[Qemu-devel] [RFC 05/29] bitmap: introduce bitmap_count_one()

[Peter Xu]

Count how many bits set in the bitmap.

Signed-off-by: Peter Xu <address@hidden>
---
 include/qemu/bitmap.h | 10 ++++++++++
 util/bitmap.c         | 15 +++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
index 460d899..9c18da0 100644
--- a/include/qemu/bitmap.h
+++ b/include/qemu/bitmap.h
@@ -83,6 +83,7 @@ int slow_bitmap_andnot(unsigned long *dst, const unsigned 
long *bitmap1,
 int slow_bitmap_intersects(const unsigned long *bitmap1,
                            const unsigned long *bitmap2, long bits);
 void slow_bitmap_invert(unsigned long *bitmap, long nbits);
+long slow_bitmap_count_one(const unsigned long *bitmap, long nbits);
 
 static inline unsigned long *bitmap_try_new(long nbits)
 {
@@ -226,6 +227,15 @@ static inline void bitmap_invert(unsigned long *bitmap, 
long nbits)
     }
 }
 
+static inline long bitmap_count_one(const unsigned long *bitmap, long nbits)
+{
+    if (small_nbits(nbits)) {
+        return (ctpopl(*bitmap & BITMAP_LAST_WORD_MASK(nbits)));
+    } else {
+        return slow_bitmap_count_one(bitmap, nbits);
+    }
+}
+
 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);
diff --git a/util/bitmap.c b/util/bitmap.c
index 9b7408c..73a1063 100644
--- a/util/bitmap.c
+++ b/util/bitmap.c
@@ -368,3 +368,18 @@ void slow_bitmap_invert(unsigned long *bitmap, long nbits)
         bitmap[k] ^= BITMAP_LAST_WORD_MASK(nbits);
     }
 }
+
+long slow_bitmap_count_one(const unsigned long *bitmap, long nbits)
+{
+    long k, lim = nbits/BITS_PER_LONG, result = 0;
+
+    for (k = 0; k < lim; k++) {
+        result += ctpopl(bitmap[k]);
+    }
+
+    if (nbits % BITS_PER_LONG) {
+        result += ctpopl(bitmap[k] & BITMAP_LAST_WORD_MASK(nbits));
+    }
+
+    return result;
+}
-- 
2.7.4