generate seek index

5 files changed, 49 insertions, 7 deletions

diff --git a/matroska/src/bin/experiment.rs b/matroska/src/bin/experiment.rs
index 9bc667c..7787f4f 100644
--- a/matroska/src/bin/experiment.rs
+++ b/matroska/src/bin/experiment.rs
@@ -3,7 +3,7 @@
     which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
     Copyright (C) 2023 metamuffin <metamuffin.org>
 */
-use jellymatroska::{matroska::MatroskaTag, read::EbmlReader, write::EbmlWriter};
+use jellymatroska::{matroska::MatroskaTag, read::EbmlReader, write::EbmlWriter, unflatten::IterWithPos};
 use std::{
     fs::File,
     io::{stdout, BufReader, BufWriter},
diff --git a/matroska/src/bin/mkvdump.rs b/matroska/src/bin/mkvdump.rs
index 6f2e063..10c697a 100644
--- a/matroska/src/bin/mkvdump.rs
+++ b/matroska/src/bin/mkvdump.rs
@@ -3,7 +3,7 @@
     which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
     Copyright (C) 2023 metamuffin <metamuffin.org>
 */
-use jellymatroska::{matroska::MatroskaTag, read::EbmlReader};
+use jellymatroska::{matroska::MatroskaTag, read::EbmlReader, unflatten::IterWithPos};
 use std::{fs::File, io::BufReader};
 
 fn main() -> anyhow::Result<()> {
diff --git a/matroska/src/read.rs b/matroska/src/read.rs
index 1211351..c99f304 100644
--- a/matroska/src/read.rs
+++ b/matroska/src/read.rs
@@ -3,7 +3,7 @@
     which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
     Copyright (C) 2023 metamuffin <metamuffin.org>
 */
-use crate::{matroska::MatroskaTag, size::EbmlSize, Master};
+use crate::{matroska::MatroskaTag, size::EbmlSize, unflatten::IterWithPos, Master};
 use anyhow::{anyhow, bail, Result};
 use log::{debug, warn};
 use std::{
@@ -159,9 +159,13 @@ impl EbmlReader {
     }
 }
 
-impl Iterator for EbmlReader {
+impl IterWithPos for EbmlReader {
     type Item = Result<MatroskaTag>;
 
+    fn position(&self) -> usize {
+        self.position
+    }
+
     fn next(&mut self) -> Option<Self::Item> {
         if let Some(t) = self.queue.pop_front() {
             // match t {
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;
diff --git a/matroska/src/write.rs b/matroska/src/write.rs
index 70ee06c..ee1c44c 100644
--- a/matroska/src/write.rs
+++ b/matroska/src/write.rs
@@ -26,6 +26,31 @@ impl EbmlWriter {
         Ok(())
     }
 
+    pub fn write_padding(&mut self, position: usize) -> Result<()> {
+        let mut size = position - self.position;
+        match size {
+            0 => return Ok(()),
+            1 => bail!("this is sadly not possible"),
+            _ => (),
+        }
+        size -= 1; // subtract tag size
+        size -= 4; // subtract vint size
+
+        // match size {
+        //     _ if size < (1 << 7) => size -= 1,
+        //     _ if size < (1 << 14) => size -= 2,
+        //     _ if size < (1 << 21) => size -= 3,
+        //     _ if size < (1 << 28) => size -= 4,
+        //     _ if size < (1 << 35) => size -= 5,
+        //     _ => bail!("padding to large"),
+        // }
+
+        self.write(&[0xec])?;
+        self.write_vint_len(size.try_into().unwrap(), 4)?;
+        self.write(&vec![0; size])?;
+        Ok(())
+    }
+
     pub fn write_tag(&mut self, tag: &MatroskaTag) -> Result<()> {
         let mut buf = vec![];
         tag.write_full(&mut buf)?;
@@ -44,6 +69,9 @@ impl EbmlWriter {
             }
             len += 1;
         }
+        self.write_vint_len(i, len)
+    }
+    pub fn write_vint_len(&mut self, i: u64, len: usize) -> Result<()> {
         let mut bytes = i.to_be_bytes();
         let trunc = &mut bytes[(8 - len)..];
         trunc[0] |= 1 << (8 - len);