QPACK: fix a prefi_int bug when integer encoding has a perfect fit

quinn-h3/src/qpack/prefix_int.rs

@@ -58,7 +58,7 @@ pub fn encode<B: BufMut>(size: u8, flags: u8, value: usize, buf: &mut B) {
     buf.write(mask | flags);
     let mut remaining = value - mask as usize;
 
-    while remaining > 128 {
+    while remaining >= 128 {
         let rest = (remaining % 128) as u8;
         buf.write(rest + 128);
         remaining /= 128;
@@ -138,4 +138,9 @@ mod test {
         let mut read = Cursor::new(&buf);
         assert!(super::decode(8, &mut read).is_err());
     }
+
+    #[test]
+    fn number_never_ends_with_0x80() {
+        check_codec(4, 0b0001, 143, &[31, 128, 1]);
+    }
 }

quinn-h3/src/qpack/prefix_string/encode.rs

@@ -56,7 +56,9 @@ impl HuffmanEncoder {
             self.buffer.reserve(((7 * end_range.byte) / 4) as usize);
         }
 
-        while self.buffer.len() <= end_range.byte as usize {
+        let forward =
+            end_range.byte as usize - self.buffer.len() + if end_range.bit > 0 { 1 } else { 0 };
+        for _ in 0..forward {
             // push filler value that will ends huffman decoding if not
             // modified
             self.buffer.push(255);