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