util: bitmap: Introduce bitmap subtraction

Performs binary subtraction of two bitmaps. Stores result in the first
operand.

src/libvirt_private.syms

@@ -1161,6 +1161,7 @@ virBitmapSetAll;
 virBitmapSetBit;
 virBitmapSize;
 virBitmapString;
+virBitmapSubtract;
 virBitmapToData;
 virBitmapToDataBuf;
 

src/util/virbitmap.c

@@ -859,3 +859,24 @@ virBitmapOverlaps(virBitmapPtr b1,
 
     return false;
 }
+
+/**
+ * virBitmapSubtract:
+ * @a: minuend/result
+ * @b: subtrahend
+ *
+ * Performs bitwise subtraction: a = a - b
+ */
+void
+virBitmapSubtract(virBitmapPtr a,
+                  virBitmapPtr b)
+{
+    size_t i;
+    size_t max = a->map_len;
+
+    if (max > b->map_len)
+        max = b->map_len;
+
+    for (i = 0; i < max; i++)
+        a->map[i] &= ~b->map[i];
+}

src/util/virbitmap.h

@@ -129,4 +129,7 @@ bool virBitmapOverlaps(virBitmapPtr b1,
                        virBitmapPtr b2)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
+void virBitmapSubtract(virBitmapPtr a, virBitmapPtr b)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
+
 #endif

tests/virbitmaptest.c

@@ -552,9 +552,55 @@ test10(const void *opaque ATTRIBUTE_UNUSED)
     return ret;
 }
 
+struct testBinaryOpData {
+    const char *a;
+    const char *b;
+    const char *res;
+};
+
+static int
+test11(const void *opaque)
+{
+    const struct testBinaryOpData *data = opaque;
+    virBitmapPtr amap = NULL;
+    virBitmapPtr bmap = NULL;
+    virBitmapPtr resmap = NULL;
+    int ret = -1;
+
+    if (virBitmapParse(data->a, 0, &amap, 256) < 0 ||
+        virBitmapParse(data->b, 0, &bmap, 256) < 0 ||
+        virBitmapParse(data->res, 0, &resmap, 256) < 0)
+        goto cleanup;
+
+    virBitmapSubtract(amap, bmap);
+
+    if (!virBitmapEqual(amap, resmap)) {
+        fprintf(stderr, "\n bitmap subtraction failed: '%s'-'%s'!='%s'\n",
+                data->a, data->b, data->res);
+        goto cleanup;
+    }
+
+    ret = 0;
+
+ cleanup:
+    virBitmapFree(amap);
+    virBitmapFree(bmap);
+    virBitmapFree(resmap);
+
+    return ret;
+}
+
+#define TESTBINARYOP(A, B, RES, FUNC)                                         \
+    testBinaryOpData.a = A;                                                   \
+    testBinaryOpData.b = B;                                                   \
+    testBinaryOpData.res = RES;                                               \
+    if (virtTestRun(virtTestCounterNext(), FUNC, &testBinaryOpData) < 0)      \
+        ret = -1;
+
 static int
 mymain(void)
 {
+    struct testBinaryOpData testBinaryOpData;
     int ret = 0;
 
     if (virtTestRun("test1", test1, NULL) < 0)
@@ -578,6 +624,15 @@ mymain(void)
     if (virtTestRun("test10", test10, NULL) < 0)
         ret = -1;
 
+    virtTestCounterReset("test11-");
+    TESTBINARYOP("0", "0", "0,^0", test11);
+    TESTBINARYOP("0-3", "0", "1-3", test11);
+    TESTBINARYOP("0-3", "0,3", "1-2", test11);
+    TESTBINARYOP("0,^0", "0", "0,^0", test11);
+    TESTBINARYOP("0-3", "0-3", "0,^0", test11);
+    TESTBINARYOP("0-3", "0,^0", "0-3", test11);
+    TESTBINARYOP("0,2", "1,3", "0,2", test11);
+
     return ret;
 }