fs/befs/btree.c

   1 /*
   2  * linux/fs/befs/btree.c
   3  *
   4  * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com>
   5  *
   6  * Licensed under the GNU GPL. See the file COPYING for details.
   7  *
   8  * 2002-02-05: Sergey S. Kostyliov added binary search within
   9  *              btree nodes.
  10  *
  11  * Many thanks to:
  12  *
  13  * Dominic Giampaolo, author of "Practical File System
  14  * Design with the Be File System", for such a helpful book.
  15  *
  16  * Marcus J. Ranum, author of the b+tree package in
  17  * comp.sources.misc volume 10. This code is not copied from that
  18  * work, but it is partially based on it.
  19  *
  20  * Makoto Kato, author of the original BeFS for linux filesystem
  21  * driver.
  22  */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/string.h>
  26 #include <linux/slab.h>
  27 #include <linux/mm.h>
  28 #include <linux/buffer_head.h>
  29
  30 #include "befs.h"
  31 #include "btree.h"
  32 #include "datastream.h"
  33
  34 /*
  35  * The btree functions in this file are built on top of the
  36  * datastream.c interface, which is in turn built on top of the
  37  * io.c interface.
  38  */
  39
  40 /* Befs B+tree structure:
  41  *
  42  * The first thing in the tree is the tree superblock. It tells you
  43  * all kinds of useful things about the tree, like where the rootnode
  44  * is located, and the size of the nodes (always 1024 with current version
  45  * of BeOS).
  46  *
  47  * The rest of the tree consists of a series of nodes. Nodes contain a header
  48  * (struct befs_btree_nodehead), the packed key data, an array of shorts
  49  * containing the ending offsets for each of the keys, and an array of
  50  * befs_off_t values. In interior nodes, the keys are the ending keys for
  51  * the childnode they point to, and the values are offsets into the
  52  * datastream containing the tree.
  53  */
  54
  55 /* Note:
  56  *
  57  * The book states 2 confusing things about befs b+trees. First,
  58  * it states that the overflow field of node headers is used by internal nodes
  59  * to point to another node that "effectively continues this one". Here is what
  60  * I believe that means. Each key in internal nodes points to another node that
  61  * contains key values less than itself. Inspection reveals that the last key
  62  * in the internal node is not the last key in the index. Keys that are
  63  * greater than the last key in the internal node go into the overflow node.
  64  * I imagine there is a performance reason for this.
  65  *
  66  * Second, it states that the header of a btree node is sufficient to
  67  * distinguish internal nodes from leaf nodes. Without saying exactly how.
  68  * After figuring out the first, it becomes obvious that internal nodes have
  69  * overflow nodes and leafnodes do not.
  70  */
  71
  72 /*
  73  * Currently, this code is only good for directory B+trees.
  74  * In order to be used for other BFS indexes, it needs to be extended to handle
  75  * duplicate keys and non-string keytypes (int32, int64, float, double).
  76  */
  77
  78 /*
  79  * In memory structure of each btree node
  80  */
  81 typedef struct {
  82         befs_host_btree_nodehead head;  /* head of node converted to cpu byteorder */
  83         struct buffer_head *bh;
  84         befs_btree_nodehead *od_node;   /* on disk node */
  85 } befs_btree_node;
  86
  87 /* local constants */
  88 static const befs_off_t befs_bt_inval = 0xffffffffffffffffULL;
  89
  90 /* local functions */
  91 static int befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
  92                                befs_btree_super * bt_super,
  93                                befs_btree_node * this_node,
  94                                befs_off_t * node_off);
  95
  96 static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
  97                               befs_btree_super * sup);
  98
  99 static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
 100                              befs_btree_node * node, befs_off_t node_off);
 101
 102 static int befs_leafnode(befs_btree_node * node);
 103
 104 static fs16 *befs_bt_keylen_index(befs_btree_node * node);
 105
 106 static fs64 *befs_bt_valarray(befs_btree_node * node);
 107
 108 static char *befs_bt_keydata(befs_btree_node * node);
 109
 110 static int befs_find_key(struct super_block *sb, befs_btree_node * node,
 111                          const char *findkey, befs_off_t * value);
 112
 113 static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
 114                              int index, u16 * keylen);
 115
 116 static int befs_compare_strings(const void *key1, int keylen1,
 117                                 const void *key2, int keylen2);
 118
 119 /**
 120  * befs_bt_read_super - read in btree superblock convert to cpu byteorder
 121  * @sb: Filesystem superblock
 122  * @ds: Datastream to read from
 123  * @sup: Buffer in which to place the btree superblock
 124  *
 125  * Calls befs_read_datastream to read in the btree superblock and
 126  * makes sure it is in cpu byteorder, byteswapping if necessary.
 127  *
 128  * On success, returns BEFS_OK and *@sup contains the btree superblock,
 129  * in cpu byte order.
 130  *
 131  * On failure, BEFS_ERR is returned.
 132  */
 133 static int
 134 befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
 135                    befs_btree_super * sup)
 136 {
 137         struct buffer_head *bh = NULL;
 138         befs_disk_btree_super *od_sup = NULL;
 139
 140         befs_debug(sb, "---> befs_btree_read_super()");
 141
 142         bh = befs_read_datastream(sb, ds, 0, NULL);
 143
 144         if (!bh) {
 145                 befs_error(sb, "Couldn't read index header.");
 146                 goto error;
 147         }
 148         od_sup = (befs_disk_btree_super *) bh->b_data;
 149         befs_dump_index_entry(sb, od_sup);
 150
 151         sup->magic = fs32_to_cpu(sb, od_sup->magic);
 152         sup->node_size = fs32_to_cpu(sb, od_sup->node_size);
 153         sup->max_depth = fs32_to_cpu(sb, od_sup->max_depth);
 154         sup->data_type = fs32_to_cpu(sb, od_sup->data_type);
 155         sup->root_node_ptr = fs64_to_cpu(sb, od_sup->root_node_ptr);
 156         sup->free_node_ptr = fs64_to_cpu(sb, od_sup->free_node_ptr);
 157         sup->max_size = fs64_to_cpu(sb, od_sup->max_size);
 158
 159         brelse(bh);
 160         if (sup->magic != BEFS_BTREE_MAGIC) {
 161                 befs_error(sb, "Index header has bad magic.");
 162                 goto error;
 163         }
 164
 165         befs_debug(sb, "<--- befs_btree_read_super()");
 166         return BEFS_OK;
 167
 168       error:
 169         befs_debug(sb, "<--- befs_btree_read_super() ERROR");
 170         return BEFS_ERR;
 171 }
 172
 173 /**
 174  * befs_bt_read_node - read in btree node and convert to cpu byteorder
 175  * @sb: Filesystem superblock
 176  * @ds: Datastream to read from
 177  * @node: Buffer in which to place the btree node
 178  * @node_off: Starting offset (in bytes) of the node in @ds
 179  *
 180  * Calls befs_read_datastream to read in the indicated btree node and
 181  * makes sure its header fields are in cpu byteorder, byteswapping if
 182  * necessary.
 183  * Note: node->bh must be NULL when this function called first
 184  * time. Don't forget brelse(node->bh) after last call.
 185  *
 186  * On success, returns BEFS_OK and *@node contains the btree node that
 187  * starts at @node_off, with the node->head fields in cpu byte order.
 188  *
 189  * On failure, BEFS_ERR is returned.
 190  */
 191
 192 static int
 193 befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
 194                   befs_btree_node * node, befs_off_t node_off)
 195 {
 196         uint off = 0;
 197
 198         befs_debug(sb, "---> befs_bt_read_node()");
 199
 200         if (node->bh)
 201                 brelse(node->bh);
 202
 203         node->bh = befs_read_datastream(sb, ds, node_off, &off);
 204         if (!node->bh) {
 205                 befs_error(sb, "befs_bt_read_node() failed to read "
 206                            "node at %Lu", node_off);
 207                 befs_debug(sb, "<--- befs_bt_read_node() ERROR");
 208
 209                 return BEFS_ERR;
 210         }
 211         node->od_node =
 212             (befs_btree_nodehead *) ((void *) node->bh->b_data + off);
 213
 214         befs_dump_index_node(sb, node->od_node);
 215
 216         node->head.left = fs64_to_cpu(sb, node->od_node->left);
 217         node->head.right = fs64_to_cpu(sb, node->od_node->right);
 218         node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow);
 219         node->head.all_key_count =
 220             fs16_to_cpu(sb, node->od_node->all_key_count);
 221         node->head.all_key_length =
 222             fs16_to_cpu(sb, node->od_node->all_key_length);
 223
 224         befs_debug(sb, "<--- befs_btree_read_node()");
 225         return BEFS_OK;
 226 }
 227
 228 /**
 229  * befs_btree_find - Find a key in a befs B+tree
 230  * @sb: Filesystem superblock
 231  * @ds: Datastream containing btree
 232  * @key: Key string to lookup in btree
 233  * @value: Value stored with @key
 234  *
 235  * On success, returns BEFS_OK and sets *@value to the value stored
 236  * with @key (usually the disk block number of an inode).
 237  *
 238  * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND.
 239  *
 240  * Algorithm:
 241  *   Read the superblock and rootnode of the b+tree.
 242  *   Drill down through the interior nodes using befs_find_key().
 243  *   Once at the correct leaf node, use befs_find_key() again to get the
 244  *   actuall value stored with the key.
 245  */
 246 int
 247 befs_btree_find(struct super_block *sb, befs_data_stream * ds,
 248                 const char *key, befs_off_t * value)
 249 {
 250         befs_btree_node *this_node = NULL;
 251         befs_btree_super bt_super;
 252         befs_off_t node_off;
 253         int res;
 254
 255         befs_debug(sb, "---> befs_btree_find() Key: %s", key);
 256
 257         if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
 258                 befs_error(sb,
 259                            "befs_btree_find() failed to read index superblock");
 260                 goto error;
 261         }
 262
 263         this_node = kmalloc(sizeof (befs_btree_node),
 264                                                 GFP_NOFS);
 265         if (!this_node) {
 266                 befs_error(sb, "befs_btree_find() failed to allocate %u "
 267                            "bytes of memory", sizeof (befs_btree_node));
 268                 goto error;
 269         }
 270
 271         this_node->bh = NULL;
 272
 273         /* read in root node */
 274         node_off = bt_super.root_node_ptr;
 275         if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 276                 befs_error(sb, "befs_btree_find() failed to read "
 277                            "node at %Lu", node_off);
 278                 goto error_alloc;
 279         }
 280
 281         while (!befs_leafnode(this_node)) {
 282                 res = befs_find_key(sb, this_node, key, &node_off);
 283                 if (res == BEFS_BT_NOT_FOUND)
 284                         node_off = this_node->head.overflow;
 285                 /* if no match, go to overflow node */
 286                 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 287                         befs_error(sb, "befs_btree_find() failed to read "
 288                                    "node at %Lu", node_off);
 289                         goto error_alloc;
 290                 }
 291         }
 292
 293         /* at the correct leaf node now */
 294
 295         res = befs_find_key(sb, this_node, key, value);
 296
 297         brelse(this_node->bh);
 298         kfree(this_node);
 299
 300         if (res != BEFS_BT_MATCH) {
 301                 befs_debug(sb, "<--- befs_btree_find() Key %s not found", key);
 302                 *value = 0;
 303                 return BEFS_BT_NOT_FOUND;
 304         }
 305         befs_debug(sb, "<--- befs_btree_find() Found key %s, value %Lu",
 306                    key, *value);
 307         return BEFS_OK;
 308
 309       error_alloc:
 310         kfree(this_node);
 311       error:
 312         *value = 0;
 313         befs_debug(sb, "<--- befs_btree_find() ERROR");
 314         return BEFS_ERR;
 315 }
 316
 317 /**
 318  * befs_find_key - Search for a key within a node
 319  * @sb: Filesystem superblock
 320  * @node: Node to find the key within
 321  * @key: Keystring to search for
 322  * @value: If key is found, the value stored with the key is put here
 323  *
 324  * finds exact match if one exists, and returns BEFS_BT_MATCH
 325  * If no exact match, finds first key in node that is greater
 326  * (alphabetically) than the search key and returns BEFS_BT_PARMATCH
 327  * (for partial match, I guess). Can you think of something better to
 328  * call it?
 329  *
 330  * If no key was a match or greater than the search key, return
 331  * BEFS_BT_NOT_FOUND.
 332  *
 333  * Use binary search instead of a linear.
 334  */
 335 static int
 336 befs_find_key(struct super_block *sb, befs_btree_node * node,
 337               const char *findkey, befs_off_t * value)
 338 {
 339         int first, last, mid;
 340         int eq;
 341         u16 keylen;
 342         int findkey_len;
 343         char *thiskey;
 344         fs64 *valarray;
 345
 346         befs_debug(sb, "---> befs_find_key() %s", findkey);
 347
 348         *value = 0;
 349
 350         findkey_len = strlen(findkey);
 351
 352         /* if node can not contain key, just skeep this node */
 353         last = node->head.all_key_count - 1;
 354         thiskey = befs_bt_get_key(sb, node, last, &keylen);
 355
 356         eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
 357         if (eq < 0) {
 358                 befs_debug(sb, "<--- befs_find_key() %s not found", findkey);
 359                 return BEFS_BT_NOT_FOUND;
 360         }
 361
 362         valarray = befs_bt_valarray(node);
 363
 364         /* simple binary search */
 365         first = 0;
 366         mid = 0;
 367         while (last >= first) {
 368                 mid = (last + first) / 2;
 369                 befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
 370                            mid);
 371                 thiskey = befs_bt_get_key(sb, node, mid, &keylen);
 372                 eq = befs_compare_strings(thiskey, keylen, findkey,
 373                                           findkey_len);
 374
 375                 if (eq == 0) {
 376                         befs_debug(sb, "<--- befs_find_key() found %s at %d",
 377                                    thiskey, mid);
 378
 379                         *value = fs64_to_cpu(sb, valarray[mid]);
 380                         return BEFS_BT_MATCH;
 381                 }
 382                 if (eq > 0)
 383                         last = mid - 1;
 384                 else
 385                         first = mid + 1;
 386         }
 387         if (eq < 0)
 388                 *value = fs64_to_cpu(sb, valarray[mid + 1]);
 389         else
 390                 *value = fs64_to_cpu(sb, valarray[mid]);
 391         befs_debug(sb, "<--- befs_find_key() found %s at %d", thiskey, mid);
 392         return BEFS_BT_PARMATCH;
 393 }
 394
 395 /**
 396  * befs_btree_read - Traverse leafnodes of a btree
 397  * @sb: Filesystem superblock
 398  * @ds: Datastream containing btree
 399  * @key_no: Key number (alphabetical order) of key to read
 400  * @bufsize: Size of the buffer to return key in
 401  * @keybuf: Pointer to a buffer to put the key in
 402  * @keysize: Length of the returned key
 403  * @value: Value stored with the returned key
 404  *
 405  * Heres how it works: Key_no is the index of the key/value pair to
 406  * return in keybuf/value.
 407  * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is
 408  * the number of charecters in the key (just a convenience).
 409  *
 410  * Algorithm:
 411  *   Get the first leafnode of the tree. See if the requested key is in that
 412  *   node. If not, follow the node->right link to the next leafnode. Repeat
 413  *   until the (key_no)th key is found or the tree is out of keys.
 414  */
 415 int
 416 befs_btree_read(struct super_block *sb, befs_data_stream * ds,
 417                 loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
 418                 befs_off_t * value)
 419 {
 420         befs_btree_node *this_node;
 421         befs_btree_super bt_super;
 422         befs_off_t node_off = 0;
 423         int cur_key;
 424         fs64 *valarray;
 425         char *keystart;
 426         u16 keylen;
 427         int res;
 428
 429         uint key_sum = 0;
 430
 431         befs_debug(sb, "---> befs_btree_read()");
 432
 433         if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
 434                 befs_error(sb,
 435                            "befs_btree_read() failed to read index superblock");
 436                 goto error;
 437         }
 438
 439         if ((this_node = kmalloc(sizeof (befs_btree_node), GFP_NOFS)) == NULL) {
 440                 befs_error(sb, "befs_btree_read() failed to allocate %u "
 441                            "bytes of memory", sizeof (befs_btree_node));
 442                 goto error;
 443         }
 444
 445         node_off = bt_super.root_node_ptr;
 446         this_node->bh = NULL;
 447
 448         /* seeks down to first leafnode, reads it into this_node */
 449         res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
 450         if (res == BEFS_BT_EMPTY) {
 451                 brelse(this_node->bh);
 452                 kfree(this_node);
 453                 *value = 0;
 454                 *keysize = 0;
 455                 befs_debug(sb, "<--- befs_btree_read() Tree is EMPTY");
 456                 return BEFS_BT_EMPTY;
 457         } else if (res == BEFS_ERR) {
 458                 goto error_alloc;
 459         }
 460
 461         /* find the leaf node containing the key_no key */
 462
 463         while (key_sum + this_node->head.all_key_count <= key_no) {
 464
 465                 /* no more nodes to look in: key_no is too large */
 466                 if (this_node->head.right == befs_bt_inval) {
 467                         *keysize = 0;
 468                         *value = 0;
 469                         befs_debug(sb,
 470                                    "<--- befs_btree_read() END of keys at %Lu",
 471                                    key_sum + this_node->head.all_key_count);
 472                         brelse(this_node->bh);
 473                         kfree(this_node);
 474                         return BEFS_BT_END;
 475                 }
 476
 477                 key_sum += this_node->head.all_key_count;
 478                 node_off = this_node->head.right;
 479
 480                 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 481                         befs_error(sb, "befs_btree_read() failed to read "
 482                                    "node at %Lu", node_off);
 483                         goto error_alloc;
 484                 }
 485         }
 486
 487         /* how many keys into this_node is key_no */
 488         cur_key = key_no - key_sum;
 489
 490         /* get pointers to datastructures within the node body */
 491         valarray = befs_bt_valarray(this_node);
 492
 493         keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
 494
 495         befs_debug(sb, "Read [%Lu,%d]: keysize %d", node_off, cur_key, keylen);
 496
 497         if (bufsize < keylen + 1) {
 498                 befs_error(sb, "befs_btree_read() keybuf too small (%u) "
 499                            "for key of size %d", bufsize, keylen);
 500                 brelse(this_node->bh);
 501                 goto error_alloc;
 502         };
 503
 504         strncpy(keybuf, keystart, keylen);
 505         *value = fs64_to_cpu(sb, valarray[cur_key]);
 506         *keysize = keylen;
 507         keybuf[keylen] = '\0';
 508
 509         befs_debug(sb, "Read [%Lu,%d]: Key \"%.*s\", Value %Lu", node_off,
 510                    cur_key, keylen, keybuf, *value);
 511
 512         brelse(this_node->bh);
 513         kfree(this_node);
 514
 515         befs_debug(sb, "<--- befs_btree_read()");
 516
 517         return BEFS_OK;
 518
 519       error_alloc:
 520         kfree(this_node);
 521
 522       error:
 523         *keysize = 0;
 524         *value = 0;
 525         befs_debug(sb, "<--- befs_btree_read() ERROR");
 526         return BEFS_ERR;
 527 }
 528
 529 /**
 530  * befs_btree_seekleaf - Find the first leafnode in the btree
 531  * @sb: Filesystem superblock
 532  * @ds: Datastream containing btree
 533  * @bt_super: Pointer to the superblock of the btree
 534  * @this_node: Buffer to return the leafnode in
 535  * @node_off: Pointer to offset of current node within datastream. Modified
 536  *              by the function.
 537  *
 538  *
 539  * Helper function for btree traverse. Moves the current position to the
 540  * start of the first leaf node.
 541  *
 542  * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
 543  */
 544 static int
 545 befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
 546                     befs_btree_super * bt_super, befs_btree_node * this_node,
 547                     befs_off_t * node_off)
 548 {
 549
 550         befs_debug(sb, "---> befs_btree_seekleaf()");
 551
 552         if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
 553                 befs_error(sb, "befs_btree_seekleaf() failed to read "
 554                            "node at %Lu", *node_off);
 555                 goto error;
 556         }
 557         befs_debug(sb, "Seekleaf to root node %Lu", *node_off);
 558
 559         if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
 560                 befs_debug(sb, "<--- befs_btree_seekleaf() Tree is EMPTY");
 561                 return BEFS_BT_EMPTY;
 562         }
 563
 564         while (!befs_leafnode(this_node)) {
 565
 566                 if (this_node->head.all_key_count == 0) {
 567                         befs_debug(sb, "befs_btree_seekleaf() encountered "
 568                                    "an empty interior node: %Lu. Using Overflow "
 569                                    "node: %Lu", *node_off,
 570                                    this_node->head.overflow);
 571                         *node_off = this_node->head.overflow;
 572                 } else {
 573                         fs64 *valarray = befs_bt_valarray(this_node);
 574                         *node_off = fs64_to_cpu(sb, valarray[0]);
 575                 }
 576                 if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
 577                         befs_error(sb, "befs_btree_seekleaf() failed to read "
 578                                    "node at %Lu", *node_off);
 579                         goto error;
 580                 }
 581
 582                 befs_debug(sb, "Seekleaf to child node %Lu", *node_off);
 583         }
 584         befs_debug(sb, "Node %Lu is a leaf node", *node_off);
 585
 586         return BEFS_OK;
 587
 588       error:
 589         befs_debug(sb, "<--- befs_btree_seekleaf() ERROR");
 590         return BEFS_ERR;
 591 }
 592
 593 /**
 594  * befs_leafnode - Determine if the btree node is a leaf node or an
 595  * interior node
 596  * @node: Pointer to node structure to test
 597  *
 598  * Return 1 if leaf, 0 if interior
 599  */
 600 static int
 601 befs_leafnode(befs_btree_node * node)
 602 {
 603         /* all interior nodes (and only interior nodes) have an overflow node */
 604         if (node->head.overflow == befs_bt_inval)
 605                 return 1;
 606         else
 607                 return 0;
 608 }
 609
 610 /**
 611  * befs_bt_keylen_index - Finds start of keylen index in a node
 612  * @node: Pointer to the node structure to find the keylen index within
 613  *
 614  * Returns a pointer to the start of the key length index array
 615  * of the B+tree node *@node
 616  *
 617  * "The length of all the keys in the node is added to the size of the
 618  * header and then rounded up to a multiple of four to get the beginning
 619  * of the key length index" (p.88, practical filesystem design).
 620  *
 621  * Except that rounding up to 8 works, and rounding up to 4 doesn't.
 622  */
 623 static fs16 *
 624 befs_bt_keylen_index(befs_btree_node * node)
 625 {
 626         const int keylen_align = 8;
 627         unsigned long int off =
 628             (sizeof (befs_btree_nodehead) + node->head.all_key_length);
 629         ulong tmp = off % keylen_align;
 630
 631         if (tmp)
 632                 off += keylen_align - tmp;
 633
 634         return (fs16 *) ((void *) node->od_node + off);
 635 }
 636
 637 /**
 638  * befs_bt_valarray - Finds the start of value array in a node
 639  * @node: Pointer to the node structure to find the value array within
 640  *
 641  * Returns a pointer to the start of the value array
 642  * of the node pointed to by the node header
 643  */
 644 static fs64 *
 645 befs_bt_valarray(befs_btree_node * node)
 646 {
 647         void *keylen_index_start = (void *) befs_bt_keylen_index(node);
 648         size_t keylen_index_size = node->head.all_key_count * sizeof (fs16);
 649
 650         return (fs64 *) (keylen_index_start + keylen_index_size);
 651 }
 652
 653 /**
 654  * befs_bt_keydata - Finds start of keydata array in a node
 655  * @node: Pointer to the node structure to find the keydata array within
 656  *
 657  * Returns a pointer to the start of the keydata array
 658  * of the node pointed to by the node header
 659  */
 660 static char *
 661 befs_bt_keydata(befs_btree_node * node)
 662 {
 663         return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
 664 }
 665
 666 /**
 667  * befs_bt_get_key - returns a pointer to the start of a key
 668  * @sb: filesystem superblock
 669  * @node: node in which to look for the key
 670  * @index: the index of the key to get
 671  * @keylen: modified to be the length of the key at @index
 672  *
 673  * Returns a valid pointer into @node on success.
 674  * Returns NULL on failure (bad input) and sets *@keylen = 0
 675  */
 676 static char *
 677 befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
 678                 int index, u16 * keylen)
 679 {
 680         int prev_key_end;
 681         char *keystart;
 682         fs16 *keylen_index;
 683
 684         if (index < 0 || index > node->head.all_key_count) {
 685                 *keylen = 0;
 686                 return NULL;
 687         }
 688
 689         keystart = befs_bt_keydata(node);
 690         keylen_index = befs_bt_keylen_index(node);
 691
 692         if (index == 0)
 693                 prev_key_end = 0;
 694         else
 695                 prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
 696
 697         *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
 698
 699         return keystart + prev_key_end;
 700 }
 701
 702 /**
 703  * befs_compare_strings - compare two strings
 704  * @key1: pointer to the first key to be compared
 705  * @keylen1: length in bytes of key1
 706  * @key2: pointer to the second key to be compared
 707  * @kelen2: length in bytes of key2
 708  *
 709  * Returns 0 if @key1 and @key2 are equal.
 710  * Returns >0 if @key1 is greater.
 711  * Returns <0 if @key2 is greater..
 712  */
 713 static int
 714 befs_compare_strings(const void *key1, int keylen1,
 715                      const void *key2, int keylen2)
 716 {
 717         int len = min_t(int, keylen1, keylen2);
 718         int result = strncmp(key1, key2, len);
 719         if (result == 0)
 720                 result = keylen1 - keylen2;
 721         return result;
 722 }
 723
 724 /* These will be used for non-string keyed btrees */
 725 #if 0
 726 static int
 727 btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
 728 {
 729         return *(int32_t *) key1 - *(int32_t *) key2;
 730 }
 731
 732 static int
 733 btree_compare_uint32(cont void *key1, int keylen1,
 734                      const void *key2, int keylen2)
 735 {
 736         if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
 737                 return 0;
 738         else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
 739                 return 1;
 740
 741         return -1;
 742 }
 743 static int
 744 btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
 745 {
 746         if (*(int64_t *) key1 == *(int64_t *) key2)
 747                 return 0;
 748         else if (*(int64_t *) key1 > *(int64_t *) key2)
 749                 return 1;
 750
 751         return -1;
 752 }
 753
 754 static int
 755 btree_compare_uint64(cont void *key1, int keylen1,
 756                      const void *key2, int keylen2)
 757 {
 758         if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
 759                 return 0;
 760         else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
 761                 return 1;
 762
 763         return -1;
 764 }
 765
 766 static int
 767 btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
 768 {
 769         float result = *(float *) key1 - *(float *) key2;
 770         if (result == 0.0f)
 771                 return 0;
 772
 773         return (result < 0.0f) ? -1 : 1;
 774 }
 775
 776 static int
 777 btree_compare_double(cont void *key1, int keylen1,
 778                      const void *key2, int keylen2)
 779 {
 780         double result = *(double *) key1 - *(double *) key2;
 781         if (result == 0.0)
 782                 return 0;
 783
 784         return (result < 0.0) ? -1 : 1;
 785 }
 786 #endif                          //0