1 files changed, 13 insertions, 3 deletions
diff --git a/matroska/src/unflatten.rs b/matroska/src/unflatten.rs
index 5e0ba31..663eebc 100644
--- a/matroska/src/unflatten.rs
+++ b/matroska/src/unflatten.rs
@@ -6,19 +6,25 @@
 use crate::{matroska::MatroskaTag, Master};
 use anyhow::Result;
 
+pub trait IterWithPos {
+    type Item;
+    fn next(&mut self) -> Option<Self::Item>;
+    fn position(&self) -> usize;
+}
+
 pub struct Unflat<'a> {
     pub item: MatroskaTag,
     pub children: Option<Unflatten<'a>>,
 }
 
 pub struct Unflatten<'a> {
-    inner: &'a mut dyn Iterator<Item = Result<MatroskaTag>>,
+    inner: &'a mut dyn IterWithPos<Item = Result<MatroskaTag>>,
     stop: bool,
     end: Option<MatroskaTag>,
 }
 
 impl<'a> Unflatten<'a> {
-    pub fn new(inner: &'a mut dyn Iterator<Item = Result<MatroskaTag>>) -> Self {
+    pub fn new(inner: &'a mut dyn IterWithPos<Item = Result<MatroskaTag>>) -> Self {
         Self {
             inner,
             stop: false,
@@ -26,7 +32,7 @@ impl<'a> Unflatten<'a> {
         }
     }
     pub fn new_with_end(
-        inner: &'a mut dyn Iterator<Item = Result<MatroskaTag>>,
+        inner: &'a mut dyn IterWithPos<Item = Result<MatroskaTag>>,
         start: MatroskaTag,
     ) -> Self {
         Self {
@@ -36,6 +42,10 @@ impl<'a> Unflatten<'a> {
         }
     }
 
+    pub fn position(&self) -> usize {
+        self.inner.position()
+    }
+
     pub fn next(&mut self) -> Option<Result<Unflat>> {
         if self.stop {
             return None;