Add support for setting network buffers. (#31)

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

Author: PiotrSikora

src/traits.rs

@@ -136,6 +136,10 @@ pub trait StreamContext: Context {
         hostcalls::get_buffer(BufferType::DownstreamData, start, max_size).unwrap()
     }
 
+    fn set_downstream_data(&self, start: usize, size: usize, value: &[u8]) {
+        hostcalls::set_buffer(BufferType::DownstreamData, start, size, value).unwrap()
+    }
+
     fn on_downstream_close(&mut self, _peer_type: PeerType) {}
 
     fn on_upstream_data(&mut self, _data_size: usize, _end_of_stream: bool) -> Action {
@@ -146,6 +150,10 @@ pub trait StreamContext: Context {
         hostcalls::get_buffer(BufferType::UpstreamData, start, max_size).unwrap()
     }
 
+    fn set_upstream_data(&self, start: usize, size: usize, value: &[u8]) {
+        hostcalls::set_buffer(BufferType::UpstreamData, start, size, value).unwrap()
+    }
+
     fn on_upstream_close(&mut self, _peer_type: PeerType) {}
 
     fn on_log(&mut self) {}