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