new starting with a new ebml impl

1 files changed, 36 insertions, 0 deletions

diff --git a/ebml/src/write.rs b/ebml/src/write.rs
new file mode 100644
index 0000000..b294d44
--- /dev/null
+++ b/ebml/src/write.rs
@@ -0,0 +1,36 @@
+use anyhow::{bail, Result};
+use std::io::Write;
+
+pub struct EbmlWriter<T> {
+    inner: T,
+    position: usize,
+}
+
+impl<T: Write> EbmlWriter<T> {
+    pub fn new(inner: T, position: usize) -> Self {
+        Self { inner, position }
+    }
+
+    pub fn write(&mut self, data: &[u8]) -> Result<()> {
+        self.inner.write_all(data)?;
+        self.position += data.len();
+        Ok(())
+    }
+
+    pub fn write_vint(&mut self, i: u64) -> Result<()> {
+        if i > (1 << 56) - 1 {
+            bail!("vint does not fit");
+        }
+        let mut len = 1;
+        while len <= 8 {
+            if i < (1 << ((7 * len) - 1)) {
+                break;
+            }
+            len += 1;
+        }
+        let mut bytes = i.to_be_bytes();
+        bytes[0] |= 1 << (8 - len);
+        self.write(&bytes)
+    }
+}
+