fix issue encoding qrcode digit only data

src/qrcode/encoder/EncoderTestCase.rs

@@ -71,6 +71,17 @@ fn testGetAlphanumericCode() {
     assert_eq!(-1, encoder::getAlphanumericCode(b'\0' as u32));
 }
 
+#[test]
+fn test_digits_only() {
+    let test_data = "374833744734397449";
+    let data = encoder::encode(test_data, ErrorCorrectionLevel::H).expect("encode");
+    let decode = crate::qrcode::decoder::decoder::decode_bitmatrix(
+        &data.getMatrix().as_ref().unwrap().clone().into(),
+    )
+    .expect("decode");
+    assert_eq!(test_data, decode.getText());
+}
+
 #[test]
 fn testChooseMode() {
     // Numeric Mode::

src/qrcode/encoder/encoder.rs

@@ -732,7 +732,7 @@ pub fn appendNumericBytes(content: &str, bits: &mut BitArray) -> Result<(), Exce
             // Encode three numeric letters in ten bits.
             let num2 = content.chars().nth(i + 1).unwrap() as u8 - b'0';
             let num3 = content.chars().nth(i + 2).unwrap() as u8 - b'0';
-            bits.appendBits((num1 * 100 + num2 * 10 + num3) as u32, 10)?;
+            bits.appendBits(num1 as u32 * 100 + num2 as u32 * 10 + num3 as u32, 10)?;
             i += 3;
         } else if i + 1 < length {
             // Encode two numeric letters in seven bits.