diff --git a/src/qrcode/cpp_port/bitmatrix_parser.rs b/src/qrcode/cpp_port/bitmatrix_parser.rs
index b70c978..d629043 100644
--- a/src/qrcode/cpp_port/bitmatrix_parser.rs
+++ b/src/qrcode/cpp_port/bitmatrix_parser.rs
@@ -149,7 +149,7 @@ pub fn ReadQRCodewords(
                     // Read a bit
                     AppendBit(
                         &mut currentByte,
-                        GetDataMaskBit(formatInfo.data_mask as u32, xx, y, None)
+                        GetDataMaskBit(formatInfo.data_mask as u32, xx, y, None)?
                             != getBit(bitMatrix, xx, y, Some(formatInfo.isMirrored)),
                     );
                     // If we've made a whole byte, save it off
@@ -214,7 +214,7 @@ pub fn ReadMQRCodewords(
                     // Read a bit
                     AppendBit(
                         &mut currentByte,
-                        GetDataMaskBit(formatInfo.data_mask as u32, xx, y, Some(true))
+                        GetDataMaskBit(formatInfo.data_mask as u32, xx, y, Some(true))?
                             != getBit(bitMatrix, xx, y, Some(formatInfo.isMirrored)),
                     );
                     bitsRead += 1;
diff --git a/src/qrcode/cpp_port/data_mask.rs b/src/qrcode/cpp_port/data_mask.rs
index 1db71c3..6effb85 100644
--- a/src/qrcode/cpp_port/data_mask.rs
+++ b/src/qrcode/cpp_port/data_mask.rs
@@ -5,6 +5,8 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use crate::common::BitMatrix;
+use crate::common::Result;
+use crate::Exceptions;
 
 /**
 * <p>Encapsulates data masks for the data bits in a QR  and micro QR code, per ISO 18004:2006 6.8.</p>
@@ -13,27 +15,33 @@ use crate::common::BitMatrix;
 * and j is row position. In fact, as the text says, i is row position and j is column position.</p>
 */
 
-pub fn GetDataMaskBit(maskIndex: u32, x: u32, y: u32, isMicro: Option<bool>) -> bool {
+pub fn GetDataMaskBit(maskIndex: u32, x: u32, y: u32, isMicro: Option<bool>) -> Result<bool> {
     let isMicro = isMicro.unwrap_or(false);
-    todo!()
-    // if (isMicro) {
-    // 	if (maskIndex < 0 || maskIndex >= 4)
-    // 		throw std::invalid_argument("QRCode maskIndex out of range");
-    // 	maskIndex = std::array{1, 4, 6, 7}[maskIndex]; // map from MQR to QR indices
-    // }
+    let mut maskIndex = maskIndex;
+    if (isMicro) {
+        if (maskIndex < 0 || maskIndex >= 4) {
+            return Err(Exceptions::illegal_argument_with(
+                "QRCode maskIndex out of range",
+            ));
+        }
+        maskIndex = [1, 4, 6, 7][maskIndex as usize]; // map from MQR to QR indices
+    }
 
-    // switch (maskIndex) {
-    // case 0: return (y + x) % 2 == 0;
-    // case 1: return y % 2 == 0;
-    // case 2: return x % 3 == 0;
-    // case 3: return (y + x) % 3 == 0;
-    // case 4: return ((y / 2) + (x / 3)) % 2 == 0;
-    // case 5: return (y * x) % 6 == 0;
-    // case 6: return ((y * x) % 6) < 3;
-    // case 7: return (y + x + ((y * x) % 3)) % 2 == 0;
-    // }
+    match (maskIndex) {
+        0 => return Ok((y + x) % 2 == 0),
+        1 => return Ok(y % 2 == 0),
+        2 => return Ok(x % 3 == 0),
+        3 => return Ok((y + x) % 3 == 0),
+        4 => return Ok(((y / 2) + (x / 3)) % 2 == 0),
+        5 => return Ok((y * x) % 6 == 0),
+        6 => return Ok(((y * x) % 6) < 3),
+        7 => return Ok((y + x + ((y * x) % 3)) % 2 == 0),
+        _ => {}
+    }
 
-    // throw std::invalid_argument("QRCode maskIndex out of range");
+    Err(Exceptions::illegal_argument_with(
+        "QRCode maskIndex out of range",
+    ))
 }
 
 pub fn GetMaskedBit(
@@ -42,6 +50,6 @@ pub fn GetMaskedBit(
     y: u32,
     maskIndex: u32,
     isMicro: Option<bool>,
-) -> bool {
-    return GetDataMaskBit(maskIndex, x, y, isMicro) != bits.get(x, y);
+) -> Result<bool> {
+    Ok(GetDataMaskBit(maskIndex, x, y, isMicro)? != bits.get(x, y))
 }