linux/fs/befs/btree.c
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   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 */
  81typedef 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 */
  88static const befs_off_t befs_bt_inval = 0xffffffffffffffffULL;
  89
  90/* local functions */
  91static 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
  96static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
  97                              befs_btree_super * sup);
  98
  99static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
 100                             befs_btree_node * node, befs_off_t node_off);
 101
 102static int befs_leafnode(befs_btree_node * node);
 103
 104static fs16 *befs_bt_keylen_index(befs_btree_node * node);
 105
 106static fs64 *befs_bt_valarray(befs_btree_node * node);
 107
 108static char *befs_bt_keydata(befs_btree_node * node);
 109
 110static int befs_find_key(struct super_block *sb, befs_btree_node * node,
 111                         const char *findkey, befs_off_t * value);
 112
 113static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
 114                             int index, u16 * keylen);
 115
 116static 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 */
 133static int
 134befs_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
 192static int
 193befs_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 */
 246int
 247befs_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 */
 335static int
 336befs_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 */
 415int
 416befs_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 = (befs_btree_node *)
 440             kmalloc(sizeof (befs_btree_node), GFP_NOFS)) == NULL) {
 441                befs_error(sb, "befs_btree_read() failed to allocate %u "
 442                           "bytes of memory", sizeof (befs_btree_node));
 443                goto error;
 444        }
 445
 446        node_off = bt_super.root_node_ptr;
 447        this_node->bh = NULL;
 448
 449        /* seeks down to first leafnode, reads it into this_node */
 450        res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
 451        if (res == BEFS_BT_EMPTY) {
 452                brelse(this_node->bh);
 453                kfree(this_node);
 454                *value = 0;
 455                *keysize = 0;
 456                befs_debug(sb, "<--- befs_btree_read() Tree is EMPTY");
 457                return BEFS_BT_EMPTY;
 458        } else if (res == BEFS_ERR) {
 459                goto error_alloc;
 460        }
 461
 462        /* find the leaf node containing the key_no key */
 463
 464        while (key_sum + this_node->head.all_key_count <= key_no) {
 465
 466                /* no more nodes to look in: key_no is too large */
 467                if (this_node->head.right == befs_bt_inval) {
 468                        *keysize = 0;
 469                        *value = 0;
 470                        befs_debug(sb,
 471                                   "<--- befs_btree_read() END of keys at %Lu",
 472                                   key_sum + this_node->head.all_key_count);
 473                        brelse(this_node->bh);
 474                        kfree(this_node);
 475                        return BEFS_BT_END;
 476                }
 477
 478                key_sum += this_node->head.all_key_count;
 479                node_off = this_node->head.right;
 480
 481                if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 482                        befs_error(sb, "befs_btree_read() failed to read "
 483                                   "node at %Lu", node_off);
 484                        goto error_alloc;
 485                }
 486        }
 487
 488        /* how many keys into this_node is key_no */
 489        cur_key = key_no - key_sum;
 490
 491        /* get pointers to datastructures within the node body */
 492        valarray = befs_bt_valarray(this_node);
 493
 494        keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
 495
 496        befs_debug(sb, "Read [%Lu,%d]: keysize %d", node_off, cur_key, keylen);
 497
 498        if (bufsize < keylen + 1) {
 499                befs_error(sb, "befs_btree_read() keybuf too small (%u) "
 500                           "for key of size %d", bufsize, keylen);
 501                brelse(this_node->bh);
 502                goto error_alloc;
 503        };
 504
 505        strncpy(keybuf, keystart, keylen);
 506        *value = fs64_to_cpu(sb, valarray[cur_key]);
 507        *keysize = keylen;
 508        keybuf[keylen] = '\0';
 509
 510        befs_debug(sb, "Read [%Lu,%d]: Key \"%.*s\", Value %Lu", node_off,
 511                   cur_key, keylen, keybuf, *value);
 512
 513        brelse(this_node->bh);
 514        kfree(this_node);
 515
 516        befs_debug(sb, "<--- befs_btree_read()");
 517
 518        return BEFS_OK;
 519
 520      error_alloc:
 521        kfree(this_node);
 522
 523      error:
 524        *keysize = 0;
 525        *value = 0;
 526        befs_debug(sb, "<--- befs_btree_read() ERROR");
 527        return BEFS_ERR;
 528}
 529
 530/**
 531 * befs_btree_seekleaf - Find the first leafnode in the btree
 532 * @sb: Filesystem superblock
 533 * @ds: Datastream containing btree
 534 * @bt_super: Pointer to the superblock of the btree
 535 * @this_node: Buffer to return the leafnode in
 536 * @node_off: Pointer to offset of current node within datastream. Modified
 537 *              by the function.
 538 *
 539 *
 540 * Helper function for btree traverse. Moves the current position to the 
 541 * start of the first leaf node.
 542 *
 543 * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
 544 */
 545static int
 546befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
 547                    befs_btree_super * bt_super, befs_btree_node * this_node,
 548                    befs_off_t * node_off)
 549{
 550
 551        befs_debug(sb, "---> befs_btree_seekleaf()");
 552
 553        if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
 554                befs_error(sb, "befs_btree_seekleaf() failed to read "
 555                           "node at %Lu", *node_off);
 556                goto error;
 557        }
 558        befs_debug(sb, "Seekleaf to root node %Lu", *node_off);
 559
 560        if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
 561                befs_debug(sb, "<--- befs_btree_seekleaf() Tree is EMPTY");
 562                return BEFS_BT_EMPTY;
 563        }
 564
 565        while (!befs_leafnode(this_node)) {
 566
 567                if (this_node->head.all_key_count == 0) {
 568                        befs_debug(sb, "befs_btree_seekleaf() encountered "
 569                                   "an empty interior node: %Lu. Using Overflow "
 570                                   "node: %Lu", *node_off,
 571                                   this_node->head.overflow);
 572                        *node_off = this_node->head.overflow;
 573                } else {
 574                        fs64 *valarray = befs_bt_valarray(this_node);
 575                        *node_off = fs64_to_cpu(sb, valarray[0]);
 576                }
 577                if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
 578                        befs_error(sb, "befs_btree_seekleaf() failed to read "
 579                                   "node at %Lu", *node_off);
 580                        goto error;
 581                }
 582
 583                befs_debug(sb, "Seekleaf to child node %Lu", *node_off);
 584        }
 585        befs_debug(sb, "Node %Lu is a leaf node", *node_off);
 586
 587        return BEFS_OK;
 588
 589      error:
 590        befs_debug(sb, "<--- befs_btree_seekleaf() ERROR");
 591        return BEFS_ERR;
 592}
 593
 594/**
 595 * befs_leafnode - Determine if the btree node is a leaf node or an 
 596 * interior node
 597 * @node: Pointer to node structure to test
 598 * 
 599 * Return 1 if leaf, 0 if interior
 600 */
 601static int
 602befs_leafnode(befs_btree_node * node)
 603{
 604        /* all interior nodes (and only interior nodes) have an overflow node */
 605        if (node->head.overflow == befs_bt_inval)
 606                return 1;
 607        else
 608                return 0;
 609}
 610
 611/**
 612 * befs_bt_keylen_index - Finds start of keylen index in a node
 613 * @node: Pointer to the node structure to find the keylen index within
 614 *
 615 * Returns a pointer to the start of the key length index array
 616 * of the B+tree node *@node
 617 *
 618 * "The length of all the keys in the node is added to the size of the
 619 * header and then rounded up to a multiple of four to get the beginning
 620 * of the key length index" (p.88, practical filesystem design).
 621 *
 622 * Except that rounding up to 8 works, and rounding up to 4 doesn't.
 623 */
 624static fs16 *
 625befs_bt_keylen_index(befs_btree_node * node)
 626{
 627        const int keylen_align = 8;
 628        unsigned long int off =
 629            (sizeof (befs_btree_nodehead) + node->head.all_key_length);
 630        ulong tmp = off % keylen_align;
 631
 632        if (tmp)
 633                off += keylen_align - tmp;
 634
 635        return (fs16 *) ((void *) node->od_node + off);
 636}
 637
 638/**
 639 * befs_bt_valarray - Finds the start of value array in a node
 640 * @node: Pointer to the node structure to find the value array within
 641 *
 642 * Returns a pointer to the start of the value array
 643 * of the node pointed to by the node header
 644 */
 645static fs64 *
 646befs_bt_valarray(befs_btree_node * node)
 647{
 648        void *keylen_index_start = (void *) befs_bt_keylen_index(node);
 649        size_t keylen_index_size = node->head.all_key_count * sizeof (fs16);
 650
 651        return (fs64 *) (keylen_index_start + keylen_index_size);
 652}
 653
 654/**
 655 * befs_bt_keydata - Finds start of keydata array in a node
 656 * @node: Pointer to the node structure to find the keydata array within
 657 *
 658 * Returns a pointer to the start of the keydata array
 659 * of the node pointed to by the node header 
 660 */
 661static char *
 662befs_bt_keydata(befs_btree_node * node)
 663{
 664        return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
 665}
 666
 667/**
 668 * befs_bt_get_key - returns a pointer to the start of a key
 669 * @sb: filesystem superblock
 670 * @node: node in which to look for the key
 671 * @index: the index of the key to get
 672 * @keylen: modified to be the length of the key at @index
 673 *
 674 * Returns a valid pointer into @node on success.
 675 * Returns NULL on failure (bad input) and sets *@keylen = 0
 676 */
 677static char *
 678befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
 679                int index, u16 * keylen)
 680{
 681        int prev_key_end;
 682        char *keystart;
 683        fs16 *keylen_index;
 684
 685        if (index < 0 || index > node->head.all_key_count) {
 686                *keylen = 0;
 687                return NULL;
 688        }
 689
 690        keystart = befs_bt_keydata(node);
 691        keylen_index = befs_bt_keylen_index(node);
 692
 693        if (index == 0)
 694                prev_key_end = 0;
 695        else
 696                prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
 697
 698        *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
 699
 700        return keystart + prev_key_end;
 701}
 702
 703/**
 704 * befs_compare_strings - compare two strings
 705 * @key1: pointer to the first key to be compared 
 706 * @keylen1: length in bytes of key1
 707 * @key2: pointer to the second key to be compared
 708 * @kelen2: length in bytes of key2
 709 *
 710 * Returns 0 if @key1 and @key2 are equal.
 711 * Returns >0 if @key1 is greater.
 712 * Returns <0 if @key2 is greater..
 713 */
 714static int
 715befs_compare_strings(const void *key1, int keylen1,
 716                     const void *key2, int keylen2)
 717{
 718        int len = min_t(int, keylen1, keylen2);
 719        int result = strncmp(key1, key2, len);
 720        if (result == 0)
 721                result = keylen1 - keylen2;
 722        return result;
 723}
 724
 725/* These will be used for non-string keyed btrees */
 726#if 0
 727static int
 728btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
 729{
 730        return *(int32_t *) key1 - *(int32_t *) key2;
 731}
 732
 733static int
 734btree_compare_uint32(cont void *key1, int keylen1,
 735                     const void *key2, int keylen2)
 736{
 737        if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
 738                return 0;
 739        else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
 740                return 1;
 741
 742        return -1;
 743}
 744static int
 745btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
 746{
 747        if (*(int64_t *) key1 == *(int64_t *) key2)
 748                return 0;
 749        else if (*(int64_t *) key1 > *(int64_t *) key2)
 750                return 1;
 751
 752        return -1;
 753}
 754
 755static int
 756btree_compare_uint64(cont void *key1, int keylen1,
 757                     const void *key2, int keylen2)
 758{
 759        if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
 760                return 0;
 761        else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
 762                return 1;
 763
 764        return -1;
 765}
 766
 767static int
 768btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
 769{
 770        float result = *(float *) key1 - *(float *) key2;
 771        if (result == 0.0f)
 772                return 0;
 773
 774        return (result < 0.0f) ? -1 : 1;
 775}
 776
 777static int
 778btree_compare_double(cont void *key1, int keylen1,
 779                     const void *key2, int keylen2)
 780{
 781        double result = *(double *) key1 - *(double *) key2;
 782        if (result == 0.0)
 783                return 0;
 784
 785        return (result < 0.0) ? -1 : 1;
 786}
 787#endif                          //0
 788
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