z80 branch, but with original (slightly more accurate) prob update

src/context_state.rs

@@ -33,13 +33,12 @@ impl<'a> Context<'a> {
 
     pub fn update(&mut self, bit: bool) {
         let old = self.state.contexts[self.index];
-        let offset = if !bit {
-            ONE_PROB as i32 >> UPDATE_RATE
+        if bit {
+            self.state.contexts[self.index] =
+                old - ((old as i32 + UPDATE_ADD) >> UPDATE_RATE) as u8;
         } else {
-            0
-        };
-
-        self.state.contexts[self.index] =
-            (offset + old as i32 - ((old as i32 + UPDATE_ADD) >> UPDATE_RATE)) as u8;
+            self.state.contexts[self.index] =
+                old + (((ONE_PROB as i32 - old as i32) + UPDATE_ADD) >> UPDATE_RATE) as u8;
+        }
     }
 }

src/main.rs

@@ -10,16 +10,12 @@ fn main() -> Result<()> {
         Some("pack") => {
             let level = args.opt_value_from_str(["-l", "--level"])?.unwrap_or(2u8);
             let use_bitstream = args.contains(["-b", "--bitstream"]);
-            let reverse = args.contains(["-r", "--reverse"]);
 
             let infile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
             let outfile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
 
             let mut data = vec![];
             File::open(infile)?.read_to_end(&mut data)?;
-            if reverse {
-                data.reverse();
-            }
 
             let mut pb = pbr::ProgressBar::new(data.len() as u64);
             pb.set_units(pbr::Units::Bytes);
@@ -43,18 +39,14 @@ fn main() -> Result<()> {
         }
         Some("unpack") => {
             let use_bitstream = args.contains(["-b", "--bitstream"]);
-            let reverse = args.contains(["-r", "--reverse"]);
 
             let infile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
             let outfile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
 
             let mut data = vec![];
             File::open(infile)?.read_to_end(&mut data)?;
-            let mut unpacked_data = upkr::unpack(&data, use_bitstream);
-            if reverse {
-                unpacked_data.reverse();
-            }
-            File::create(outfile)?.write_all(&unpacked_data)?;
+            let packed_data = upkr::unpack(&data, use_bitstream);
+            File::create(outfile)?.write_all(&packed_data)?;
         }
         Some(other) => {
             bail!("Unknown subcommand '{}'", other);