From 2b50419947185eb62f142e4e7a78b95af63bb6a1 Mon Sep 17 00:00:00 2001
From: Zachary Dremann <dremann@gmail.com>
Date: Fri, 15 May 2020 16:56:36 -0400
Subject: [PATCH 1/2] Add some simple crc32 reader tests

---
 src/crc32.rs | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/src/crc32.rs b/src/crc32.rs
index d84af9a1..0bc60f5d 100644
--- a/src/crc32.rs
+++ b/src/crc32.rs
@@ -50,3 +50,40 @@ impl<R: Read> Read for Crc32Reader<R>
         Ok(count)
     }
 }
+
+#[cfg(test)]
+mod tests
+{
+    use super::*;
+    use std::io::Read;
+    use std::io::Cursor;
+
+    #[test]
+    fn test_empty_reader()
+    {
+        let data: &[u8] = b"";
+        let mut buf = [0; 1];
+
+        let mut reader = Crc32Reader::new(data, 0);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+
+        let mut reader = Crc32Reader::new(data, 1);
+        assert!(reader.read(&mut buf).unwrap_err().to_string().contains("Invalid checksum"));
+    }
+
+    #[test]
+    fn test_byte_by_byte()
+    {
+        let data: &[u8] = b"1234";
+        let mut buf = [0; 1];
+
+        let mut reader = Crc32Reader::new(data, 0x9be3e0a3);
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+        // Can keep reading 0 bytes after the end
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+}

From b3c836d9c32efa120cdd5366280f940d3c3b985c Mon Sep 17 00:00:00 2001
From: Zachary Dremann <dremann@gmail.com>
Date: Fri, 15 May 2020 17:05:26 -0400
Subject: [PATCH 2/2] Ensure crc32 checksum is checked only at the end of the
 reader

The caller can pass in an empty slice for reading, which should return
`Ok(0)`, not raise an error about an invalid checksum prematurely
---
 src/crc32.rs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/crc32.rs b/src/crc32.rs
index 0bc60f5d..ed0101e6 100644
--- a/src/crc32.rs
+++ b/src/crc32.rs
@@ -42,7 +42,7 @@ impl<R: Read> Read for Crc32Reader<R>
     {
         let count = match self.inner.read(buf)
         {
-            Ok(0) if !self.check_matches() => { return Err(io::Error::new(io::ErrorKind::Other, "Invalid checksum")) },
+            Ok(0) if !buf.is_empty() && !self.check_matches() => { return Err(io::Error::new(io::ErrorKind::Other, "Invalid checksum")) },
             Ok(n) => n,
             Err(e) => return Err(e),
         };
@@ -52,7 +52,7 @@ impl<R: Read> Read for Crc32Reader<R>
 }
 
 #[cfg(test)]
-mod tests
+mod test
 {
     use super::*;
     use std::io::Read;
@@ -86,4 +86,15 @@ mod tests
         // Can keep reading 0 bytes after the end
         assert_eq!(reader.read(&mut buf).unwrap(), 0);
     }
+
+    #[test]
+    fn test_zero_read()
+    {
+        let data: &[u8] = b"1234";
+        let mut buf = [0; 5];
+
+        let mut reader = Crc32Reader::new(data, 0x9be3e0a3);
+        assert_eq!(reader.read(&mut buf[..0]).unwrap(), 0);
+        assert_eq!(reader.read(&mut buf).unwrap(), 4);
+    }
 }