From 4c7192582dccd6fa29e6c4191920d536a9155f54 Mon Sep 17 00:00:00 2001
From: "Dustin C. Hatch" <dustin@hatch.name>
Date: Fri, 12 Jan 2024 09:42:31 -0600
Subject: [PATCH] checksum: Fix EOF handling

Using `Read::read_exact` is not the correct way to read a file in
chunks.  When it returns `UnexpectedEof`, the buffer has data in it, but
is zero-padded to the end.  This causes the calculated checksum to be
incorrect.
---
 src/main.rs | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 209bff4..cf49f57 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -303,14 +303,11 @@ fn checksum(path: impl AsRef<Path>) -> std::io::Result<Vec<u8>> {
     let mut blake = Blake2b512::new();
     loop {
         let mut buf = vec![0u8; 16384];
-        match f.read_exact(&mut buf) {
-            Ok(_) => blake.update(buf),
-            Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => {
-                blake.update(buf);
-                break;
-            }
-            Err(e) => return Err(e),
+        let sz = f.read(&mut buf)?;
+        if sz == 0 {
+            break;
         }
+        blake.update(&buf[..sz]);
     }
     Ok(blake.finalize().to_vec())
 }