range: add Range structure

Sometimes we need to pass ranges around, add a
handy structure for this purpose.

Note: memory.c defines its own concept of AddrRange structure for
working with 128 addresses.  It's necessary there for doing range math.
This is not needed for most users: struct Range is
much simpler, and is only used for passing the range around.

Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/qemu/range.h

@@ -1,6 +1,22 @@
 #ifndef QEMU_RANGE_H
 #define QEMU_RANGE_H
 
+#include <inttypes.h>
+
+/*
+ * Operations on 64 bit address ranges.
+ * Notes:
+ *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
+ *   - this can not represent a full 0 to ~0x0LL range.
+ */
+
+/* A structure representing a range of addresses. */
+struct Range {
+    uint64_t begin; /* First byte of the range, or 0 if empty. */
+    uint64_t end;   /* 1 + the last byte. 0 if range empty or ends at ~0x0LL. */
+};
+typedef struct Range Range;
+
 /* Get last byte of a range from offset + length.
  * Undefined for ranges that wrap around 0. */
 static inline uint64_t range_get_last(uint64_t offset, uint64_t len)