diff --git a/legendary/models/chunk.py b/legendary/models/chunk.py
index b3bed1d..7229be4 100644
--- a/legendary/models/chunk.py
+++ b/legendary/models/chunk.py
@@ -111,8 +111,11 @@ class Chunk:
 
         return _chunk
 
-    def write(self, compress=True):
-        bio = BytesIO()
+    def write(self, fp=None, compress=True):
+        if not fp:
+            bio = BytesIO()
+        else:
+            bio = fp
 
         self.uncompressed_size = self.compressed_size = len(self.data)
         if compress or self.compressed:
@@ -139,4 +142,5 @@ class Chunk:
         # finally, add the data
         bio.write(self._data)
 
-        return bio.getvalue()
+        if not fp:
+            return bio.getvalue()
diff --git a/legendary/models/manifest.py b/legendary/models/manifest.py
index bfa5d9b..54fe2c4 100644
--- a/legendary/models/manifest.py
+++ b/legendary/models/manifest.py
@@ -135,8 +135,9 @@ class Manifest:
 
         return _manifest
 
-    def write(self, compress=True):
+    def write(self, fp=None, compress=True):
         body_bio = BytesIO()
+
         self.meta.write(body_bio)
         self.chunk_data_list.write(body_bio)
         self.file_manifest_list.write(body_bio)
@@ -151,7 +152,11 @@ class Manifest:
             self.data = zlib.compress(self.data)
             self.size_compressed = len(self.data)
 
-        bio = BytesIO()
+        if not fp:
+            bio = BytesIO()
+        else:
+            bio = fp
+
         bio.write(struct.pack('<I', self.header_magic))
         bio.write(struct.pack('<I', self.header_size))
         bio.write(struct.pack('<I', self.size_uncompressed))
@@ -161,7 +166,8 @@ class Manifest:
         bio.write(struct.pack('<I', self.version))
         bio.write(self.data)
 
-        return bio.getvalue()
+        if not fp:
+            return bio.getvalue()
 
 
 class ManifestMeta: