Handle near-converged state

src/main.rs

@@ -16,21 +16,46 @@ fn get_symbol(model: &Model, low: f64, high: f64) -> Option<u8> {
 }
 
 fn encode(input: &[u8], model: &Model) -> Vec<u8> {
+    const HALF: u64 = 1 << (u64::BITS - 1);
+    const LOW_CONVERGE: u64 = 0b10 << (u64::BITS - 2);
+    const HIGH_CONVERGE: u64 = 0b01 << (u64::BITS - 2);
+
     let mut output = BitWriter::new();
+
     let mut high = u64::MAX;
     let mut low = u64::MIN;
+    let mut pending_bits = 0;
+
     for symbol in input {
         let range = high - low;
         let p = model.get(symbol).expect("Invalid/Unsupported data");
         high = low + (range as f64 * p.1) as u64;
         low = low + (range as f64 * p.0) as u64;
         loop {
-            if high < 1 << 63 {
+            if high < HALF {
                 output.write(false);
                 print!("0");
-            } else if low >= 1 << (u64::BITS - 1) {
+                while pending_bits > 0 {
                     output.write(true);
                     print!("1");
+                    pending_bits -= 1;
+                }
+            } else if low >= HALF {
+                output.write(true);
+                print!("1");
+                while pending_bits > 0 {
+                    output.write(true);
+                    print!("0");
+                    pending_bits -= 1;
+                }
+            } else if low >= LOW_CONVERGE && high < HIGH_CONVERGE {
+                println!("BET");
+                pending_bits += 1;
+                low <<= 1;
+                low &= HALF - 1;
+                high <<= 1;
+                high &= HALF + 1;
+                continue;
             } else {
                 break;
             }