Add a simple native bitmap

Nothing fancy at all.

Signed-off-by: Zach Brown <zab@versity.com>

utils/src/bitmap.c

@@ -0,0 +1,57 @@
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <strings.h>
+
+#include "sparse.h"
+#include "util.h"
+#include "bitmap.h"
+
+/*
+ * Just a quick simple native bitmap.
+ */
+
+void set_bit(unsigned long *bits, u64 nr)
+{
+	bits[nr / BITS_PER_LONG] |= 1UL << (nr & (BITS_PER_LONG - 1));
+}
+
+void clear_bit(unsigned long *bits, u64 nr)
+{
+	bits[nr / BITS_PER_LONG] &= ~(1UL << (nr & (BITS_PER_LONG - 1)));
+}
+
+u64 find_next_set_bit(unsigned long *map, u64 from, u64 total)
+{
+	unsigned long bits;
+	u64 base;
+	u64 nr;
+	int bit;
+
+	base = from & ~((unsigned long)BITS_PER_LONG - 1);
+	map += from / BITS_PER_LONG;
+
+	while (base < total) {
+		bits = *map;
+
+		while (bits) {
+			bit = ffsl(bits) - 1;
+			nr = base + bit;
+
+			if (nr >= from)
+				return min(nr, total);
+
+			bits &= ~(1UL << bit);
+		}
+
+		base += BITS_PER_LONG;
+		map++;
+	}
+
+	return total;
+}
+
+unsigned long *alloc_bits(u64 max)
+{
+	return calloc(DIV_ROUND_UP(max, BITS_PER_LONG), sizeof(unsigned long));
+}
+

utils/src/bitmap.h

@@ -0,0 +1,9 @@
+#ifndef _BITMAP_H_
+#define _BITMAP_H_
+
+void set_bit(unsigned long *bits, u64 nr);
+void clear_bit(unsigned long *bits, u64 nr);
+u64 find_next_set_bit(unsigned long *start, u64 from, u64 total);
+unsigned long *alloc_bits(u64 max);
+
+#endif