xref: /openbmc/linux/fs/befs/btree.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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  */
82 typedef 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 */
89 static const befs_off_t befs_bt_inval = 0xffffffffffffffffULL;
90 
91 /* local functions */
92 static 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 
97 static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
98 			      befs_btree_super * sup);
99 
100 static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
101 			     befs_btree_node * node, befs_off_t node_off);
102 
103 static int befs_leafnode(befs_btree_node * node);
104 
105 static u16 *befs_bt_keylen_index(befs_btree_node * node);
106 
107 static befs_off_t *befs_bt_valarray(befs_btree_node * node);
108 
109 static char *befs_bt_keydata(befs_btree_node * node);
110 
111 static int befs_find_key(struct super_block *sb, befs_btree_node * node,
112 			 const char *findkey, befs_off_t * value);
113 
114 static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
115 			     int index, u16 * keylen);
116 
117 static 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  */
134 static int
135 befs_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 
193 static int
194 befs_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  */
247 int
248 befs_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  */
336 static int
337 befs_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  */
416 int
417 befs_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  */
546 static int
547 befs_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  */
602 static int
603 befs_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  */
625 static u16 *
626 befs_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  */
646 static befs_off_t *
647 befs_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  */
662 static char *
663 befs_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  */
678 static char *
679 befs_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  */
715 static int
716 befs_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
728 static int
729 btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
730 {
731 	return *(int32_t *) key1 - *(int32_t *) key2;
732 }
733 
734 static int
735 btree_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 }
745 static int
746 btree_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 
756 static int
757 btree_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 
768 static int
769 btree_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 
778 static int
779 btree_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
789