/*
 *	BITMAP.C -	makebitmap, setbit, testbit
 *			bit-map manipulation routines.
 *
 *	Copyright (c) Allen I. Holub, all rights reserved.  This program may
 *		for copied for personal, non-profit use only.
 *
 */
 
#ifdef DEBUG
#include <stdio.h>
#endif
 
#include "tools.h"
 

BITMAP	*makebitmap( size )
unsigned size;
{
	/*	Make a bit map with "size" bits.  The first entry in
	 *	the map is an "unsigned int" representing the maximum
	 *	bit.  The map itself is concatenated to this integer.
	 *	Return a pointer to a map on success, 0 if there's
	 *	not enough memory.
	 */

	unsigned *map, numbytes;
	extern char *malloc ();

	numbytes = (size >> 3) + ((size & 0x07) ? 1 : 0 );

#ifdef DEBUG
	printf("Making a %d bit map (%d bytes required)\n", size, numbytes);
#endif

	if( map = (unsigned *) malloc( numbytes + sizeof(unsigned) ))
		*map = size;

	return ((BITMAP *)map);
}

setbit( c, map, val )
unsigned	c, val;
char		*map;
{
	/*	Set bit c in the map to val.
	 *	If c > map-size, 0 is returned, else 1 is returned.
	 */

	if( c >= *(unsigned *)map )	/* if c >= map size */
		return 0;

	map += sizeof(unsigned);	/* skip past size */
	
	if( val )
		map[c >> 3] |= 1 << (c & 0x07);
	else
		map[c >> 3] &= ~(1 << (c & 0x07));

	return( 1 );
}

testbit( c, map )
unsigned	c;
char		*map;
{
	/*	Return 1 if the bit corresponding to c in map is set.
	 *	0 if it is not.
	 */

	if( c >= *(unsigned *)map )
		return 0;

	map += sizeof(unsigned);
	
	return(map[ c >> 3 ] & (1 << (c & 0x07)));
}