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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 withing
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#include "endian.h"
34
35/*
36 * The btree functions in this file are built on top of the
37 * datastream.c interface, which is in turn built on top of the
38 * io.c interface.
39 */
40
41/* Befs B+tree structure:
42 *
43 * The first thing in the tree is the tree superblock. It tells you
44 * all kinds of useful things about the tree, like where the rootnode
45 * is located, and the size of the nodes (always 1024 with current version
46 * of BeOS).
47 *
48 * The rest of the tree consists of a series of nodes. Nodes contain a header
49 * (struct befs_btree_nodehead), the packed key data, an array of shorts
50 * containing the ending offsets for each of the keys, and an array of
51 * befs_off_t values. In interior nodes, the keys are the ending keys for
52 * the childnode they point to, and the values are offsets into the
53 * datastream containing the tree.
54 */
55
56/* Note:
57 *
58 * The book states 2 confusing things about befs b+trees. First,
59 * it states that the overflow field of node headers is used by internal nodes
60 * to point to another node that "effectively continues this one". Here is what
61 * I believe that means. Each key in internal nodes points to another node that
62 * contains key values less than itself. Inspection reveals that the last key
63 * in the internal node is not the last key in the index. Keys that are
64 * greater than the last key in the internal node go into the overflow node.
65 * I imagine there is a performance reason for this.
66 *
67 * Second, it states that the header of a btree node is sufficient to
68 * distinguish internal nodes from leaf nodes. Without saying exactly how.
69 * After figuring out the first, it becomes obvious that internal nodes have
70 * overflow nodes and leafnodes do not.
71 */
72
73/*
74 * Currently, this code is only good for directory B+trees.
75 * In order to be used for other BFS indexes, it needs to be extended to handle
76 * duplicate keys and non-string keytypes (int32, int64, float, double).
77 */
78
79/*
80 * In memory structure of each btree node
81 */
82typedef struct {
83 befs_btree_nodehead head; /* head of node converted to cpu byteorder */
84 struct buffer_head *bh;
85 befs_btree_nodehead *od_node; /* on disk node */
86} befs_btree_node;
87
88/* local constants */
89static const befs_off_t befs_bt_inval = 0xffffffffffffffffULL;
90
91/* local functions */
92static int befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
93 befs_btree_super * bt_super,
94 befs_btree_node * this_node,
95 befs_off_t * node_off);
96
97static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
98 befs_btree_super * sup);
99
100static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
101 befs_btree_node * node, befs_off_t node_off);
102
103static int befs_leafnode(befs_btree_node * node);
104
105static u16 *befs_bt_keylen_index(befs_btree_node * node);
106
107static befs_off_t *befs_bt_valarray(befs_btree_node * node);
108
109static char *befs_bt_keydata(befs_btree_node * node);
110
111static int befs_find_key(struct super_block *sb, befs_btree_node * node,
112 const char *findkey, befs_off_t * value);
113
114static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
115 int index, u16 * keylen);
116
117static int befs_compare_strings(const void *key1, int keylen1,
118 const void *key2, int keylen2);
119
120/**
121 * befs_bt_read_super - read in btree superblock convert to cpu byteorder
122 * @sb: Filesystem superblock
123 * @ds: Datastream to read from
124 * @sup: Buffer in which to place the btree superblock
125 *
126 * Calls befs_read_datastream to read in the btree superblock and
127 * makes sure it is in cpu byteorder, byteswapping if necessary.
128 *
129 * On success, returns BEFS_OK and *@sup contains the btree superblock,
130 * in cpu byte order.
131 *
132 * On failure, BEFS_ERR is returned.
133 */
134static int
135befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
136 befs_btree_super * sup)
137{
138 struct buffer_head *bh = NULL;
139 befs_btree_super *od_sup = NULL;
140
141 befs_debug(sb, "---> befs_btree_read_super()");
142
143 bh = befs_read_datastream(sb, ds, 0, NULL);
144
145 if (!bh) {
146 befs_error(sb, "Couldn't read index header.");
147 goto error;
148 }
149 od_sup = (befs_btree_super *) bh->b_data;
150 befs_dump_index_entry(sb, od_sup);
151
152 sup->magic = fs32_to_cpu(sb, od_sup->magic);
153 sup->node_size = fs32_to_cpu(sb, od_sup->node_size);
154 sup->max_depth = fs32_to_cpu(sb, od_sup->max_depth);
155 sup->data_type = fs32_to_cpu(sb, od_sup->data_type);
156 sup->root_node_ptr = fs64_to_cpu(sb, od_sup->root_node_ptr);
157 sup->free_node_ptr = fs64_to_cpu(sb, od_sup->free_node_ptr);
158 sup->max_size = fs64_to_cpu(sb, od_sup->max_size);
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, "<--- befs_btree_read_super()");
167 return BEFS_OK;
168
169 error:
170 befs_debug(sb, "<--- befs_btree_read_super() ERROR");
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 called first
185 * time. 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
193static int
194befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
195 befs_btree_node * node, befs_off_t node_off)
196{
197 uint off = 0;
198
199 befs_debug(sb, "---> befs_bt_read_node()");
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, "befs_bt_read_node() failed to read "
207 "node at %Lu", node_off);
208 befs_debug(sb, "<--- befs_bt_read_node() ERROR");
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, "<--- befs_btree_read_node()");
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 sucess, 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 * actuall value stored with the key.
246 */
247int
248befs_btree_find(struct super_block *sb, befs_data_stream * ds,
249 const char *key, befs_off_t * value)
250{
251 befs_btree_node *this_node = NULL;
252 befs_btree_super bt_super;
253 befs_off_t node_off;
254 int res;
255
256 befs_debug(sb, "---> befs_btree_find() Key: %s", 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 = (befs_btree_node *) kmalloc(sizeof (befs_btree_node),
265 GFP_NOFS);
266 if (!this_node) {
267 befs_error(sb, "befs_btree_find() failed to allocate %u "
268 "bytes of memory", sizeof (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 %Lu", 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 (res == BEFS_BT_NOT_FOUND)
285 node_off = this_node->head.overflow;
286 /* if no match, go to overflow node */
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 %Lu", node_off);
290 goto error_alloc;
291 }
292 }
293
294 /* at the correct leaf node now */
295
296 res = befs_find_key(sb, this_node, key, value);
297
298 brelse(this_node->bh);
299 kfree(this_node);
300
301 if (res != BEFS_BT_MATCH) {
302 befs_debug(sb, "<--- befs_btree_find() Key %s not found", key);
303 *value = 0;
304 return BEFS_BT_NOT_FOUND;
305 }
306 befs_debug(sb, "<--- befs_btree_find() Found key %s, value %Lu",
307 key, *value);
308 return BEFS_OK;
309
310 error_alloc:
311 kfree(this_node);
312 error:
313 *value = 0;
314 befs_debug(sb, "<--- befs_btree_find() ERROR");
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 * @key: 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 no exact match, finds first key in node that is greater
327 * (alphabetically) than the search key and returns BEFS_BT_PARMATCH
328 * (for partial match, I guess). Can you think of something better to
329 * call it?
330 *
331 * If no key was a match or greater than the search key, return
332 * BEFS_BT_NOT_FOUND.
333 *
334 * Use binary search instead of a linear.
335 */
336static int
337befs_find_key(struct super_block *sb, befs_btree_node * node,
338 const char *findkey, befs_off_t * value)
339{
340 int first, last, mid;
341 int eq;
342 u16 keylen;
343 int findkey_len;
344 char *thiskey;
345 befs_off_t *valarray;
346
347 befs_debug(sb, "---> befs_find_key() %s", findkey);
348
349 *value = 0;
350
351 findkey_len = strlen(findkey);
352
353 /* if node can not contain key, just skeep this node */
354 last = node->head.all_key_count - 1;
355 thiskey = befs_bt_get_key(sb, node, last, &keylen);
356
357 eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
358 if (eq < 0) {
359 befs_debug(sb, "<--- befs_find_key() %s not found", findkey);
360 return BEFS_BT_NOT_FOUND;
361 }
362
363 valarray = befs_bt_valarray(node);
364
365 /* simple binary search */
366 first = 0;
367 mid = 0;
368 while (last >= first) {
369 mid = (last + first) / 2;
370 befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
371 mid);
372 thiskey = befs_bt_get_key(sb, node, mid, &keylen);
373 eq = befs_compare_strings(thiskey, keylen, findkey,
374 findkey_len);
375
376 if (eq == 0) {
377 befs_debug(sb, "<--- befs_find_key() found %s at %d",
378 thiskey, mid);
379
380 *value = fs64_to_cpu(sb, valarray[mid]);
381 return BEFS_BT_MATCH;
382 }
383 if (eq > 0)
384 last = mid - 1;
385 else
386 first = mid + 1;
387 }
388 if (eq < 0)
389 *value = fs64_to_cpu(sb, valarray[mid + 1]);
390 else
391 *value = fs64_to_cpu(sb, valarray[mid]);
392 befs_debug(sb, "<--- befs_find_key() found %s at %d", thiskey, mid);
393 return BEFS_BT_PARMATCH;
394}
395
396/**
397 * befs_btree_read - Traverse leafnodes of a btree
398 * @sb: Filesystem superblock
399 * @ds: Datastream containing btree
400 * @key_no: Key number (alphabetical order) of key to read
401 * @bufsize: Size of the buffer to return key in
402 * @keybuf: Pointer to a buffer to put the key in
403 * @keysize: Length of the returned key
404 * @value: Value stored with the returned key
405 *
406 * Heres how it works: Key_no is the index of the key/value pair to
407 * return in keybuf/value.
408 * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is
409 * the number of charecters in the key (just a convenience).
410 *
411 * Algorithm:
412 * Get the first leafnode of the tree. See if the requested key is in that
413 * node. If not, follow the node->right link to the next leafnode. Repeat
414 * until the (key_no)th key is found or the tree is out of keys.
415 */
416int
417befs_btree_read(struct super_block *sb, befs_data_stream * ds,
418 loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
419 befs_off_t * value)
420{
421 befs_btree_node *this_node;
422 befs_btree_super bt_super;
423 befs_off_t node_off = 0;
424 int cur_key;
425 befs_off_t *valarray;
426 char *keystart;
427 u16 keylen;
428 int res;
429
430 uint key_sum = 0;
431
432 befs_debug(sb, "---> befs_btree_read()");
433
434 if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
435 befs_error(sb,
436 "befs_btree_read() failed to read index superblock");
437 goto error;
438 }
439
440 if ((this_node = (befs_btree_node *)
441 kmalloc(sizeof (befs_btree_node), GFP_NOFS)) == NULL) {
442 befs_error(sb, "befs_btree_read() failed to allocate %u "
443 "bytes of memory", sizeof (befs_btree_node));
444 goto error;
445 }
446
447 node_off = bt_super.root_node_ptr;
448 this_node->bh = NULL;
449
450 /* seeks down to first leafnode, reads it into this_node */
451 res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
452 if (res == BEFS_BT_EMPTY) {
453 brelse(this_node->bh);
454 kfree(this_node);
455 *value = 0;
456 *keysize = 0;
457 befs_debug(sb, "<--- befs_btree_read() Tree is EMPTY");
458 return BEFS_BT_EMPTY;
459 } else if (res == BEFS_ERR) {
460 goto error_alloc;
461 }
462
463 /* find the leaf node containing the key_no key */
464
465 while (key_sum + this_node->head.all_key_count <= key_no) {
466
467 /* no more nodes to look in: key_no is too large */
468 if (this_node->head.right == befs_bt_inval) {
469 *keysize = 0;
470 *value = 0;
471 befs_debug(sb,
472 "<--- befs_btree_read() END of keys at %Lu",
473 key_sum + this_node->head.all_key_count);
474 brelse(this_node->bh);
475 kfree(this_node);
476 return BEFS_BT_END;
477 }
478
479 key_sum += this_node->head.all_key_count;
480 node_off = this_node->head.right;
481
482 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
483 befs_error(sb, "befs_btree_read() failed to read "
484 "node at %Lu", node_off);
485 goto error_alloc;
486 }
487 }
488
489 /* how many keys into this_node is key_no */
490 cur_key = key_no - key_sum;
491
492 /* get pointers to datastructures within the node body */
493 valarray = befs_bt_valarray(this_node);
494
495 keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
496
497 befs_debug(sb, "Read [%Lu,%d]: keysize %d", node_off, cur_key, keylen);
498
499 if (bufsize < keylen + 1) {
500 befs_error(sb, "befs_btree_read() keybuf too small (%u) "
501 "for key of size %d", bufsize, keylen);
502 brelse(this_node->bh);
503 goto error_alloc;
504 };
505
506 strncpy(keybuf, keystart, keylen);
507 *value = fs64_to_cpu(sb, valarray[cur_key]);
508 *keysize = keylen;
509 keybuf[keylen] = '\0';
510
511 befs_debug(sb, "Read [%Lu,%d]: Key \"%.*s\", Value %Lu", node_off,
512 cur_key, keylen, keybuf, *value);
513
514 brelse(this_node->bh);
515 kfree(this_node);
516
517 befs_debug(sb, "<--- befs_btree_read()");
518
519 return BEFS_OK;
520
521 error_alloc:
522 kfree(this_node);
523
524 error:
525 *keysize = 0;
526 *value = 0;
527 befs_debug(sb, "<--- befs_btree_read() ERROR");
528 return BEFS_ERR;
529}
530
531/**
532 * befs_btree_seekleaf - Find the first leafnode in the btree
533 * @sb: Filesystem superblock
534 * @ds: Datastream containing btree
535 * @bt_super: Pointer to the superblock of the btree
536 * @this_node: Buffer to return the leafnode in
537 * @node_off: Pointer to offset of current node within datastream. Modified
538 * by the function.
539 *
540 *
541 * Helper function for btree traverse. Moves the current position to the
542 * start of the first leaf node.
543 *
544 * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
545 */
546static int
547befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
548 befs_btree_super * bt_super, befs_btree_node * this_node,
549 befs_off_t * node_off)
550{
551
552 befs_debug(sb, "---> befs_btree_seekleaf()");
553
554 if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
555 befs_error(sb, "befs_btree_seekleaf() failed to read "
556 "node at %Lu", *node_off);
557 goto error;
558 }
559 befs_debug(sb, "Seekleaf to root node %Lu", *node_off);
560
561 if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
562 befs_debug(sb, "<--- befs_btree_seekleaf() Tree is EMPTY");
563 return BEFS_BT_EMPTY;
564 }
565
566 while (!befs_leafnode(this_node)) {
567
568 if (this_node->head.all_key_count == 0) {
569 befs_debug(sb, "befs_btree_seekleaf() encountered "
570 "an empty interior node: %Lu. Using Overflow "
571 "node: %Lu", *node_off,
572 this_node->head.overflow);
573 *node_off = this_node->head.overflow;
574 } else {
575 befs_off_t *valarray = befs_bt_valarray(this_node);
576 *node_off = fs64_to_cpu(sb, valarray[0]);
577 }
578 if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
579 befs_error(sb, "befs_btree_seekleaf() failed to read "
580 "node at %Lu", *node_off);
581 goto error;
582 }
583
584 befs_debug(sb, "Seekleaf to child node %Lu", *node_off);
585 }
586 befs_debug(sb, "Node %Lu is a leaf node", *node_off);
587
588 return BEFS_OK;
589
590 error:
591 befs_debug(sb, "<--- befs_btree_seekleaf() ERROR");
592 return BEFS_ERR;
593}
594
595/**
596 * befs_leafnode - Determine if the btree node is a leaf node or an
597 * interior node
598 * @node: Pointer to node structure to test
599 *
600 * Return 1 if leaf, 0 if interior
601 */
602static int
603befs_leafnode(befs_btree_node * node)
604{
605 /* all interior nodes (and only interior nodes) have an overflow node */
606 if (node->head.overflow == befs_bt_inval)
607 return 1;
608 else
609 return 0;
610}
611
612/**
613 * befs_bt_keylen_index - Finds start of keylen index in a node
614 * @node: Pointer to the node structure to find the keylen index within
615 *
616 * Returns a pointer to the start of the key length index array
617 * of the B+tree node *@node
618 *
619 * "The length of all the keys in the node is added to the size of the
620 * header and then rounded up to a multiple of four to get the beginning
621 * of the key length index" (p.88, practical filesystem design).
622 *
623 * Except that rounding up to 8 works, and rounding up to 4 doesn't.
624 */
625static u16 *
626befs_bt_keylen_index(befs_btree_node * node)
627{
628 const int keylen_align = 8;
629 unsigned long int off =
630 (sizeof (befs_btree_nodehead) + node->head.all_key_length);
631 ulong tmp = off % keylen_align;
632
633 if (tmp)
634 off += keylen_align - tmp;
635
636 return (u16 *) ((void *) node->od_node + off);
637}
638
639/**
640 * befs_bt_valarray - Finds the start of value array in a node
641 * @node: Pointer to the node structure to find the value array within
642 *
643 * Returns a pointer to the start of the value array
644 * of the node pointed to by the node header
645 */
646static befs_off_t *
647befs_bt_valarray(befs_btree_node * node)
648{
649 void *keylen_index_start = (void *) befs_bt_keylen_index(node);
650 size_t keylen_index_size = node->head.all_key_count * sizeof (u16);
651
652 return (befs_off_t *) (keylen_index_start + keylen_index_size);
653}
654
655/**
656 * befs_bt_keydata - Finds start of keydata array in a node
657 * @node: Pointer to the node structure to find the keydata array within
658 *
659 * Returns a pointer to the start of the keydata array
660 * of the node pointed to by the node header
661 */
662static char *
663befs_bt_keydata(befs_btree_node * node)
664{
665 return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
666}
667
668/**
669 * befs_bt_get_key - returns a pointer to the start of a key
670 * @sb: filesystem superblock
671 * @node: node in which to look for the key
672 * @index: the index of the key to get
673 * @keylen: modified to be the length of the key at @index
674 *
675 * Returns a valid pointer into @node on success.
676 * Returns NULL on failure (bad input) and sets *@keylen = 0
677 */
678static char *
679befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
680 int index, u16 * keylen)
681{
682 int prev_key_end;
683 char *keystart;
684 u16 *keylen_index;
685
686 if (index < 0 || index > node->head.all_key_count) {
687 *keylen = 0;
688 return NULL;
689 }
690
691 keystart = befs_bt_keydata(node);
692 keylen_index = befs_bt_keylen_index(node);
693
694 if (index == 0)
695 prev_key_end = 0;
696 else
697 prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
698
699 *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
700
701 return keystart + prev_key_end;
702}
703
704/**
705 * befs_compare_strings - compare two strings
706 * @key1: pointer to the first key to be compared
707 * @keylen1: length in bytes of key1
708 * @key2: pointer to the second key to be compared
709 * @kelen2: length in bytes of key2
710 *
711 * Returns 0 if @key1 and @key2 are equal.
712 * Returns >0 if @key1 is greater.
713 * Returns <0 if @key2 is greater..
714 */
715static int
716befs_compare_strings(const void *key1, int keylen1,
717 const void *key2, int keylen2)
718{
719 int len = min_t(int, keylen1, keylen2);
720 int result = strncmp(key1, key2, len);
721 if (result == 0)
722 result = keylen1 - keylen2;
723 return result;
724}
725
726/* These will be used for non-string keyed btrees */
727#if 0
728static int
729btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
730{
731 return *(int32_t *) key1 - *(int32_t *) key2;
732}
733
734static int
735btree_compare_uint32(cont void *key1, int keylen1,
736 const void *key2, int keylen2)
737{
738 if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
739 return 0;
740 else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
741 return 1;
742
743 return -1;
744}
745static int
746btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
747{
748 if (*(int64_t *) key1 == *(int64_t *) key2)
749 return 0;
750 else if (*(int64_t *) key1 > *(int64_t *) key2)
751 return 1;
752
753 return -1;
754}
755
756static int
757btree_compare_uint64(cont void *key1, int keylen1,
758 const void *key2, int keylen2)
759{
760 if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
761 return 0;
762 else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
763 return 1;
764
765 return -1;
766}
767
768static int
769btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
770{
771 float result = *(float *) key1 - *(float *) key2;
772 if (result == 0.0f)
773 return 0;
774
775 return (result < 0.0f) ? -1 : 1;
776}
777
778static int
779btree_compare_double(cont void *key1, int keylen1,
780 const void *key2, int keylen2)
781{
782 double result = *(double *) key1 - *(double *) key2;
783 if (result == 0.0)
784 return 0;
785
786 return (result < 0.0) ? -1 : 1;
787}
788#endif //0