common/os/bitmap.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */


/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * Operations on bitmaps of arbitrary size
 * A bitmap is a vector of 1 or more ulongs.
 * The user of the package is responsible for range checks and keeping
 * track of sizes.
 */

#include <sys/types.h>
#include <sys/bitmap.h>
#include <sys/debug.h>      /* ASSERT */

/*
 * Return index of first available bit in denoted bitmap, or -1 for
 * failure.  Size is the cardinality of the bitmap; that is, the
 * number of bits.
 * No side-effects.  In particular, does not update bitmap.
 * Caller is responsible for range checks.
 */
index_t
bt_availbit(ulong_t *bitmap, size_t nbits)
{
    index_t maxword;    /* index of last in map */
    index_t wx;     /* word index in map */

    /*
     * Look for a word with a bit off.
     * Subtract one from nbits because we're converting it to a
     * a range of indices.
     */
    nbits -= 1;
    maxword = nbits >> BT_ULSHIFT;
    for (wx = 0; wx <= maxword; wx++)
        if (bitmap[wx] != ~0)
            break;

    if (wx <= maxword) {
        /*
         * Found a word with a bit off.  Now find the bit in the word.
         */
        index_t bx; /* bit index in word */
        index_t maxbit; /* last bit to look at */
        ulong_t     word;
        ulong_t     bit;

        maxbit = wx == maxword ? nbits & BT_ULMASK : BT_NBIPUL - 1;
        word = bitmap[wx];
        bit = 1;
        for (bx = 0; bx <= maxbit; bx++, bit <<= 1) {
            if (!(word & bit)) {
                return (wx << BT_ULSHIFT | bx);
            }
        }
    }
    return (-1);
}


/*
 * Find highest order bit that is on, and is within or below
 * the word specified by wx.
 */
int
bt_gethighbit(ulong_t *mapp, int wx)
{
    ulong_t word;

    while ((word = mapp[wx]) == 0) {
        wx--;
        if (wx < 0) {
            return (-1);
        }
    }
    return (wx << BT_ULSHIFT | (highbit(word) - 1));
}


/*
 * Search the bitmap for a consecutive pattern of 1's.
 * Search starts at position pos1.
 * Returns 1 on success and 0 on failure.
 * Side effects.
 * Returns indices to the first bit (pos1)
 * and one past the last bit (pos2) in the pattern.
 */
int
bt_range(ulong_t *bitmap, size_t *pos1, size_t *pos2, size_t end_pos)
{
    size_t pos;

    for (pos = *pos1; pos < end_pos; pos++)
        if (BT_TEST(bitmap, pos))
            break;

    if (pos == end_pos)
        return (0);

    *pos1 = pos;

    for (; pos < end_pos; pos++)
        if (!BT_TEST(bitmap, pos))
            break;
    *pos2 = pos;

    return (1);
}


/*
 * return the parity of the supplied long
 *
 * this works by successively partitioning the argument in half, and
 * setting the parity of the result to the parity of the 2 halfs, until
 * only one bit is left
 */
int
odd_parity(ulong_t i)
{
#ifdef _LP64
    i ^= i >> 32;
#endif
    i ^= i >> 16;
    i ^= i >> 8;
    i ^= i >> 4;
    i ^= i >> 2;
    i ^= i >> 1;

    return (i & 0x01);
}


/*
 * get the lowest bit in the range of 'start' and 'stop', inclusive.
 * I.e., if caller calls bt_getlowbit(map, X, Y), any value between X and Y,
 * including X and Y can be returned.
 * Neither start nor stop is required to align with word boundaries.
 * If a bit is set in the range, the bit position is returned; otherwise,
 * a -1 is returned.
 */
int
bt_getlowbit(ulong_t *map, size_t start, size_t stop)
{
    ulong_t     word;
    int     counter = start >> BT_ULSHIFT;
    int     limit = stop >> BT_ULSHIFT;
    index_t     partial_start = start & BT_ULMASK;
    index_t     partial_stop = stop & BT_ULMASK;

    if (start > stop) {
        return (-1);
    }

    /*
     * The range between 'start' and 'stop' can be very large, and the
     * '1' bits in this range can be sparse.
     * For performance reason, the underlying implementation operates
     * on words, not on bits.
     */
    word = map[counter];

    if (partial_start) {
        /*
         * Since the start is not aligned on word boundary, we
         * need to patch the unwanted low order bits with 0's before
         * operating on the first bitmap word.
         */
        word = word & (BT_ULMAXMASK << partial_start);
    }

    /*
     * Locate a word from the map array with one of the bits set.
     */

    while ((word == 0) && (counter < limit)) {
        word = map[++counter];
    }

    /*
     * The end of range has similar problems if it is not aligned.
     * Taking care of the end which is not aligned.
     */

    if ((counter == limit) && (partial_stop != BT_ULMASK)) {
        /*
         * Take care the partial word by patch the high order
         * bits with 0's. Here we dealing with the case that
         * the last word of the bitmap is not aligned.
         */

        ASSERT(partial_stop < BT_ULMASK);
        word = word & (~(BT_ULMAXMASK << partial_stop + 1));
    }

    /*
     * Examine the word.
     */
    if (word == 0) {
        return (-1);
    } else {
        return ((counter << BT_ULSHIFT) | (lowbit(word) - 1));
    }
}

/*
 * Copy the bitmap.
 */
void
bt_copy(ulong_t *from, ulong_t *to, ulong_t size)
{
    ulong_t i;
    for (i = 0; i < size; i++)
        *to++ = *from++;
}