memory: Add methods to return error on short writes and reads

Add GuestMemory::write_all_at_addr, GuestMemory::read_exact_at_addr
which return error if the entire write or read cannot be completed.

Also rename write_slice_at_addr to write_at_addr, read_slice_at_addr to
read_at_addr to make the entire set of four methods consistent in naming
with the methods of std::io::Write and std::io::Read.

Context:
https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1387624/16/devices/src/virtio/tpm.rs#75

TEST=cargo test

Change-Id: Ia0775b75281ccf8030c84b41f9018a511204b8c9
Reviewed-on: https://chromium-review.googlesource.com/1407156
Commit-Ready: David Tolnay <dtolnay@chromium.org>
Tested-by: David Tolnay <dtolnay@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/devices/src/virtio/p9.rs b/devices/src/virtio/p9.rs
index e9bdbb7..50ceedb 100644
--- a/devices/src/virtio/p9.rs
+++ b/devices/src/virtio/p9.rs
@@ -135,7 +135,7 @@ where
             let len = min(buf.len(), (current.len - self.offset) as usize);
             let count = self
                 .mem
-                .read_slice_at_addr(&mut buf[..len], addr)
+                .read_at_addr(&mut buf[..len], addr)
                 .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
 
             // |count| has to fit into a u32 because it must be less than or equal to
@@ -191,7 +191,7 @@ where
             let len = min(buf.len(), (current.len - self.offset) as usize);
             let count = self
                 .mem
-                .write_slice_at_addr(&buf[..len], addr)
+                .write_at_addr(&buf[..len], addr)
                 .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
 
             // |count| has to fit into a u32 because it must be less than or equal to