[Qemu-devel] [PATCH v4 1/4] bitmap: bitmap_count_one_with_offset

[Wei Wang <wei.w.wang@intel.com>]

Count the number of 1s in a bitmap starting from an offset.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Michael S. Tsirkin <mst@redhat.com>
---
 include/qemu/bitmap.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
index 509eedd..e3f31f1 100644
--- a/include/qemu/bitmap.h
+++ b/include/qemu/bitmap.h
@@ -228,6 +228,19 @@ static inline long bitmap_count_one(const unsigned long *bitmap, long nbits)
     }
 }
 
+static inline long bitmap_count_one_with_offset(const unsigned long *bitmap,
+                                                long offset, long nbits)
+{
+    long aligned_offset = QEMU_ALIGN_DOWN(offset, BITS_PER_LONG);
+    long redundant_bits = offset - aligned_offset;
+    long bits_to_count = nbits + redundant_bits;
+    const unsigned long *bitmap_start = bitmap +
+                                        aligned_offset / BITS_PER_LONG;
+
+    return bitmap_count_one(bitmap_start, bits_to_count) -
+           bitmap_count_one(bitmap_start, redundant_bits);
+}
+
 void bitmap_set(unsigned long *map, long i, long len);
 void bitmap_set_atomic(unsigned long *map, long i, long len);
 void bitmap_clear(unsigned long *map, long start, long nr);
-- 
1.8.3.1