swlpc Git

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/*
	Similar to the old efuns
	except uses an array of ints for the bits.

	Automatically extended truncated etc.
*/

array empty = [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
	];

#define INT_LENGTH 30	/* 32 gives negative numbers :( */

int test_bit(array a, int bit) {

	int	x = bit / INT_LENGTH,
		y = bit % INT_LENGTH;

	if (sizeof(a) < x)
		return 0;
	else
		return (a[x] & (1 << y))?1:0;

}

/* 	returns a NEW array */
array
set_bit((int|array) a, int bit, int value)
{
array res;
int x = bit / INT_LENGTH, y = bit % INT_LENGTH, r;

	if (!a) res = [ ];
	else res = a + [ ];	/* force a copy - blech */
	if (sizeof(res) <= x) {	/* extend */
		r = x - sizeof(res);
		res = res + empty[..r];
	}
	if (value) res[x] = res[x] | (1 << y);
	else {
		res[x] = res[x] & (~(1 << y));
		/* truncate if necessary */
		for (r = sizeof(res) - 1; r >= 0 && (!res[r]); r--) { }
		res = res[..r];	
	}
	return res;
}

query_size (array a) {
	return sizeof (a) * INT_LENGTH;
	}


#if 0
test()
{
array b;
	b = set_bit(b, 16, 1);
	b = set_bit(b, 32, 1);
	return b;
}

btt()
{
	return 1 << 31;
}

bt()
{
	return 8 >> 2;
}
#endif