range.h

GEEKOS是一个免费的操作系统内核

/*
 * Range checking
 * Copyright (c) 2003, David H. Hovemeyer <[e-mail]>
 * $Revision: 1.7 $
 * 
 * This is free software.  You are permitted to use,
 * redistribute, and modify it as specified in the file "COPYING".
 */

#ifndef GEEKOS_RANGE_H
#define GEEKOS_RANGE_H

#include <geekos/ktypes.h>

/*
 * TODO: think about these, make sure they're correct
 */

/**
 * Check that given range is "proper".
 * @param start the start of the range
 * @param size the size of the range
 * @return true if range is properly within the space
 *   0(inclusive)..ULONG_MAX(inclusive)
 */
static __inline__ bool
Check_Range_Proper(ulong_t start, ulong_t size)
{
    /*
     * Wrap around is only permitted if the sum is zero.
     * E.g., start=ULONG_MAX, size==1 is a valid range.
     */
    ulong_t sum = start + size;
    return start <= sum || (sum == 0);
}

/**
 * Check that given range lies entirely under the
 * maximum value specified (exclusive).
 * @param start the start of the range
 * @param size the size of the range
 * @param max the lowest address NOT allowed to be in the range
 * @return true if range falls entirely within the range
 *   0(inclusive)..max(exclusive)
 */
static __inline__ bool
Check_Range_Under(ulong_t start, ulong_t size, ulong_t max)
{
    if (!Check_Range_Proper(start, size))
	return false;

    return start < max && (start + size) <= max;
}

#endif  /* GEEKOS_RANGE_H */