From e743acc0093fdb790509f64014ad8858ecfe0839 Mon Sep 17 00:00:00 2001
Message-Id: <e743acc0093fdb790509f64014ad8858ecfe0839@dist-git>
From: Martin Kletzander <mkletzan@redhat.com>
Date: Wed, 31 Jan 2018 16:32:16 +0100
Subject: [PATCH] util: Introduce virBitmapShrink

https://bugzilla.redhat.com/show_bug.cgi?id=1289368

Sometimes the size of the bitmap matters and it might not be guessed correctly
when parsing from some type of input.  For example virBitmapNewData() has Byte
granularity, virBitmapNewString() has nibble granularity and so on.
virBitmapParseUnlimited() can be tricked into creating huge bitmap that's not
needed (e.g.: "0-2,^99999999").  This function provides a way to shrink the
bitmap.  It is not supposed to free any memory.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
(cherry picked from commit baca005367cf60743f67df44440fc316e6d20c19)
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
---
 src/libvirt_private.syms |  1 +
 src/util/virbitmap.c     | 23 +++++++++++++++++++++++
 src/util/virbitmap.h     |  2 ++
 3 files changed, 26 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 8cc8cbcc90..7dd4621b70 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1382,6 +1382,7 @@ virBitmapParseUnlimited;
 virBitmapSetAll;
 virBitmapSetBit;
 virBitmapSetBitExpand;
+virBitmapShrink;
 virBitmapSize;
 virBitmapSubtract;
 virBitmapToData;
diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c
index 7338f0255a..b2c5c7a6a5 100644
--- a/src/util/virbitmap.c
+++ b/src/util/virbitmap.c
@@ -1196,3 +1196,26 @@ virBitmapSubtract(virBitmapPtr a,
     for (i = 0; i < max; i++)
         a->map[i] &= ~b->map[i];
 }
+
+
+/**
+ * virBitmapShrink:
+ * @map: Pointer to bitmap
+ * @b: last bit position to be excluded from bitmap
+ *
+ * Resizes the bitmap so that no more than @b bits will fit into it.  Nothing
+ * will change if the size is already smaller than @b.
+ *
+ * NB: Does not adjust the map->map_len so that a subsequent virBitmapExpand
+ * doesn't necessarily need to reallocate.
+ */
+void
+virBitmapShrink(virBitmapPtr map,
+                size_t b)
+{
+    if (!map)
+        return;
+
+    if (map->max_bit >= b)
+        map->max_bit = b;
+}
diff --git a/src/util/virbitmap.h b/src/util/virbitmap.h
index 7b2bea8b53..2464814055 100644
--- a/src/util/virbitmap.h
+++ b/src/util/virbitmap.h
@@ -153,4 +153,6 @@ void virBitmapIntersect(virBitmapPtr a, virBitmapPtr b)
 void virBitmapSubtract(virBitmapPtr a, virBitmapPtr b)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
+void virBitmapShrink(virBitmapPtr map, size_t b);
+
 #endif
-- 
2.16.1