[CRIU] [PATCH 1/6] bitops: Add find_next_bit helper

[Cyrill Gorcunov]

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 include/bitops.h |   60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/include/bitops.h b/include/bitops.h
index 42f57b3..797a7da 100644
--- a/include/bitops.h
+++ b/include/bitops.h
@@ -5,6 +5,7 @@
 
 #define DIV_ROUND_UP(n,d)	(((n) + (d) - 1) / (d))
 #define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, 8 * sizeof(long))
+#define BITS_PER_LONG		(sizeof(long) * 8)
 
 #define DECLARE_BITMAP(name, bits)		\
 	unsigned long name[BITS_TO_LONGS(bits)]
@@ -46,6 +47,65 @@ static inline void clear_bit(int nr, volatile unsigned long *addr)
 	asm volatile("btr %1,%0" : ADDR : "Ir" (nr));
 }
 
+/**
+ * __ffs - find first set bit in word
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+static inline unsigned long __ffs(unsigned long word)
+{
+	asm("bsf %1,%0"
+	    : "=r" (word)
+	    : "rm" (word));
+	return word;
+}
+
+#define BITOP_WORD(nr)		((nr) / BITS_PER_LONG)
+
+/*
+ * Find the next set bit in a memory region.
+ */
+static inline unsigned long
+find_next_bit(const unsigned long *addr, unsigned long size,
+	      unsigned long offset)
+{
+	const unsigned long *p = addr + BITOP_WORD(offset);
+	unsigned long result = offset & ~(BITS_PER_LONG - 1);
+	unsigned long tmp;
+
+	if (offset >= size)
+		return size;
+	size -= result;
+	offset %= BITS_PER_LONG;
+	if (offset) {
+		tmp = *(p++);
+		tmp &= (~0UL << offset);
+		if (size < BITS_PER_LONG)
+			goto found_first;
+		if (tmp)
+			goto found_middle;
+		size -= BITS_PER_LONG;
+		result += BITS_PER_LONG;
+	}
+	while (size & ~(BITS_PER_LONG - 1)) {
+		if ((tmp = *(p++)))
+			goto found_middle;
+		result += BITS_PER_LONG;
+		size -= BITS_PER_LONG;
+	}
+	if (!size)
+		return result;
+	tmp = *p;
+
+found_first:
+	tmp &= (~0UL >> (BITS_PER_LONG - size));
+	if (tmp == 0UL)		/* Are any bits set? */
+		return result + size;	/* Nope. */
+found_middle:
+	return result + __ffs(tmp);
+}
+
 #else /* CONFIG_X86_64 */
 # error x86-32 is not implemented yet
 #endif /* CONFIG_X86_64 */
-- 
1.7.7.6