1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License"). You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22 /* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
23 /* All Rights Reserved */
24
25
26 /*
27 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
28 * Use is subject to license terms.
29 */
30
31 #pragma ident "%Z%%M% %I% %E% SMI"
32
33 /*
34 * Operations on bitmaps of arbitrary size
35 * A bitmap is a vector of 1 or more ulongs.
36 * The user of the package is responsible for range checks and keeping
37 * track of sizes.
38 */
39
40 #include <sys/types.h>
41 #include <sys/bitmap.h>
42 #include <sys/debug.h> /* ASSERT */
43
44 /*
45 * Return index of first available bit in denoted bitmap, or -1 for
46 * failure. Size is the cardinality of the bitmap; that is, the
47 * number of bits.
48 * No side-effects. In particular, does not update bitmap.
49 * Caller is responsible for range checks.
50 */
51 index_t
bt_availbit(ulong_t * bitmap,size_t nbits)52 bt_availbit(ulong_t *bitmap, size_t nbits)
53 {
54 index_t maxword; /* index of last in map */
55 index_t wx; /* word index in map */
56
57 /*
58 * Look for a word with a bit off.
59 * Subtract one from nbits because we're converting it to a
60 * a range of indices.
61 */
62 nbits -= 1;
63 maxword = nbits >> BT_ULSHIFT;
64 for (wx = 0; wx <= maxword; wx++)
65 if (bitmap[wx] != ~0)
66 break;
67
68 if (wx <= maxword) {
69 /*
70 * Found a word with a bit off. Now find the bit in the word.
71 */
72 index_t bx; /* bit index in word */
73 index_t maxbit; /* last bit to look at */
74 ulong_t word;
75 ulong_t bit;
76
77 maxbit = wx == maxword ? nbits & BT_ULMASK : BT_NBIPUL - 1;
78 word = bitmap[wx];
79 bit = 1;
80 for (bx = 0; bx <= maxbit; bx++, bit <<= 1) {
81 if (!(word & bit)) {
82 return (wx << BT_ULSHIFT | bx);
83 }
84 }
85 }
86 return (-1);
87 }
88
89
90 /*
91 * Find highest order bit that is on, and is within or below
92 * the word specified by wx.
93 */
94 int
bt_gethighbit(ulong_t * mapp,int wx)95 bt_gethighbit(ulong_t *mapp, int wx)
96 {
97 ulong_t word;
98
99 while ((word = mapp[wx]) == 0) {
100 wx--;
101 if (wx < 0) {
102 return (-1);
103 }
104 }
105 return (wx << BT_ULSHIFT | (highbit(word) - 1));
106 }
107
108
109 /*
110 * Search the bitmap for a consecutive pattern of 1's.
111 * Search starts at position pos1.
112 * Returns 1 on success and 0 on failure.
113 * Side effects.
114 * Returns indices to the first bit (pos1)
115 * and one past the last bit (pos2) in the pattern.
116 */
117 int
bt_range(ulong_t * bitmap,size_t * pos1,size_t * pos2,size_t end_pos)118 bt_range(ulong_t *bitmap, size_t *pos1, size_t *pos2, size_t end_pos)
119 {
120 size_t pos;
121
122 for (pos = *pos1; pos < end_pos; pos++)
123 if (BT_TEST(bitmap, pos))
124 break;
125
126 if (pos == end_pos)
127 return (0);
128
129 *pos1 = pos;
130
131 for (; pos < end_pos; pos++)
132 if (!BT_TEST(bitmap, pos))
133 break;
134 *pos2 = pos;
135
136 return (1);
137 }
138
139
140 /*
141 * return the parity of the supplied long
142 *
143 * this works by successively partitioning the argument in half, and
144 * setting the parity of the result to the parity of the 2 halfs, until
145 * only one bit is left
146 */
147 int
odd_parity(ulong_t i)148 odd_parity(ulong_t i)
149 {
150 #ifdef _LP64
151 i ^= i >> 32;
152 #endif
153 i ^= i >> 16;
154 i ^= i >> 8;
155 i ^= i >> 4;
156 i ^= i >> 2;
157 i ^= i >> 1;
158
159 return (i & 0x01);
160 }
161
162
163 /*
164 * get the lowest bit in the range of 'start' and 'stop', inclusive.
165 * I.e., if caller calls bt_getlowbit(map, X, Y), any value between X and Y,
166 * including X and Y can be returned.
167 * Neither start nor stop is required to align with word boundaries.
168 * If a bit is set in the range, the bit position is returned; otherwise,
169 * a -1 is returned.
170 */
171 int
bt_getlowbit(ulong_t * map,size_t start,size_t stop)172 bt_getlowbit(ulong_t *map, size_t start, size_t stop)
173 {
174 ulong_t word;
175 int counter = start >> BT_ULSHIFT;
176 int limit = stop >> BT_ULSHIFT;
177 index_t partial_start = start & BT_ULMASK;
178 index_t partial_stop = stop & BT_ULMASK;
179
180 if (start > stop) {
181 return (-1);
182 }
183
184 /*
185 * The range between 'start' and 'stop' can be very large, and the
186 * '1' bits in this range can be sparse.
187 * For performance reason, the underlying implementation operates
188 * on words, not on bits.
189 */
190 word = map[counter];
191
192 if (partial_start) {
193 /*
194 * Since the start is not aligned on word boundary, we
195 * need to patch the unwanted low order bits with 0's before
196 * operating on the first bitmap word.
197 */
198 word = word & (BT_ULMAXMASK << partial_start);
199 }
200
201 /*
202 * Locate a word from the map array with one of the bits set.
203 */
204
205 while ((word == 0) && (counter < limit)) {
206 word = map[++counter];
207 }
208
209 /*
210 * The end of range has similar problems if it is not aligned.
211 * Taking care of the end which is not aligned.
212 */
213
214 if ((counter == limit) && (partial_stop != BT_ULMASK)) {
215 /*
216 * Take care the partial word by patch the high order
217 * bits with 0's. Here we dealing with the case that
218 * the last word of the bitmap is not aligned.
219 */
220
221 ASSERT(partial_stop < BT_ULMASK);
222 word = word & (~(BT_ULMAXMASK << partial_stop + 1));
223 }
224
225 /*
226 * Examine the word.
227 */
228 if (word == 0) {
229 return (-1);
230 } else {
231 return ((counter << BT_ULSHIFT) | (lowbit(word) - 1));
232 }
233 }
234
235 /*
236 * Copy the bitmap.
237 */
238 void
bt_copy(ulong_t * from,ulong_t * to,ulong_t size)239 bt_copy(ulong_t *from, ulong_t *to, ulong_t size)
240 {
241 ulong_t i;
242 for (i = 0; i < size; i++)
243 *to++ = *from++;
244 }
245