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 struct befs_btree_node {
  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 };
  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                                struct 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                              struct befs_btree_node *node,
 101                              befs_off_t node_off);
 102
 103 static int befs_leafnode(struct befs_btree_node *node);
 104
 105 static fs16 *befs_bt_keylen_index(struct befs_btree_node *node);
 106
 107 static fs64 *befs_bt_valarray(struct befs_btree_node *node);
 108
 109 static char *befs_bt_keydata(struct befs_btree_node *node);
 110
 111 static int befs_find_key(struct super_block *sb,
 112                          struct befs_btree_node *node,
 113                          const char *findkey, befs_off_t * value);
 114
 115 static char *befs_bt_get_key(struct super_block *sb,
 116                              struct befs_btree_node *node,
 117                              int index, u16 * keylen);
 118
 119 static int befs_compare_strings(const void *key1, int keylen1,
 120                                 const void *key2, int keylen2);
 121
 122 /**
 123  * befs_bt_read_super - read in btree superblock convert to cpu byteorder
 124  * @sb: Filesystem superblock
 125  * @ds: Datastream to read from
 126  * @sup: Buffer in which to place the btree superblock
 127  *
 128  * Calls befs_read_datastream to read in the btree superblock and
 129  * makes sure it is in cpu byteorder, byteswapping if necessary.
 130  *
 131  * On success, returns BEFS_OK and *@sup contains the btree superblock,
 132  * in cpu byte order.
 133  *
 134  * On failure, BEFS_ERR is returned.
 135  */
 136 static int
 137 befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
 138                    befs_btree_super * sup)
 139 {
 140         struct buffer_head *bh;
 141         befs_disk_btree_super *od_sup;
 142
 143         befs_debug(sb, "---> %s", __func__);
 144
 145         bh = befs_read_datastream(sb, ds, 0, NULL);
 146
 147         if (!bh) {
 148                 befs_error(sb, "Couldn't read index header.");
 149                 goto error;
 150         }
 151         od_sup = (befs_disk_btree_super *) bh->b_data;
 152         befs_dump_index_entry(sb, od_sup);
 153
 154         sup->magic = fs32_to_cpu(sb, od_sup->magic);
 155         sup->node_size = fs32_to_cpu(sb, od_sup->node_size);
 156         sup->max_depth = fs32_to_cpu(sb, od_sup->max_depth);
 157         sup->data_type = fs32_to_cpu(sb, od_sup->data_type);
 158         sup->root_node_ptr = fs64_to_cpu(sb, od_sup->root_node_ptr);
 159         sup->free_node_ptr = fs64_to_cpu(sb, od_sup->free_node_ptr);
 160         sup->max_size = fs64_to_cpu(sb, od_sup->max_size);
 161
 162         brelse(bh);
 163         if (sup->magic != BEFS_BTREE_MAGIC) {
 164                 befs_error(sb, "Index header has bad magic.");
 165                 goto error;
 166         }
 167
 168         befs_debug(sb, "<--- %s", __func__);
 169         return BEFS_OK;
 170
 171       error:
 172         befs_debug(sb, "<--- %s ERROR", __func__);
 173         return BEFS_ERR;
 174 }
 175
 176 /**
 177  * befs_bt_read_node - read in btree node and convert to cpu byteorder
 178  * @sb: Filesystem superblock
 179  * @ds: Datastream to read from
 180  * @node: Buffer in which to place the btree node
 181  * @node_off: Starting offset (in bytes) of the node in @ds
 182  *
 183  * Calls befs_read_datastream to read in the indicated btree node and
 184  * makes sure its header fields are in cpu byteorder, byteswapping if
 185  * necessary.
 186  * Note: node->bh must be NULL when this function called first
 187  * time. Don't forget brelse(node->bh) after last call.
 188  *
 189  * On success, returns BEFS_OK and *@node contains the btree node that
 190  * starts at @node_off, with the node->head fields in cpu byte order.
 191  *
 192  * On failure, BEFS_ERR is returned.
 193  */
 194
 195 static int
 196 befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
 197                   struct befs_btree_node *node, befs_off_t node_off)
 198 {
 199         uint off = 0;
 200
 201         befs_debug(sb, "---> %s", __func__);
 202
 203         if (node->bh)
 204                 brelse(node->bh);
 205
 206         node->bh = befs_read_datastream(sb, ds, node_off, &off);
 207         if (!node->bh) {
 208                 befs_error(sb, "%s failed to read "
 209                            "node at %llu", __func__, node_off);
 210                 befs_debug(sb, "<--- %s ERROR", __func__);
 211
 212                 return BEFS_ERR;
 213         }
 214         node->od_node =
 215             (befs_btree_nodehead *) ((void *) node->bh->b_data + off);
 216
 217         befs_dump_index_node(sb, node->od_node);
 218
 219         node->head.left = fs64_to_cpu(sb, node->od_node->left);
 220         node->head.right = fs64_to_cpu(sb, node->od_node->right);
 221         node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow);
 222         node->head.all_key_count =
 223             fs16_to_cpu(sb, node->od_node->all_key_count);
 224         node->head.all_key_length =
 225             fs16_to_cpu(sb, node->od_node->all_key_length);
 226
 227         befs_debug(sb, "<--- %s", __func__);
 228         return BEFS_OK;
 229 }
 230
 231 /**
 232  * befs_btree_find - Find a key in a befs B+tree
 233  * @sb: Filesystem superblock
 234  * @ds: Datastream containing btree
 235  * @key: Key string to lookup in btree
 236  * @value: Value stored with @key
 237  *
 238  * On success, returns BEFS_OK and sets *@value to the value stored
 239  * with @key (usually the disk block number of an inode).
 240  *
 241  * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND.
 242  *
 243  * Algorithm:
 244  *   Read the superblock and rootnode of the b+tree.
 245  *   Drill down through the interior nodes using befs_find_key().
 246  *   Once at the correct leaf node, use befs_find_key() again to get the
 247  *   actuall value stored with the key.
 248  */
 249 int
 250 befs_btree_find(struct super_block *sb, befs_data_stream * ds,
 251                 const char *key, befs_off_t * value)
 252 {
 253         struct befs_btree_node *this_node;
 254         befs_btree_super bt_super;
 255         befs_off_t node_off;
 256         int res;
 257
 258         befs_debug(sb, "---> %s Key: %s", __func__, key);
 259
 260         if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
 261                 befs_error(sb,
 262                            "befs_btree_find() failed to read index superblock");
 263                 goto error;
 264         }
 265
 266         this_node = kmalloc(sizeof(struct befs_btree_node),
 267                                                 GFP_NOFS);
 268         if (!this_node) {
 269                 befs_error(sb, "befs_btree_find() failed to allocate %zu "
 270                            "bytes of memory", sizeof(struct befs_btree_node));
 271                 goto error;
 272         }
 273
 274         this_node->bh = NULL;
 275
 276         /* read in root node */
 277         node_off = bt_super.root_node_ptr;
 278         if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 279                 befs_error(sb, "befs_btree_find() failed to read "
 280                            "node at %llu", node_off);
 281                 goto error_alloc;
 282         }
 283
 284         while (!befs_leafnode(this_node)) {
 285                 res = befs_find_key(sb, this_node, key, &node_off);
 286                 if (res == BEFS_BT_NOT_FOUND)
 287                         node_off = this_node->head.overflow;
 288                 /* if no match, go to overflow node */
 289                 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 290                         befs_error(sb, "befs_btree_find() failed to read "
 291                                    "node at %llu", node_off);
 292                         goto error_alloc;
 293                 }
 294         }
 295
 296         /* at the correct leaf node now */
 297
 298         res = befs_find_key(sb, this_node, key, value);
 299
 300         brelse(this_node->bh);
 301         kfree(this_node);
 302
 303         if (res != BEFS_BT_MATCH) {
 304                 befs_debug(sb, "<--- %s Key %s not found", __func__, key);
 305                 *value = 0;
 306                 return BEFS_BT_NOT_FOUND;
 307         }
 308         befs_debug(sb, "<--- %s Found key %s, value %llu", __func__,
 309                    key, *value);
 310         return BEFS_OK;
 311
 312       error_alloc:
 313         kfree(this_node);
 314       error:
 315         *value = 0;
 316         befs_debug(sb, "<--- %s ERROR", __func__);
 317         return BEFS_ERR;
 318 }
 319
 320 /**
 321  * befs_find_key - Search for a key within a node
 322  * @sb: Filesystem superblock
 323  * @node: Node to find the key within
 324  * @findkey: Keystring to search for
 325  * @value: If key is found, the value stored with the key is put here
 326  *
 327  * finds exact match if one exists, and returns BEFS_BT_MATCH
 328  * If no exact match, finds first key in node that is greater
 329  * (alphabetically) than the search key and returns BEFS_BT_PARMATCH
 330  * (for partial match, I guess). Can you think of something better to
 331  * call it?
 332  *
 333  * If no key was a match or greater than the search key, return
 334  * BEFS_BT_NOT_FOUND.
 335  *
 336  * Use binary search instead of a linear.
 337  */
 338 static int
 339 befs_find_key(struct super_block *sb, struct befs_btree_node *node,
 340               const char *findkey, befs_off_t * value)
 341 {
 342         int first, last, mid;
 343         int eq;
 344         u16 keylen;
 345         int findkey_len;
 346         char *thiskey;
 347         fs64 *valarray;
 348
 349         befs_debug(sb, "---> %s %s", __func__, findkey);
 350
 351         *value = 0;
 352
 353         findkey_len = strlen(findkey);
 354
 355         /* if node can not contain key, just skeep this node */
 356         last = node->head.all_key_count - 1;
 357         thiskey = befs_bt_get_key(sb, node, last, &keylen);
 358
 359         eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
 360         if (eq < 0) {
 361                 befs_debug(sb, "<--- %s %s not found", __func__, findkey);
 362                 return BEFS_BT_NOT_FOUND;
 363         }
 364
 365         valarray = befs_bt_valarray(node);
 366
 367         /* simple binary search */
 368         first = 0;
 369         mid = 0;
 370         while (last >= first) {
 371                 mid = (last + first) / 2;
 372                 befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
 373                            mid);
 374                 thiskey = befs_bt_get_key(sb, node, mid, &keylen);
 375                 eq = befs_compare_strings(thiskey, keylen, findkey,
 376                                           findkey_len);
 377
 378                 if (eq == 0) {
 379                         befs_debug(sb, "<--- %s found %s at %d",
 380                                    __func__, thiskey, mid);
 381
 382                         *value = fs64_to_cpu(sb, valarray[mid]);
 383                         return BEFS_BT_MATCH;
 384                 }
 385                 if (eq > 0)
 386                         last = mid - 1;
 387                 else
 388                         first = mid + 1;
 389         }
 390         if (eq < 0)
 391                 *value = fs64_to_cpu(sb, valarray[mid + 1]);
 392         else
 393                 *value = fs64_to_cpu(sb, valarray[mid]);
 394         befs_debug(sb, "<--- %s found %s at %d", __func__, thiskey, mid);
 395         return BEFS_BT_PARMATCH;
 396 }
 397
 398 /**
 399  * befs_btree_read - Traverse leafnodes of a btree
 400  * @sb: Filesystem superblock
 401  * @ds: Datastream containing btree
 402  * @key_no: Key number (alphabetical order) of key to read
 403  * @bufsize: Size of the buffer to return key in
 404  * @keybuf: Pointer to a buffer to put the key in
 405  * @keysize: Length of the returned key
 406  * @value: Value stored with the returned key
 407  *
 408  * Heres how it works: Key_no is the index of the key/value pair to
 409  * return in keybuf/value.
 410  * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is
 411  * the number of characters in the key (just a convenience).
 412  *
 413  * Algorithm:
 414  *   Get the first leafnode of the tree. See if the requested key is in that
 415  *   node. If not, follow the node->right link to the next leafnode. Repeat
 416  *   until the (key_no)th key is found or the tree is out of keys.
 417  */
 418 int
 419 befs_btree_read(struct super_block *sb, befs_data_stream * ds,
 420                 loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
 421                 befs_off_t * value)
 422 {
 423         struct befs_btree_node *this_node;
 424         befs_btree_super bt_super;
 425         befs_off_t node_off = 0;
 426         int cur_key;
 427         fs64 *valarray;
 428         char *keystart;
 429         u16 keylen;
 430         int res;
 431
 432         uint key_sum = 0;
 433
 434         befs_debug(sb, "---> %s", __func__);
 435
 436         if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
 437                 befs_error(sb,
 438                            "befs_btree_read() failed to read index superblock");
 439                 goto error;
 440         }
 441
 442         this_node = kmalloc(sizeof(struct befs_btree_node), GFP_NOFS);
 443         if (this_node == NULL) {
 444                 befs_error(sb, "befs_btree_read() failed to allocate %zu "
 445                            "bytes of memory", sizeof(struct befs_btree_node));
 446                 goto error;
 447         }
 448
 449         node_off = bt_super.root_node_ptr;
 450         this_node->bh = NULL;
 451
 452         /* seeks down to first leafnode, reads it into this_node */
 453         res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
 454         if (res == BEFS_BT_EMPTY) {
 455                 brelse(this_node->bh);
 456                 kfree(this_node);
 457                 *value = 0;
 458                 *keysize = 0;
 459                 befs_debug(sb, "<--- %s Tree is EMPTY", __func__);
 460                 return BEFS_BT_EMPTY;
 461         } else if (res == BEFS_ERR) {
 462                 goto error_alloc;
 463         }
 464
 465         /* find the leaf node containing the key_no key */
 466
 467         while (key_sum + this_node->head.all_key_count <= key_no) {
 468
 469                 /* no more nodes to look in: key_no is too large */
 470                 if (this_node->head.right == befs_bt_inval) {
 471                         *keysize = 0;
 472                         *value = 0;
 473                         befs_debug(sb,
 474                                    "<--- %s END of keys at %llu", __func__,
 475                                    (unsigned long long)
 476                                    key_sum + this_node->head.all_key_count);
 477                         brelse(this_node->bh);
 478                         kfree(this_node);
 479                         return BEFS_BT_END;
 480                 }
 481
 482                 key_sum += this_node->head.all_key_count;
 483                 node_off = this_node->head.right;
 484
 485                 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 486                         befs_error(sb, "%s failed to read node at %llu",
 487                                   __func__, (unsigned long long)node_off);
 488                         goto error_alloc;
 489                 }
 490         }
 491
 492         /* how many keys into this_node is key_no */
 493         cur_key = key_no - key_sum;
 494
 495         /* get pointers to datastructures within the node body */
 496         valarray = befs_bt_valarray(this_node);
 497
 498         keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
 499
 500         befs_debug(sb, "Read [%llu,%d]: keysize %d",
 501                    (long long unsigned int)node_off, (int)cur_key,
 502                    (int)keylen);
 503
 504         if (bufsize < keylen + 1) {
 505                 befs_error(sb, "%s keybuf too small (%zu) "
 506                            "for key of size %d", __func__, bufsize, keylen);
 507                 brelse(this_node->bh);
 508                 goto error_alloc;
 509         }
 510
 511         strlcpy(keybuf, keystart, keylen + 1);
 512         *value = fs64_to_cpu(sb, valarray[cur_key]);
 513         *keysize = keylen;
 514
 515         befs_debug(sb, "Read [%llu,%d]: Key \"%.*s\", Value %llu", node_off,
 516                    cur_key, keylen, keybuf, *value);
 517
 518         brelse(this_node->bh);
 519         kfree(this_node);
 520
 521         befs_debug(sb, "<--- %s", __func__);
 522
 523         return BEFS_OK;
 524
 525       error_alloc:
 526         kfree(this_node);
 527
 528       error:
 529         *keysize = 0;
 530         *value = 0;
 531         befs_debug(sb, "<--- %s ERROR", __func__);
 532         return BEFS_ERR;
 533 }
 534
 535 /**
 536  * befs_btree_seekleaf - Find the first leafnode in the btree
 537  * @sb: Filesystem superblock
 538  * @ds: Datastream containing btree
 539  * @bt_super: Pointer to the superblock of the btree
 540  * @this_node: Buffer to return the leafnode in
 541  * @node_off: Pointer to offset of current node within datastream. Modified
 542  *              by the function.
 543  *
 544  *
 545  * Helper function for btree traverse. Moves the current position to the
 546  * start of the first leaf node.
 547  *
 548  * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
 549  */
 550 static int
 551 befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
 552                     befs_btree_super *bt_super,
 553                     struct befs_btree_node *this_node,
 554                     befs_off_t * node_off)
 555 {
 556
 557         befs_debug(sb, "---> %s", __func__);
 558
 559         if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
 560                 befs_error(sb, "%s failed to read "
 561                            "node at %llu", __func__, *node_off);
 562                 goto error;
 563         }
 564         befs_debug(sb, "Seekleaf to root node %llu", *node_off);
 565
 566         if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
 567                 befs_debug(sb, "<--- %s Tree is EMPTY", __func__);
 568                 return BEFS_BT_EMPTY;
 569         }
 570
 571         while (!befs_leafnode(this_node)) {
 572
 573                 if (this_node->head.all_key_count == 0) {
 574                         befs_debug(sb, "%s encountered "
 575                                    "an empty interior node: %llu. Using Overflow "
 576                                    "node: %llu", __func__, *node_off,
 577                                    this_node->head.overflow);
 578                         *node_off = this_node->head.overflow;
 579                 } else {
 580                         fs64 *valarray = befs_bt_valarray(this_node);
 581                         *node_off = fs64_to_cpu(sb, valarray[0]);
 582                 }
 583                 if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
 584                         befs_error(sb, "%s failed to read "
 585                                    "node at %llu", __func__, *node_off);
 586                         goto error;
 587                 }
 588
 589                 befs_debug(sb, "Seekleaf to child node %llu", *node_off);
 590         }
 591         befs_debug(sb, "Node %llu is a leaf node", *node_off);
 592
 593         return BEFS_OK;
 594
 595       error:
 596         befs_debug(sb, "<--- %s ERROR", __func__);
 597         return BEFS_ERR;
 598 }
 599
 600 /**
 601  * befs_leafnode - Determine if the btree node is a leaf node or an
 602  * interior node
 603  * @node: Pointer to node structure to test
 604  *
 605  * Return 1 if leaf, 0 if interior
 606  */
 607 static int
 608 befs_leafnode(struct befs_btree_node *node)
 609 {
 610         /* all interior nodes (and only interior nodes) have an overflow node */
 611         if (node->head.overflow == befs_bt_inval)
 612                 return 1;
 613         else
 614                 return 0;
 615 }
 616
 617 /**
 618  * befs_bt_keylen_index - Finds start of keylen index in a node
 619  * @node: Pointer to the node structure to find the keylen index within
 620  *
 621  * Returns a pointer to the start of the key length index array
 622  * of the B+tree node *@node
 623  *
 624  * "The length of all the keys in the node is added to the size of the
 625  * header and then rounded up to a multiple of four to get the beginning
 626  * of the key length index" (p.88, practical filesystem design).
 627  *
 628  * Except that rounding up to 8 works, and rounding up to 4 doesn't.
 629  */
 630 static fs16 *
 631 befs_bt_keylen_index(struct befs_btree_node *node)
 632 {
 633         const int keylen_align = 8;
 634         unsigned long int off =
 635             (sizeof (befs_btree_nodehead) + node->head.all_key_length);
 636         ulong tmp = off % keylen_align;
 637
 638         if (tmp)
 639                 off += keylen_align - tmp;
 640
 641         return (fs16 *) ((void *) node->od_node + off);
 642 }
 643
 644 /**
 645  * befs_bt_valarray - Finds the start of value array in a node
 646  * @node: Pointer to the node structure to find the value array within
 647  *
 648  * Returns a pointer to the start of the value array
 649  * of the node pointed to by the node header
 650  */
 651 static fs64 *
 652 befs_bt_valarray(struct befs_btree_node *node)
 653 {
 654         void *keylen_index_start = (void *) befs_bt_keylen_index(node);
 655         size_t keylen_index_size = node->head.all_key_count * sizeof (fs16);
 656
 657         return (fs64 *) (keylen_index_start + keylen_index_size);
 658 }
 659
 660 /**
 661  * befs_bt_keydata - Finds start of keydata array in a node
 662  * @node: Pointer to the node structure to find the keydata array within
 663  *
 664  * Returns a pointer to the start of the keydata array
 665  * of the node pointed to by the node header
 666  */
 667 static char *
 668 befs_bt_keydata(struct befs_btree_node *node)
 669 {
 670         return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
 671 }
 672
 673 /**
 674  * befs_bt_get_key - returns a pointer to the start of a key
 675  * @sb: filesystem superblock
 676  * @node: node in which to look for the key
 677  * @index: the index of the key to get
 678  * @keylen: modified to be the length of the key at @index
 679  *
 680  * Returns a valid pointer into @node on success.
 681  * Returns NULL on failure (bad input) and sets *@keylen = 0
 682  */
 683 static char *
 684 befs_bt_get_key(struct super_block *sb, struct befs_btree_node *node,
 685                 int index, u16 * keylen)
 686 {
 687         int prev_key_end;
 688         char *keystart;
 689         fs16 *keylen_index;
 690
 691         if (index < 0 || index > node->head.all_key_count) {
 692                 *keylen = 0;
 693                 return NULL;
 694         }
 695
 696         keystart = befs_bt_keydata(node);
 697         keylen_index = befs_bt_keylen_index(node);
 698
 699         if (index == 0)
 700                 prev_key_end = 0;
 701         else
 702                 prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
 703
 704         *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
 705
 706         return keystart + prev_key_end;
 707 }
 708
 709 /**
 710  * befs_compare_strings - compare two strings
 711  * @key1: pointer to the first key to be compared
 712  * @keylen1: length in bytes of key1
 713  * @key2: pointer to the second key to be compared
 714  * @keylen2: length in bytes of key2
 715  *
 716  * Returns 0 if @key1 and @key2 are equal.
 717  * Returns >0 if @key1 is greater.
 718  * Returns <0 if @key2 is greater..
 719  */
 720 static int
 721 befs_compare_strings(const void *key1, int keylen1,
 722                      const void *key2, int keylen2)
 723 {
 724         int len = min_t(int, keylen1, keylen2);
 725         int result = strncmp(key1, key2, len);
 726         if (result == 0)
 727                 result = keylen1 - keylen2;
 728         return result;
 729 }
 730
 731 /* These will be used for non-string keyed btrees */
 732 #if 0
 733 static int
 734 btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
 735 {
 736         return *(int32_t *) key1 - *(int32_t *) key2;
 737 }
 738
 739 static int
 740 btree_compare_uint32(cont void *key1, int keylen1,
 741                      const void *key2, int keylen2)
 742 {
 743         if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
 744                 return 0;
 745         else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
 746                 return 1;
 747
 748         return -1;
 749 }
 750 static int
 751 btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
 752 {
 753         if (*(int64_t *) key1 == *(int64_t *) key2)
 754                 return 0;
 755         else if (*(int64_t *) key1 > *(int64_t *) key2)
 756                 return 1;
 757
 758         return -1;
 759 }
 760
 761 static int
 762 btree_compare_uint64(cont void *key1, int keylen1,
 763                      const void *key2, int keylen2)
 764 {
 765         if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
 766                 return 0;
 767         else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
 768                 return 1;
 769
 770         return -1;
 771 }
 772
 773 static int
 774 btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
 775 {
 776         float result = *(float *) key1 - *(float *) key2;
 777         if (result == 0.0f)
 778                 return 0;
 779
 780         return (result < 0.0f) ? -1 : 1;
 781 }
 782
 783 static int
 784 btree_compare_double(cont void *key1, int keylen1,
 785                      const void *key2, int keylen2)
 786 {
 787         double result = *(double *) key1 - *(double *) key2;
 788         if (result == 0.0)
 789                 return 0;
 790
 791         return (result < 0.0) ? -1 : 1;
 792 }
 793 #endif                          //0