refactor: add copy method to CompressionEngine and update mode_diff to use it

src/compression.rs

@@ -44,14 +44,18 @@ pub trait CompressionEngine {
         true
     }
 
-    fn cat(&self, file_path: PathBuf) -> Result<()> {
+    fn copy(&self, file_path: PathBuf, writer: &mut dyn Write) -> Result<()> {
         let mut reader = self.open(file_path)?;
-        let mut stdout = io::stdout().lock();
-        io::copy(&mut reader, &mut stdout)?;
-        stdout.flush()?;
+        io::copy(&mut reader, writer)?;
+        writer.flush()?;
         Ok(())
     }
 
+    fn cat(&self, file_path: PathBuf) -> Result<()> {
+        let mut stdout = io::stdout().lock();
+        self.copy(file_path, &mut stdout)
+    }
+
     fn magic(&self, file_path: PathBuf) -> Result<String> {
         let mut buffer = [0; libc::BUFSIZ as usize];
         let mut reader = self.open(file_path)?;

src/compression/gzip.rs

@@ -40,6 +40,13 @@ impl CompressionEngine for CompressionEngineGZip {
 
         Ok(Box::new(AutoFinishGzEncoder::new(gzip_write)))
     }
+
+    fn copy(&self, file_path: PathBuf, writer: &mut dyn Write) -> Result<()> {
+        let mut reader = self.open(file_path)?;
+        io::copy(&mut reader, writer)?;
+        writer.flush()?;
+        Ok(())
+    }
 }
 
 pub struct AutoFinishGzEncoder<W: Write> {

src/compression/lz4.rs

@@ -38,5 +38,12 @@ impl CompressionEngine for CompressionEngineLZ4 {
 
         Ok(Box::new(lz4_write))
     }
+
+    fn copy(&self, file_path: PathBuf, writer: &mut dyn Write) -> Result<()> {
+        let mut reader = self.open(file_path)?;
+        io::copy(&mut reader, writer)?;
+        writer.flush()?;
+        Ok(())
+    }
 }
 

src/compression/none.rs

@@ -30,4 +30,11 @@ impl CompressionEngine for CompressionEngineNone {
         debug!("COMPRESSION: Writting to {:?} using {:?}", file_path, *self);
         Ok(Box::new(File::create(file_path)?))
     }
+
+    fn copy(&self, file_path: PathBuf, writer: &mut dyn Write) -> Result<()> {
+        let mut reader = self.open(file_path)?;
+        io::copy(&mut reader, writer)?;
+        writer.flush()?;
+        Ok(())
+    }
 }

src/main.rs

@@ -535,8 +535,11 @@ fn mode_diff(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &mut Vec<S
             let stdout_a = unsafe { std::fs::File::from_raw_fd(fd_a_write) };
             let stdout_b = unsafe { std::fs::File::from_raw_fd(fd_b_write) };
 
-            compression_engine_a.cat(item_path_a.clone())?;
-            compression_engine_b.cat(item_path_b.clone())?;
+            let mut stdout_a = unsafe { std::fs::File::from_raw_fd(fd_a_write) };
+            let mut stdout_b = unsafe { std::fs::File::from_raw_fd(fd_b_write) };
+
+            compression_engine_a.copy(item_path_a.clone(), &mut stdout_a)?;
+            compression_engine_b.copy(item_path_b.clone(), &mut stdout_b)?;
 
             let output = child.wait_with_output().expect("Failed to wait on diff command");