calculate and encode window size correctly

Author: KillingSpark

src/encoding/frame_header.rs

@@ -45,8 +45,11 @@ impl FrameHeader {
         // `Window_Descriptor
         // TODO: https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#window_descriptor
         if !self.single_segment {
-            let exponent = 7;
-            output.push(exponent << 3);
+            if let Some(window_size) = self.window_size {
+                let log = window_size.next_power_of_two().ilog2();
+                let exponent = if log > 10 { log - 10 } else { 1 } as u8;
+                output.push(exponent << 3);
+            }
         }
 
         if let Some(id) = self.dictionary_id {

src/encoding/match_generator.rs

@@ -50,7 +50,7 @@ impl Matcher for MatchGeneratorDriver {
     }
 
     fn window_size(&self) -> u64 {
-        256 * 1024
+        self.match_generator.max_window_size as u64
     }
 
     fn get_next_space(&mut self) -> Vec<u8> {