1 files changed, 96 insertions, 0 deletions
diff --git a/ebml/src/read.rs b/ebml/src/read.rs
new file mode 100644
index 0000000..0ffb24c
--- /dev/null
+++ b/ebml/src/read.rs
@@ -0,0 +1,96 @@
+use std::io::{Read, Seek};
+
+use anyhow::{bail, Result};
+use log::debug;
+use webm_iterable::matroska_spec::MatroskaSpec;
+
+use crate::format::matroska::{Master, MatroskaTag};
+
+trait ReadAndSeek: Read + Seek {}
+impl<T: Read + Seek> ReadAndSeek for T {}
+
+pub struct EbmlReader {
+    inner: Box<dyn ReadAndSeek>,
+    pub position: usize,
+}
+
+pub trait EbmlRead: Sized {
+    fn read(r: &mut EbmlReader) -> Result<Self>;
+}
+
+impl EbmlReader {
+    pub fn new<T: Seek + Read + 'static>(inner: T) -> Self {
+        Self {
+            inner: Box::new(inner),
+            position: 0,
+        }
+    }
+
+    pub fn read_byte(&mut self) -> Result<u8> {
+        let mut b = [0u8];
+        self.inner.read_exact(&mut b)?;
+        self.position += 1;
+        Ok(b[0])
+    }
+    pub fn read_buf(&mut self, size: impl Into<usize>) -> Result<Vec<u8>> {
+        let size = size.into();
+        let mut b = vec![0u8; size];
+        self.inner.read_exact(&mut b)?;
+        self.position += size;
+        Ok(b)
+    }
+    pub fn read_vint_len(&mut self) -> Result<(u64, usize)> {
+        let s = self.read_byte()?;
+        let len = s.leading_zeros() + 1;
+        let mut value = s as u64;
+        value -= 1 << (8 - len);
+        for _ in 0..(len - 1) {
+            value <<= 8;
+            value += self.read_byte()? as u64;
+        }
+        Ok((value, len as usize))
+    }
+    pub fn read_vint(&mut self) -> Result<u64> {
+        Ok(self.read_vint_len()?.0)
+    }
+    pub fn read_utf8(&mut self, size: impl Into<usize>) -> Result<String> {
+        let b = self.read_buf(size)?;
+        Ok(String::from_utf8(b)?)
+    }
+
+    pub fn read_tag_id(&mut self) -> Result<u64> {
+        let (value, len) = self.read_vint_len()?;
+        Ok(value + (1 << (7 * len)))
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum EbmlSize {
+    Exact(usize),
+    Unknown,
+}
+impl EbmlSize {
+    #[rustfmt::skip]
+    pub fn from_vint((value, len): (u64, usize)) -> EbmlSize {
+        match len {
+            1 => if value == ((1 << (7))     - 1) { return Self::Unknown; },
+            2 => if value == ((1 << (7 * 2)) - 1) { return Self::Unknown; },
+            3 => if value == ((1 << (7 * 3)) - 1) { return Self::Unknown; },
+            4 => if value == ((1 << (7 * 4)) - 1) { return Self::Unknown; },
+            5 => if value == ((1 << (7 * 5)) - 1) { return Self::Unknown; },
+            6 => if value == ((1 << (7 * 6)) - 1) { return Self::Unknown; },
+            7 => if value == ((1 << (7 * 7)) - 1) { return Self::Unknown; },
+            8 => if value == ((1 << (7 * 8)) - 1) { return Self::Unknown; },
+            _ => {},
+        }
+        Self::Exact(len)
+    }
+}
+impl Into<usize> for EbmlSize {
+    fn into(self) -> usize {
+        match self {
+            EbmlSize::Exact(s) => s,
+            EbmlSize::Unknown => panic!("unknown size, where it should have been known"),
+        }
+    }
+}