source: mainline/uspace/lib/ext4/libext4_bitmap.c@ a872fc09

/*
 * Copyright (c) 2011 Frantisek Princ
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libext4
 * @{
 */ 

/**
 * @file        libext4_bitmap.c
 * @brief       Ext4 bitmap operations.
 */

#include <errno.h>
#include <libblock.h>
#include <sys/types.h>
#include "libext4.h"

void ext4_bitmap_free_bit(uint8_t *bitmap, uint32_t index)
{
        uint32_t byte_index = index / 8;
        uint32_t bit_index = index % 8;

        uint8_t *target = bitmap + byte_index;

        *target &= ~ (1 << bit_index);
}

void ext4_bitmap_set_bit(uint8_t *bitmap, uint32_t index)
{
        uint32_t byte_index = index / 8;
        uint32_t bit_index = index % 8;

        uint8_t *target = bitmap + byte_index;

        *target |= 1 << bit_index;
}

bool ext4_bitmap_is_free_bit(uint8_t *bitmap, uint32_t index)
{
        uint32_t byte_index = index / 8;
        uint32_t bit_index = index % 8;

        uint8_t *target = bitmap + byte_index;

        if (*target & (1 << bit_index)) {
                return false;
        } else {
                return true;
        }

}

int ext4_bitmap_find_free_byte_and_set_bit(uint8_t *bitmap, uint32_t start, uint32_t *index, uint32_t max)
{
        uint32_t idx;
        if (start % 8) {
                idx = start + (8 - (start % 8));
        } else {
                idx = start;
        }

        uint8_t *pos = bitmap + (idx / 8);

        while (idx < max) {

                if (*pos == 0) {
                        *pos |= 1;

                        *index = idx;
                        return EOK;
                }

                idx += 8;
                ++pos;
        }

        return ENOSPC;
}

int ext4_bitmap_find_free_bit_and_set(uint8_t *bitmap, uint32_t start_idx,
                uint32_t *index, uint32_t max)
{
        uint8_t *pos = bitmap + (start_idx / 8);
        uint32_t idx = start_idx;
        bool byte_part = false;

        // Check the rest of byte
        while ((idx % 8) != 0) {
                byte_part = true;

                if ((*pos & (1 << (idx % 8))) == 0) {
                        *pos |= (1 << (idx % 8));
                        *index = idx;
                        return EOK;
                }

                ++idx;
        }

        if (byte_part) {
                ++pos;
        }

        while (idx < max) {

                if ((*pos & 255) != 255) {
                        // free bit found
                        break;
                }

                idx += 8;
                ++pos;
        }


        if (idx < max) {
                for (uint8_t i = 0; i < 8; ++i) {
                        if ((*pos & (1 << i)) == 0) {
                                // free bit found
                                *pos |=  (1 << i);
                                *index = idx;
                                return EOK;
                        }
                        idx++;
                }
        }

        return ENOSPC;
}

/**
 * @}
 */