unpack-objects.c

   1 #include "cache.h"
   2 #include "object.h"
   3 #include "delta.h"
   4
   5 static int dry_run;
   6 static int nr_entries;
   7 static const char *base_name;
   8 static const char unpack_usage[] = "git-unpack-objects basename";
   9
  10 struct pack_entry {
  11         unsigned int offset; /* network byte order */
  12         unsigned char sha1[20];
  13 };
  14
  15 static void *pack_base;
  16 static unsigned long pack_size;
  17 static void *index_base;
  18 static unsigned long index_size;
  19
  20 static struct pack_entry **pack_list;
  21
  22 static void *map_file(const char *suffix, unsigned long *sizep)
  23 {
  24         static char pathname[PATH_MAX];
  25         unsigned long len;
  26         int fd;
  27         struct stat st;
  28         void *map;
  29
  30         len = snprintf(pathname, PATH_MAX, "%s.%s", base_name, suffix);
  31         if (len >= PATH_MAX)
  32                 die("bad pack base-name");
  33         fd = open(pathname, O_RDONLY);
  34         if (fd < 0 || fstat(fd, &st))
  35                 die("unable to open '%s'", pathname);
  36         len = st.st_size;
  37         if (!len)
  38                 die("bad pack file '%s'", pathname);
  39         map = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
  40         if (-1 == (int)(long)map)
  41                 die("unable to mmap '%s'", pathname);
  42         close(fd);
  43         *sizep = len;
  44         return map;
  45 }
  46
  47 static int sort_by_offset(const void *_a, const void *_b)
  48 {
  49         struct pack_entry *a = *(struct pack_entry **)_a;
  50         struct pack_entry *b = *(struct pack_entry **)_b;
  51         unsigned int o1, o2;
  52
  53         o1 = ntohl(a->offset);
  54         o2 = ntohl(b->offset);
  55         return o1 < o2 ? -1 : 1;
  56 }
  57
  58 static int check_index(void)
  59 {
  60         unsigned int *array = index_base;
  61         unsigned int nr;
  62         int i;
  63
  64         if (index_size < 4*256)
  65                 return error("index file too small");
  66         nr = 0;
  67         for (i = 0; i < 256; i++) {
  68                 unsigned int n = ntohl(array[i]);
  69                 if (n < nr)
  70                         return error("non-monotonic index");
  71                 nr = n;
  72         }
  73         if (index_size != 4*256 + nr * 24) {
  74                 printf("index_size=%lu, expected %u (%u)\n",
  75                        index_size, 4*256 + nr * 24, nr);
  76                 return error("wrong index file size");
  77         }
  78
  79         nr_entries = nr;
  80         pack_list = xmalloc(nr * sizeof(struct pack_entry *));
  81         for (i = 0; i < nr; i++)
  82                 pack_list[i] = index_base + 4*256 + i*24;
  83
  84         qsort(pack_list, nr, sizeof(*pack_list), sort_by_offset);
  85
  86         printf("%d entries\n", nr);
  87         return 0;
  88 }
  89
  90 static int unpack_non_delta_entry(struct pack_entry *entry,
  91                                   int kind,
  92                                   unsigned char *data,
  93                                   unsigned long size,
  94                                   unsigned long left)
  95 {
  96         int st;
  97         z_stream stream;
  98         char *buffer;
  99         unsigned char sha1[20];
 100         char *type_s;
 101
 102         printf("%s %c %lu\n", sha1_to_hex(entry->sha1), kind, size);
 103         if (dry_run)
 104                 return 0;
 105
 106         buffer = xmalloc(size + 1);
 107         buffer[size] = 0;
 108         memset(&stream, 0, sizeof(stream));
 109         stream.next_in = data;
 110         stream.avail_in = left;
 111         stream.next_out = buffer;
 112         stream.avail_out = size;
 113
 114         inflateInit(&stream);
 115         st = inflate(&stream, Z_FINISH);
 116         inflateEnd(&stream);
 117         if ((st != Z_STREAM_END) || stream.total_out != size)
 118                 goto err_finish;
 119         switch (kind) {
 120         case 'C': type_s = "commit"; break;
 121         case 'T': type_s = "tree"; break;
 122         case 'B': type_s = "blob"; break;
 123         default: goto err_finish;
 124         }
 125         if (write_sha1_file(buffer, size, type_s, sha1) < 0)
 126                 die("failed to write %s (%s)",
 127                     sha1_to_hex(entry->sha1), type_s);
 128         printf("%s %s\n", sha1_to_hex(sha1), type_s);
 129         if (memcmp(sha1, entry->sha1, 20))
 130                 die("resulting %s have wrong SHA1", type_s);
 131
 132  finish:
 133         st = 0;
 134         free(buffer);
 135         return st;
 136  err_finish:
 137         st = -1;
 138         goto finish;
 139 }
 140
 141 static int find_pack_entry(unsigned char *sha1, struct pack_entry **ent)
 142 {
 143         int *level1_ofs = index_base;
 144         int hi = ntohl(level1_ofs[*sha1]);
 145         int lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
 146         void *index = index_base + 4*256;
 147
 148         do {
 149                 int mi = (lo + hi) / 2;
 150                 int cmp = memcmp(index + 24 * mi + 4, sha1, 20);
 151                 if (!cmp) {
 152                         *ent = index + 24 * mi;
 153                         return 1;
 154                 }
 155                 if (cmp > 0)
 156                         hi = mi;
 157                 else
 158                         lo = mi+1;
 159         } while (lo < hi);
 160         return 0;
 161 }
 162
 163 /* forward declaration for a mutually recursive function */
 164 static void unpack_entry(struct pack_entry *);
 165
 166 static int unpack_delta_entry(struct pack_entry *entry,
 167                               unsigned char *base_sha1,
 168                               unsigned long delta_size,
 169                               unsigned long left)
 170 {
 171         void *data, *delta_data, *result, *base;
 172         unsigned long data_size, result_size, base_size;
 173         z_stream stream;
 174         int st;
 175         char type[20];
 176         unsigned char sha1[20];
 177
 178         if (left < 20)
 179                 die("truncated pack file");
 180         data = base_sha1 + 20;
 181         data_size = left - 20;
 182         printf("%s D %lu", sha1_to_hex(entry->sha1), delta_size);
 183         printf(" %s\n", sha1_to_hex(base_sha1));
 184
 185         if (dry_run)
 186                 return 0;
 187
 188         /* pack+5 is the base sha1, unless we have it, we need to
 189          * unpack it first.
 190          */
 191         if (!has_sha1_file(base_sha1)) {
 192                 struct pack_entry *base;
 193                 if (!find_pack_entry(base_sha1, &base))
 194                         die("cannot find delta-pack base object");
 195                 unpack_entry(base);
 196         }
 197         delta_data = xmalloc(delta_size);
 198
 199         memset(&stream, 0, sizeof(stream));
 200
 201         stream.next_in = data;
 202         stream.avail_in = data_size;
 203         stream.next_out = delta_data;
 204         stream.avail_out = delta_size;
 205
 206         inflateInit(&stream);
 207         st = inflate(&stream, Z_FINISH);
 208         inflateEnd(&stream);
 209         if ((st != Z_STREAM_END) || stream.total_out != delta_size)
 210                 die("delta data unpack failed");
 211
 212         base = read_sha1_file(base_sha1, type, &base_size);
 213         if (!base)
 214                 die("failed to read delta-pack base object %s", sha1_to_hex(base_sha1));
 215         result = patch_delta(base, base_size,
 216                              delta_data, delta_size,
 217                              &result_size);
 218         if (!result)
 219                 die("failed to apply delta");
 220         free(delta_data);
 221
 222         if (write_sha1_file(result, result_size, type, sha1) < 0)
 223                 die("failed to write %s (%s)",
 224                     sha1_to_hex(entry->sha1), type);
 225         free(result);
 226         printf("%s %s\n", sha1_to_hex(sha1), type);
 227         if (memcmp(sha1, entry->sha1, 20))
 228                 die("resulting %s have wrong SHA1", type);
 229         return 0;
 230 }
 231
 232 static void unpack_entry(struct pack_entry *entry)
 233 {
 234         unsigned long offset, size, left;
 235         unsigned char *pack;
 236
 237         /* Have we done this one already due to deltas based on it? */
 238         if (lookup_object(entry->sha1))
 239                 return;
 240
 241         offset = ntohl(entry->offset);
 242         if (offset > pack_size - 5)
 243                 die("object offset outside of pack file");
 244         pack = pack_base + offset;
 245         size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
 246         left = pack_size - offset - 5;
 247         switch (*pack) {
 248         case 'C': case 'T': case 'B':
 249                 unpack_non_delta_entry(entry, *pack, pack+5, size, left);
 250                 break;
 251         case 'D':
 252                 unpack_delta_entry(entry, pack+5, size, left);
 253                 break;
 254         default:
 255                 die("corrupted pack file");
 256         }
 257 }
 258
 259 /*
 260  * We unpack from the end, older files first. Now, usually
 261  * there are deltas etc, so we'll not actually write the
 262  * objects in that order, but we might as well try..
 263  */
 264 static void unpack_all(void)
 265 {
 266         int i = nr_entries;
 267
 268         while (--i >= 0) {
 269                 struct pack_entry *entry = pack_list[i];
 270                 unpack_entry(entry);
 271         }
 272 }
 273
 274 int main(int argc, char **argv)
 275 {
 276         int i;
 277
 278         for (i = 1 ; i < argc; i++) {
 279                 const char *arg = argv[i];
 280
 281                 if (*arg == '-') {
 282                         if (!strcmp(arg, "-n")) {
 283                                 dry_run = 1;
 284                                 continue;
 285                         }
 286                         usage(unpack_usage);
 287                 }
 288                 if (base_name)
 289                         usage(unpack_usage);
 290                 base_name = arg;
 291         }
 292         if (!base_name)
 293                 usage(unpack_usage);
 294         index_base = map_file("idx", &index_size);
 295         pack_base = map_file("pack", &pack_size);
 296         if (check_index() < 0)
 297                 die("bad index file");
 298         unpack_all();
 299         return 0;
 300 }