query.find() - large array support on 32-bit systems

Author: Ivan Dlugos

lib/src/bindings/signatures.dart

@@ -79,7 +79,7 @@ typedef obx_box_is_empty_native_t = Int32 Function(Pointer<Void> box, Pointer<Ui
 // typedef Pointer<Int8> -> char[]
 // typedef Pointer<Int32> -> int (e.g. obx_qb_cond);
 
-// query builider
+// query builder
 typedef obx_query_builder_native_t = Pointer<Void> Function(Pointer<Void> store, Uint32 entity_id);
 typedef obx_query_builder_dart_t = Pointer<Void> Function(Pointer<Void> store, int entity_id);
 
@@ -150,10 +150,10 @@ typedef obx_query_count_dart_t = int Function(Pointer<Void> query, Pointer<Uint6
 
 typedef obx_query_describe_t = Pointer<Utf8> Function(Pointer<Void> query);
 
-typedef obx_query_visit_native_t = Int32 Function(
-    Pointer<Void> query, Pointer<Void> visitor, Pointer<Void> user_data, Uint64 offset, Uint64 limit);
-typedef obx_query_visit_dart_t = int Function(
-    Pointer<Void> query, Pointer<Void> visitor, Pointer<Void> user_data, int offset, int limit);
+typedef obx_query_visit_native_t = Int32 Function(Pointer<Void> query,
+    Pointer<NativeFunction<obx_data_visitor_native_t>> visitor, Pointer<Void> user_data, Uint64 offset, Uint64 limit);
+typedef obx_query_visit_dart_t = int Function(Pointer<Void> query,
+    Pointer<NativeFunction<obx_data_visitor_native_t>> visitor, Pointer<Void> user_data, int offset, int limit);
 
 // Utilities
 

lib/src/query/query.dart

@@ -7,6 +7,7 @@ import "../store.dart";
 import "../common.dart";
 import "../bindings/bindings.dart";
 import "../bindings/constants.dart";
+import "../bindings/data_visitor.dart";
 import "../bindings/flatbuffers.dart";
 import "../bindings/helpers.dart";
 import "../bindings/structs.dart";
@@ -571,11 +572,25 @@ class Query<T> {
 
   List<T> find({int offset = 0, int limit = 0}) {
     return _store.runInTransaction(TxMode.Read, () {
-      final bytesArray = checkObxPtr(bindings.obx_query_find(_cQuery, offset, limit), "find");
-      try {
-        return _fbManager.unmarshalArray(bytesArray);
-      } finally {
-        bindings.obx_bytes_array_free(bytesArray);
+      if (bindings.obx_supports_bytes_array() == 1) {
+        final bytesArray = checkObxPtr(bindings.obx_query_find(_cQuery, offset, limit), "find");
+        try {
+          return _fbManager.unmarshalArray(bytesArray);
+        } finally {
+          bindings.obx_bytes_array_free(bytesArray);
+        }
+      } else {
+        final results = <T>[];
+        final visitor = DataVisitor((Pointer<Uint8> dataPtr, int length) {
+          final bytes = dataPtr.asTypedList(length);
+          results.add(_fbManager.unmarshal(bytes));
+          return true;
+        });
+
+        final err = bindings.obx_query_visit(_cQuery, visitor.fn, visitor.userData, offset, limit);
+        visitor.close();
+        checkObx(err);
+        return results;
       }
     });
   }

test/query_test.dart

@@ -204,6 +204,21 @@ void main() {
     q.close();
   });
 
+  test(".find works on large arrays", () {
+    // This would fail on 32-bit system if objectbox-c obx_supports_bytes_array() wasn't respected
+    final length = 10 * 1000;
+    final largeString = 'A' * length;
+    expect(largeString.length, length);
+
+    box.put(TestEntity(tString: largeString));
+    box.put(TestEntity(tString: largeString));
+
+    List<TestEntity> items = box.query(TestEntity_.id.greaterThan(0)).build().find();
+    expect(items.length, 2);
+    expect(items[0].tString, largeString);
+    expect(items[1].tString, largeString);
+  });
+
   test(".count items after grouping with and/or", () {
     box.put(TestEntity(tString: "Hello"));
     box.put(TestEntity(tString: "Goodbye"));