Make the roundtrip encoding pass

This is done by storing box names and their contents instead of just raw bytes

src/mp4box/meta.rs

@@ -21,7 +21,7 @@ pub enum MetaBox {
         hdlr: HdlrBox,
 
         #[serde(skip)]
-        data: Vec<u8>,
+        data: Vec<(BoxType, Vec<u8>)>,
     },
 }
 
@@ -41,7 +41,13 @@ impl MetaBox {
                     size += ilst.box_size();
                 }
             }
-            Self::Unknown { hdlr, data } => size += hdlr.box_size() + data.len() as u64,
+            Self::Unknown { hdlr, data } => {
+                size += hdlr.box_size()
+                    + data
+                        .iter()
+                        .map(|(_, data)| data.len() as u64 + HEADER_SIZE)
+                        .sum::<u64>()
+            }
         }
         size
     }
@@ -147,8 +153,27 @@ impl<R: Read + Seek> ReadBox<&mut R> for MetaBox {
                 Ok(MetaBox::Mdir { ilst })
             }
             _ => {
-                let mut data = vec![0u8; (end - current) as usize];
-                reader.read_exact(&mut data)?;
+                let mut data = Vec::new();
+
+                while current < end {
+                    // Get box header.
+                    let header = BoxHeader::read(reader)?;
+                    let BoxHeader { name, size: s } = header;
+
+                    match name {
+                        BoxType::HdlrBox => {
+                            skip_box(reader, s)?;
+                        }
+                        _ => {
+                            let mut box_data = vec![0; (s - HEADER_SIZE) as usize];
+                            reader.read_exact(&mut box_data)?;
+
+                            data.push((name, box_data));
+                        }
+                    }
+
+                    current = reader.stream_position()?;
+                }
 
                 Ok(MetaBox::Unknown { hdlr, data })
             }
@@ -178,7 +203,12 @@ impl<W: Write> WriteBox<&mut W> for MetaBox {
                     ilst.write_box(writer)?;
                 }
             }
-            Self::Unknown { data, .. } => writer.write_all(data)?,
+            Self::Unknown { data, .. } => {
+                for (box_type, data) in data {
+                    BoxHeader::new(*box_type, data.len() as u64 + HEADER_SIZE).write(writer)?;
+                    writer.write_all(data)?;
+                }
+            }
         }
         Ok(size)
     }
@@ -235,10 +265,14 @@ mod tests {
 
         let meta_box = MetaBox::read_box(&mut reader, header.size).unwrap();
 
-
         // this contains \xa9too box in the ilst
         // it designates the tool that created the file, but is not yet supported by this crate
-        assert_eq!(meta_box, MetaBox::Mdir { ilst: Some(IlstBox::default()) });
+        assert_eq!(
+            meta_box,
+            MetaBox::Mdir {
+                ilst: Some(IlstBox::default())
+            }
+        );
     }
 
     #[test]
@@ -247,10 +281,10 @@ mod tests {
             handler_type: FourCC::from(*b"test"),
             ..Default::default()
         };
-        let src_data = b"123";
+        let src_data = (BoxType::UnknownBox(0x42494241), b"123".to_vec());
         let src_box = MetaBox::Unknown {
             hdlr: src_hdlr,
-            data: src_data.to_vec(),
+            data: vec![src_data],
         };
 
         let mut buf = Vec::new();