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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
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 */
81struct 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 */
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 struct 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 struct befs_btree_node *node,
101 befs_off_t node_off);
102
103static int befs_leafnode(struct befs_btree_node *node);
104
105static fs16 *befs_bt_keylen_index(struct befs_btree_node *node);
106
107static fs64 *befs_bt_valarray(struct befs_btree_node *node);
108
109static char *befs_bt_keydata(struct befs_btree_node *node);
110
111static int befs_find_key(struct super_block *sb,
112 struct befs_btree_node *node,
113 const char *findkey, befs_off_t * value);
114
115static char *befs_bt_get_key(struct super_block *sb,
116 struct befs_btree_node *node,
117 int index, u16 * keylen);
118
119static 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 */
136static int
137befs_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
195static int
196befs_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 */
249int
250befs_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 */
338static int
339befs_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 */
418int
419befs_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 */
550static int
551befs_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 */
607static int
608befs_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 */
630static fs16 *
631befs_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 */
651static fs64 *
652befs_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 */
667static char *
668befs_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 */
683static char *
684befs_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 */
720static int
721befs_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
733static int
734btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
735{
736 return *(int32_t *) key1 - *(int32_t *) key2;
737}
738
739static int
740btree_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}
750static int
751btree_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
761static int
762btree_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
773static int
774btree_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
783static int
784btree_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