source: bootcd/isolinux/syslinux-6.03/gpxe/src/core/bitmap.c

/*
 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <errno.h>
#include <gpxe/bitmap.h>

/** @file
 *
 * Bitmaps for multicast downloads
 *
 */

/**
 * Resize bitmap
 *
 * @v bitmap            Bitmap
 * @v new_length        New length of bitmap, in bits
 * @ret rc              Return status code
 */
int bitmap_resize ( struct bitmap *bitmap, unsigned int new_length ) {
        unsigned int old_num_blocks;
        unsigned int new_num_blocks;
        size_t new_size;
        bitmap_block_t *new_blocks;

        old_num_blocks = BITMAP_INDEX ( bitmap->length + BITMAP_BLKSIZE - 1 );
        new_num_blocks = BITMAP_INDEX ( new_length + BITMAP_BLKSIZE - 1 );

        if ( old_num_blocks != new_num_blocks ) {
                new_size = ( new_num_blocks * sizeof ( bitmap->blocks[0] ) );
                new_blocks = realloc ( bitmap->blocks, new_size );
                if ( ! new_blocks ) {
                        DBGC ( bitmap, "Bitmap %p could not resize to %d "
                               "bits\n", bitmap, new_length );
                        return -ENOMEM;
                }
                bitmap->blocks = new_blocks;
        }
        bitmap->length = new_length;

        while ( old_num_blocks < new_num_blocks ) {
                bitmap->blocks[old_num_blocks++] = 0;
        }

        DBGC ( bitmap, "Bitmap %p resized to %d bits\n", bitmap, new_length );
        return 0;
}

/**
 * Test bit in bitmap
 *
 * @v bitmap            Bitmap
 * @v bit               Bit index
 * @ret is_set          Bit is set
 */
int bitmap_test ( struct bitmap *bitmap, unsigned int bit ) {
        unsigned int index = BITMAP_INDEX ( bit );
        bitmap_block_t mask = BITMAP_MASK ( bit );

        if ( bit >= bitmap->length )
                return 0;
        return ( bitmap->blocks[index] & mask );
}

/**
 * Set bit in bitmap
 *
 * @v bitmap            Bitmap
 * @v bit               Bit index
 */
void bitmap_set ( struct bitmap *bitmap, unsigned int bit ) {
        unsigned int index = BITMAP_INDEX ( bit );
        bitmap_block_t mask = BITMAP_MASK ( bit );

        DBGC ( bitmap, "Bitmap %p setting bit %d\n", bitmap, bit );

        /* Update bitmap */
        bitmap->blocks[index] |= mask;

        /* Update first gap counter */
        while ( bitmap_test ( bitmap, bitmap->first_gap ) ) {
                bitmap->first_gap++;
        }
}