sys_util: add write_zeroes_all() function

In the same spirit as write_all() for the standard io::Write::write()
function, add a write_zeroes_all() function with a default
implementation that calls write_zeroes() in a loop until the requested
length is met.  This will allow write_zeroes implementations that don't
necessarily fulfill the entire requested length.

BUG=None
TEST=cargo test -p sys_util write_zeroes

Change-Id: I0fc3a4b3fe8904946e253ab8a2687555b12657be
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1811466
Reviewed-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Cody Schuffelen <schuffelen@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/qcow_utils/src/qcow_img.rs b/qcow_utils/src/qcow_img.rs
index 08040a1..b4ad422 100644
--- a/qcow_utils/src/qcow_img.rs
+++ b/qcow_utils/src/qcow_img.rs
@@ -264,7 +264,7 @@ fn dd(file_path: &str, source_path: &str, count: Option<usize>) -> std::result::
         let nread = src_file.read(&mut buf[..this_count]).map_err(|_| ())?;
         // If this block is all zeros, then use write_zeros so the output file is sparse.
         if buf.iter().all(|b| *b == 0) {
-            qcow_file.write_zeroes(CHUNK_SIZE).map_err(|_| ())?;
+            qcow_file.write_zeroes_all(CHUNK_SIZE).map_err(|_| ())?;
         } else {
             qcow_file.write(&buf).map_err(|_| ())?;
         }