Use nullptr.cast() instead of nullptr

This can speed up performance when binding strings

moor_ffi/lib/src/ffi/utils.dart

@@ -9,3 +9,11 @@ extension FreePointerExtension on Pointer {
     ffi.free(this);
   }
 }
+
+/// Loads a null-pointer with a specified type.
+///
+/// The [nullptr] getter from `dart:ffi` can be slow due to being a
+/// `Pointer<Null>` on which the VM has to perform runtime type checks. See also
+/// https://github.com/dart-lang/sdk/issues/39488
+@pragma('vm:prefer-inline')
+Pointer<T> nullPtr<T extends NativeType>() => nullptr.cast<T>();

moor_ffi/lib/src/impl/database.dart

@@ -37,7 +37,7 @@ class Database {
     final pathC = CBlob.allocateString(fileName);
 
     final resultCode =
-        bindings.sqlite3_open_v2(pathC, dbOut, _openingFlags, nullptr.cast());
+        bindings.sqlite3_open_v2(pathC, dbOut, _openingFlags, nullPtr());
     final dbPointer = dbOut.value;
 
     dbOut.free();
@@ -96,7 +96,7 @@ class Database {
     final errorOut = allocate<Pointer<CBlob>>();
 
     final result =
-        bindings.sqlite3_exec(_db, sqlPtr, nullptr, nullptr, errorOut);
+        bindings.sqlite3_exec(_db, sqlPtr, nullPtr(), nullPtr(), errorOut);
 
     sqlPtr.free();
 
@@ -123,7 +123,7 @@ class Database {
     final sqlPtr = CBlob.allocateString(sql);
 
     final resultCode =
-        bindings.sqlite3_prepare_v2(_db, sqlPtr, -1, stmtOut, nullptr.cast());
+        bindings.sqlite3_prepare_v2(_db, sqlPtr, -1, stmtOut, nullPtr());
     sqlPtr.free();
 
     final stmt = stmtOut.value;

moor_ffi/lib/src/impl/prepared_statement.dart

@@ -113,7 +113,7 @@ class PreparedStatement {
           final ptr = CBlob.allocateString(param);
           _allocatedWhileBinding.add(ptr);
 
-          bindings.sqlite3_bind_text(_stmt, i, ptr, -1, nullptr);
+          bindings.sqlite3_bind_text(_stmt, i, ptr, -1, nullPtr());
         } else if (param is Uint8List) {
           // avoid binding a null-pointer, as sqlite would treat that as NULL
           // in sql which is different from x''
@@ -124,7 +124,7 @@ class PreparedStatement {
           assert(!ptr.isNullPointer);
           _allocatedWhileBinding.add(ptr);
 
-          bindings.sqlite3_bind_blob(_stmt, i, ptr, param.length, nullptr);
+          bindings.sqlite3_bind_blob(_stmt, i, ptr, param.length, nullPtr());
         }
       }
     }

moor_ffi/pubspec.yaml

@@ -16,6 +16,7 @@ dependencies:
 dev_dependencies:
   test: ^1.6.0
   path: ^1.6.0
+  benchmark_harness: ^1.0.0
 
 flutter:
   plugin:

moor_ffi/tool/benchmark/select_string_variable.dart

@@ -0,0 +1,26 @@
+import 'package:benchmark_harness/benchmark_harness.dart';
+import 'package:moor_ffi/database.dart';
+
+class SelectStringBenchmark extends BenchmarkBase {
+  SelectStringBenchmark() : super('SELECT a string variable');
+
+  PreparedStatement statement;
+  Database database;
+
+  @override
+  void setup() {
+    database = Database.memory();
+    statement = database.prepare('SELECT ?;');
+  }
+
+  @override
+  void run() {
+    statement.select(const ['hello sqlite, can you return this string?']);
+  }
+
+  @override
+  void teardown() {
+    statement.close();
+    database.close();
+  }
+}

moor_ffi/tool/benchmarks.dart

@@ -0,0 +1,11 @@
+import 'benchmark/select_string_variable.dart';
+
+void main() {
+  final benchmarks = [
+    SelectStringBenchmark(),
+  ];
+
+  for (final benchmark in benchmarks) {
+    benchmark.report();
+  }
+}