Fix audio data extraction

The audio data was initially read and written by chunks of 2352 bytes,
which is the usual sector size for audio CDs. However, this didn't work
on images with a 2448-byte sector size (2352 bytes data + 96 bytes
sub-channel data): we would end up reading data from the NRG footer.

The data is now read/written by 4 MiB (which is faster anyway), and we
make sure to read the remaining bytes if the audio data size is not a
multiple of 4 MiB.

src/raw_audio.rs

@@ -41,6 +41,8 @@ pub fn extract_nrg_raw_audio(in_fd: &mut File,
                              img_path: &String,
                              metadata: &NrgMetadata)
                              -> Result<(), NrgError> {
+    const BUF_SIZE: usize = 1024 * 1024 * 4; // 4 MiB
+
     // Seek to the first audio byte
     let skip_bytes = get_daox_track1_index1(metadata);
     try!(in_fd.seek(SeekFrom::Start(skip_bytes)));
@@ -51,21 +53,34 @@ pub fn extract_nrg_raw_audio(in_fd: &mut File,
 
     // Read/write audio data
     let mut cur_offset = skip_bytes;
-    while cur_offset < metadata.chunk_offset {
-        let mut audio_buf = [0u8; 2352];
+    while cur_offset + BUF_SIZE as u64 <= metadata.chunk_offset {
+        let mut audio_buf = [0u8; BUF_SIZE];
 
         let mut nbytes = try!(in_fd.read(&mut audio_buf));
-        if nbytes != 2352 {
+        if nbytes != BUF_SIZE {
             return Err(NrgError::AudioReadError);
         }
         cur_offset += nbytes as u64;
 
         nbytes = try!(out_fd.write(&audio_buf));
-        if nbytes != 2352 {
+        if nbytes != BUF_SIZE {
             return Err(NrgError::AudioWriteError);
         }
     }
 
+    // Read/write the last bytes
+    let remaining: usize = (metadata.chunk_offset - cur_offset) as usize;
+    let mut audio_buf = vec![0u8; remaining];
+    let mut nbytes = try!(in_fd.read(&mut audio_buf));
+    if nbytes != remaining {
+        return Err(NrgError::AudioReadError);
+    }
+    cur_offset += nbytes as u64;
+    nbytes = try!(out_fd.write(&audio_buf));
+    if nbytes != remaining {
+        return Err(NrgError::AudioWriteError);
+    }
+
     assert_eq!(cur_offset, metadata.chunk_offset);
     Ok(())
 }