From d735464e56547220831d2457de63a09ff132d8c4 Mon Sep 17 00:00:00 2001
From: Nikita Strygin <nikita6@bk.ru>
Date: Tue, 14 Feb 2023 23:52:11 +0300
Subject: [PATCH] Allow Hdlr to be not the first in the Meta box

While the spec says that the hdlr box should be the first one, not all
implementations follow that. Actually look over all boxes in Meta to
find Hdlr.

Also add a test for such weirdly-formatted box

Change the way unknown MetaBox is stored: store a list of boxes instead
of raw bytes
---
 src/mp4box/meta.rs | 103 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 88 insertions(+), 15 deletions(-)

diff --git a/src/mp4box/meta.rs b/src/mp4box/meta.rs
index df57c77..6e155a2 100644
--- a/src/mp4box/meta.rs
+++ b/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
     }
@@ -89,17 +95,41 @@ impl<R: Read + Seek> ReadBox<&mut R> for MetaBox {
             return Err(Error::UnsupportedBoxVersion(BoxType::UdtaBox, version));
         }
 
-        let hdlr_header = BoxHeader::read(reader)?;
-        if hdlr_header.name != BoxType::HdlrBox {
-            return Err(Error::BoxNotFound(BoxType::HdlrBox));
-        }
-        let hdlr = HdlrBox::read_box(reader, hdlr_header.size)?;
-
-        let mut ilst = None;
-
         let mut current = reader.stream_position()?;
         let end = start + size;
 
+        let content_start = current;
+
+        // find the hdlr box
+        let mut hdlr = None;
+        while current < end {
+            // Get box header.
+            let header = BoxHeader::read(reader)?;
+            let BoxHeader { name, size: s } = header;
+
+            match name {
+                BoxType::HdlrBox => {
+                    hdlr = Some(HdlrBox::read_box(reader, s)?);
+                }
+                _ => {
+                    // XXX warn!()
+                    skip_box(reader, s)?;
+                }
+            }
+
+            current = reader.stream_position()?;
+        }
+
+        let Some(hdlr) = hdlr else {
+            return Err(Error::BoxNotFound(BoxType::HdlrBox));
+        };
+
+        // rewind and handle the other boxes
+        reader.seek(SeekFrom::Start(content_start))?;
+        current = reader.stream_position()?;
+
+        let mut ilst = None;
+
         match hdlr.handler_type {
             MDIR => {
                 while current < end {
@@ -123,8 +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 })
             }
@@ -154,7 +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)
     }
@@ -202,16 +256,35 @@ mod tests {
         assert_eq!(dst_box, src_box);
     }
 
+    #[test]
+    fn test_meta_hdrl_non_first() {
+        let data = b"\x00\x00\x00\x7fmeta\x00\x00\x00\x00\x00\x00\x00Qilst\x00\x00\x00I\xa9too\x00\x00\x00Adata\x00\x00\x00\x01\x00\x00\x00\x00TMPGEnc Video Mastering Works 7 Version 7.0.15.17\x00\x00\x00\"hdlr\x00\x00\x00\x00\x00\x00\x00\x00mdirappl\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00";
+        let mut reader = Cursor::new(data);
+        let header = BoxHeader::read(&mut reader).unwrap();
+        assert_eq!(header.name, BoxType::MetaBox);
+
+        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())
+            }
+        );
+    }
+
     #[test]
     fn test_meta_unknown() {
         let src_hdlr = HdlrBox {
             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();