quick and dirty SLP check

lib/services/coins/bitcoincash/bch_utils.dart

@@ -0,0 +1,29 @@
+import 'dart:typed_data';
+
+import 'package:bitcoindart/src/utils/constants/op.dart' as op;
+import 'package:bitcoindart/src/utils/script.dart' as bscript;
+
+abstract final class BchUtils {
+  static bool isSLP(Uint8List scriptPubKey) {
+    const id = [83, 76, 80, 0]; // 'SLP\x00'
+    final decompiled = bscript.decompile(scriptPubKey);
+
+    if (decompiled != null &&
+        decompiled.length > 1 &&
+        decompiled.first == op.OPS["OP_RETURN"]) {
+      final _id = decompiled[1];
+
+      if (_id is List<int> && _id.length == id.length) {
+        for (int i = 0; i < id.length; i++) {
+          if (_id[i] != id[i]) {
+            return false;
+          }
+        }
+        // lists match!
+        return true;
+      }
+    }
+
+    return false;
+  }
+}

test/services/coins/bitcoincash/bch_utils_test.dart

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+import 'package:flutter_test/flutter_test.dart';
+import 'package:stackwallet/services/coins/bitcoincash/bch_utils.dart';
+import 'package:stackwallet/utilities/extensions/impl/string.dart';
+
+void main() {
+  test("script pub key check for SLP is true", () {
+    expect(
+      BchUtils.isSLP(
+          "6a04534c500001010747454e45534953044d5430320f4d757461626c652054657374"
+                  "2030321668747470733a2f2f46756c6c537461636b2e63617368200e9a18"
+                  "8911ec0f2ac10cc9425b457d10ba14151a64eb4640f95ed7dab9e8f62601"
+                  "004c00080000000000000001"
+              .toUint8ListFromHex),
+      true,
+    );
+  });
+
+  test("script pub key check for SLP is not true", () {
+    expect(
+      BchUtils.isSLP("76a914a78bb9aa1b54c859b5fe72e6f6f576248b3231c888ac"
+          .toUint8ListFromHex),
+      false,
+    );
+  });
+}