bitmap: add virBitmapCountBits

Sometimes it's handy to know how many bits are set.

* src/util/bitmap.h (virBitmapCountBits): New prototype.
(virBitmapNextSetBit): Use correct type.
* src/util/bitmap.c (virBitmapNextSetBit): Likewise.
(virBitmapSetAll): Maintain invariant of clear tail bits.
(virBitmapCountBits): New function.
* src/libvirt_private.syms (bitmap.h): Export it.
* tests/virbitmaptest.c (test2): Test it.

(cherry picked from commit 0711c4b7)

src/libvirt_private.syms

@@ -9,6 +9,7 @@
 virBitmapClearAll;
 virBitmapClearBit;
 virBitmapCopy;
+virBitmapCountBits;
 virBitmapEqual;
 virBitmapFormat;
 virBitmapFree;

src/util/bitmap.c

@@ -35,6 +35,7 @@
 #include "buf.h"
 #include "util.h"
 #include "c-ctype.h"
+#include "count-one-bits.h"
 
 
 struct _virBitmap {
@@ -527,8 +528,15 @@ size_t virBitmapSize(virBitmapPtr bitmap)
  */
 void virBitmapSetAll(virBitmapPtr bitmap)
 {
+    int tail = bitmap->max_bit % VIR_BITMAP_BITS_PER_UNIT;
+
     memset(bitmap->map, 0xff,
            bitmap->map_len * (VIR_BITMAP_BITS_PER_UNIT / CHAR_BIT));
+
+    /* Ensure tail bits are clear.  */
+    if (tail)
+        bitmap->map[bitmap->map_len - 1] &=
+            -1UL >> (VIR_BITMAP_BITS_PER_UNIT - tail);
 }
 
 /**
@@ -585,10 +593,10 @@ bool virBitmapIsAllSet(virBitmapPtr bitmap)
  *
  * returns the position of the found bit, or -1 if no bit found.
  */
-int virBitmapNextSetBit(virBitmapPtr bitmap, int pos)
+ssize_t virBitmapNextSetBit(virBitmapPtr bitmap, ssize_t pos)
 {
-    int nl;
-    int nb;
+    size_t nl;
+    size_t nb;
     unsigned long bits;
 
     if (pos < 0)
@@ -613,3 +621,16 @@ int virBitmapNextSetBit(virBitmapPtr bitmap, int pos)
 
     return ffsl(bits) - 1 + nl * VIR_BITMAP_BITS_PER_UNIT;
 }
+
+/* Return the number of bits currently set in the map.  */
+size_t
+virBitmapCountBits(virBitmapPtr bitmap)
+{
+    size_t i;
+    size_t ret = 0;
+
+    for (i = 0; i < bitmap->map_len; i++)
+        ret += count_one_bits_l(bitmap->map[i]);
+
+    return ret;
+}

src/util/bitmap.h

 /*
  * bitmap.h: Simple bitmap operations
  *
+ * Copyright (C) 2012 Red Hat, Inc.
  * Copyright (C) 2010 Novell, Inc.
  *
  * This library is free software; you can redistribute it and/or
@@ -99,7 +100,10 @@ void virBitmapClearAll(virBitmapPtr bitmap)
 bool virBitmapIsAllSet(virBitmapPtr bitmap)
     ATTRIBUTE_NONNULL(1);
 
-int virBitmapNextSetBit(virBitmapPtr bitmap, int pos)
+ssize_t virBitmapNextSetBit(virBitmapPtr bitmap, ssize_t pos)
+    ATTRIBUTE_NONNULL(1);
+
+size_t virBitmapCountBits(virBitmapPtr bitmap)
     ATTRIBUTE_NONNULL(1);
 
 #endif

tests/virbitmaptest.c

@@ -99,6 +99,9 @@ static int test2(const void *data ATTRIBUTE_UNUSED)
     if (testBit(bitmap, 100, 1020, false) < 0)
         goto error;
 
+    if (virBitmapCountBits(bitmap) != 48)
+        goto error;
+
     bitsString2 = virBitmapFormat(bitmap);
     if (strcmp(bitsString1, bitsString2))
         goto error;
@@ -106,6 +109,8 @@ static int test2(const void *data ATTRIBUTE_UNUSED)
     virBitmapSetAll(bitmap);
     if (testBit(bitmap, 0, size - 1, true) < 0)
         goto error;
+    if (virBitmapCountBits(bitmap) != size)
+        goto error;
 
     if (!virBitmapIsAllSet(bitmap))
         goto error;
@@ -113,6 +118,8 @@ static int test2(const void *data ATTRIBUTE_UNUSED)
     virBitmapClearAll(bitmap);
     if (testBit(bitmap, 0, size - 1, false) < 0)
         goto error;
+    if (virBitmapCountBits(bitmap) != 0)
+        goto error;
 
     ret = 0;