range: add some more functions

Add some more functions that will be used in memory-device context.

range_init(): Init using lower bound and size, check for validity
range_init_nofail(): Init using lower bound and size, validity asserted
range_size(): Extract the size of a range
range_overlaps_range(): Check for overlaps of two ranges
range_contains_range(): Check if one range is contained in the other

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20181214131043.25071-2-david@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

include/qemu/range.h

@@ -112,6 +112,68 @@ static inline uint64_t range_upb(Range *range)
     return range->upb;
 }
 
+/*
+ * Initialize @range to span the interval [@lob,@lob + @size - 1].
+ * @size may be 0. If the range would overflow, returns -ERANGE, otherwise
+ * 0.
+ */
+static inline int QEMU_WARN_UNUSED_RESULT range_init(Range *range, uint64_t lob,
+                                                     uint64_t size)
+{
+    if (lob + size < lob) {
+        return -ERANGE;
+    }
+    range->lob = lob;
+    range->upb = lob + size - 1;
+    range_invariant(range);
+    return 0;
+}
+
+/*
+ * Initialize @range to span the interval [@lob,@lob + @size - 1].
+ * @size may be 0. Range must not overflow.
+ */
+static inline void range_init_nofail(Range *range, uint64_t lob, uint64_t size)
+{
+    range->lob = lob;
+    range->upb = lob + size - 1;
+    range_invariant(range);
+}
+
+/*
+ * Get the size of @range.
+ */
+static inline uint64_t range_size(const Range *range)
+{
+    return range->upb - range->lob + 1;
+}
+
+/*
+ * Check if @range1 overlaps with @range2. If one of the ranges is empty,
+ * the result is always "false".
+ */
+static inline bool range_overlaps_range(const Range *range1,
+                                        const Range *range2)
+{
+    if (range_is_empty(range1) || range_is_empty(range2)) {
+        return false;
+    }
+    return !(range2->upb < range1->lob || range1->upb < range2->lob);
+}
+
+/*
+ * Check if @range1 contains @range2. If one of the ranges is empty,
+ * the result is always "false".
+ */
+static inline bool range_contains_range(const Range *range1,
+                                        const Range *range2)
+{
+    if (range_is_empty(range1) || range_is_empty(range2)) {
+        return false;
+    }
+    return range1->lob <= range2->lob && range1->upb >= range2->upb;
+}
+
 /*
  * Extend @range to the smallest interval that includes @extend_by, too.
  */