guest_memory: provide default file_offset implementation

bonzini · jiangliu · commit 4e29019443ba · 2020-02-19T16:59:23.000+08:00
Just like for example as_slice, not having a file and offset behind a
memory region is a sane default.  Add it to the GuestMemoryRegion
trait.

Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
diff --git a/src/guest_memory.rs b/src/guest_memory.rs
@@ -216,7 +216,9 @@ pub trait GuestMemoryRegion: Bytes<MemoryRegionAddress, E = Error> {
     }
 
     /// Returns information regarding the file and offset backing this memory region.
-    fn file_offset(&self) -> Option<&FileOffset>;
+    fn file_offset(&self) -> Option<&FileOffset> {
+        None
+    }
 
     /// Returns a slice corresponding to the data in the region.
     ///

Original file line number	Diff line number	Diff line change
`@@ -216,7 +216,9 @@ pub trait GuestMemoryRegion: Bytes<MemoryRegionAddress, E = Error> {`
`216`	`216`	`}`
`217`	`217`
`218`	`218`	`/// Returns information regarding the file and offset backing this memory region.`
`219`		`- fn file_offset(&self) -> Option<&FileOffset>;`
	`219`	`+ fn file_offset(&self) -> Option<&FileOffset> {`
	`220`	`+ None`
	`221`	`+ }`
`220`	`222`
`221`	`223`	`/// Returns a slice corresponding to the data in the region.`
`222`	`224`	`///`