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, const 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, const befs_data_stream *ds,
  97                               befs_btree_super * sup);
  98
  99 static int befs_bt_read_node(struct super_block *sb, const 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, const 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
 160         brelse(bh);
 161         if (sup->magic != BEFS_BTREE_MAGIC) {
 162                 befs_error(sb, "Index header has bad magic.");
 163                 goto error;
 164         }
 165
 166         befs_debug(sb, "<--- %s", __func__);
 167         return BEFS_OK;
 168
 169       error:
 170         befs_debug(sb, "<--- %s ERROR", __func__);
 171         return BEFS_ERR;
 172 }
 173
 174 /**
 175  * befs_bt_read_node - read in btree node and convert to cpu byteorder
 176  * @sb: Filesystem superblock
 177  * @ds: Datastream to read from
 178  * @node: Buffer in which to place the btree node
 179  * @node_off: Starting offset (in bytes) of the node in @ds
 180  *
 181  * Calls befs_read_datastream to read in the indicated btree node and
 182  * makes sure its header fields are in cpu byteorder, byteswapping if
 183  * necessary.
 184  * Note: node->bh must be NULL when this function is called the first time.
 185  * Don't forget brelse(node->bh) after last call.
 186  *
 187  * On success, returns BEFS_OK and *@node contains the btree node that
 188  * starts at @node_off, with the node->head fields in cpu byte order.
 189  *
 190  * On failure, BEFS_ERR is returned.
 191  */
 192
 193 static int
 194 befs_bt_read_node(struct super_block *sb, const befs_data_stream *ds,
 195                   struct befs_btree_node *node, befs_off_t node_off)
 196 {
 197         uint off = 0;
 198
 199         befs_debug(sb, "---> %s", __func__);
 200
 201         if (node->bh)
 202                 brelse(node->bh);
 203
 204         node->bh = befs_read_datastream(sb, ds, node_off, &off);
 205         if (!node->bh) {
 206                 befs_error(sb, "%s failed to read "
 207                            "node at %llu", __func__, node_off);
 208                 befs_debug(sb, "<--- %s ERROR", __func__);
 209
 210                 return BEFS_ERR;
 211         }
 212         node->od_node =
 213             (befs_btree_nodehead *) ((void *) node->bh->b_data + off);
 214
 215         befs_dump_index_node(sb, node->od_node);
 216
 217         node->head.left = fs64_to_cpu(sb, node->od_node->left);
 218         node->head.right = fs64_to_cpu(sb, node->od_node->right);
 219         node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow);
 220         node->head.all_key_count =
 221             fs16_to_cpu(sb, node->od_node->all_key_count);
 222         node->head.all_key_length =
 223             fs16_to_cpu(sb, node->od_node->all_key_length);
 224
 225         befs_debug(sb, "<--- %s", __func__);
 226         return BEFS_OK;
 227 }
 228
 229 /**
 230  * befs_btree_find - Find a key in a befs B+tree
 231  * @sb: Filesystem superblock
 232  * @ds: Datastream containing btree
 233  * @key: Key string to lookup in btree
 234  * @value: Value stored with @key
 235  *
 236  * On success, returns BEFS_OK and sets *@value to the value stored
 237  * with @key (usually the disk block number of an inode).
 238  *
 239  * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND.
 240  *
 241  * Algorithm:
 242  *   Read the superblock and rootnode of the b+tree.
 243  *   Drill down through the interior nodes using befs_find_key().
 244  *   Once at the correct leaf node, use befs_find_key() again to get the
 245  *   actual value stored with the key.
 246  */
 247 int
 248 befs_btree_find(struct super_block *sb, const befs_data_stream *ds,
 249                 const char *key, befs_off_t * value)
 250 {
 251         struct befs_btree_node *this_node;
 252         befs_btree_super bt_super;
 253         befs_off_t node_off;
 254         int res;
 255
 256         befs_debug(sb, "---> %s Key: %s", __func__, key);
 257
 258         if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
 259                 befs_error(sb,
 260                            "befs_btree_find() failed to read index superblock");
 261                 goto error;
 262         }
 263
 264         this_node = kmalloc(sizeof(struct befs_btree_node),
 265                                                 GFP_NOFS);
 266         if (!this_node) {
 267                 befs_error(sb, "befs_btree_find() failed to allocate %zu "
 268                            "bytes of memory", sizeof(struct befs_btree_node));
 269                 goto error;
 270         }
 271
 272         this_node->bh = NULL;
 273
 274         /* read in root node */
 275         node_off = bt_super.root_node_ptr;
 276         if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 277                 befs_error(sb, "befs_btree_find() failed to read "
 278                            "node at %llu", node_off);
 279                 goto error_alloc;
 280         }
 281
 282         while (!befs_leafnode(this_node)) {
 283                 res = befs_find_key(sb, this_node, key, &node_off);
 284                 /* if no key set, try the overflow node */
 285                 if (res == BEFS_BT_OVERFLOW)
 286                         node_off = this_node->head.overflow;
 287                 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
 288                         befs_error(sb, "befs_btree_find() failed to read "
 289                                    "node at %llu", node_off);
 290                         goto error_alloc;
 291                 }
 292         }
 293
 294         /* at a leaf node now, check if it is correct */
 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_error(sb, "<--- %s Key %s not found", __func__, key);
 302                 befs_debug(sb, "<--- %s ERROR", __func__);
 303                 *value = 0;
 304                 return BEFS_BT_NOT_FOUND;
 305         }
 306         befs_debug(sb, "<--- %s Found key %s, value %llu", __func__,
 307                    key, *value);
 308         return BEFS_OK;
 309
 310       error_alloc:
 311         kfree(this_node);
 312       error:
 313         *value = 0;
 314         befs_debug(sb, "<--- %s ERROR", __func__);
 315         return BEFS_ERR;
 316 }
 317
 318 /**
 319  * befs_find_key - Search for a key within a node
 320  * @sb: Filesystem superblock
 321  * @node: Node to find the key within
 322  * @findkey: Keystring to search for
 323  * @value: If key is found, the value stored with the key is put here
 324  *
 325  * Finds exact match if one exists, and returns BEFS_BT_MATCH.
 326  * If there is no match and node's value array is too small for key, return
 327  * BEFS_BT_OVERFLOW.
 328  * If no match and node should countain this key, return BEFS_BT_NOT_FOUND.
 329  *
 330  * Uses binary search instead of a linear.
 331  */
 332 static int
 333 befs_find_key(struct super_block *sb, struct befs_btree_node *node,
 334               const char *findkey, befs_off_t * value)
 335 {
 336         int first, last, mid;
 337         int eq;
 338         u16 keylen;
 339         int findkey_len;
 340         char *thiskey;
 341         fs64 *valarray;
 342
 343         befs_debug(sb, "---> %s %s", __func__, findkey);
 344
 345         findkey_len = strlen(findkey);
 346
 347         /* if node can not contain key, just skip this node */
 348         last = node->head.all_key_count - 1;
 349         thiskey = befs_bt_get_key(sb, node, last, &keylen);
 350
 351         eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
 352         if (eq < 0) {
 353                 befs_debug(sb, "<--- node can't contain %s", findkey);
 354                 return BEFS_BT_OVERFLOW;
 355         }
 356
 357         valarray = befs_bt_valarray(node);
 358
 359         /* simple binary search */
 360         first = 0;
 361         mid = 0;
 362         while (last >= first) {
 363                 mid = (last + first) / 2;
 364                 befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
 365                            mid);
 366                 thiskey = befs_bt_get_key(sb, node, mid, &keylen);
 367                 eq = befs_compare_strings(thiskey, keylen, findkey,
 368                                           findkey_len);
 369
 370                 if (eq == 0) {
 371                         befs_debug(sb, "<--- %s found %s at %d",
 372                                    __func__, thiskey, mid);
 373
 374                         *value = fs64_to_cpu(sb, valarray[mid]);
 375                         return BEFS_BT_MATCH;
 376                 }
 377                 if (eq > 0)
 378                         last = mid - 1;
 379                 else
 380                         first = mid + 1;
 381         }
 382
 383         /* return an existing value so caller can arrive to a leaf node */
 384         if (eq < 0)
 385                 *value = fs64_to_cpu(sb, valarray[mid + 1]);
 386         else
 387                 *value = fs64_to_cpu(sb, valarray[mid]);
 388         befs_error(sb, "<--- %s %s not found", __func__, findkey);
 389         befs_debug(sb, "<--- %s ERROR", __func__);
 390         return BEFS_BT_NOT_FOUND;
 391 }
 392
 393 /**
 394  * befs_btree_read - Traverse leafnodes of a btree
 395  * @sb: Filesystem superblock
 396  * @ds: Datastream containing btree
 397  * @key_no: Key number (alphabetical order) of key to read
 398  * @bufsize: Size of the buffer to return key in
 399  * @keybuf: Pointer to a buffer to put the key in
 400  * @keysize: Length of the returned key
 401  * @value: Value stored with the returned key
 402  *
 403  * Here's how it works: Key_no is the index of the key/value pair to
 404  * return in keybuf/value.
 405  * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is
 406  * the number of characters in the key (just a convenience).
 407  *
 408  * Algorithm:
 409  *   Get the first leafnode of the tree. See if the requested key is in that
 410  *   node. If not, follow the node->right link to the next leafnode. Repeat
 411  *   until the (key_no)th key is found or the tree is out of keys.
 412  */
 413 int
 414 befs_btree_read(struct super_block *sb, const befs_data_stream *ds,
 415                 loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
 416                 befs_off_t * value)
 417 {
 418         struct befs_btree_node *this_node;
 419         befs_btree_super bt_super;
 420         befs_off_t node_off;
 421         int cur_key;
 422         fs64 *valarray;
 423         char *keystart;
 424         u16 keylen;
 425         int res;
 426
 427         uint key_sum = 0;
 428
 429         befs_debug(sb, "---> %s", __func__);
 430
 431         if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
 432                 befs_error(sb,
 433                            "befs_btree_read() failed to read index superblock");
 434                 goto error;
 435         }
 436
 437         this_node = kmalloc(sizeof(struct befs_btree_node), GFP_NOFS);
 438         if (this_node == NULL) {
 439                 befs_error(sb, "befs_btree_read() failed to allocate %zu "
 440                            "bytes of memory", sizeof(struct befs_btree_node));
 441                 goto error;
 442         }
 443
 444         node_off = bt_super.root_node_ptr;
 445         this_node->bh = NULL;
 446
 447         /* seeks down to first leafnode, reads it into this_node */
 448         res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
 449         if (res == BEFS_BT_EMPTY) {
 450                 brelse(this_node->bh);
 451                 kfree(this_node);
 452                 *value = 0;
 453                 *keysize = 0;
 454                 befs_debug(sb, "<--- %s Tree is EMPTY", __func__);
 455                 return BEFS_BT_EMPTY;
 456         } else if (res == BEFS_ERR) {
 457                 goto error_alloc;
 458         }
 459
 460         /* find the leaf node containing the key_no key */
 461
 462         while (key_sum + this_node->head.all_key_count <= key_no) {
 463
 464                 /* no more nodes to look in: key_no is too large */
 465                 if (this_node->head.right == BEFS_BT_INVAL) {
 466                         *keysize = 0;
 467                         *value = 0;
 468                         befs_debug(sb,
 469                                    "<--- %s END of keys at %llu", __func__,
 470                                    (unsigned long long)
 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, "%s failed to read node at %llu",
 482                                   __func__, (unsigned long long)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 [%llu,%d]: keysize %d",
 496                    (long long unsigned int)node_off, (int)cur_key,
 497                    (int)keylen);
 498
 499         if (bufsize < keylen + 1) {
 500                 befs_error(sb, "%s keybuf too small (%zu) "
 501                            "for key of size %d", __func__, bufsize, keylen);
 502                 brelse(this_node->bh);
 503                 goto error_alloc;
 504         }
 505
 506         strlcpy(keybuf, keystart, keylen + 1);
 507         *value = fs64_to_cpu(sb, valarray[cur_key]);
 508         *keysize = keylen;
 509
 510         befs_debug(sb, "Read [%llu,%d]: Key \"%.*s\", Value %llu", node_off,
 511                    cur_key, keylen, keybuf, *value);
 512
 513         brelse(this_node->bh);
 514         kfree(this_node);
 515
 516         befs_debug(sb, "<--- %s", __func__);
 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, "<--- %s ERROR", __func__);
 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  * 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, const befs_data_stream *ds,
 546                     befs_btree_super *bt_super,
 547                     struct befs_btree_node *this_node,
 548                     befs_off_t * node_off)
 549 {
 550
 551         befs_debug(sb, "---> %s", __func__);
 552
 553         if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
 554                 befs_error(sb, "%s failed to read "
 555                            "node at %llu", __func__, *node_off);
 556                 goto error;
 557         }
 558         befs_debug(sb, "Seekleaf to root node %llu", *node_off);
 559
 560         if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
 561                 befs_debug(sb, "<--- %s Tree is EMPTY", __func__);
 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, "%s encountered "
 569                                    "an empty interior node: %llu. Using Overflow "
 570                                    "node: %llu", __func__, *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, "%s failed to read "
 579                                    "node at %llu", __func__, *node_off);
 580                         goto error;
 581                 }
 582
 583                 befs_debug(sb, "Seekleaf to child node %llu", *node_off);
 584         }
 585         befs_debug(sb, "Node %llu is a leaf node", *node_off);
 586
 587         return BEFS_OK;
 588
 589       error:
 590         befs_debug(sb, "<--- %s ERROR", __func__);
 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  */
 601 static int
 602 befs_leafnode(struct 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  */
 624 static fs16 *
 625 befs_bt_keylen_index(struct 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  */
 645 static fs64 *
 646 befs_bt_valarray(struct 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  */
 661 static char *
 662 befs_bt_keydata(struct 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  */
 677 static char *
 678 befs_bt_get_key(struct super_block *sb, struct 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  * @keylen2: 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  */
 714 static int
 715 befs_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
 727 static int
 728 btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
 729 {
 730         return *(int32_t *) key1 - *(int32_t *) key2;
 731 }
 732
 733 static int
 734 btree_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 }
 744 static int
 745 btree_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
 755 static int
 756 btree_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
 767 static int
 768 btree_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
 777 static int
 778 btree_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