Updated Crc64Nvme to have a JS and VM implementation due to the int size difference between platforms

Author: tyllark

packages/smithy/smithy_aws/lib/src/http/interceptors/crc64nvme_js.dart

@@ -0,0 +1,22 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import 'package:crclib/crclib.dart';
+
+/// CRC-64/NVME implementation for JavaScript/Web.
+///
+/// On JS, only 32-bit integers are supported, so we use BigInt for 64-bit values.
+/// Parameters are defined here:
+/// https://reveng.sourceforge.io/crc-catalogue/all.htm#crc.cat.crc-64-nvme
+/// https://nvmexpress.org/wp-content/uploads/NVM-Express-NVM-Command-Set-Specification-1.0d-2023.12.28-Ratified.pdf
+class Crc64Nvme extends ParametricCrc {
+  Crc64Nvme()
+    : super(
+        64,
+        BigInt.parse('ad93d23594c93659', radix: 16),
+        BigInt.parse('ffffffffffffffff', radix: 16),
+        BigInt.parse('ffffffffffffffff', radix: 16),
+        inputReflected: true,
+        outputReflected: true,
+      );
+}

packages/smithy/smithy_aws/lib/src/http/interceptors/crc64nvme_vm.dart

@@ -0,0 +1,22 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import 'package:crclib/crclib.dart';
+
+/// CRC-64/NVME implementation for Dart VM.
+///
+/// On the VM, 64-bit integers are supported natively, so we use int.
+/// Parameters are defined here:
+/// https://reveng.sourceforge.io/crc-catalogue/all.htm#crc.cat.crc-64-nvme
+/// https://nvmexpress.org/wp-content/uploads/NVM-Express-NVM-Command-Set-Specification-1.0d-2023.12.28-Ratified.pdf
+class Crc64Nvme extends ParametricCrc {
+  Crc64Nvme()
+    : super(
+        64,
+        0xad93d23594c93659,
+        0xffffffffffffffff,
+        0xffffffffffffffff,
+        inputReflected: true,
+        outputReflected: true,
+      );
+}

packages/smithy/smithy_aws/lib/src/http/interceptors/with_checksum.dart

@@ -10,13 +10,21 @@ import 'package:crclib/catalog.dart';
 import 'package:crclib/crclib.dart';
 import 'package:crypto/crypto.dart';
 import 'package:smithy/smithy.dart';
+import 'package:smithy_aws/src/http/interceptors/crc64nvme_js.dart'
+    if (dart.library.io) 'crc64nvme_vm.dart';
 
 class _CrcValueToHeaderConverter extends Converter<CrcValue, String> {
   const _CrcValueToHeaderConverter();
 
   @override
   String convert(CrcValue input) {
-    return base64Encode(hex.decode(input.toRadixString(16)));
+    // Convert to BigInt to ensure unsigned representation
+    final bigIntValue = input.toBigInt();
+    final hexString = bigIntValue.toRadixString(16);
+    
+    // Pad with leading zero if odd length (hex.decode requires even length)
+    final paddedHex = hexString.length.isOdd ? '0$hexString' : hexString;
+    return base64Encode(hex.decode(paddedHex));
   }
 
   @override
@@ -91,18 +99,3 @@ class WithChecksum extends HttpRequestInterceptor {
     return request;
   }
 }
-
-// Parameters are defined here
-// https://reveng.sourceforge.io/crc-catalogue/all.htm#crc.cat.crc-64-nvme
-// https://nvmexpress.org/wp-content/uploads/NVM-Express-NVM-Command-Set-Specification-1.0d-2023.12.28-Ratified.pdf
-class Crc64Nvme extends ParametricCrc {
-  Crc64Nvme()
-    : super(
-        64,
-        BigInt.parse('ad93d23594c93659', radix: 16),
-        BigInt.parse('ffffffffffffffff', radix: 16),
-        BigInt.parse('ffffffffffffffff', radix: 16),
-        inputReflected: true,
-        outputReflected: true,
-      );
-}