tree-walk.c

   1 #include "cache.h"
   2 #include "tree-walk.h"
   3 #include "tree.h"
   4
   5 static const char *get_mode(const char *str, unsigned int *modep)
   6 {
   7         unsigned char c;
   8         unsigned int mode = 0;
   9
  10         if (*str == ' ')
  11                 return NULL;
  12
  13         while ((c = *str++) != ' ') {
  14                 if (c < '0' || c > '7')
  15                         return NULL;
  16                 mode = (mode << 3) + (c - '0');
  17         }
  18         *modep = mode;
  19         return str;
  20 }
  21
  22 static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned long size)
  23 {
  24         const char *path;
  25         unsigned int mode, len;
  26
  27         if (size < 24 || buf[size - 21])
  28                 die("corrupt tree file");
  29
  30         path = get_mode(buf, &mode);
  31         if (!path || !*path)
  32                 die("corrupt tree file");
  33         len = strlen(path) + 1;
  34
  35         /* Initialize the descriptor entry */
  36         desc->entry.path = path;
  37         desc->entry.mode = mode;
  38         desc->entry.sha1 = (const unsigned char *)(path + len);
  39 }
  40
  41 void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
  42 {
  43         desc->buffer = buffer;
  44         desc->size = size;
  45         if (size)
  46                 decode_tree_entry(desc, buffer, size);
  47 }
  48
  49 void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
  50 {
  51         unsigned long size = 0;
  52         void *buf = NULL;
  53
  54         if (sha1) {
  55                 buf = read_object_with_reference(sha1, tree_type, &size, NULL);
  56                 if (!buf)
  57                         die("unable to read tree %s", sha1_to_hex(sha1));
  58         }
  59         init_tree_desc(desc, buf, size);
  60         return buf;
  61 }
  62
  63 static void entry_clear(struct name_entry *a)
  64 {
  65         memset(a, 0, sizeof(*a));
  66 }
  67
  68 static void entry_extract(struct tree_desc *t, struct name_entry *a)
  69 {
  70         *a = t->entry;
  71 }
  72
  73 void update_tree_entry(struct tree_desc *desc)
  74 {
  75         const void *buf = desc->buffer;
  76         const unsigned char *end = desc->entry.sha1 + 20;
  77         unsigned long size = desc->size;
  78         unsigned long len = end - (const unsigned char *)buf;
  79
  80         if (size < len)
  81                 die("corrupt tree file");
  82         buf = end;
  83         size -= len;
  84         desc->buffer = buf;
  85         desc->size = size;
  86         if (size)
  87                 decode_tree_entry(desc, buf, size);
  88 }
  89
  90 int tree_entry(struct tree_desc *desc, struct name_entry *entry)
  91 {
  92         if (!desc->size)
  93                 return 0;
  94
  95         *entry = desc->entry;
  96         update_tree_entry(desc);
  97         return 1;
  98 }
  99
 100 void setup_traverse_info(struct traverse_info *info, const char *base)
 101 {
 102         int pathlen = strlen(base);
 103         static struct traverse_info dummy;
 104
 105         memset(info, 0, sizeof(*info));
 106         if (pathlen && base[pathlen-1] == '/')
 107                 pathlen--;
 108         info->pathlen = pathlen ? pathlen + 1 : 0;
 109         info->name.path = base;
 110         info->name.sha1 = (void *)(base + pathlen + 1);
 111         if (pathlen)
 112                 info->prev = &dummy;
 113 }
 114
 115 char *make_traverse_path(char *path, const struct traverse_info *info, const struct name_entry *n)
 116 {
 117         int len = tree_entry_len(n->path, n->sha1);
 118         int pathlen = info->pathlen;
 119
 120         path[pathlen + len] = 0;
 121         for (;;) {
 122                 memcpy(path + pathlen, n->path, len);
 123                 if (!pathlen)
 124                         break;
 125                 path[--pathlen] = '/';
 126                 n = &info->name;
 127                 len = tree_entry_len(n->path, n->sha1);
 128                 info = info->prev;
 129                 pathlen -= len;
 130         }
 131         return path;
 132 }
 133
 134 struct tree_desc_skip {
 135         struct tree_desc_skip *prev;
 136         const void *ptr;
 137 };
 138
 139 struct tree_desc_x {
 140         struct tree_desc d;
 141         struct tree_desc_skip *skip;
 142 };
 143
 144 static int name_compare(const char *a, int a_len,
 145                         const char *b, int b_len)
 146 {
 147         int len = (a_len < b_len) ? a_len : b_len;
 148         int cmp = memcmp(a, b, len);
 149         if (cmp)
 150                 return cmp;
 151         return (a_len - b_len);
 152 }
 153
 154 static int check_entry_match(const char *a, int a_len, const char *b, int b_len)
 155 {
 156         /*
 157          * The caller wants to pick *a* from a tree or nothing.
 158          * We are looking at *b* in a tree.
 159          *
 160          * (0) If a and b are the same name, we are trivially happy.
 161          *
 162          * There are three possibilities where *a* could be hiding
 163          * behind *b*.
 164          *
 165          * (1) *a* == "t",   *b* == "ab"  i.e. *b* sorts earlier than *a* no
 166          *                                matter what.
 167          * (2) *a* == "t",   *b* == "t-2" and "t" is a subtree in the tree;
 168          * (3) *a* == "t-2", *b* == "t"   and "t-2" is a blob in the tree.
 169          *
 170          * Otherwise we know *a* won't appear in the tree without
 171          * scanning further.
 172          */
 173
 174         int cmp = name_compare(a, a_len, b, b_len);
 175
 176         /* Most common case first -- reading sync'd trees */
 177         if (!cmp)
 178                 return cmp;
 179
 180         if (0 < cmp) {
 181                 /* a comes after b; it does not matter if it is case (3)
 182                 if (b_len < a_len && !memcmp(a, b, b_len) && a[b_len] < '/')
 183                         return 1;
 184                 */
 185                 return 1; /* keep looking */
 186         }
 187
 188         /* b comes after a; are we looking at case (2)? */
 189         if (a_len < b_len && !memcmp(a, b, a_len) && b[a_len] < '/')
 190                 return 1; /* keep looking */
 191
 192         return -1; /* a cannot appear in the tree */
 193 }
 194
 195 /*
 196  * From the extended tree_desc, extract the first name entry, while
 197  * paying attention to the candidate "first" name.  Most importantly,
 198  * when looking for an entry, if there are entries that sorts earlier
 199  * in the tree object representation than that name, skip them and
 200  * process the named entry first.  We will remember that we haven't
 201  * processed the first entry yet, and in the later call skip the
 202  * entry we processed early when update_extended_entry() is called.
 203  *
 204  * E.g. if the underlying tree object has these entries:
 205  *
 206  *    blob    "t-1"
 207  *    blob    "t-2"
 208  *    tree    "t"
 209  *    blob    "t=1"
 210  *
 211  * and the "first" asks for "t", remember that we still need to
 212  * process "t-1" and "t-2" but extract "t".  After processing the
 213  * entry "t" from this call, the caller will let us know by calling
 214  * update_extended_entry() that we can remember "t" has been processed
 215  * already.
 216  */
 217
 218 static void extended_entry_extract(struct tree_desc_x *t,
 219                                    struct name_entry *a,
 220                                    const char *first,
 221                                    int first_len)
 222 {
 223         const char *path;
 224         int len;
 225         struct tree_desc probe;
 226         struct tree_desc_skip *skip;
 227
 228         /*
 229          * Extract the first entry from the tree_desc, but skip the
 230          * ones that we already returned in earlier rounds.
 231          */
 232         while (1) {
 233                 if (!t->d.size) {
 234                         entry_clear(a);
 235                         break; /* not found */
 236                 }
 237                 entry_extract(&t->d, a);
 238                 for (skip = t->skip; skip; skip = skip->prev)
 239                         if (a->path == skip->ptr)
 240                                 break; /* found */
 241                 if (!skip)
 242                         break;
 243                 /* We have processed this entry already. */
 244                 update_tree_entry(&t->d);
 245         }
 246
 247         if (!first || !a->path)
 248                 return;
 249
 250         /*
 251          * The caller wants "first" from this tree, or nothing.
 252          */
 253         path = a->path;
 254         len = tree_entry_len(a->path, a->sha1);
 255         switch (check_entry_match(first, first_len, path, len)) {
 256         case -1:
 257                 entry_clear(a);
 258         case 0:
 259                 return;
 260         default:
 261                 break;
 262         }
 263
 264         /*
 265          * We need to look-ahead -- we suspect that a subtree whose
 266          * name is "first" may be hiding behind the current entry "path".
 267          */
 268         probe = t->d;
 269         while (probe.size) {
 270                 entry_extract(&probe, a);
 271                 path = a->path;
 272                 len = tree_entry_len(a->path, a->sha1);
 273                 switch (check_entry_match(first, first_len, path, len)) {
 274                 case -1:
 275                         entry_clear(a);
 276                 case 0:
 277                         return;
 278                 default:
 279                         update_tree_entry(&probe);
 280                         break;
 281                 }
 282                 /* keep looking */
 283         }
 284         entry_clear(a);
 285 }
 286
 287 static void update_extended_entry(struct tree_desc_x *t, struct name_entry *a)
 288 {
 289         if (t->d.entry.path == a->path) {
 290                 update_tree_entry(&t->d);
 291         } else {
 292                 /* we have returned this entry early */
 293                 struct tree_desc_skip *skip = xmalloc(sizeof(*skip));
 294                 skip->ptr = a->path;
 295                 skip->prev = t->skip;
 296                 t->skip = skip;
 297         }
 298 }
 299
 300 static void free_extended_entry(struct tree_desc_x *t)
 301 {
 302         struct tree_desc_skip *p, *s;
 303
 304         for (s = t->skip; s; s = p) {
 305                 p = s->prev;
 306                 free(s);
 307         }
 308 }
 309
 310 int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info)
 311 {
 312         int ret = 0;
 313         struct name_entry *entry = xmalloc(n*sizeof(*entry));
 314         int i;
 315         struct tree_desc_x *tx = xcalloc(n, sizeof(*tx));
 316
 317         for (i = 0; i < n; i++)
 318                 tx[i].d = t[i];
 319
 320         for (;;) {
 321                 unsigned long mask, dirmask;
 322                 const char *first = NULL;
 323                 int first_len = 0;
 324                 struct name_entry *e;
 325                 int len;
 326
 327                 for (i = 0; i < n; i++) {
 328                         e = entry + i;
 329                         extended_entry_extract(tx + i, e, NULL, 0);
 330                 }
 331
 332                 /*
 333                  * A tree may have "t-2" at the current location even
 334                  * though it may have "t" that is a subtree behind it,
 335                  * and another tree may return "t".  We want to grab
 336                  * all "t" from all trees to match in such a case.
 337                  */
 338                 for (i = 0; i < n; i++) {
 339                         e = entry + i;
 340                         if (!e->path)
 341                                 continue;
 342                         len = tree_entry_len(e->path, e->sha1);
 343                         if (!first) {
 344                                 first = e->path;
 345                                 first_len = len;
 346                                 continue;
 347                         }
 348                         if (name_compare(e->path, len, first, first_len) < 0) {
 349                                 first = e->path;
 350                                 first_len = len;
 351                         }
 352                 }
 353
 354                 if (first) {
 355                         for (i = 0; i < n; i++) {
 356                                 e = entry + i;
 357                                 extended_entry_extract(tx + i, e, first, first_len);
 358                                 /* Cull the ones that are not the earliest */
 359                                 if (!e->path)
 360                                         continue;
 361                                 len = tree_entry_len(e->path, e->sha1);
 362                                 if (name_compare(e->path, len, first, first_len))
 363                                         entry_clear(e);
 364                         }
 365                 }
 366
 367                 /* Now we have in entry[i] the earliest name from the trees */
 368                 mask = 0;
 369                 dirmask = 0;
 370                 for (i = 0; i < n; i++) {
 371                         if (!entry[i].path)
 372                                 continue;
 373                         mask |= 1ul << i;
 374                         if (S_ISDIR(entry[i].mode))
 375                                 dirmask |= 1ul << i;
 376                 }
 377                 if (!mask)
 378                         break;
 379                 ret = info->fn(n, mask, dirmask, entry, info);
 380                 if (ret < 0)
 381                         break;
 382                 mask &= ret;
 383                 ret = 0;
 384                 for (i = 0; i < n; i++)
 385                         if (mask & (1ul << i))
 386                                 update_extended_entry(tx + i, entry + i);
 387         }
 388         free(entry);
 389         for (i = 0; i < n; i++)
 390                 free_extended_entry(tx + i);
 391         free(tx);
 392         return ret;
 393 }
 394
 395 static int find_tree_entry(struct tree_desc *t, const char *name, unsigned char *result, unsigned *mode)
 396 {
 397         int namelen = strlen(name);
 398         while (t->size) {
 399                 const char *entry;
 400                 const unsigned char *sha1;
 401                 int entrylen, cmp;
 402
 403                 sha1 = tree_entry_extract(t, &entry, mode);
 404                 update_tree_entry(t);
 405                 entrylen = tree_entry_len(entry, sha1);
 406                 if (entrylen > namelen)
 407                         continue;
 408                 cmp = memcmp(name, entry, entrylen);
 409                 if (cmp > 0)
 410                         continue;
 411                 if (cmp < 0)
 412                         break;
 413                 if (entrylen == namelen) {
 414                         hashcpy(result, sha1);
 415                         return 0;
 416                 }
 417                 if (name[entrylen] != '/')
 418                         continue;
 419                 if (!S_ISDIR(*mode))
 420                         break;
 421                 if (++entrylen == namelen) {
 422                         hashcpy(result, sha1);
 423                         return 0;
 424                 }
 425                 return get_tree_entry(sha1, name + entrylen, result, mode);
 426         }
 427         return -1;
 428 }
 429
 430 int get_tree_entry(const unsigned char *tree_sha1, const char *name, unsigned char *sha1, unsigned *mode)
 431 {
 432         int retval;
 433         void *tree;
 434         unsigned long size;
 435         struct tree_desc t;
 436         unsigned char root[20];
 437
 438         tree = read_object_with_reference(tree_sha1, tree_type, &size, root);
 439         if (!tree)
 440                 return -1;
 441
 442         if (name[0] == '\0') {
 443                 hashcpy(sha1, root);
 444                 return 0;
 445         }
 446
 447         init_tree_desc(&t, tree, size);
 448         retval = find_tree_entry(&t, name, sha1, mode);
 449         free(tree);
 450         return retval;
 451 }