Add bitops.c for find_next_bit_le()

The upcoming buddy changes are going to need a find_next_bit_le().

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

utils/src/bitops.c

@@ -0,0 +1,60 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "sparse.h"
+#include "util.h"
+#include "bitops.h"
+
+#if (__SIZEOF_LONG__  == 8)
+typedef __le64 lelong;
+#define lelong_to_cpu le64_to_cpu
+
+#elif (__SIZEOF_LONG__  == 4)
+typedef __le32 lelong;
+#define lelong_to_cpu le32_to_cpu
+
+#else
+#error "no sizeof long define?"
+#endif
+
+/*
+ * I'd have used ffsl(), but defining _GNU_SOURCE caused build errors
+ * in glibc.  The gcc builtin has the added bonus of returning 0 for the
+ * least significant bit instead of 1.
+ */
+#define ctzl __builtin_ctzl
+
+int find_next_bit_le(void *addr, long size, int start)
+{
+	lelong * __packed longs = addr;
+	unsigned long off = 0;
+	unsigned long masked;
+
+	/* skip past whole longs before start */
+	if (start >= BITS_PER_LONG) {
+		longs += start / BITS_PER_LONG;
+		off = start & ~(BITS_PER_LONG - 1);
+		start -= off;
+	}
+
+	/* mask off low bits if start isn't aligned */
+	if (start) {
+		masked = lelong_to_cpu(*longs) & ~((1 << (start)) - 1);
+		if (masked)
+			return min(ctzl(masked), size);
+
+		off += BITS_PER_LONG;
+		longs++;
+	}
+
+	/* then search remaining longs */
+	while (off < size) {
+		if (*longs)
+			return min(off + ctzl(lelong_to_cpu(*longs)), size);
+		longs++;
+		off += BITS_PER_LONG;
+	}
+
+	return size;
+}

utils/src/bitops.h

@@ -75,4 +75,6 @@ static inline int test_and_clear_bit_le(int nr, void *addr)
 	return ret;
 }
 
+int find_next_bit_le(void *addr, long size, int start);
+
 #endif