1 /*
2  *  linux/fs/hfs/bfind.c
3  *
4  * Copyright (C) 2001
5  * Brad Boyer (flar@allandria.com)
6  * (C) 2003 Ardis Technologies <roman@ardistech.com>
7  *
8  * Search routines for btrees
9  */
10 
11 #include <linux/slab.h>
12 #include "btree.h"
13 
hfs_find_init(struct hfs_btree * tree,struct hfs_find_data * fd)14 int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
15 {
16 	void *ptr;
17 
18 	fd->tree = tree;
19 	fd->bnode = NULL;
20 	ptr = kmalloc(tree->max_key_len * 2 + 4, GFP_KERNEL);
21 	if (!ptr)
22 		return -ENOMEM;
23 	fd->search_key = ptr;
24 	fd->key = ptr + tree->max_key_len + 2;
25 	dprint(DBG_BNODE_REFS, "find_init: %d (%p)\n", tree->cnid, __builtin_return_address(0));
26 	mutex_lock(&tree->tree_lock);
27 	return 0;
28 }
29 
hfs_find_exit(struct hfs_find_data * fd)30 void hfs_find_exit(struct hfs_find_data *fd)
31 {
32 	hfs_bnode_put(fd->bnode);
33 	kfree(fd->search_key);
34 	dprint(DBG_BNODE_REFS, "find_exit: %d (%p)\n", fd->tree->cnid, __builtin_return_address(0));
35 	mutex_unlock(&fd->tree->tree_lock);
36 	fd->tree = NULL;
37 }
38 
39 /* Find the record in bnode that best matches key (not greater than...)*/
__hfs_brec_find(struct hfs_bnode * bnode,struct hfs_find_data * fd)40 int __hfs_brec_find(struct hfs_bnode *bnode, struct hfs_find_data *fd)
41 {
42 	int cmpval;
43 	u16 off, len, keylen;
44 	int rec;
45 	int b, e;
46 	int res;
47 
48 	b = 0;
49 	e = bnode->num_recs - 1;
50 	res = -ENOENT;
51 	do {
52 		rec = (e + b) / 2;
53 		len = hfs_brec_lenoff(bnode, rec, &off);
54 		keylen = hfs_brec_keylen(bnode, rec);
55 		if (keylen == 0) {
56 			res = -EINVAL;
57 			goto fail;
58 		}
59 		hfs_bnode_read(bnode, fd->key, off, keylen);
60 		cmpval = bnode->tree->keycmp(fd->key, fd->search_key);
61 		if (!cmpval) {
62 			e = rec;
63 			res = 0;
64 			goto done;
65 		}
66 		if (cmpval < 0)
67 			b = rec + 1;
68 		else
69 			e = rec - 1;
70 	} while (b <= e);
71 	if (rec != e && e >= 0) {
72 		len = hfs_brec_lenoff(bnode, e, &off);
73 		keylen = hfs_brec_keylen(bnode, e);
74 		if (keylen == 0) {
75 			res = -EINVAL;
76 			goto fail;
77 		}
78 		hfs_bnode_read(bnode, fd->key, off, keylen);
79 	}
80 done:
81 	fd->record = e;
82 	fd->keyoffset = off;
83 	fd->keylength = keylen;
84 	fd->entryoffset = off + keylen;
85 	fd->entrylength = len - keylen;
86 fail:
87 	return res;
88 }
89 
90 /* Traverse a B*Tree from the root to a leaf finding best fit to key */
91 /* Return allocated copy of node found, set recnum to best record */
hfs_brec_find(struct hfs_find_data * fd)92 int hfs_brec_find(struct hfs_find_data *fd)
93 {
94 	struct hfs_btree *tree;
95 	struct hfs_bnode *bnode;
96 	u32 nidx, parent;
97 	__be32 data;
98 	int height, res;
99 
100 	tree = fd->tree;
101 	if (fd->bnode)
102 		hfs_bnode_put(fd->bnode);
103 	fd->bnode = NULL;
104 	nidx = tree->root;
105 	if (!nidx)
106 		return -ENOENT;
107 	height = tree->depth;
108 	res = 0;
109 	parent = 0;
110 	for (;;) {
111 		bnode = hfs_bnode_find(tree, nidx);
112 		if (IS_ERR(bnode)) {
113 			res = PTR_ERR(bnode);
114 			bnode = NULL;
115 			break;
116 		}
117 		if (bnode->height != height)
118 			goto invalid;
119 		if (bnode->type != (--height ? HFS_NODE_INDEX : HFS_NODE_LEAF))
120 			goto invalid;
121 		bnode->parent = parent;
122 
123 		res = __hfs_brec_find(bnode, fd);
124 		if (!height)
125 			break;
126 		if (fd->record < 0)
127 			goto release;
128 
129 		parent = nidx;
130 		hfs_bnode_read(bnode, &data, fd->entryoffset, 4);
131 		nidx = be32_to_cpu(data);
132 		hfs_bnode_put(bnode);
133 	}
134 	fd->bnode = bnode;
135 	return res;
136 
137 invalid:
138 	printk(KERN_ERR "hfs: inconsistency in B*Tree (%d,%d,%d,%u,%u)\n",
139 		height, bnode->height, bnode->type, nidx, parent);
140 	res = -EIO;
141 release:
142 	hfs_bnode_put(bnode);
143 	return res;
144 }
145 
hfs_brec_read(struct hfs_find_data * fd,void * rec,int rec_len)146 int hfs_brec_read(struct hfs_find_data *fd, void *rec, int rec_len)
147 {
148 	int res;
149 
150 	res = hfs_brec_find(fd);
151 	if (res)
152 		return res;
153 	if (fd->entrylength > rec_len)
154 		return -EINVAL;
155 	hfs_bnode_read(fd->bnode, rec, fd->entryoffset, fd->entrylength);
156 	return 0;
157 }
158 
hfs_brec_goto(struct hfs_find_data * fd,int cnt)159 int hfs_brec_goto(struct hfs_find_data *fd, int cnt)
160 {
161 	struct hfs_btree *tree;
162 	struct hfs_bnode *bnode;
163 	int idx, res = 0;
164 	u16 off, len, keylen;
165 
166 	bnode = fd->bnode;
167 	tree = bnode->tree;
168 
169 	if (cnt < 0) {
170 		cnt = -cnt;
171 		while (cnt > fd->record) {
172 			cnt -= fd->record + 1;
173 			fd->record = bnode->num_recs - 1;
174 			idx = bnode->prev;
175 			if (!idx) {
176 				res = -ENOENT;
177 				goto out;
178 			}
179 			hfs_bnode_put(bnode);
180 			bnode = hfs_bnode_find(tree, idx);
181 			if (IS_ERR(bnode)) {
182 				res = PTR_ERR(bnode);
183 				bnode = NULL;
184 				goto out;
185 			}
186 		}
187 		fd->record -= cnt;
188 	} else {
189 		while (cnt >= bnode->num_recs - fd->record) {
190 			cnt -= bnode->num_recs - fd->record;
191 			fd->record = 0;
192 			idx = bnode->next;
193 			if (!idx) {
194 				res = -ENOENT;
195 				goto out;
196 			}
197 			hfs_bnode_put(bnode);
198 			bnode = hfs_bnode_find(tree, idx);
199 			if (IS_ERR(bnode)) {
200 				res = PTR_ERR(bnode);
201 				bnode = NULL;
202 				goto out;
203 			}
204 		}
205 		fd->record += cnt;
206 	}
207 
208 	len = hfs_brec_lenoff(bnode, fd->record, &off);
209 	keylen = hfs_brec_keylen(bnode, fd->record);
210 	if (keylen == 0) {
211 		res = -EINVAL;
212 		goto out;
213 	}
214 	fd->keyoffset = off;
215 	fd->keylength = keylen;
216 	fd->entryoffset = off + keylen;
217 	fd->entrylength = len - keylen;
218 	hfs_bnode_read(bnode, fd->key, off, keylen);
219 out:
220 	fd->bnode = bnode;
221 	return res;
222 }
223