implement WriteStream

src/fot/stream.rs

@@ -38,3 +38,46 @@ impl<'a> ReadStream<'a> {
         Ok(self.rdr.read_u32::<LittleEndian>()?)
     }
 }
+
+pub struct WriteStream {
+    buf: Cursor<Vec<u8>>,
+}
+
+impl WriteStream {
+    pub fn new(capacity: usize) -> WriteStream {
+        WriteStream {
+            buf: Cursor::new(Vec::with_capacity(capacity)),
+        }
+    }
+
+    pub fn into_raw(self, offset: usize, size: usize) -> Raw {
+        let buf_size = self.buf.get_ref().len();
+        Raw {
+            offset: offset,
+            size: if size == 0 { buf_size } else { size },
+            mem: self.buf.into_inner(),
+        }
+    }
+
+    pub fn offset(&self) -> usize {
+        self.buf.position() as usize
+    }
+
+    pub fn write_bytes(&mut self, bytes: &[u8]) {
+        self.buf.get_mut().extend(bytes.iter());
+    }
+
+    pub fn write<T: Decoder>(&mut self, val: &T) -> Result<()> {
+        let mut raw = val.encode()?;
+        self.buf.get_mut().append(&mut raw.mem);
+        Ok(())
+    }
+
+    pub fn write_u16(&mut self, val: u16) -> Result<()> {
+        Ok(self.buf.write_u16::<LittleEndian>(val)?)
+    }
+
+    pub fn write_u32(&mut self, val: u32) -> Result<()> {
+        Ok(self.buf.write_u32::<LittleEndian>(val)?)
+    }
+}