pci: add helper functions to check ranges overlap.

add helper function to check ranges overlap suggested by
Michael S. Tsirkin <mst@redhat.com>.
His original suggestion was to use [first, last], however I chosen
to use offset, length pair, i.e. [offset, offset + length)
because pci configuration space related functions all uses offset and length
pair, so it helps to avoid to type constant twice.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/hw/pci.h b/hw/pci.h
index 8e5d64aa68..7991bfdf49 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -406,4 +406,33 @@ PCIBus *pci_apb_init(target_phys_addr_t special_base,
 PCIBus *sh_pci_register_bus(pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
                             void *pic, int devfn_min, int nirq);
 
+/* These are not pci specific. Should move into a separate header.
+ * Only pci.c uses them, so keep them here for now.
+ */
+
+/* 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)
+{
+    return offset + len - 1;
+}
+
+/* Check whether a given range covers a given byte. */
+static inline int range_covers_byte(uint64_t offset, uint64_t len,
+                                    uint64_t byte)
+{
+    return offset <= byte && byte <= range_get_last(offset, len);
+}
+
+/* Check whether 2 given ranges overlap.
+ * Undefined if ranges that wrap around 0. */
+static inline int ranges_overlap(uint64_t first1, uint64_t len1,
+                                 uint64_t first2, uint64_t len2)
+{
+    uint64_t last1 = range_get_last(first1, len1);
+    uint64_t last2 = range_get_last(first2, len2);
+
+    return !(last2 < first1 || last1 < first2);
+}
+
 #endif