xref: /openbmc/linux/fs/befs/btree.c (revision 73919280)
1 /*
2  * linux/fs/befs/btree.c
3  *
4  * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com>
5  *
6  * Licensed under the GNU GPL. See the file COPYING for details.
7  *
8  * 2002-02-05: Sergey S. Kostyliov added binary search within
9  * 		btree nodes.
10  *
11  * Many thanks to:
12  *
13  * Dominic Giampaolo, author of "Practical File System
14  * Design with the Be File System", for such a helpful book.
15  *
16  * Marcus J. Ranum, author of the b+tree package in
17  * comp.sources.misc volume 10. This code is not copied from that
18  * work, but it is partially based on it.
19  *
20  * Makoto Kato, author of the original BeFS for linux filesystem
21  * driver.
22  */
23 
24 #include <linux/kernel.h>
25 #include <linux/string.h>
26 #include <linux/slab.h>
27 #include <linux/mm.h>
28 #include <linux/buffer_head.h>
29 
30 #include "befs.h"
31 #include "btree.h"
32 #include "datastream.h"
33 
34 /*
35  * The btree functions in this file are built on top of the
36  * datastream.c interface, which is in turn built on top of the
37  * io.c interface.
38  */
39 
40 /* Befs B+tree structure:
41  *
42  * The first thing in the tree is the tree superblock. It tells you
43  * all kinds of useful things about the tree, like where the rootnode
44  * is located, and the size of the nodes (always 1024 with current version
45  * of BeOS).
46  *
47  * The rest of the tree consists of a series of nodes. Nodes contain a header
48  * (struct befs_btree_nodehead), the packed key data, an array of shorts
49  * containing the ending offsets for each of the keys, and an array of
50  * befs_off_t values. In interior nodes, the keys are the ending keys for
51  * the childnode they point to, and the values are offsets into the
52  * datastream containing the tree.
53  */
54 
55 /* Note:
56  *
57  * The book states 2 confusing things about befs b+trees. First,
58  * it states that the overflow field of node headers is used by internal nodes
59  * to point to another node that "effectively continues this one". Here is what
60  * I believe that means. Each key in internal nodes points to another node that
61  * contains key values less than itself. Inspection reveals that the last key
62  * in the internal node is not the last key in the index. Keys that are
63  * greater than the last key in the internal node go into the overflow node.
64  * I imagine there is a performance reason for this.
65  *
66  * Second, it states that the header of a btree node is sufficient to
67  * distinguish internal nodes from leaf nodes. Without saying exactly how.
68  * After figuring out the first, it becomes obvious that internal nodes have
69  * overflow nodes and leafnodes do not.
70  */
71 
72 /*
73  * Currently, this code is only good for directory B+trees.
74  * In order to be used for other BFS indexes, it needs to be extended to handle
75  * duplicate keys and non-string keytypes (int32, int64, float, double).
76  */
77 
78 /*
79  * In memory structure of each btree node
80  */
81 struct befs_btree_node {
82 	befs_host_btree_nodehead head;	/* head of node converted to cpu byteorder */
83 	struct buffer_head *bh;
84 	befs_btree_nodehead *od_node;	/* on disk node */
85 };
86 
87 /* local constants */
88 static const befs_off_t BEFS_BT_INVAL = 0xffffffffffffffffULL;
89 
90 /* local functions */
91 static int befs_btree_seekleaf(struct super_block *sb, const befs_data_stream *ds,
92 			       befs_btree_super * bt_super,
93 			       struct befs_btree_node *this_node,
94 			       befs_off_t * node_off);
95 
96 static int befs_bt_read_super(struct super_block *sb, const befs_data_stream *ds,
97 			      befs_btree_super * sup);
98 
99 static int befs_bt_read_node(struct super_block *sb, const befs_data_stream *ds,
100 			     struct befs_btree_node *node,
101 			     befs_off_t node_off);
102 
103 static int befs_leafnode(struct befs_btree_node *node);
104 
105 static fs16 *befs_bt_keylen_index(struct befs_btree_node *node);
106 
107 static fs64 *befs_bt_valarray(struct befs_btree_node *node);
108 
109 static char *befs_bt_keydata(struct befs_btree_node *node);
110 
111 static int befs_find_key(struct super_block *sb,
112 			 struct befs_btree_node *node,
113 			 const char *findkey, befs_off_t * value);
114 
115 static char *befs_bt_get_key(struct super_block *sb,
116 			     struct befs_btree_node *node,
117 			     int index, u16 * keylen);
118 
119 static int befs_compare_strings(const void *key1, int keylen1,
120 				const void *key2, int keylen2);
121 
122 /**
123  * befs_bt_read_super() - read in btree superblock convert to cpu byteorder
124  * @sb:        Filesystem superblock
125  * @ds:        Datastream to read from
126  * @sup:       Buffer in which to place the btree superblock
127  *
128  * Calls befs_read_datastream to read in the btree superblock and
129  * makes sure it is in cpu byteorder, byteswapping if necessary.
130  * Return: BEFS_OK on success and if *@sup contains the btree superblock in cpu
131  * byte order. Otherwise return BEFS_ERR on error.
132  */
133 static int
befs_bt_read_super(struct super_block * sb,const befs_data_stream * ds,befs_btree_super * sup)134 befs_bt_read_super(struct super_block *sb, const befs_data_stream *ds,
135 		   befs_btree_super * sup)
136 {
137 	struct buffer_head *bh;
138 	befs_disk_btree_super *od_sup;
139 
140 	befs_debug(sb, "---> %s", __func__);
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 
157 	brelse(bh);
158 	if (sup->magic != BEFS_BTREE_MAGIC) {
159 		befs_error(sb, "Index header has bad magic.");
160 		goto error;
161 	}
162 
163 	befs_debug(sb, "<--- %s", __func__);
164 	return BEFS_OK;
165 
166       error:
167 	befs_debug(sb, "<--- %s ERROR", __func__);
168 	return BEFS_ERR;
169 }
170 
171 /**
172  * befs_bt_read_node - read in btree node and convert to cpu byteorder
173  * @sb: Filesystem superblock
174  * @ds: Datastream to read from
175  * @node: Buffer in which to place the btree node
176  * @node_off: Starting offset (in bytes) of the node in @ds
177  *
178  * Calls befs_read_datastream to read in the indicated btree node and
179  * makes sure its header fields are in cpu byteorder, byteswapping if
180  * necessary.
181  * Note: node->bh must be NULL when this function is called the first time.
182  * Don't forget brelse(node->bh) after last call.
183  *
184  * On success, returns BEFS_OK and *@node contains the btree node that
185  * starts at @node_off, with the node->head fields in cpu byte order.
186  *
187  * On failure, BEFS_ERR is returned.
188  */
189 
190 static int
befs_bt_read_node(struct super_block * sb,const befs_data_stream * ds,struct befs_btree_node * node,befs_off_t node_off)191 befs_bt_read_node(struct super_block *sb, const befs_data_stream *ds,
192 		  struct befs_btree_node *node, befs_off_t node_off)
193 {
194 	uint off = 0;
195 
196 	befs_debug(sb, "---> %s", __func__);
197 
198 	if (node->bh)
199 		brelse(node->bh);
200 
201 	node->bh = befs_read_datastream(sb, ds, node_off, &off);
202 	if (!node->bh) {
203 		befs_error(sb, "%s failed to read "
204 			   "node at %llu", __func__, node_off);
205 		befs_debug(sb, "<--- %s ERROR", __func__);
206 
207 		return BEFS_ERR;
208 	}
209 	node->od_node =
210 	    (befs_btree_nodehead *) ((void *) node->bh->b_data + off);
211 
212 	befs_dump_index_node(sb, node->od_node);
213 
214 	node->head.left = fs64_to_cpu(sb, node->od_node->left);
215 	node->head.right = fs64_to_cpu(sb, node->od_node->right);
216 	node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow);
217 	node->head.all_key_count =
218 	    fs16_to_cpu(sb, node->od_node->all_key_count);
219 	node->head.all_key_length =
220 	    fs16_to_cpu(sb, node->od_node->all_key_length);
221 
222 	befs_debug(sb, "<--- %s", __func__);
223 	return BEFS_OK;
224 }
225 
226 /**
227  * befs_btree_find - Find a key in a befs B+tree
228  * @sb: Filesystem superblock
229  * @ds: Datastream containing btree
230  * @key: Key string to lookup in btree
231  * @value: Value stored with @key
232  *
233  * On success, returns BEFS_OK and sets *@value to the value stored
234  * with @key (usually the disk block number of an inode).
235  *
236  * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND.
237  *
238  * Algorithm:
239  *   Read the superblock and rootnode of the b+tree.
240  *   Drill down through the interior nodes using befs_find_key().
241  *   Once at the correct leaf node, use befs_find_key() again to get the
242  *   actual value stored with the key.
243  */
244 int
befs_btree_find(struct super_block * sb,const befs_data_stream * ds,const char * key,befs_off_t * value)245 befs_btree_find(struct super_block *sb, const befs_data_stream *ds,
246 		const char *key, befs_off_t * value)
247 {
248 	struct befs_btree_node *this_node;
249 	befs_btree_super bt_super;
250 	befs_off_t node_off;
251 	int res;
252 
253 	befs_debug(sb, "---> %s Key: %s", __func__, key);
254 
255 	if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
256 		befs_error(sb,
257 			   "befs_btree_find() failed to read index superblock");
258 		goto error;
259 	}
260 
261 	this_node = kmalloc(sizeof(struct befs_btree_node),
262 						GFP_NOFS);
263 	if (!this_node) {
264 		befs_error(sb, "befs_btree_find() failed to allocate %zu "
265 			   "bytes of memory", sizeof(struct befs_btree_node));
266 		goto error;
267 	}
268 
269 	this_node->bh = NULL;
270 
271 	/* read in root node */
272 	node_off = bt_super.root_node_ptr;
273 	if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
274 		befs_error(sb, "befs_btree_find() failed to read "
275 			   "node at %llu", node_off);
276 		goto error_alloc;
277 	}
278 
279 	while (!befs_leafnode(this_node)) {
280 		res = befs_find_key(sb, this_node, key, &node_off);
281 		/* if no key set, try the overflow node */
282 		if (res == BEFS_BT_OVERFLOW)
283 			node_off = this_node->head.overflow;
284 		if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
285 			befs_error(sb, "befs_btree_find() failed to read "
286 				   "node at %llu", node_off);
287 			goto error_alloc;
288 		}
289 	}
290 
291 	/* at a leaf node now, check if it is correct */
292 	res = befs_find_key(sb, this_node, key, value);
293 
294 	brelse(this_node->bh);
295 	kfree(this_node);
296 
297 	if (res != BEFS_BT_MATCH) {
298 		befs_error(sb, "<--- %s Key %s not found", __func__, key);
299 		befs_debug(sb, "<--- %s ERROR", __func__);
300 		*value = 0;
301 		return BEFS_BT_NOT_FOUND;
302 	}
303 	befs_debug(sb, "<--- %s Found key %s, value %llu", __func__,
304 		   key, *value);
305 	return BEFS_OK;
306 
307       error_alloc:
308 	kfree(this_node);
309       error:
310 	*value = 0;
311 	befs_debug(sb, "<--- %s ERROR", __func__);
312 	return BEFS_ERR;
313 }
314 
315 /**
316  * befs_find_key - Search for a key within a node
317  * @sb: Filesystem superblock
318  * @node: Node to find the key within
319  * @findkey: Keystring to search for
320  * @value: If key is found, the value stored with the key is put here
321  *
322  * Finds exact match if one exists, and returns BEFS_BT_MATCH.
323  * If there is no match and node's value array is too small for key, return
324  * BEFS_BT_OVERFLOW.
325  * If no match and node should countain this key, return BEFS_BT_NOT_FOUND.
326  *
327  * Uses binary search instead of a linear.
328  */
329 static int
befs_find_key(struct super_block * sb,struct befs_btree_node * node,const char * findkey,befs_off_t * value)330 befs_find_key(struct super_block *sb, struct befs_btree_node *node,
331 	      const char *findkey, befs_off_t * value)
332 {
333 	int first, last, mid;
334 	int eq;
335 	u16 keylen;
336 	int findkey_len;
337 	char *thiskey;
338 	fs64 *valarray;
339 
340 	befs_debug(sb, "---> %s %s", __func__, findkey);
341 
342 	findkey_len = strlen(findkey);
343 
344 	/* if node can not contain key, just skip this node */
345 	last = node->head.all_key_count - 1;
346 	thiskey = befs_bt_get_key(sb, node, last, &keylen);
347 
348 	eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
349 	if (eq < 0) {
350 		befs_debug(sb, "<--- node can't contain %s", findkey);
351 		return BEFS_BT_OVERFLOW;
352 	}
353 
354 	valarray = befs_bt_valarray(node);
355 
356 	/* simple binary search */
357 	first = 0;
358 	mid = 0;
359 	while (last >= first) {
360 		mid = (last + first) / 2;
361 		befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
362 			   mid);
363 		thiskey = befs_bt_get_key(sb, node, mid, &keylen);
364 		eq = befs_compare_strings(thiskey, keylen, findkey,
365 					  findkey_len);
366 
367 		if (eq == 0) {
368 			befs_debug(sb, "<--- %s found %s at %d",
369 				   __func__, thiskey, mid);
370 
371 			*value = fs64_to_cpu(sb, valarray[mid]);
372 			return BEFS_BT_MATCH;
373 		}
374 		if (eq > 0)
375 			last = mid - 1;
376 		else
377 			first = mid + 1;
378 	}
379 
380 	/* return an existing value so caller can arrive to a leaf node */
381 	if (eq < 0)
382 		*value = fs64_to_cpu(sb, valarray[mid + 1]);
383 	else
384 		*value = fs64_to_cpu(sb, valarray[mid]);
385 	befs_error(sb, "<--- %s %s not found", __func__, findkey);
386 	befs_debug(sb, "<--- %s ERROR", __func__);
387 	return BEFS_BT_NOT_FOUND;
388 }
389 
390 /**
391  * befs_btree_read - Traverse leafnodes of a btree
392  * @sb: Filesystem superblock
393  * @ds: Datastream containing btree
394  * @key_no: Key number (alphabetical order) of key to read
395  * @bufsize: Size of the buffer to return key in
396  * @keybuf: Pointer to a buffer to put the key in
397  * @keysize: Length of the returned key
398  * @value: Value stored with the returned key
399  *
400  * Here's how it works: Key_no is the index of the key/value pair to
401  * return in keybuf/value.
402  * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is
403  * the number of characters in the key (just a convenience).
404  *
405  * Algorithm:
406  *   Get the first leafnode of the tree. See if the requested key is in that
407  *   node. If not, follow the node->right link to the next leafnode. Repeat
408  *   until the (key_no)th key is found or the tree is out of keys.
409  */
410 int
befs_btree_read(struct super_block * sb,const befs_data_stream * ds,loff_t key_no,size_t bufsize,char * keybuf,size_t * keysize,befs_off_t * value)411 befs_btree_read(struct super_block *sb, const befs_data_stream *ds,
412 		loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
413 		befs_off_t * value)
414 {
415 	struct befs_btree_node *this_node;
416 	befs_btree_super bt_super;
417 	befs_off_t node_off;
418 	int cur_key;
419 	fs64 *valarray;
420 	char *keystart;
421 	u16 keylen;
422 	int res;
423 
424 	uint key_sum = 0;
425 
426 	befs_debug(sb, "---> %s", __func__);
427 
428 	if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
429 		befs_error(sb,
430 			   "befs_btree_read() failed to read index superblock");
431 		goto error;
432 	}
433 
434 	this_node = kmalloc(sizeof(struct befs_btree_node), GFP_NOFS);
435 	if (this_node == NULL) {
436 		befs_error(sb, "befs_btree_read() failed to allocate %zu "
437 			   "bytes of memory", sizeof(struct befs_btree_node));
438 		goto error;
439 	}
440 
441 	node_off = bt_super.root_node_ptr;
442 	this_node->bh = NULL;
443 
444 	/* seeks down to first leafnode, reads it into this_node */
445 	res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
446 	if (res == BEFS_BT_EMPTY) {
447 		brelse(this_node->bh);
448 		kfree(this_node);
449 		*value = 0;
450 		*keysize = 0;
451 		befs_debug(sb, "<--- %s Tree is EMPTY", __func__);
452 		return BEFS_BT_EMPTY;
453 	} else if (res == BEFS_ERR) {
454 		goto error_alloc;
455 	}
456 
457 	/* find the leaf node containing the key_no key */
458 
459 	while (key_sum + this_node->head.all_key_count <= key_no) {
460 
461 		/* no more nodes to look in: key_no is too large */
462 		if (this_node->head.right == BEFS_BT_INVAL) {
463 			*keysize = 0;
464 			*value = 0;
465 			befs_debug(sb,
466 				   "<--- %s END of keys at %llu", __func__,
467 				   (unsigned long long)
468 				   key_sum + this_node->head.all_key_count);
469 			brelse(this_node->bh);
470 			kfree(this_node);
471 			return BEFS_BT_END;
472 		}
473 
474 		key_sum += this_node->head.all_key_count;
475 		node_off = this_node->head.right;
476 
477 		if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
478 			befs_error(sb, "%s failed to read node at %llu",
479 				  __func__, (unsigned long long)node_off);
480 			goto error_alloc;
481 		}
482 	}
483 
484 	/* how many keys into this_node is key_no */
485 	cur_key = key_no - key_sum;
486 
487 	/* get pointers to datastructures within the node body */
488 	valarray = befs_bt_valarray(this_node);
489 
490 	keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
491 
492 	befs_debug(sb, "Read [%llu,%d]: keysize %d",
493 		   (long long unsigned int)node_off, (int)cur_key,
494 		   (int)keylen);
495 
496 	if (bufsize < keylen + 1) {
497 		befs_error(sb, "%s keybuf too small (%zu) "
498 			   "for key of size %d", __func__, bufsize, keylen);
499 		brelse(this_node->bh);
500 		goto error_alloc;
501 	}
502 
503 	strscpy(keybuf, keystart, keylen + 1);
504 	*value = fs64_to_cpu(sb, valarray[cur_key]);
505 	*keysize = keylen;
506 
507 	befs_debug(sb, "Read [%llu,%d]: Key \"%.*s\", Value %llu", node_off,
508 		   cur_key, keylen, keybuf, *value);
509 
510 	brelse(this_node->bh);
511 	kfree(this_node);
512 
513 	befs_debug(sb, "<--- %s", __func__);
514 
515 	return BEFS_OK;
516 
517       error_alloc:
518 	kfree(this_node);
519 
520       error:
521 	*keysize = 0;
522 	*value = 0;
523 	befs_debug(sb, "<--- %s ERROR", __func__);
524 	return BEFS_ERR;
525 }
526 
527 /**
528  * befs_btree_seekleaf - Find the first leafnode in the btree
529  * @sb: Filesystem superblock
530  * @ds: Datastream containing btree
531  * @bt_super: Pointer to the superblock of the btree
532  * @this_node: Buffer to return the leafnode in
533  * @node_off: Pointer to offset of current node within datastream. Modified
534  * 		by the function.
535  *
536  * Helper function for btree traverse. Moves the current position to the
537  * start of the first leaf node.
538  *
539  * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
540  */
541 static int
befs_btree_seekleaf(struct super_block * sb,const befs_data_stream * ds,befs_btree_super * bt_super,struct befs_btree_node * this_node,befs_off_t * node_off)542 befs_btree_seekleaf(struct super_block *sb, const befs_data_stream *ds,
543 		    befs_btree_super *bt_super,
544 		    struct befs_btree_node *this_node,
545 		    befs_off_t * node_off)
546 {
547 
548 	befs_debug(sb, "---> %s", __func__);
549 
550 	if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
551 		befs_error(sb, "%s failed to read "
552 			   "node at %llu", __func__, *node_off);
553 		goto error;
554 	}
555 	befs_debug(sb, "Seekleaf to root node %llu", *node_off);
556 
557 	if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
558 		befs_debug(sb, "<--- %s Tree is EMPTY", __func__);
559 		return BEFS_BT_EMPTY;
560 	}
561 
562 	while (!befs_leafnode(this_node)) {
563 
564 		if (this_node->head.all_key_count == 0) {
565 			befs_debug(sb, "%s encountered "
566 				   "an empty interior node: %llu. Using Overflow "
567 				   "node: %llu", __func__, *node_off,
568 				   this_node->head.overflow);
569 			*node_off = this_node->head.overflow;
570 		} else {
571 			fs64 *valarray = befs_bt_valarray(this_node);
572 			*node_off = fs64_to_cpu(sb, valarray[0]);
573 		}
574 		if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
575 			befs_error(sb, "%s failed to read "
576 				   "node at %llu", __func__, *node_off);
577 			goto error;
578 		}
579 
580 		befs_debug(sb, "Seekleaf to child node %llu", *node_off);
581 	}
582 	befs_debug(sb, "Node %llu is a leaf node", *node_off);
583 
584 	return BEFS_OK;
585 
586       error:
587 	befs_debug(sb, "<--- %s ERROR", __func__);
588 	return BEFS_ERR;
589 }
590 
591 /**
592  * befs_leafnode - Determine if the btree node is a leaf node or an
593  * interior node
594  * @node: Pointer to node structure to test
595  *
596  * Return 1 if leaf, 0 if interior
597  */
598 static int
befs_leafnode(struct befs_btree_node * node)599 befs_leafnode(struct befs_btree_node *node)
600 {
601 	/* all interior nodes (and only interior nodes) have an overflow node */
602 	if (node->head.overflow == BEFS_BT_INVAL)
603 		return 1;
604 	else
605 		return 0;
606 }
607 
608 /**
609  * befs_bt_keylen_index - Finds start of keylen index in a node
610  * @node: Pointer to the node structure to find the keylen index within
611  *
612  * Returns a pointer to the start of the key length index array
613  * of the B+tree node *@node
614  *
615  * "The length of all the keys in the node is added to the size of the
616  * header and then rounded up to a multiple of four to get the beginning
617  * of the key length index" (p.88, practical filesystem design).
618  *
619  * Except that rounding up to 8 works, and rounding up to 4 doesn't.
620  */
621 static fs16 *
befs_bt_keylen_index(struct befs_btree_node * node)622 befs_bt_keylen_index(struct befs_btree_node *node)
623 {
624 	const int keylen_align = 8;
625 	unsigned long int off =
626 	    (sizeof (befs_btree_nodehead) + node->head.all_key_length);
627 	ulong tmp = off % keylen_align;
628 
629 	if (tmp)
630 		off += keylen_align - tmp;
631 
632 	return (fs16 *) ((void *) node->od_node + off);
633 }
634 
635 /**
636  * befs_bt_valarray - Finds the start of value array in a node
637  * @node: Pointer to the node structure to find the value array within
638  *
639  * Returns a pointer to the start of the value array
640  * of the node pointed to by the node header
641  */
642 static fs64 *
befs_bt_valarray(struct befs_btree_node * node)643 befs_bt_valarray(struct befs_btree_node *node)
644 {
645 	void *keylen_index_start = (void *) befs_bt_keylen_index(node);
646 	size_t keylen_index_size = node->head.all_key_count * sizeof (fs16);
647 
648 	return (fs64 *) (keylen_index_start + keylen_index_size);
649 }
650 
651 /**
652  * befs_bt_keydata - Finds start of keydata array in a node
653  * @node: Pointer to the node structure to find the keydata array within
654  *
655  * Returns a pointer to the start of the keydata array
656  * of the node pointed to by the node header
657  */
658 static char *
befs_bt_keydata(struct befs_btree_node * node)659 befs_bt_keydata(struct befs_btree_node *node)
660 {
661 	return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
662 }
663 
664 /**
665  * befs_bt_get_key - returns a pointer to the start of a key
666  * @sb: filesystem superblock
667  * @node: node in which to look for the key
668  * @index: the index of the key to get
669  * @keylen: modified to be the length of the key at @index
670  *
671  * Returns a valid pointer into @node on success.
672  * Returns NULL on failure (bad input) and sets *@keylen = 0
673  */
674 static char *
befs_bt_get_key(struct super_block * sb,struct befs_btree_node * node,int index,u16 * keylen)675 befs_bt_get_key(struct super_block *sb, struct befs_btree_node *node,
676 		int index, u16 * keylen)
677 {
678 	int prev_key_end;
679 	char *keystart;
680 	fs16 *keylen_index;
681 
682 	if (index < 0 || index > node->head.all_key_count) {
683 		*keylen = 0;
684 		return NULL;
685 	}
686 
687 	keystart = befs_bt_keydata(node);
688 	keylen_index = befs_bt_keylen_index(node);
689 
690 	if (index == 0)
691 		prev_key_end = 0;
692 	else
693 		prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
694 
695 	*keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
696 
697 	return keystart + prev_key_end;
698 }
699 
700 /**
701  * befs_compare_strings - compare two strings
702  * @key1: pointer to the first key to be compared
703  * @keylen1: length in bytes of key1
704  * @key2: pointer to the second key to be compared
705  * @keylen2: length in bytes of key2
706  *
707  * Returns 0 if @key1 and @key2 are equal.
708  * Returns >0 if @key1 is greater.
709  * Returns <0 if @key2 is greater.
710  */
711 static int
befs_compare_strings(const void * key1,int keylen1,const void * key2,int keylen2)712 befs_compare_strings(const void *key1, int keylen1,
713 		     const void *key2, int keylen2)
714 {
715 	int len = min_t(int, keylen1, keylen2);
716 	int result = strncmp(key1, key2, len);
717 	if (result == 0)
718 		result = keylen1 - keylen2;
719 	return result;
720 }
721 
722 /* These will be used for non-string keyed btrees */
723 #if 0
724 static int
725 btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
726 {
727 	return *(int32_t *) key1 - *(int32_t *) key2;
728 }
729 
730 static int
731 btree_compare_uint32(cont void *key1, int keylen1,
732 		     const void *key2, int keylen2)
733 {
734 	if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
735 		return 0;
736 	else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
737 		return 1;
738 
739 	return -1;
740 }
741 static int
742 btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
743 {
744 	if (*(int64_t *) key1 == *(int64_t *) key2)
745 		return 0;
746 	else if (*(int64_t *) key1 > *(int64_t *) key2)
747 		return 1;
748 
749 	return -1;
750 }
751 
752 static int
753 btree_compare_uint64(cont void *key1, int keylen1,
754 		     const void *key2, int keylen2)
755 {
756 	if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
757 		return 0;
758 	else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
759 		return 1;
760 
761 	return -1;
762 }
763 
764 static int
765 btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
766 {
767 	float result = *(float *) key1 - *(float *) key2;
768 	if (result == 0.0f)
769 		return 0;
770 
771 	return (result < 0.0f) ? -1 : 1;
772 }
773 
774 static int
775 btree_compare_double(cont void *key1, int keylen1,
776 		     const void *key2, int keylen2)
777 {
778 	double result = *(double *) key1 - *(double *) key2;
779 	if (result == 0.0)
780 		return 0;
781 
782 	return (result < 0.0) ? -1 : 1;
783 }
784 #endif				//0
785