git.oblomov.eu Git - git/blob - pack-write.c

   1 #include "cache.h"
   2 #include "pack.h"
   3 #include "csum-file.h"
   4
   5 void reset_pack_idx_option(struct pack_idx_option *opts)
   6 {
   7         memset(opts, 0, sizeof(*opts));
   8         opts->version = 2;
   9         opts->off32_limit = 0x7fffffff;
  10 }
  11
  12 static int sha1_compare(const void *_a, const void *_b)
  13 {
  14         struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
  15         struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
  16         return hashcmp(a->sha1, b->sha1);
  17 }
  18
  19 static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
  20 {
  21         return (offset >> 31) || (opts->off32_limit < offset);
  22 }
  23
  24 /*
  25  * On entry *sha1 contains the pack content SHA1 hash, on exit it is
  26  * the SHA1 hash of sorted object names. The objects array passed in
  27  * will be sorted by SHA1 on exit.
  28  */
  29 const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
  30                            int nr_objects, const struct pack_idx_option *opts,
  31                            unsigned char *sha1)
  32 {
  33         struct sha1file *f;
  34         struct pack_idx_entry **sorted_by_sha, **list, **last;
  35         off_t last_obj_offset = 0;
  36         uint32_t array[256];
  37         int i, fd;
  38         git_SHA_CTX ctx;
  39         uint32_t index_version;
  40
  41         if (nr_objects) {
  42                 sorted_by_sha = objects;
  43                 list = sorted_by_sha;
  44                 last = sorted_by_sha + nr_objects;
  45                 for (i = 0; i < nr_objects; ++i) {
  46                         if (objects[i]->offset > last_obj_offset)
  47                                 last_obj_offset = objects[i]->offset;
  48                 }
  49                 qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
  50                       sha1_compare);
  51         }
  52         else
  53                 sorted_by_sha = list = last = NULL;
  54
  55         if (opts->flags & WRITE_IDX_VERIFY) {
  56                 assert(index_name);
  57                 f = sha1fd_check(index_name);
  58         } else {
  59                 if (!index_name) {
  60                         static char tmpfile[PATH_MAX];
  61                         fd = odb_mkstemp(tmpfile, sizeof(tmpfile), "pack/tmp_idx_XXXXXX");
  62                         index_name = xstrdup(tmpfile);
  63                 } else {
  64                         unlink(index_name);
  65                         fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
  66                 }
  67                 if (fd < 0)
  68                         die_errno("unable to create '%s'", index_name);
  69                 f = sha1fd(fd, index_name);
  70         }
  71
  72         /* if last object's offset is >= 2^31 we should use index V2 */
  73         index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
  74
  75         /* index versions 2 and above need a header */
  76         if (index_version >= 2) {
  77                 struct pack_idx_header hdr;
  78                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
  79                 hdr.idx_version = htonl(index_version);
  80                 sha1write(f, &hdr, sizeof(hdr));
  81         }
  82
  83         /*
  84          * Write the first-level table (the list is sorted,
  85          * but we use a 256-entry lookup to be able to avoid
  86          * having to do eight extra binary search iterations).
  87          */
  88         for (i = 0; i < 256; i++) {
  89                 struct pack_idx_entry **next = list;
  90                 while (next < last) {
  91                         struct pack_idx_entry *obj = *next;
  92                         if (obj->sha1[0] != i)
  93                                 break;
  94                         next++;
  95                 }
  96                 array[i] = htonl(next - sorted_by_sha);
  97                 list = next;
  98         }
  99         sha1write(f, array, 256 * 4);
 100
 101         /* compute the SHA1 hash of sorted object names. */
 102         git_SHA1_Init(&ctx);
 103
 104         /*
 105          * Write the actual SHA1 entries..
 106          */
 107         list = sorted_by_sha;
 108         for (i = 0; i < nr_objects; i++) {
 109                 struct pack_idx_entry *obj = *list++;
 110                 if (index_version < 2) {
 111                         uint32_t offset = htonl(obj->offset);
 112                         sha1write(f, &offset, 4);
 113                 }
 114                 sha1write(f, obj->sha1, 20);
 115                 git_SHA1_Update(&ctx, obj->sha1, 20);
 116         }
 117
 118         if (index_version >= 2) {
 119                 unsigned int nr_large_offset = 0;
 120
 121                 /* write the crc32 table */
 122                 list = sorted_by_sha;
 123                 for (i = 0; i < nr_objects; i++) {
 124                         struct pack_idx_entry *obj = *list++;
 125                         uint32_t crc32_val = htonl(obj->crc32);
 126                         sha1write(f, &crc32_val, 4);
 127                 }
 128
 129                 /* write the 32-bit offset table */
 130                 list = sorted_by_sha;
 131                 for (i = 0; i < nr_objects; i++) {
 132                         struct pack_idx_entry *obj = *list++;
 133                         uint32_t offset;
 134
 135                         offset = (need_large_offset(obj->offset, opts)
 136                                   ? (0x80000000 | nr_large_offset++)
 137                                   : obj->offset);
 138                         offset = htonl(offset);
 139                         sha1write(f, &offset, 4);
 140                 }
 141
 142                 /* write the large offset table */
 143                 list = sorted_by_sha;
 144                 while (nr_large_offset) {
 145                         struct pack_idx_entry *obj = *list++;
 146                         uint64_t offset = obj->offset;
 147                         uint32_t split[2];
 148
 149                         if (!need_large_offset(offset, opts))
 150                                 continue;
 151                         split[0] = htonl(offset >> 32);
 152                         split[1] = htonl(offset & 0xffffffff);
 153                         sha1write(f, split, 8);
 154                         nr_large_offset--;
 155                 }
 156         }
 157
 158         sha1write(f, sha1, 20);
 159         sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
 160                             ? CSUM_CLOSE : CSUM_FSYNC));
 161         git_SHA1_Final(sha1, &ctx);
 162         return index_name;
 163 }
 164
 165 /*
 166  * Update pack header with object_count and compute new SHA1 for pack data
 167  * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
 168  * is also returned in new_pack_sha1.
 169  *
 170  * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
 171  * (without the header update) is computed and validated against the
 172  * one provided in partial_pack_sha1.  The validation is performed at
 173  * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
 174  * data (i.e. from partial_pack_offset to the end) is then computed and
 175  * returned in partial_pack_sha1.
 176  *
 177  * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
 178  * partial_pack_sha1 can refer to the same buffer if the caller is not
 179  * interested in the resulting SHA1 of pack data above partial_pack_offset.
 180  */
 181 void fixup_pack_header_footer(int pack_fd,
 182                          unsigned char *new_pack_sha1,
 183                          const char *pack_name,
 184                          uint32_t object_count,
 185                          unsigned char *partial_pack_sha1,
 186                          off_t partial_pack_offset)
 187 {
 188         int aligned_sz, buf_sz = 8 * 1024;
 189         git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
 190         struct pack_header hdr;
 191         char *buf;
 192
 193         git_SHA1_Init(&old_sha1_ctx);
 194         git_SHA1_Init(&new_sha1_ctx);
 195
 196         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 197                 die_errno("Failed seeking to start of '%s'", pack_name);
 198         if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 199                 die_errno("Unable to reread header of '%s'", pack_name);
 200         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 201                 die_errno("Failed seeking to start of '%s'", pack_name);
 202         git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
 203         hdr.hdr_entries = htonl(object_count);
 204         git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
 205         write_or_die(pack_fd, &hdr, sizeof(hdr));
 206         partial_pack_offset -= sizeof(hdr);
 207
 208         buf = xmalloc(buf_sz);
 209         aligned_sz = buf_sz - sizeof(hdr);
 210         for (;;) {
 211                 ssize_t m, n;
 212                 m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
 213                         partial_pack_offset : aligned_sz;
 214                 n = xread(pack_fd, buf, m);
 215                 if (!n)
 216                         break;
 217                 if (n < 0)
 218                         die_errno("Failed to checksum '%s'", pack_name);
 219                 git_SHA1_Update(&new_sha1_ctx, buf, n);
 220
 221                 aligned_sz -= n;
 222                 if (!aligned_sz)
 223                         aligned_sz = buf_sz;
 224
 225                 if (!partial_pack_sha1)
 226                         continue;
 227
 228                 git_SHA1_Update(&old_sha1_ctx, buf, n);
 229                 partial_pack_offset -= n;
 230                 if (partial_pack_offset == 0) {
 231                         unsigned char sha1[20];
 232                         git_SHA1_Final(sha1, &old_sha1_ctx);
 233                         if (hashcmp(sha1, partial_pack_sha1) != 0)
 234                                 die("Unexpected checksum for %s "
 235                                     "(disk corruption?)", pack_name);
 236                         /*
 237                          * Now let's compute the SHA1 of the remainder of the
 238                          * pack, which also means making partial_pack_offset
 239                          * big enough not to matter anymore.
 240                          */
 241                         git_SHA1_Init(&old_sha1_ctx);
 242                         partial_pack_offset = ~partial_pack_offset;
 243                         partial_pack_offset -= MSB(partial_pack_offset, 1);
 244                 }
 245         }
 246         free(buf);
 247
 248         if (partial_pack_sha1)
 249                 git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
 250         git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
 251         write_or_die(pack_fd, new_pack_sha1, 20);
 252         fsync_or_die(pack_fd, pack_name);
 253 }
 254
 255 char *index_pack_lockfile(int ip_out)
 256 {
 257         char packname[46];
 258
 259         /*
 260          * The first thing we expect from index-pack's output
 261          * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
 262          * %40s is the newly created pack SHA1 name.  In the "keep"
 263          * case, we need it to remove the corresponding .keep file
 264          * later on.  If we don't get that then tough luck with it.
 265          */
 266         if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
 267             memcmp(packname, "keep\t", 5) == 0) {
 268                 char path[PATH_MAX];
 269                 packname[45] = 0;
 270                 snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
 271                          get_object_directory(), packname + 5);
 272                 return xstrdup(path);
 273         }
 274         return NULL;
 275 }
 276
 277 /*
 278  * The per-object header is a pretty dense thing, which is
 279  *  - first byte: low four bits are "size", then three bits of "type",
 280  *    and the high bit is "size continues".
 281  *  - each byte afterwards: low seven bits are size continuation,
 282  *    with the high bit being "size continues"
 283  */
 284 int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
 285 {
 286         int n = 1;
 287         unsigned char c;
 288
 289         if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
 290                 die("bad type %d", type);
 291
 292         c = (type << 4) | (size & 15);
 293         size >>= 4;
 294         while (size) {
 295                 *hdr++ = c | 0x80;
 296                 c = size & 0x7f;
 297                 size >>= 7;
 298                 n++;
 299         }
 300         *hdr = c;
 301         return n;
 302 }