta_head;
1122                stream.avail_out = sizeof(delta_head);
1123
1124                inflateInit(&stream);
1125                do {
1126                        in = use_pack(p, w_curs, offset, &stream.avail_in);
1127                        stream.next_in = in;
1128                        st = inflate(&stream, Z_FINISH);
1129                        offset += stream.next_in - in;
1130                } while ((st == Z_OK || st == Z_BUF_ERROR)
1131                        && stream.total_out < sizeof(delta_head));
1132                inflateEnd(&stream);
1133                if ((st != Z_STREAM_END) &&
1134                    stream.total_out != sizeof(delta_head))
1135                        die("delta data unpack-initial failed");
1136
1137                /* Examine the initial part of the delta to figure out
1138                 * the result size.
1139                 */
1140                data = delta_head;
1141
1142                /* ignore base size */
1143                get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
1144
1145                /* Read the result size */
1146                result_size = get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
1147                *sizep = result_size;
1148        }
1149        return 0;
1150}
1151
1152static unsigned long unpack_object_header(struct packed_git *p,
1153                struct pack_window **w_curs,
1154                unsigned long offset,
1155                enum object_type *type,
1156                unsigned long *sizep)
1157{
1158        unsigned char *base;
1159        unsigned int left;
1160        unsigned long used;
1161
1162        /* use_pack() assures us we have [base, base + 20) available
1163         * as a range that we can look at at.  (Its actually the hash
1164         * size that is assured.)  With our object header encoding
1165         * the maximum deflated object size is 2^137, which is just
1166         * insane, so we know won't exceed what we have been given.
1167         */
1168        base = use_pack(p, w_curs, offset, &left);
1169        used = unpack_object_header_gently(base, left, type, sizep);
1170        if (!used)
1171                die("object offset outside of pack file");
1172
1173        return offset + used;
1174}
1175
1176void packed_object_info_detail(struct packed_git *p,
1177                               unsigned long offset,
1178                               char *type,
1179                               unsigned long *size,
1180                               unsigned long *store_size,
1181                               unsigned int *delta_chain_length,
1182                               unsigned char *base_sha1)
1183{
1184        struct pack_window *w_curs = NULL;
1185        unsigned long obj_offset, val;
1186        unsigned char *next_sha1;
1187        enum object_type kind;
1188
1189        *delta_chain_length = 0;
1190        obj_offset = offset;
1191        offset = unpack_object_header(p, &w_curs, offset, &kind, size);
1192
1193        for (;;) {
1194                switch (kind) {
1195                default:
1196                        die("pack %s contains unknown object type %d",
1197                            p->pack_name, kind);
1198                case OBJ_COMMIT:
1199                case OBJ_TREE:
1200                case OBJ_BLOB:
1201                case OBJ_TAG:
1202                        strcpy(type, type_names[kind]);
1203                        *store_size = 0; /* notyet */
1204                        unuse_pack(&w_curs);
1205                        return;
1206                case OBJ_OFS_DELTA:
1207                        get_delta_base(p, &w_curs, offset, kind,
1208                                obj_offset, &offset);
1209                        if (*delta_chain_length == 0) {
1210                                /* TODO: find base_sha1 as pointed by offset */
1211                        }
1212                        break;
1213                case OBJ_REF_DELTA:
1214                        next_sha1 = use_pack(p, &w_curs, offset, NULL);
1215                        if (*delta_chain_length == 0)
1216                                hashcpy(base_sha1, next_sha1);
1217                        offset = find_pack_entry_one(next_sha1, p);
1218                        break;
1219                }
1220                obj_offset = offset;
1221                offset = unpack_object_header(p, &w_curs, offset, &kind, &val);
1222                (*delta_chain_length)++;
1223        }
1224}
1225
1226static int packed_object_info(struct packed_git *p, unsigned long offset,
1227                              char *type, unsigned long *sizep)
1228{
1229        struct pack_window *w_curs = NULL;
1230        unsigned long size, obj_offset = offset;
1231        enum object_type kind;
1232        int r;
1233
1234        offset = unpack_object_header(p, &w_curs, offset, &kind, &size);
1235
1236        switch (kind) {
1237        case OBJ_OFS_DELTA:
1238        case OBJ_REF_DELTA:
1239                r = packed_delta_info(p, &w_curs, offset, kind,
1240                        obj_offset, type, sizep);
1241                unuse_pack(&w_curs);
1242                return r;
1243        case OBJ_COMMIT:
1244        case OBJ_TREE:
1245        case OBJ_BLOB:
1246        case OBJ_TAG:
1247                strcpy(type, type_names[kind]);
1248                unuse_pack(&w_curs);
1249                break;
1250        default:
1251                die("pack %s contains unknown object type %d",
1252                    p->pack_name, kind);
1253        }
1254        if (sizep)
1255                *sizep = size;
1256        return 0;
1257}
1258
1259static void *unpack_compressed_entry(struct packed_git *p,
1260                                    struct pack_window **w_curs,
1261                                    unsigned long offset,
1262                                    unsigned long size)
1263{
1264        int st;
1265        z_stream stream;
1266        unsigned char *buffer, *in;
1267
1268        buffer = xmalloc(size + 1);
1269        buffer[size] = 0;
1270        memset(&stream, 0, sizeof(stream));
1271        stream.next_out = buffer;
1272        stream.avail_out = size;
1273
1274        inflateInit(&stream);
1275        do {
1276                in = use_pack(p, w_curs, offset, &stream.avail_in);
1277                stream.next_in = in;
1278                st = inflate(&stream, Z_FINISH);
1279                offset += stream.next_in - in;
1280        } while (st == Z_OK || st == Z_BUF_ERROR);
1281        inflateEnd(&stream);
1282        if ((st != Z_STREAM_END) || stream.total_out != size) {
1283                free(buffer);
1284                return NULL;
1285        }
1286
1287        return buffer;
1288}
1289
1290static void *unpack_delta_entry(struct packed_git *p,
1291                                struct pack_window **w_curs,
1292                                unsigned long offset,
1293                                unsigned long delta_size,
1294                                enum object_type kind,
1295                                unsigned long obj_offset,
1296                                char *type,
1297                                unsigned long *sizep)
1298{
1299        void *delta_data, *result, *base;
1300        unsigned long result_size, base_size, base_offset;
1301
1302        offset = get_delta_base(p, w_curs, offset, kind,
1303                obj_offset, &base_offset);
1304        base = unpack_entry(p, base_offset, type, &base_size);
1305        if (!base)
1306                die("failed to read delta base object at %lu from %s",
1307                    base_offset, p->pack_name);
1308
1309        delta_data = unpack_compressed_entry(p, w_curs, offset, delta_size);
1310        result = patch_delta(base, base_size,
1311                             delta_data, delta_size,
1312                             &result_size);
1313        if (!result)
1314                die("failed to apply delta");
1315        free(delta_data);
1316        free(base);
1317        *sizep = result_size;
1318        return result;
1319}
1320
1321void *unpack_entry(struct packed_git *p, unsigned long offset,
1322                          char *type, unsigned long *sizep)
1323{
1324        struct pack_window *w_curs = NULL;
1325        unsigned long size, obj_offset = offset;
1326        enum object_type kind;
1327        void *retval;
1328
1329        offset = unpack_object_header(p, &w_curs, offset, &kind, &size);
1330        switch (kind) {
1331        case OBJ_OFS_DELTA:
1332        case OBJ_REF_DELTA:
1333                retval = unpack_delta_entry(p, &w_curs, offset, size,
1334                        kind, obj_offset, type, sizep);
1335                break;
1336        case OBJ_COMMIT:
1337        case OBJ_TREE:
1338        case OBJ_BLOB:
1339        case OBJ_TAG:
1340                strcpy(type, type_names[kind]);
1341                *sizep = size;
1342                retval = unpack_compressed_entry(p, &w_curs, offset, size);
1343                break;
1344        default:
1345                die("unknown object type %i in %s", kind, p->pack_name);
1346        }
1347        unuse_pack(&w_curs);
1348        return retval;
1349}
1350
1351int num_packed_objects(const struct packed_git *p)
1352{
1353        /* See check_packed_git_idx() */
1354        return (p->index_size - 20 - 20 - 4*256) / 24;
1355}
1356
1357int nth_packed_object_sha1(const struct packed_git *p, int n,
1358                           unsigned char* sha1)
1359{
1360        void *index = p->index_base + 256;
1361        if (n < 0 || num_packed_objects(p) <= n)
1362                return -1;
1363        hashcpy(sha1, (unsigned char *) index + (24 * n) + 4);
1364        return 0;
1365}
1366
1367unsigned long find_pack_entry_one(const unsigned char *sha1,
1368                                  struct packed_git *p)
1369{
1370        uint32_t *level1_ofs = p->index_base;
1371        int hi = ntohl(level1_ofs[*sha1]);
1372        int lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
1373        void *index = p->index_base + 256;
1374
1375        do {
1376                int mi = (lo + hi) / 2;
1377                int cmp = hashcmp((unsigned char *)index + (24 * mi) + 4, sha1);
1378                if (!cmp)
1379                        return ntohl(*((uint32_t *)((char *)index + (24 * mi))));
1380                if (cmp > 0)
1381                        hi = mi;
1382                else
1383                        lo = mi+1;
1384        } while (lo < hi);
1385        return 0;
1386}
1387
1388static int matches_pack_name(struct packed_git *p, const char *ig)
1389{
1390        const char *last_c, *c;
1391
1392        if (!strcmp(p->pack_name, ig))
1393                return 0;
1394
1395        for (c = p->pack_name, last_c = c; *c;)
1396                if (*c == '/')
1397                        last_c = ++c;
1398                else
1399                        ++c;
1400        if (!strcmp(last_c, ig))
1401                return 0;
1402
1403        return 1;
1404}
1405
1406static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e, const char **ignore_packed)
1407{
1408        struct packed_git *p;
1409        unsigned long offset;
1410
1411        prepare_packed_git();
1412
1413        for (p = packed_git; p; p = p->next) {
1414                if (ignore_packed) {
1415                        const char **ig;
1416                        for (ig = ignore_packed; *ig; ig++)
1417                                if (!matches_pack_name(p, *ig))
1418                                        break;
1419                        if (*ig)
1420                                continue;
1421                }
1422                offset = find_pack_entry_one(sha1, p);
1423                if (offset) {
1424                        /*
1425                         * We are about to tell the caller where they can
1426                         * locate the requested object.  We better make
1427                         * sure the packfile is still here and can be
1428                         * accessed before supplying that answer, as
1429                         * it may have been deleted since the index
1430                         * was loaded!
1431                         */
1432                        if (p->pack_fd == -1 && open_packed_git(p)) {
1433                                error("packfile %s cannot be accessed", p->pack_name);
1434                                continue;
1435                        }
1436                        e->offset = offset;
1437                        e->p = p;
1438                        hashcpy(e->sha1, sha1);
1439                        return 1;
1440                }
1441        }
1442        return 0;
1443}
1444
1445struct packed_git *find_sha1_pack(const unsigned char *sha1, 
1446                                  struct packed_git *packs)
1447{
1448        struct packed_git *p;
1449
1450        for (p = packs; p; p = p->next) {
1451                if (find_pack_entry_one(sha1, p))
1452                        return p;
1453        }
1454        return NULL;
1455        
1456}
1457
1458static int sha1_loose_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
1459{
1460        int status;
1461        unsigned long mapsize, size;
1462        void *map;
1463        z_stream stream;
1464        char hdr[128];
1465
1466        map = map_sha1_file(sha1, &mapsize);
1467        if (!map)
1468                return error("unable to find %s", sha1_to_hex(sha1));
1469        if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
1470                status = error("unable to unpack %s header",
1471                               sha1_to_hex(sha1));
1472        if (parse_sha1_header(hdr, type, &size) < 0)
1473                status = error("unable to parse %s header", sha1_to_hex(sha1));
1474        else {
1475                status = 0;
1476                if (sizep)
1477                        *sizep = size;
1478        }
1479        inflateEnd(&stream);
1480        munmap(map, mapsize);
1481        return status;
1482}
1483
1484int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
1485{
1486        struct pack_entry e;
1487
1488        if (!find_pack_entry(sha1, &e, NULL)) {
1489                reprepare_packed_git();
1490                if (!find_pack_entry(sha1, &e, NULL))
1491                        return sha1_loose_object_info(sha1, type, sizep);
1492        }
1493        return packed_object_info(e.p, e.offset, type, sizep);
1494}
1495
1496static void *read_packed_sha1(const unsigned char *sha1, char *type, unsigned long *size)
1497{
1498        struct pack_entry e;
1499
1500        if (!find_pack_entry(sha1, &e, NULL))
1501                return NULL;
1502        else
1503                return unpack_entry(e.p, e.offset, type, size);
1504}
1505
1506/*
1507 * This is meant to hold a *small* number of objects that you would
1508 * want read_sha1_file() to be able to return, but yet you do not want
1509 * to write them into the object store (e.g. a browse-only
1510 * application).
1511 */
1512static struct cached_object {
1513        unsigned char sha1[20];
1514        const char *type;
1515        void *buf;
1516        unsigned long size;
1517} *cached_objects;
1518static int cached_object_nr, cached_object_alloc;
1519
1520static struct cached_object *find_cached_object(const unsigned char *sha1)
1521{
1522        int i;
1523        struct cached_object *co = cached_objects;
1524
1525        for (i = 0; i < cached_object_nr; i++, co++) {
1526                if (!hashcmp(co->sha1, sha1))
1527                        return co;
1528        }
1529        return NULL;
1530}
1531
1532int pretend_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *sha1)
1533{
1534        struct cached_object *co;
1535
1536        hash_sha1_file(buf, len, type, sha1);
1537        if (has_sha1_file(sha1) || find_cached_object(sha1))
1538                return 0;
1539        if (cached_object_alloc <= cached_object_nr) {
1540                cached_object_alloc = alloc_nr(cached_object_alloc);
1541                cached_objects = xrealloc(cached_objects,
1542                                          sizeof(*cached_objects) *
1543                                          cached_object_alloc);
1544        }
1545        co = &cached_objects[cached_object_nr++];
1546        co->size = len;
1547        co->type = strdup(type);
1548        co->buf = xmalloc(len);
1549        memcpy(co->buf, buf, len);
1550        hashcpy(co->sha1, sha1);
1551        return 0;
1552}
1553
1554void *read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
1555{
1556        unsigned long mapsize;
1557        void *map, *buf;
1558        struct cached_object *co;
1559
1560        co = find_cached_object(sha1);
1561        if (co) {
1562                buf = xmalloc(co->size + 1);
1563                memcpy(buf, co->buf, co->size);
1564                ((char*)buf)[co->size] = 0;
1565                strcpy(type, co->type);
1566                *size = co->size;
1567                return buf;
1568        }
1569
1570        buf = read_packed_sha1(sha1, type, size);
1571        if (buf)
1572                return buf;
1573        map = map_sha1_file(sha1, &mapsize);
1574        if (map) {
1575                buf = unpack_sha1_file(map, mapsize, type, size);
1576                munmap(map, mapsize);
1577                return buf;
1578        }
1579        reprepare_packed_git();
1580        return read_packed_sha1(sha1, type, size);
1581}
1582
1583void *read_object_with_reference(const unsigned char *sha1,
1584                                 const char *required_type,
1585                                 unsigned long *size,
1586                                 unsigned char *actual_sha1_return)
1587{
1588        char type[20];
1589        void *buffer;
1590        unsigned long isize;
1591        unsigned char actual_sha1[20];
1592
1593        hashcpy(actual_sha1, sha1);
1594        while (1) {
1595                int ref_length = -1;
1596                const char *ref_type = NULL;
1597
1598                buffer = read_sha1_file(actual_sha1, type, &isize);
1599                if (!buffer)
1600                        return NULL;
1601                if (!strcmp(type, required_type)) {
1602                        *size = isize;
1603                        if (actual_sha1_return)
1604                                hashcpy(actual_sha1_return, actual_sha1);
1605                        return buffer;
1606                }
1607                /* Handle references */
1608                else if (!strcmp(type, commit_type))
1609                        ref_type = "tree ";
1610                else if (!strcmp(type, tag_type))
1611                        ref_type = "object ";
1612                else {
1613                        free(buffer);
1614                        return NULL;
1615                }
1616                ref_length = strlen(ref_type);
1617
1618                if (memcmp(buffer, ref_type, ref_length) ||
1619                    get_sha1_hex((char *) buffer + ref_length, actual_sha1)) {
1620                        free(buffer);
1621                        return NULL;
1622                }
1623                free(buffer);
1624                /* Now we have the ID of the referred-to object in
1625                 * actual_sha1.  Check again. */
1626        }
1627}
1628
1629static void write_sha1_file_prepare(void *buf, unsigned long len,
1630                                    const char *type, unsigned char *sha1,
1631                                    unsigned char *hdr, int *hdrlen)
1632{
1633        SHA_CTX c;
1634
1635        /* Generate the header */
1636        *hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
1637
1638        /* Sha1.. */
1639        SHA1_Init(&c);
1640        SHA1_Update(&c, hdr, *hdrlen);
1641        SHA1_Update(&c, buf, len);
1642        SHA1_Final(sha1, &c);
1643}
1644
1645/*
1646 * Link the tempfile to the final place, possibly creating the
1647 * last directory level as you do so.
1648 *
1649 * Returns the errno on failure, 0 on success.
1650 */
1651static int link_temp_to_file(const char *tmpfile, const char *filename)
1652{
1653        int ret;
1654        char *dir;
1655
1656        if (!link(tmpfile, filename))
1657                return 0;
1658
1659        /*
1660         * Try to mkdir the last path component if that failed.
1661         *
1662         * Re-try the "link()" regardless of whether the mkdir
1663         * succeeds, since a race might mean that somebody
1664         * else succeeded.
1665         */
1666        ret = errno;
1667        dir = strrchr(filename, '/');
1668        if (dir) {
1669                *dir = 0;
1670                if (!mkdir(filename, 0777) && adjust_shared_perm(filename)) {
1671                        *dir = '/';
1672                        return -2;
1673                }
1674                *dir = '/';
1675                if (!link(tmpfile, filename))
1676                        return 0;
1677                ret = errno;
1678        }
1679        return ret;
1680}
1681
1682/*
1683 * Move the just written object into its final resting place
1684 */
1685int move_temp_to_file(const char *tmpfile, const char *filename)
1686{
1687        int ret = link_temp_to_file(tmpfile, filename);
1688
1689        /*
1690         * Coda hack - coda doesn't like cross-directory links,
1691         * so we fall back to a rename, which will mean that it
1692         * won't be able to check collisions, but that's not a
1693         * big deal.
1694         *
1695         * The same holds for FAT formatted media.
1696         *
1697         * When this succeeds, we just return 0. We have nothing
1698         * left to unlink.
1699         */
1700        if (ret && ret != EEXIST) {
1701                if (!rename(tmpfile, filename))
1702                        return 0;
1703                ret = errno;
1704        }
1705        unlink(tmpfile);
1706        if (ret) {
1707                if (ret != EEXIST) {
1708                        return error("unable to write sha1 filename %s: %s\n", filename, strerror(ret));
1709                }
1710                /* FIXME!!! Collision check here ? */
1711        }
1712
1713        return 0;
1714}
1715
1716static int write_buffer(int fd, const void *buf, size_t len)
1717{
1718        if (write_in_full(fd, buf, len) < 0)
1719                return error("file write error (%s)", strerror(errno));
1720        return 0;
1721}
1722
1723static int write_binary_header(unsigned char *hdr, enum object_type type, unsigned long len)
1724{
1725        int hdr_len;
1726        unsigned char c;
1727
1728        c = (type << 4) | (len & 15);
1729        len >>= 4;
1730        hdr_len = 1;
1731        while (len) {
1732                *hdr++ = c | 0x80;
1733                hdr_len++;
1734                c = (len & 0x7f);
1735                len >>= 7;
1736        }
1737        *hdr = c;
1738        return hdr_len;
1739}
1740
1741static void setup_object_header(z_stream *stream, const char *type, unsigned long len)
1742{
1743        int obj_type, hdr;
1744
1745        if (use_legacy_headers) {
1746                while (deflate(stream, 0) == Z_OK)
1747                        /* nothing */;
1748                return;
1749        }
1750        if (!strcmp(type, blob_type))
1751                obj_type = OBJ_BLOB;
1752        else if (!strcmp(type, tree_type))
1753                obj_type = OBJ_TREE;
1754        else if (!strcmp(type, commit_type))
1755                obj_type = OBJ_COMMIT;
1756        else if (!strcmp(type, tag_type))
1757                obj_type = OBJ_TAG;
1758        else
1759                die("trying to generate bogus object of type '%s'", type);
1760        hdr = write_binary_header(stream->next_out, obj_type, len);
1761        stream->total_out = hdr;
1762        stream->next_out += hdr;
1763        stream->avail_out -= hdr;
1764}
1765
1766int hash_sha1_file(void *buf, unsigned long len, const char *type,
1767                   unsigned char *sha1)
1768{
1769        unsigned char hdr[50];
1770        int hdrlen;
1771        write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
1772        return 0;
1773}
1774
1775int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
1776{
1777        int size;
1778        unsigned char *compressed;
1779        z_stream stream;
1780        unsigned char sha1[20];
1781        char *filename;
1782        static char tmpfile[PATH_MAX];
1783        unsigned char hdr[50];
1784        int fd, hdrlen;
1785
1786        /* Normally if we have it in the pack then we do not bother writing
1787         * it out into .git/objects/??/?{38} file.
1788         */
1789        write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
1790        filename = sha1_file_name(sha1);
1791        if (returnsha1)
1792                hashcpy(returnsha1, sha1);
1793        if (has_sha1_file(sha1))
1794                return 0;
1795        fd = open(filename, O_RDONLY);
1796        if (fd >= 0) {
1797                /*
1798                 * FIXME!!! We might do collision checking here, but we'd
1799                 * need to uncompress the old file and check it. Later.
1800                 */
1801                close(fd);
1802                return 0;
1803        }
1804
1805        if (errno != ENOENT) {
1806                return error("sha1 file %s: %s\n", filename, strerror(errno));
1807        }
1808
1809        snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
1810
1811        fd = mkstemp(tmpfile);
1812        if (fd < 0) {
1813                if (errno == EPERM)
1814                        return error("insufficient permission for adding an object to repository database %s\n", get_object_directory());
1815                else
1816                        return error("unable to create temporary sha1 filename %s: %s\n", tmpfile, strerror(errno));
1817        }
1818
1819        /* Set it up */
1820        memset(&stream, 0, sizeof(stream));
1821        deflateInit(&stream, zlib_compression_level);
1822        size = 8 + deflateBound(&stream, len+hdrlen);
1823        compressed = xmalloc(size);
1824
1825        /* Compress it */
1826        stream.next_out = compressed;
1827        stream.avail_out = size;
1828
1829        /* First header.. */
1830        stream.next_in = hdr;
1831        stream.avail_in = hdrlen;
1832        setup_object_header(&stream, type, len);
1833
1834        /* Then the data itself.. */
1835        stream.next_in = buf;
1836        stream.avail_in = len;
1837        while (deflate(&stream, Z_FINISH) == Z_OK)
1838                /* nothing */;
1839        deflateEnd(&stream);
1840        size = stream.total_out;
1841
1842        if (write_buffer(fd, compressed, size) < 0)
1843                die("unable to write sha1 file");
1844        fchmod(fd, 0444);
1845        close(fd);
1846        free(compressed);
1847
1848        return move_temp_to_file(tmpfile, filename);
1849}
1850
1851/*
1852 * We need to unpack and recompress the object for writing
1853 * it out to a different file.
1854 */
1855static void *repack_object(const unsigned char *sha1, unsigned long *objsize)
1856{
1857        size_t size;
1858        z_stream stream;
1859        unsigned char *unpacked;
1860        unsigned long len;
1861        char type[20];
1862        char hdr[50];
1863        int hdrlen;
1864        void *buf;
1865
1866        /* need to unpack and recompress it by itself */
1867        unpacked = read_packed_sha1(sha1, type, &len);
1868        if (!unpacked)
1869                error("cannot read sha1_file for %s", sha1_to_hex(sha1));
1870
1871        hdrlen = sprintf(hdr, "%s %lu", type, len) + 1;
1872
1873        /* Set it up */
1874        memset(&stream, 0, sizeof(stream));
1875        deflateInit(&stream, zlib_compression_level);
1876        size = deflateBound(&stream, len + hdrlen);
1877        buf = xmalloc(size);
1878
1879        /* Compress it */
1880        stream.next_out = buf;
1881        stream.avail_out = size;
1882
1883        /* First header.. */
1884        stream.next_in = (void *)hdr;
1885        stream.avail_in = hdrlen;
1886        while (deflate(&stream, 0) == Z_OK)
1887                /* nothing */;
1888
1889        /* Then the data itself.. */
1890        stream.next_in = unpacked;
1891        stream.avail_in = len;
1892        while (deflate(&stream, Z_FINISH) == Z_OK)
1893                /* nothing */;
1894        deflateEnd(&stream);
1895        free(unpacked);
1896
1897        *objsize = stream.total_out;
1898        return buf;
1899}
1900
1901int write_sha1_to_fd(int fd, const unsigned char *sha1)
1902{
1903        int retval;
1904        unsigned long objsize;
1905        void *buf = map_sha1_file(sha1, &objsize);
1906
1907        if (buf) {
1908                retval = write_buffer(fd, buf, objsize);
1909                munmap(buf, objsize);
1910                return retval;
1911        }
1912
1913        buf = repack_object(sha1, &objsize);
1914        retval = write_buffer(fd, buf, objsize);
1915        free(buf);
1916        return retval;
1917}
1918
1919int write_sha1_from_fd(const unsigned char *sha1, int fd, char *buffer,
1920                       size_t bufsize, size_t *bufposn)
1921{
1922        char tmpfile[PATH_MAX];
1923        int local;
1924        z_stream stream;
1925        unsigned char real_sha1[20];
1926        unsigned char discard[4096];
1927        int ret;
1928        SHA_CTX c;
1929
1930        snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
1931
1932        local = mkstemp(tmpfile);
1933        if (local < 0) {
1934                if (errno == EPERM)
1935                        return error("insufficient permission for adding an object to repository database %s\n", get_object_directory());
1936                else
1937                        return error("unable to create temporary sha1 filename %s: %s\n", tmpfile, strerror(errno));
1938        }
1939
1940        memset(&stream, 0, sizeof(stream));
1941
1942        inflateInit(&stream);
1943
1944        SHA1_Init(&c);
1945
1946        do {
1947                ssize_t size;
1948                if (*bufposn) {
1949                        stream.avail_in = *bufposn;
1950                        stream.next_in = (unsigned char *) buffer;
1951                        do {
1952                                stream.next_out = discard;
1953                                stream.avail_out = sizeof(discard);
1954                                ret = inflate(&stream, Z_SYNC_FLUSH);
1955                                SHA1_Update(&c, discard, sizeof(discard) -
1956                                            stream.avail_out);
1957                        } while (stream.avail_in && ret == Z_OK);
1958                        if (write_buffer(local, buffer, *bufposn - stream.avail_in) < 0)
1959                                die("unable to write sha1 file");
1960                        memmove(buffer, buffer + *bufposn - stream.avail_in,
1961                                stream.avail_in);
1962                        *bufposn = stream.avail_in;
1963                        if (ret != Z_OK)
1964                                break;
1965                }
1966                size = xread(fd, buffer + *bufposn, bufsize - *bufposn);
1967                if (size <= 0) {
1968                        close(local);
1969                        unlink(tmpfile);
1970                        if (!size)
1971                                return error("Connection closed?");
1972                        perror("Reading from connection");
1973                        return -1;
1974                }
1975                *bufposn += size;
1976        } while (1);
1977        inflateEnd(&stream);
1978
1979        close(local);
1980        SHA1_Final(real_sha1, &c);
1981        if (ret != Z_STREAM_END) {
1982                unlink(tmpfile);
1983                return error("File %s corrupted", sha1_to_hex(sha1));
1984        }
1985        if (hashcmp(sha1, real_sha1)) {
1986                unlink(tmpfile);
1987                return error("File %s has bad hash", sha1_to_hex(sha1));
1988        }
1989
1990        return move_temp_to_file(tmpfile, sha1_file_name(sha1));
1991}
1992
1993int has_pack_index(const unsigned char *sha1)
1994{
1995        struct stat st;
1996        if (stat(sha1_pack_index_name(sha1), &st))
1997                return 0;
1998        return 1;
1999}
2000
2001int has_pack_file(const unsigned char *sha1)
2002{
2003        struct stat st;
2004        if (stat(sha1_pack_name(sha1), &st))
2005                return 0;
2006        return 1;
2007}
2008
2009int has_sha1_pack(const unsigned char *sha1, const char **ignore_packed)
2010{
2011        struct pack_entry e;
2012        return find_pack_entry(sha1, &e, ignore_packed);
2013}
2014
2015int has_sha1_file(const unsigned char *sha1)
2016{
2017        struct stat st;
2018        struct pack_entry e;
2019
2020        if (find_pack_entry(sha1, &e, NULL))
2021                return 1;
2022        return find_sha1_file(sha1, &st) ? 1 : 0;
2023}
2024
2025/*
2026 * reads from fd as long as possible into a supplied buffer of size bytes.
2027 * If necessary the buffer's size is increased using realloc()
2028 *
2029 * returns 0 if anything went fine and -1 otherwise
2030 *
2031 * NOTE: both buf and size may change, but even when -1 is returned
2032 * you still have to free() it yourself.
2033 */
2034int read_pipe(int fd, char** return_buf, unsigned long* return_size)
2035{
2036        char* buf = *return_buf;
2037        unsigned long size = *return_size;
2038        int iret;
2039        unsigned long off = 0;
2040
2041        do {
2042                iret = xread(fd, buf + off, size - off);
2043                if (iret > 0) {
2044                        off += iret;
2045                        if (off == size) {
2046                                size *= 2;
2047                                buf = xrealloc(buf, size);
2048                        }
2049                }
2050        } while (iret > 0);
2051
2052        *return_buf = buf;
2053        *return_size = off;
2054
2055        if (iret < 0)
2056                return -1;
2057        return 0;
2058}
2059
2060int index_pipe(unsigned char *sha1, int fd, const char *type, int write_object)
2061{
2062        unsigned long size = 4096;
2063        char *buf = xmalloc(size);
2064        int ret;
2065
2066        if (read_pipe(fd, &buf, &size)) {
2067                free(buf);
2068                return -1;
2069        }
2070
2071        if (!type)
2072                type = blob_type;
2073        if (write_object)
2074                ret = write_sha1_file(buf, size, type, sha1);
2075        else
2076                ret = hash_sha1_file(buf, size, type, sha1);
2077        free(buf);
2078        return ret;
2079}
2080
2081int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object, const char *type)
2082{
2083        unsigned long size = st->st_size;
2084        void *buf;
2085        int ret, re_allocated = 0;
2086
2087        buf = "";
2088        if (size)
2089                buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
2090        close(fd);
2091
2092        if (!type)
2093                type = blob_type;
2094
2095        /*
2096         * Convert blobs to git internal format
2097         */
2098        if (!strcmp(type, blob_type)) {
2099                unsigned long nsize = size;
2100                char *nbuf = buf;
2101                if (convert_to_git(NULL, &nbuf, &nsize)) {
2102                        if (size)
2103                                munmap(buf, size);
2104                        size = nsize;
2105                        buf = nbuf;
2106                        re_allocated = 1;
2107                }
2108        }
2109
2110        if (write_object)
2111                ret = write_sha1_file(buf, size, type, sha1);
2112        else
2113                ret = hash_sha1_file(buf, size, type, sha1);
2114        if (re_allocated) {
2115                free(buf);
2116                return ret;
2117        }
2118        if (size)
2119                munmap(buf, size);
2120        return ret;
2121}
2122
2123int index_path(unsigned char *sha1, const char *path, struct stat *st, int write_object)
2124{
2125        int fd;
2126        char *target;
2127
2128        switch (st->st_mode & S_IFMT) {
2129        case S_IFREG:
2130                fd = open(path, O_RDONLY);
2131                if (fd < 0)
2132                        return error("open(\"%s\"): %s", path,
2133                                     strerror(errno));
2134                if (index_fd(sha1, fd, st, write_object, NULL) < 0)
2135                        return error("%s: failed to insert into database",
2136                                     path);
2137                break;
2138        case S_IFLNK:
2139                target = xmalloc(st->st_size+1);
2140                if (readlink(path, target, st->st_size+1) != st->st_size) {
2141                        char *errstr = strerror(errno);
2142                        free(target);
2143                        return error("readlink(\"%s\"): %s", path,
2144                                     errstr);
2145                }
2146                if (!write_object)
2147                        hash_sha1_file(target, st->st_size, blob_type, sha1);
2148                else if (write_sha1_file(target, st->st_size, blob_type, sha1))
2149                        return error("%s: failed to insert into database",
2150                                     path);
2151                free(target);
2152                break;
2153        default:
2154                return error("%s: unsupported file type", path);
2155        }
2156        return 0;
2157}
2158
2159int read_pack_header(int fd, struct pack_header *header)
2160{
2161        char *c = (char*)header;
2162        ssize_t remaining = sizeof(struct pack_header);
2163        do {
2164                ssize_t r = xread(fd, c, remaining);
2165                if (r <= 0)
2166                        /* "eof before pack header was fully read" */
2167                        return PH_ERROR_EOF;
2168                remaining -= r;
2169                c += r;
2170        } while (remaining > 0);
2171        if (header->hdr_signature != htonl(PACK_SIGNATURE))
2172                /* "protocol error (pack signature mismatch detected)" */
2173                return PH_ERROR_PACK_SIGNATURE;
2174        if (!pack_version_ok(header->hdr_version))
2175                /* "protocol error (pack version unsupported)" */
2176                return PH_ERROR_PROTOCOL;
2177        return 0;
2178}