Implement writing a barebones EBML header from scratch

src/bin/stub.rs

@@ -0,0 +1,12 @@
+extern crate lab_ebml;
+
+use std::io::{Cursor, stdout, Write};
+use lab_ebml::webm::*;
+
+pub fn main() {
+    let mut cursor = Cursor::new(Vec::new());
+
+    encode_webm_element(WebmElement::EbmlHead, &mut cursor).unwrap();
+
+    stdout().write_all(&cursor.get_ref()).unwrap();
+}

src/ebml.rs

@@ -4,6 +4,7 @@ use std::fmt::{Display, Formatter, Result as FmtResult};
 use std::io::{Cursor, Error as IoError, ErrorKind, Result as IoResult, Write, Seek, SeekFrom};
 
 pub const EBML_HEAD_ID: u64 = 0x0A45DFA3;
+pub const DOC_TYPE_ID: u64 = 0x0282;
 pub const VOID_ID: u64 = 0x6C;
 
 #[derive(Debug, PartialEq)]

src/webm.rs

@@ -1,3 +1,4 @@
+use std::io::{Error as IoError, ErrorKind, Result as IoResult, Write, Seek};
 use bytes::{BigEndian, ByteOrder};
 use ebml::*;
 
@@ -79,6 +80,18 @@ fn decode_simple_block(bytes: &[u8]) -> Result<WebmElement, Error> {
     }
 }
 
+pub fn encode_webm_element<T: Write + Seek>(element: WebmElement, output: &mut T) -> IoResult<()> {
+    let mut start = 0;
+    match element {
+        WebmElement::EbmlHead => {
+            encode_element(EBML_HEAD_ID, output, |output| {
+                encode_string(DOC_TYPE_ID, "webm", output)
+            })
+        }
+        _ => Err(IoError::new(ErrorKind::InvalidInput, WriteError::OutOfRange))
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use tests::TEST_FILE;