Root/fs/befs/btree.c

1/*
2 * linux/fs/befs/btree.c
3 *
4 * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com>
5 *
6 * Licensed under the GNU GPL. See the file COPYING for details.
7 *
8 * 2002-02-05: Sergey S. Kostyliov added binary search 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
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
788

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