git.ozlabs.org Git - ccan/blob - ccan/tdb2/tdb.c

   1 #include "private.h"
   2 #include <ccan/tdb2/tdb2.h>
   3 #include <ccan/build_assert/build_assert.h>
   4 #include <ccan/likely/likely.h>
   5 #include <assert.h>
   6
   7 /* The null return. */
   8 struct tdb_data tdb_null = { .dptr = NULL, .dsize = 0 };
   9
  10 /* all contexts, to ensure no double-opens (fcntl locks don't nest!) */
  11 static struct tdb_context *tdbs = NULL;
  12
  13 PRINTF_FMT(4, 5) static void
  14 null_log_fn(struct tdb_context *tdb,
  15             enum tdb_debug_level level, void *priv,
  16             const char *fmt, ...)
  17 {
  18 }
  19
  20 static bool tdb_already_open(dev_t device, ino_t ino)
  21 {
  22         struct tdb_context *i;
  23
  24         for (i = tdbs; i; i = i->next) {
  25                 if (i->device == device && i->inode == ino) {
  26                         return true;
  27                 }
  28         }
  29
  30         return false;
  31 }
  32
  33 static uint64_t random_number(struct tdb_context *tdb)
  34 {
  35         int fd;
  36         uint64_t ret = 0;
  37         struct timeval now;
  38
  39         fd = open("/dev/urandom", O_RDONLY);
  40         if (fd >= 0) {
  41                 if (tdb_read_all(fd, &ret, sizeof(ret))) {
  42                         tdb->log(tdb, TDB_DEBUG_TRACE, tdb->log_priv,
  43                                  "tdb_open: random from /dev/urandom\n");
  44                         close(fd);
  45                         return ret;
  46                 }
  47                 close(fd);
  48         }
  49         /* FIXME: Untested!  Based on Wikipedia protocol description! */
  50         fd = open("/dev/egd-pool", O_RDWR);
  51         if (fd >= 0) {
  52                 /* Command is 1, next byte is size we want to read. */
  53                 char cmd[2] = { 1, sizeof(uint64_t) };
  54                 if (write(fd, cmd, sizeof(cmd)) == sizeof(cmd)) {
  55                         char reply[1 + sizeof(uint64_t)];
  56                         int r = read(fd, reply, sizeof(reply));
  57                         if (r > 1) {
  58                                 tdb->log(tdb, TDB_DEBUG_TRACE, tdb->log_priv,
  59                                          "tdb_open: %u random bytes from"
  60                                          " /dev/egd-pool\n", r-1);
  61                                 /* Copy at least some bytes. */
  62                                 memcpy(&ret, reply+1, r - 1);
  63                                 if (reply[0] == sizeof(uint64_t)
  64                                     && r == sizeof(reply)) {
  65                                         close(fd);
  66                                         return ret;
  67                                 }
  68                         }
  69                 }
  70                 close(fd);
  71         }
  72
  73         /* Fallback: pid and time. */
  74         gettimeofday(&now, NULL);
  75         ret = getpid() * 100132289ULL + now.tv_sec * 1000000ULL + now.tv_usec;
  76         tdb->log(tdb, TDB_DEBUG_TRACE, tdb->log_priv,
  77                  "tdb_open: random from getpid and time\n");
  78         return ret;
  79 }
  80
  81 struct new_database {
  82         struct tdb_header hdr;
  83         struct tdb_freelist flist;
  84 };
  85
  86 /* initialise a new database */
  87 static int tdb_new_database(struct tdb_context *tdb,
  88                             struct tdb_attribute_seed *seed,
  89                             struct tdb_header *hdr)
  90 {
  91         /* We make it up in memory, then write it out if not internal */
  92         struct new_database newdb;
  93         unsigned int magic_len;
  94
  95         /* Fill in the header */
  96         newdb.hdr.version = TDB_VERSION;
  97         if (seed)
  98                 newdb.hdr.hash_seed = seed->seed;
  99         else
 100                 newdb.hdr.hash_seed = random_number(tdb);
 101         newdb.hdr.hash_test = TDB_HASH_MAGIC;
 102         newdb.hdr.hash_test = tdb->khash(&newdb.hdr.hash_test,
 103                                          sizeof(newdb.hdr.hash_test),
 104                                          newdb.hdr.hash_seed,
 105                                          tdb->hash_priv);
 106         memset(newdb.hdr.reserved, 0, sizeof(newdb.hdr.reserved));
 107         /* Initial hashes are empty. */
 108         memset(newdb.hdr.hashtable, 0, sizeof(newdb.hdr.hashtable));
 109
 110         /* Free is empty. */
 111         newdb.hdr.free_list = offsetof(struct new_database, flist);
 112         memset(&newdb.flist, 0, sizeof(newdb.flist));
 113         set_header(NULL, &newdb.flist.hdr, 0,
 114                    sizeof(newdb.flist) - sizeof(newdb.flist.hdr),
 115                    sizeof(newdb.flist) - sizeof(newdb.flist.hdr), 1);
 116
 117         /* Magic food */
 118         memset(newdb.hdr.magic_food, 0, sizeof(newdb.hdr.magic_food));
 119         strcpy(newdb.hdr.magic_food, TDB_MAGIC_FOOD);
 120
 121         /* This creates an endian-converted database, as if read from disk */
 122         magic_len = sizeof(newdb.hdr.magic_food);
 123         tdb_convert(tdb,
 124                     (char *)&newdb.hdr + magic_len, sizeof(newdb) - magic_len);
 125
 126         *hdr = newdb.hdr;
 127
 128         if (tdb->flags & TDB_INTERNAL) {
 129                 tdb->map_size = sizeof(newdb);
 130                 tdb->map_ptr = malloc(tdb->map_size);
 131                 if (!tdb->map_ptr) {
 132                         tdb->ecode = TDB_ERR_OOM;
 133                         return -1;
 134                 }
 135                 memcpy(tdb->map_ptr, &newdb, tdb->map_size);
 136                 return 0;
 137         }
 138         if (lseek(tdb->fd, 0, SEEK_SET) == -1)
 139                 return -1;
 140
 141         if (ftruncate(tdb->fd, 0) == -1)
 142                 return -1;
 143
 144         if (!tdb_pwrite_all(tdb->fd, &newdb, sizeof(newdb), 0)) {
 145                 tdb->ecode = TDB_ERR_IO;
 146                 return -1;
 147         }
 148         return 0;
 149 }
 150
 151 struct tdb_context *tdb_open(const char *name, int tdb_flags,
 152                              int open_flags, mode_t mode,
 153                              union tdb_attribute *attr)
 154 {
 155         struct tdb_context *tdb;
 156         struct stat st;
 157         int save_errno;
 158         uint64_t hash_test;
 159         unsigned v;
 160         struct tdb_header hdr;
 161         struct tdb_attribute_seed *seed = NULL;
 162
 163         tdb = malloc(sizeof(*tdb));
 164         if (!tdb) {
 165                 /* Can't log this */
 166                 errno = ENOMEM;
 167                 goto fail;
 168         }
 169         tdb->name = NULL;
 170         tdb->map_ptr = NULL;
 171         tdb->direct_access = 0;
 172         tdb->fd = -1;
 173         tdb->map_size = sizeof(struct tdb_header);
 174         tdb->ecode = TDB_SUCCESS;
 175         tdb->flags = tdb_flags;
 176         tdb->log = null_log_fn;
 177         tdb->log_priv = NULL;
 178         tdb->transaction = NULL;
 179         tdb_hash_init(tdb);
 180         tdb_io_init(tdb);
 181         tdb_lock_init(tdb);
 182
 183         while (attr) {
 184                 switch (attr->base.attr) {
 185                 case TDB_ATTRIBUTE_LOG:
 186                         tdb->log = attr->log.log_fn;
 187                         tdb->log_priv = attr->log.log_private;
 188                         break;
 189                 case TDB_ATTRIBUTE_HASH:
 190                         tdb->khash = attr->hash.hash_fn;
 191                         tdb->hash_priv = attr->hash.hash_private;
 192                         break;
 193                 case TDB_ATTRIBUTE_SEED:
 194                         seed = &attr->seed;
 195                         break;
 196                 default:
 197                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 198                                  "tdb_open: unknown attribute type %u\n",
 199                                  attr->base.attr);
 200                         errno = EINVAL;
 201                         goto fail;
 202                 }
 203                 attr = attr->base.next;
 204         }
 205
 206         if ((open_flags & O_ACCMODE) == O_WRONLY) {
 207                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 208                          "tdb_open: can't open tdb %s write-only\n", name);
 209                 errno = EINVAL;
 210                 goto fail;
 211         }
 212
 213         if ((open_flags & O_ACCMODE) == O_RDONLY) {
 214                 tdb->read_only = true;
 215                 /* read only databases don't do locking */
 216                 tdb->flags |= TDB_NOLOCK;
 217                 tdb->mmap_flags = PROT_READ;
 218         } else {
 219                 tdb->read_only = false;
 220                 tdb->mmap_flags = PROT_READ | PROT_WRITE;
 221         }
 222
 223         /* internal databases don't need any of the rest. */
 224         if (tdb->flags & TDB_INTERNAL) {
 225                 tdb->flags |= (TDB_NOLOCK | TDB_NOMMAP);
 226                 if (tdb_new_database(tdb, seed, &hdr) != 0) {
 227                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 228                                  "tdb_open: tdb_new_database failed!");
 229                         goto fail;
 230                 }
 231                 tdb_convert(tdb, &hdr.hash_seed, sizeof(hdr.hash_seed));
 232                 tdb->hash_seed = hdr.hash_seed;
 233                 tdb_flist_init(tdb);
 234                 return tdb;
 235         }
 236
 237         if ((tdb->fd = open(name, open_flags, mode)) == -1) {
 238                 tdb->log(tdb, TDB_DEBUG_WARNING, tdb->log_priv,
 239                          "tdb_open: could not open file %s: %s\n",
 240                          name, strerror(errno));
 241                 goto fail;      /* errno set by open(2) */
 242         }
 243
 244         /* on exec, don't inherit the fd */
 245         v = fcntl(tdb->fd, F_GETFD, 0);
 246         fcntl(tdb->fd, F_SETFD, v | FD_CLOEXEC);
 247
 248         /* ensure there is only one process initialising at once */
 249         if (tdb_lock_open(tdb) == -1) {
 250                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 251                          "tdb_open: failed to get open lock on %s: %s\n",
 252                          name, strerror(errno));
 253                 goto fail;      /* errno set by tdb_brlock */
 254         }
 255
 256         if (!tdb_pread_all(tdb->fd, &hdr, sizeof(hdr), 0)
 257             || strcmp(hdr.magic_food, TDB_MAGIC_FOOD) != 0) {
 258                 if (!(open_flags & O_CREAT)
 259                     || tdb_new_database(tdb, seed, &hdr) == -1) {
 260                         if (errno == 0) {
 261                                 errno = EIO; /* ie bad format or something */
 262                         }
 263                         goto fail;
 264                 }
 265         } else if (hdr.version != TDB_VERSION) {
 266                 if (hdr.version == bswap_64(TDB_VERSION))
 267                         tdb->flags |= TDB_CONVERT;
 268                 else {
 269                         /* wrong version */
 270                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 271                                  "tdb_open: %s is unknown version 0x%llx\n",
 272                                  name, (long long)hdr.version);
 273                         errno = EIO;
 274                         goto fail;
 275                 }
 276         }
 277
 278         tdb_convert(tdb, &hdr, sizeof(hdr));
 279         tdb->hash_seed = hdr.hash_seed;
 280         hash_test = TDB_HASH_MAGIC;
 281         hash_test = tdb_hash(tdb, &hash_test, sizeof(hash_test));
 282         if (hdr.hash_test != hash_test) {
 283                 /* wrong hash variant */
 284                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 285                          "tdb_open: %s uses a different hash function\n",
 286                          name);
 287                 errno = EIO;
 288                 goto fail;
 289         }
 290
 291         if (fstat(tdb->fd, &st) == -1)
 292                 goto fail;
 293
 294         /* Is it already in the open list?  If so, fail. */
 295         if (tdb_already_open(st.st_dev, st.st_ino)) {
 296                 /* FIXME */
 297                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 298                          "tdb_open: %s (%d,%d) is already open in this process\n",
 299                          name, (int)st.st_dev, (int)st.st_ino);
 300                 errno = EBUSY;
 301                 goto fail;
 302         }
 303
 304         tdb->name = strdup(name);
 305         if (!tdb->name) {
 306                 errno = ENOMEM;
 307                 goto fail;
 308         }
 309
 310         tdb->device = st.st_dev;
 311         tdb->inode = st.st_ino;
 312         tdb_unlock_open(tdb);
 313
 314         /* This make sure we have current map_size and mmap. */
 315         tdb->methods->oob(tdb, tdb->map_size + 1, true);
 316
 317         if (tdb_flist_init(tdb) == -1)
 318                 goto fail;
 319
 320         tdb->next = tdbs;
 321         tdbs = tdb;
 322         return tdb;
 323
 324  fail:
 325         save_errno = errno;
 326
 327         if (!tdb)
 328                 return NULL;
 329
 330 #ifdef TDB_TRACE
 331         close(tdb->tracefd);
 332 #endif
 333         if (tdb->map_ptr) {
 334                 if (tdb->flags & TDB_INTERNAL) {
 335                         free(tdb->map_ptr);
 336                 } else
 337                         tdb_munmap(tdb);
 338         }
 339         free((char *)tdb->name);
 340         if (tdb->fd != -1)
 341                 if (close(tdb->fd) != 0)
 342                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 343                                  "tdb_open: failed to close tdb->fd"
 344                                  " on error!\n");
 345         free(tdb);
 346         errno = save_errno;
 347         return NULL;
 348 }
 349
 350 /* FIXME: modify, don't rewrite! */
 351 static int update_rec_hdr(struct tdb_context *tdb,
 352                           tdb_off_t off,
 353                           tdb_len_t keylen,
 354                           tdb_len_t datalen,
 355                           struct tdb_used_record *rec,
 356                           uint64_t h)
 357 {
 358         uint64_t dataroom = rec_data_length(rec) + rec_extra_padding(rec);
 359
 360         if (set_header(tdb, rec, keylen, datalen, keylen + dataroom, h))
 361                 return -1;
 362
 363         return tdb_write_convert(tdb, off, rec, sizeof(*rec));
 364 }
 365
 366 /* Returns -1 on error, 0 on OK */
 367 static int replace_data(struct tdb_context *tdb,
 368                         struct hash_info *h,
 369                         struct tdb_data key, struct tdb_data dbuf,
 370                         tdb_off_t old_off, tdb_len_t old_room,
 371                         bool growing)
 372 {
 373         tdb_off_t new_off;
 374
 375         /* Allocate a new record. */
 376         new_off = alloc(tdb, key.dsize, dbuf.dsize, h->h, growing);
 377         if (unlikely(new_off == TDB_OFF_ERR))
 378                 return -1;
 379
 380         /* We didn't like the existing one: remove it. */
 381         if (old_off) {
 382                 add_free_record(tdb, old_off,
 383                                 sizeof(struct tdb_used_record)
 384                                 + key.dsize + old_room);
 385                 if (replace_in_hash(tdb, h, new_off) == -1)
 386                         return -1;
 387         } else {
 388                 if (add_to_hash(tdb, h, new_off) == -1)
 389                         return -1;
 390         }
 391
 392         new_off += sizeof(struct tdb_used_record);
 393         if (tdb->methods->write(tdb, new_off, key.dptr, key.dsize) == -1)
 394                 return -1;
 395
 396         new_off += key.dsize;
 397         if (tdb->methods->write(tdb, new_off, dbuf.dptr, dbuf.dsize) == -1)
 398                 return -1;
 399
 400         /* FIXME: tdb_increment_seqnum(tdb); */
 401         return 0;
 402 }
 403
 404 int tdb_store(struct tdb_context *tdb,
 405               struct tdb_data key, struct tdb_data dbuf, int flag)
 406 {
 407         struct hash_info h;
 408         tdb_off_t off;
 409         tdb_len_t old_room = 0;
 410         struct tdb_used_record rec;
 411         int ret;
 412
 413         off = find_and_lock(tdb, key, F_WRLCK, &h, &rec, NULL);
 414         if (unlikely(off == TDB_OFF_ERR))
 415                 return -1;
 416
 417         /* Now we have lock on this hash bucket. */
 418         if (flag == TDB_INSERT) {
 419                 if (off) {
 420                         tdb->ecode = TDB_ERR_EXISTS;
 421                         goto fail;
 422                 }
 423         } else {
 424                 if (off) {
 425                         old_room = rec_data_length(&rec)
 426                                 + rec_extra_padding(&rec);
 427                         if (old_room >= dbuf.dsize) {
 428                                 /* Can modify in-place.  Easy! */
 429                                 if (update_rec_hdr(tdb, off,
 430                                                    key.dsize, dbuf.dsize,
 431                                                    &rec, h.h))
 432                                         goto fail;
 433                                 if (tdb->methods->write(tdb, off + sizeof(rec)
 434                                                         + key.dsize,
 435                                                         dbuf.dptr, dbuf.dsize))
 436                                         goto fail;
 437                                 tdb_unlock_hashes(tdb, h.hlock_start,
 438                                                   h.hlock_range, F_WRLCK);
 439                                 return 0;
 440                         }
 441                         /* FIXME: See if right record is free? */
 442                 } else {
 443                         if (flag == TDB_MODIFY) {
 444                                 /* if the record doesn't exist and we
 445                                    are in TDB_MODIFY mode then we should fail
 446                                    the store */
 447                                 tdb->ecode = TDB_ERR_NOEXIST;
 448                                 goto fail;
 449                         }
 450                 }
 451         }
 452
 453         /* If we didn't use the old record, this implies we're growing. */
 454         ret = replace_data(tdb, &h, key, dbuf, off, old_room, off != 0);
 455         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 456         return ret;
 457
 458 fail:
 459         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 460         return -1;
 461 }
 462
 463 int tdb_append(struct tdb_context *tdb,
 464                struct tdb_data key, struct tdb_data dbuf)
 465 {
 466         struct hash_info h;
 467         tdb_off_t off;
 468         struct tdb_used_record rec;
 469         tdb_len_t old_room = 0, old_dlen;
 470         unsigned char *newdata;
 471         struct tdb_data new_dbuf;
 472         int ret;
 473
 474         off = find_and_lock(tdb, key, F_WRLCK, &h, &rec, NULL);
 475         if (unlikely(off == TDB_OFF_ERR))
 476                 return -1;
 477
 478         if (off) {
 479                 old_dlen = rec_data_length(&rec);
 480                 old_room = old_dlen + rec_extra_padding(&rec);
 481
 482                 /* Fast path: can append in place. */
 483                 if (rec_extra_padding(&rec) >= dbuf.dsize) {
 484                         if (update_rec_hdr(tdb, off, key.dsize,
 485                                            old_dlen + dbuf.dsize, &rec, h.h))
 486                                 goto fail;
 487
 488                         off += sizeof(rec) + key.dsize + old_dlen;
 489                         if (tdb->methods->write(tdb, off, dbuf.dptr,
 490                                                 dbuf.dsize) == -1)
 491                                 goto fail;
 492
 493                         /* FIXME: tdb_increment_seqnum(tdb); */
 494                         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range,
 495                                           F_WRLCK);
 496                         return 0;
 497                 }
 498                 /* FIXME: Check right record free? */
 499
 500                 /* Slow path. */
 501                 newdata = malloc(key.dsize + old_dlen + dbuf.dsize);
 502                 if (!newdata) {
 503                         tdb->ecode = TDB_ERR_OOM;
 504                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 505                                  "tdb_append: cannot allocate %llu bytes!\n",
 506                                  (long long)key.dsize + old_dlen + dbuf.dsize);
 507                         goto fail;
 508                 }
 509                 if (tdb->methods->read(tdb, off + sizeof(rec) + key.dsize,
 510                                        newdata, old_dlen) != 0) {
 511                         free(newdata);
 512                         goto fail;
 513                 }
 514                 memcpy(newdata + old_dlen, dbuf.dptr, dbuf.dsize);
 515                 new_dbuf.dptr = newdata;
 516                 new_dbuf.dsize = old_dlen + dbuf.dsize;
 517         } else {
 518                 newdata = NULL;
 519                 new_dbuf = dbuf;
 520         }
 521
 522         /* If they're using tdb_append(), it implies they're growing record. */
 523         ret = replace_data(tdb, &h, key, new_dbuf, off, old_room, true);
 524         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 525         free(newdata);
 526
 527         return ret;
 528
 529 fail:
 530         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 531         return -1;
 532 }
 533
 534 struct tdb_data tdb_fetch(struct tdb_context *tdb, struct tdb_data key)
 535 {
 536         tdb_off_t off;
 537         struct tdb_used_record rec;
 538         struct hash_info h;
 539         struct tdb_data ret;
 540
 541         off = find_and_lock(tdb, key, F_RDLCK, &h, &rec, NULL);
 542         if (unlikely(off == TDB_OFF_ERR))
 543                 return tdb_null;
 544
 545         if (!off) {
 546                 tdb->ecode = TDB_ERR_NOEXIST;
 547                 ret = tdb_null;
 548         } else {
 549                 ret.dsize = rec_data_length(&rec);
 550                 ret.dptr = tdb_alloc_read(tdb, off + sizeof(rec) + key.dsize,
 551                                           ret.dsize);
 552         }
 553
 554         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_RDLCK);
 555         return ret;
 556 }
 557
 558 int tdb_delete(struct tdb_context *tdb, struct tdb_data key)
 559 {
 560         tdb_off_t off;
 561         struct tdb_used_record rec;
 562         struct hash_info h;
 563
 564         off = find_and_lock(tdb, key, F_WRLCK, &h, &rec, NULL);
 565         if (unlikely(off == TDB_OFF_ERR))
 566                 return -1;
 567
 568         if (!off) {
 569                 tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 570                 tdb->ecode = TDB_ERR_NOEXIST;
 571                 return -1;
 572         }
 573
 574         if (delete_from_hash(tdb, &h) == -1)
 575                 goto unlock_err;
 576
 577         /* Free the deleted entry. */
 578         if (add_free_record(tdb, off,
 579                             sizeof(struct tdb_used_record)
 580                             + rec_key_length(&rec)
 581                             + rec_data_length(&rec)
 582                             + rec_extra_padding(&rec)) != 0)
 583                 goto unlock_err;
 584
 585         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 586         return 0;
 587
 588 unlock_err:
 589         tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 590         return -1;
 591 }
 592
 593 int tdb_close(struct tdb_context *tdb)
 594 {
 595         struct tdb_context **i;
 596         int ret = 0;
 597
 598         /* FIXME:
 599         if (tdb->transaction) {
 600                 tdb_transaction_cancel(tdb);
 601         }
 602         */
 603         tdb_trace(tdb, "tdb_close");
 604
 605         if (tdb->map_ptr) {
 606                 if (tdb->flags & TDB_INTERNAL)
 607                         free(tdb->map_ptr);
 608                 else
 609                         tdb_munmap(tdb);
 610         }
 611         free((char *)tdb->name);
 612         if (tdb->fd != -1) {
 613                 ret = close(tdb->fd);
 614                 tdb->fd = -1;
 615         }
 616         free(tdb->lockrecs);
 617
 618         /* Remove from contexts list */
 619         for (i = &tdbs; *i; i = &(*i)->next) {
 620                 if (*i == tdb) {
 621                         *i = tdb->next;
 622                         break;
 623                 }
 624         }
 625
 626 #ifdef TDB_TRACE
 627         close(tdb->tracefd);
 628 #endif
 629         free(tdb);
 630
 631         return ret;
 632 }
 633
 634 enum TDB_ERROR tdb_error(struct tdb_context *tdb)
 635 {
 636         return tdb->ecode;
 637 }
 638
 639 const char *tdb_errorstr(struct tdb_context *tdb)
 640 {
 641         /* Gcc warns if you miss a case in the switch, so use that. */
 642         switch (tdb->ecode) {
 643         case TDB_SUCCESS: return "Success";
 644         case TDB_ERR_CORRUPT: return "Corrupt database";
 645         case TDB_ERR_IO: return "IO Error";
 646         case TDB_ERR_LOCK: return "Locking error";
 647         case TDB_ERR_OOM: return "Out of memory";
 648         case TDB_ERR_EXISTS: return "Record exists";
 649         case TDB_ERR_NESTING: return "Transaction already started";
 650         case TDB_ERR_EINVAL: return "Invalid parameter";
 651         case TDB_ERR_NOEXIST: return "Record does not exist";
 652         case TDB_ERR_RDONLY: return "write not permitted";
 653         }
 654         return "Invalid error code";
 655 }