pack-write.c

   1 #include "cache.h"
   2 #include "pack.h"
   3 #include "csum-file.h"
   4
   5 uint32_t pack_idx_default_version = 2;
   6 uint32_t pack_idx_off32_limit = 0x7fffffff;
   7
   8 static int sha1_compare(const void *_a, const void *_b)
   9 {
  10         struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
  11         struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
  12         return hashcmp(a->sha1, b->sha1);
  13 }
  14
  15 /*
  16  * On entry *sha1 contains the pack content SHA1 hash, on exit it is
  17  * the SHA1 hash of sorted object names. The objects array passed in
  18  * will be sorted by SHA1 on exit.
  19  */
  20 char *write_idx_file(char *index_name, struct pack_idx_entry **objects,
  21                      int nr_objects, unsigned char *sha1)
  22 {
  23         struct sha1file *f;
  24         struct pack_idx_entry **sorted_by_sha, **list, **last;
  25         off_t last_obj_offset = 0;
  26         uint32_t array[256];
  27         int i, fd;
  28         git_SHA_CTX ctx;
  29         uint32_t index_version;
  30
  31         if (nr_objects) {
  32                 sorted_by_sha = objects;
  33                 list = sorted_by_sha;
  34                 last = sorted_by_sha + nr_objects;
  35                 for (i = 0; i < nr_objects; ++i) {
  36                         if (objects[i]->offset > last_obj_offset)
  37                                 last_obj_offset = objects[i]->offset;
  38                 }
  39                 qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
  40                       sha1_compare);
  41         }
  42         else
  43                 sorted_by_sha = list = last = NULL;
  44
  45         if (!index_name) {
  46                 static char tmpfile[PATH_MAX];
  47                 snprintf(tmpfile, sizeof(tmpfile),
  48                          "%s/pack/tmp_idx_XXXXXX", get_object_directory());
  49                 fd = xmkstemp(tmpfile);
  50                 index_name = xstrdup(tmpfile);
  51         } else {
  52                 unlink(index_name);
  53                 fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
  54         }
  55         if (fd < 0)
  56                 die("unable to create %s: %s", index_name, strerror(errno));
  57         f = sha1fd(fd, index_name);
  58
  59         /* if last object's offset is >= 2^31 we should use index V2 */
  60         index_version = (last_obj_offset >> 31) ? 2 : pack_idx_default_version;
  61
  62         /* index versions 2 and above need a header */
  63         if (index_version >= 2) {
  64                 struct pack_idx_header hdr;
  65                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
  66                 hdr.idx_version = htonl(index_version);
  67                 sha1write(f, &hdr, sizeof(hdr));
  68         }
  69
  70         /*
  71          * Write the first-level table (the list is sorted,
  72          * but we use a 256-entry lookup to be able to avoid
  73          * having to do eight extra binary search iterations).
  74          */
  75         for (i = 0; i < 256; i++) {
  76                 struct pack_idx_entry **next = list;
  77                 while (next < last) {
  78                         struct pack_idx_entry *obj = *next;
  79                         if (obj->sha1[0] != i)
  80                                 break;
  81                         next++;
  82                 }
  83                 array[i] = htonl(next - sorted_by_sha);
  84                 list = next;
  85         }
  86         sha1write(f, array, 256 * 4);
  87
  88         /* compute the SHA1 hash of sorted object names. */
  89         git_SHA1_Init(&ctx);
  90
  91         /*
  92          * Write the actual SHA1 entries..
  93          */
  94         list = sorted_by_sha;
  95         for (i = 0; i < nr_objects; i++) {
  96                 struct pack_idx_entry *obj = *list++;
  97                 if (index_version < 2) {
  98                         uint32_t offset = htonl(obj->offset);
  99                         sha1write(f, &offset, 4);
 100                 }
 101                 sha1write(f, obj->sha1, 20);
 102                 git_SHA1_Update(&ctx, obj->sha1, 20);
 103         }
 104
 105         if (index_version >= 2) {
 106                 unsigned int nr_large_offset = 0;
 107
 108                 /* write the crc32 table */
 109                 list = sorted_by_sha;
 110                 for (i = 0; i < nr_objects; i++) {
 111                         struct pack_idx_entry *obj = *list++;
 112                         uint32_t crc32_val = htonl(obj->crc32);
 113                         sha1write(f, &crc32_val, 4);
 114                 }
 115
 116                 /* write the 32-bit offset table */
 117                 list = sorted_by_sha;
 118                 for (i = 0; i < nr_objects; i++) {
 119                         struct pack_idx_entry *obj = *list++;
 120                         uint32_t offset = (obj->offset <= pack_idx_off32_limit) ?
 121                                 obj->offset : (0x80000000 | nr_large_offset++);
 122                         offset = htonl(offset);
 123                         sha1write(f, &offset, 4);
 124                 }
 125
 126                 /* write the large offset table */
 127                 list = sorted_by_sha;
 128                 while (nr_large_offset) {
 129                         struct pack_idx_entry *obj = *list++;
 130                         uint64_t offset = obj->offset;
 131                         if (offset > pack_idx_off32_limit) {
 132                                 uint32_t split[2];
 133                                 split[0] = htonl(offset >> 32);
 134                                 split[1] = htonl(offset & 0xffffffff);
 135                                 sha1write(f, split, 8);
 136                                 nr_large_offset--;
 137                         }
 138                 }
 139         }
 140
 141         sha1write(f, sha1, 20);
 142         sha1close(f, NULL, CSUM_FSYNC);
 143         git_SHA1_Final(sha1, &ctx);
 144         return index_name;
 145 }
 146
 147 /*
 148  * Update pack header with object_count and compute new SHA1 for pack data
 149  * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
 150  * is also returned in new_pack_sha1.
 151  *
 152  * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
 153  * (without the header update) is computed and validated against the
 154  * one provided in partial_pack_sha1.  The validation is performed at
 155  * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
 156  * data (i.e. from partial_pack_offset to the end) is then computed and
 157  * returned in partial_pack_sha1.
 158  *
 159  * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
 160  * partial_pack_sha1 can refer to the same buffer if the caller is not
 161  * interested in the resulting SHA1 of pack data above partial_pack_offset.
 162  */
 163 void fixup_pack_header_footer(int pack_fd,
 164                          unsigned char *new_pack_sha1,
 165                          const char *pack_name,
 166                          uint32_t object_count,
 167                          unsigned char *partial_pack_sha1,
 168                          off_t partial_pack_offset)
 169 {
 170         int aligned_sz, buf_sz = 8 * 1024;
 171         git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
 172         struct pack_header hdr;
 173         char *buf;
 174
 175         git_SHA1_Init(&old_sha1_ctx);
 176         git_SHA1_Init(&new_sha1_ctx);
 177
 178         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 179                 die("Failed seeking to start of %s: %s", pack_name, strerror(errno));
 180         if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 181                 die("Unable to reread header of %s: %s", pack_name, strerror(errno));
 182         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 183                 die("Failed seeking to start of %s: %s", pack_name, strerror(errno));
 184         git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
 185         hdr.hdr_entries = htonl(object_count);
 186         git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
 187         write_or_die(pack_fd, &hdr, sizeof(hdr));
 188         partial_pack_offset -= sizeof(hdr);
 189
 190         buf = xmalloc(buf_sz);
 191         aligned_sz = buf_sz - sizeof(hdr);
 192         for (;;) {
 193                 ssize_t m, n;
 194                 m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
 195                         partial_pack_offset : aligned_sz;
 196                 n = xread(pack_fd, buf, m);
 197                 if (!n)
 198                         break;
 199                 if (n < 0)
 200                         die("Failed to checksum %s: %s", pack_name, strerror(errno));
 201                 git_SHA1_Update(&new_sha1_ctx, buf, n);
 202
 203                 aligned_sz -= n;
 204                 if (!aligned_sz)
 205                         aligned_sz = buf_sz;
 206
 207                 if (!partial_pack_sha1)
 208                         continue;
 209
 210                 git_SHA1_Update(&old_sha1_ctx, buf, n);
 211                 partial_pack_offset -= n;
 212                 if (partial_pack_offset == 0) {
 213                         unsigned char sha1[20];
 214                         git_SHA1_Final(sha1, &old_sha1_ctx);
 215                         if (hashcmp(sha1, partial_pack_sha1) != 0)
 216                                 die("Unexpected checksum for %s "
 217                                     "(disk corruption?)", pack_name);
 218                         /*
 219                          * Now let's compute the SHA1 of the remainder of the
 220                          * pack, which also means making partial_pack_offset
 221                          * big enough not to matter anymore.
 222                          */
 223                         git_SHA1_Init(&old_sha1_ctx);
 224                         partial_pack_offset = ~partial_pack_offset;
 225                         partial_pack_offset -= MSB(partial_pack_offset, 1);
 226                 }
 227         }
 228         free(buf);
 229
 230         if (partial_pack_sha1)
 231                 git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
 232         git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
 233         write_or_die(pack_fd, new_pack_sha1, 20);
 234         fsync_or_die(pack_fd, pack_name);
 235 }
 236
 237 char *index_pack_lockfile(int ip_out)
 238 {
 239         char packname[46];
 240
 241         /*
 242          * The first thing we expects from index-pack's output
 243          * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
 244          * %40s is the newly created pack SHA1 name.  In the "keep"
 245          * case, we need it to remove the corresponding .keep file
 246          * later on.  If we don't get that then tough luck with it.
 247          */
 248         if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
 249             memcmp(packname, "keep\t", 5) == 0) {
 250                 char path[PATH_MAX];
 251                 packname[45] = 0;
 252                 snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
 253                          get_object_directory(), packname + 5);
 254                 return xstrdup(path);
 255         }
 256         return NULL;
 257 }