diff --git a/src/fot/decoder.rs b/src/fot/decoder.rs
index 0610243..2bf77ae 100644
--- a/src/fot/decoder.rs
+++ b/src/fot/decoder.rs
@@ -1,10 +1,11 @@
 use super::raw::Raw;
+use super::stream::WriteStream;
 use anyhow::Result;
 use std::str;
 
 pub trait Decoder: Sized {
     fn decode(raw: &Raw, offset: usize, size: usize) -> Result<Self>;
-    fn encode(&self) -> Result<Raw>;
+    fn encode(&self, wd: &mut WriteStream) -> Result<()>;
     fn get_enc_size(&self) -> usize;
 }
 
@@ -23,14 +24,10 @@ impl Decoder for String {
         }
     }
 
-    fn encode(&self) -> Result<Raw> {
-        let mut str = self.as_bytes().to_vec();
-        str.push(0);
-        Ok(Raw {
-            offset: 0,
-            size: str.len(),
-            mem: str,
-        })
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+        wd.write_bytes(self.as_bytes());
+        wd.write_u8(0)?;
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {
diff --git a/src/fot/esh.rs b/src/fot/esh.rs
index e5c1cee..d81adfd 100644
--- a/src/fot/esh.rs
+++ b/src/fot/esh.rs
@@ -119,8 +119,7 @@ impl Decoder for ESHValue {
         })
     }
 
-    fn encode(&self) -> Result<Raw> {
-        let mut wd = WriteStream::new(self.get_enc_size());
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
         match self {
             ESHValue::Unknown(unk) => {
                 wd.write_u32(unk.data_type)?;
@@ -191,7 +190,7 @@ impl Decoder for ESHValue {
             }
         };
 
-        Ok(wd.into_raw(0, 0))
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {
@@ -268,8 +267,7 @@ impl Decoder for ESH {
         })
     }
 
-    fn encode(&self) -> Result<Raw> {
-        let mut wd = WriteStream::new(self.get_enc_size());
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
         wd.write(&self.tag)?;
 
         wd.write_u32(self.props.len() as u32)?;
@@ -278,7 +276,7 @@ impl Decoder for ESH {
             wd.write(value)?;
         }
 
-        Ok(wd.into_raw(0, 0))
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {
diff --git a/src/fot/fstring.rs b/src/fot/fstring.rs
index 84f0539..3d4d7e6 100644
--- a/src/fot/fstring.rs
+++ b/src/fot/fstring.rs
@@ -1,7 +1,8 @@
 use super::decoder::Decoder;
 use super::raw::Raw;
+use super::stream::WriteStream;
 use anyhow::Result;
-use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
+use byteorder::{LittleEndian, ReadBytesExt};
 use encoding_rs::WINDOWS_1251;
 use std::borrow::Borrow;
 use std::fmt;
@@ -53,26 +54,20 @@ impl Decoder for FString {
         }
     }
 
-    fn encode(&self) -> Result<Raw> {
-        let mut buf = vec![0u8; 4];
-        let mut wdr = Cursor::new(&mut buf[..]);
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
         let (chars, _, _) = WINDOWS_1251.encode(self.str.as_str());
         if self.encoding == FStringEncoding::ANSI {
-            wdr.write_u32::<LittleEndian>(chars.len() as u32 & !(1 << 31))?;
-            buf.extend(chars.iter());
+            wd.write_u32(chars.len() as u32 & !(1 << 31))?;
+            wd.write_bytes(&chars);
         } else {
             // WCS2
-            wdr.write_u32::<LittleEndian>(chars.len() as u32 | (1 << 31))?;
+            wd.write_u32(chars.len() as u32 | (1 << 31))?;
             for &c in chars.iter() {
-                buf.push(c);
-                buf.push(0);
+                wd.write_u8(c)?;
+                wd.write_u8(0)?;
             }
         };
-        Ok(Raw {
-            offset: 0,
-            size: buf.len(),
-            mem: buf,
-        })
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {
diff --git a/src/fot/save.rs b/src/fot/save.rs
index 8a2ce50..f3897ee 100644
--- a/src/fot/save.rs
+++ b/src/fot/save.rs
@@ -1,5 +1,6 @@
 use super::decoder::Decoder;
 use super::raw::Raw;
+use super::stream::WriteStream;
 use super::world::World;
 use anyhow::anyhow;
 use anyhow::Result;
@@ -50,7 +51,12 @@ impl Save {
     }
 
     pub fn save(&self, path: &Path) -> Result<()> {
-        self.raw.assemble_file(path, vec![self.world.encode()?])?;
+        let raw = {
+            let mut wd = WriteStream::new(0);
+            wd.write(&self.world)?;
+            wd.into_raw(self.world.offset, self.world.size)
+        };
+        self.raw.assemble_file(path, vec![raw])?;
 
         Ok(())
     }
diff --git a/src/fot/sgd.rs b/src/fot/sgd.rs
index 7f5526e..29a6503 100644
--- a/src/fot/sgd.rs
+++ b/src/fot/sgd.rs
@@ -48,8 +48,7 @@ impl Decoder for SGD {
         })
     }
 
-    fn encode(&self) -> Result<Raw> {
-        let mut wd = WriteStream::new(self.enc_size);
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
         wd.write(&self.tag)?;
         wd.write_bytes(&self.unk1);
 
@@ -66,7 +65,7 @@ impl Decoder for SGD {
             }
         }
 
-        Ok(wd.into_raw(0, 0))
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {
diff --git a/src/fot/ssg.rs b/src/fot/ssg.rs
index 86186fe..ada266d 100644
--- a/src/fot/ssg.rs
+++ b/src/fot/ssg.rs
@@ -18,11 +18,10 @@ impl Decoder for SSG {
         Ok(SSG { tag, unk1 })
     }
 
-    fn encode(&self) -> Result<Raw> {
-        let mut wd = WriteStream::new(self.get_enc_size());
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
         wd.write(&self.tag)?;
         wd.write_bytes(&self.unk1);
-        Ok(wd.into_raw(0, 0x14))
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {
diff --git a/src/fot/stream.rs b/src/fot/stream.rs
index 07a9908..db34383 100644
--- a/src/fot/stream.rs
+++ b/src/fot/stream.rs
@@ -116,6 +116,10 @@ impl WriteStream {
         self.buf.get_mut().extend(bytes.iter());
     }
 
+    pub fn reserve(&mut self, size: usize) {
+        self.buf.get_mut().reserve(size);
+    }
+
     pub fn write_opt<T: DecoderCtx<DCtx, ECtx>, DCtx, ECtx>(
         &mut self,
         val: &T,
@@ -128,9 +132,11 @@ impl WriteStream {
     }
 
     pub fn write<T: Decoder>(&mut self, val: &T) -> Result<()> {
-        let mut raw = val.encode()?;
-        self.skip(raw.mem.len());
-        self.buf.get_mut().append(&mut raw.mem);
+        //let mut raw = val.encode()?;
+        //self.skip(raw.mem.len());
+        //self.buf.get_mut().append(&mut raw.mem);
+        self.reserve(val.get_enc_size());
+        val.encode(self)?;
         Ok(())
     }
 
diff --git a/src/fot/tag.rs b/src/fot/tag.rs
index b939f68..58224fd 100644
--- a/src/fot/tag.rs
+++ b/src/fot/tag.rs
@@ -17,11 +17,10 @@ impl Decoder for Tag {
         Ok(Tag { name, version })
     }
 
-    fn encode(&self) -> Result<Raw> {
-        let mut wd = WriteStream::new(self.get_enc_size());
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
         wd.write(&self.name)?;
         wd.write(&self.version)?;
-        Ok(wd.into_raw(0, self.get_enc_size()))
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {
diff --git a/src/fot/world.rs b/src/fot/world.rs
index 5d013b2..dc82ee1 100644
--- a/src/fot/world.rs
+++ b/src/fot/world.rs
@@ -88,7 +88,7 @@ impl Decoder for World {
         })
     }
 
-    fn encode(&self) -> Result<Raw> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
         let data = {
             let mut wd = WriteStream::new(self.uncompressed_size as usize);
             
@@ -101,14 +101,13 @@ impl Decoder for World {
             let raw = wd.into_raw(0, 0);
             deflate_bytes_zlib(&raw.mem)
         };
-
-        let mut wd = WriteStream::new(self.get_enc_size());
+        
         wd.write(&self.tag)?;
         wd.write_u32(self.uncompressed_size)?;
         wd.write_u32(self.uncompressed_size)?;
         wd.write_bytes(&data);
 
-        Ok(wd.into_raw(self.offset, self.size))
+        Ok(())
     }
 
     fn get_enc_size(&self) -> usize {