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, 1 insertions, 1 deletions

diff --git a/kernel_loader/src/lib.rs b/kernel_loader/src/lib.rs
index 42b43de..13ada13 100644
--- a/kernel_loader/src/lib.rs
+++ b/kernel_loader/src/lib.rs
@@ -163,7 +163,7 @@ pub fn load_cmdline(
     }
 
     guest_mem
-        .write_slice_at_addr(cmdline.to_bytes_with_nul(), guest_addr)
+        .write_at_addr(cmdline.to_bytes_with_nul(), guest_addr)
         .map_err(|_| Error::CommandLineCopy)?;
 
     Ok(())