[vm/ffi] Remove Pointer.offsetBy.

Fixes #35883

Change-Id: Idf4b113d655a6cf7063f1ee7732ddd2001247dee
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/121124
Reviewed-by: Martin Kustermann <[email protected]>
Reviewed-by: Daco Harkes <[email protected]>
Commit-Queue: Samir Jindel <[email protected]>

Author: sjindel-google

pkg/vm/lib/transformations/ffi.dart

@@ -229,7 +229,7 @@ class FfiTransformer extends Transformer {
         castMethod = index.getMember('dart:ffi', 'Pointer', 'cast'),
         loadMethod = index.getMember('dart:ffi', 'Pointer', 'load'),
         storeMethod = index.getMember('dart:ffi', 'Pointer', 'store'),
-        offsetByMethod = index.getMember('dart:ffi', 'Pointer', 'offsetBy'),
+        offsetByMethod = index.getMember('dart:ffi', 'Pointer', '_offsetBy'),
         elementAtMethod = index.getMember('dart:ffi', 'Pointer', 'elementAt'),
         addressOfField = index.getMember('dart:ffi', 'Struct', 'addressOf'),
         structFromPointer =

samples/ffi/sample_ffi_data.dart

@@ -46,21 +46,6 @@ main(List<String> arguments) {
     print('After free, address is zero: ${p.address}');
   }
 
-  {
-    // pointer arithmetic can be done with element offsets or bytes
-    Pointer<Int64> p1 = allocate<Int64>(count: 2);
-    print('p1 address: ${p1.address}');
-
-    Pointer<Int64> p2 = p1.elementAt(1);
-    print('p1.elementAt(1) address: ${p2.address}');
-    p2.value = 100;
-
-    Pointer<Int64> p3 = p1.offsetBy(8);
-    print('p1.offsetBy(8) address: ${p3.address}');
-    print('p1.offsetBy(8) value: ${p3.value}');
-    free(p1);
-  }
-
   {
     // allocating too much throws an exception
     try {

sdk/lib/_internal/vm/lib/ffi_patch.dart

@@ -115,7 +115,7 @@ class Pointer<T extends NativeType> {
       Pointer.fromAddress(address + sizeOf<T>() * index);
 
   @patch
-  Pointer<T> offsetBy(int offsetInBytes) =>
+  Pointer<T> _offsetBy(int offsetInBytes) =>
       Pointer.fromAddress(address + offsetInBytes);
 
   @patch

sdk/lib/ffi/ffi.dart

@@ -99,11 +99,6 @@ class Pointer<T extends NativeType> extends NativeType {
   /// Pointer arithmetic (takes element size into account).
   external Pointer<T> elementAt(int index);
 
-  /// Pointer arithmetic (byte offset).
-  // TODO(dacoharkes): remove this?
-  // https://github.com/dart-lang/sdk/issues/35883
-  external Pointer<T> offsetBy(int offsetInBytes);
-
   /// Cast Pointer<T> to a Pointer<V>.
   external Pointer<U> cast<U extends NativeType>();
 

sdk_nnbd/lib/_internal/vm/lib/ffi_patch.dart

@@ -117,7 +117,7 @@ class Pointer<T extends NativeType> {
       Pointer.fromAddress(address + sizeOf<T>() * index);
 
   @patch
-  Pointer<T> offsetBy(int offsetInBytes) =>
+  Pointer<T> _offsetBy(int offsetInBytes) =>
       Pointer.fromAddress(address + offsetInBytes);
 
   @patch

sdk_nnbd/lib/ffi/ffi.dart

@@ -100,11 +100,6 @@ class Pointer<T extends NativeType> extends NativeType {
   /// Pointer arithmetic (takes element size into account).
   external Pointer<T> elementAt(int index);
 
-  /// Pointer arithmetic (byte offset).
-  // TODO(dacoharkes): remove this?
-  // https://github.com/dart-lang/sdk/issues/35883
-  external Pointer<T> offsetBy(int offsetInBytes);
-
   /// Cast Pointer<T> to a Pointer<V>.
   external Pointer<U> cast<U extends NativeType>();
 

tests/ffi/aliasing_test.dart

@@ -15,7 +15,7 @@ import 'dart:ffi';
 import "package:ffi/ffi.dart";
 import "package:expect/expect.dart";
 
-import 'dylib_utils.dart';
+import 'ffi_test_helpers.dart';
 
 void main() {
   for (int i = 0; i < 100; ++i) {
@@ -170,8 +170,6 @@ void testAliasFromAddressViaMemory2() {
 typedef NativeQuadOpSigned = Int64 Function(Int8, Int16, Int32, Int64);
 typedef QuadOp = int Function(int, int, int, int);
 
-DynamicLibrary ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");
-
 QuadOp intComputation = ffiTestFunctions
     .lookupFunction<NativeQuadOpSigned, QuadOp>("IntComputation");
 

tests/ffi/data_test.dart

@@ -11,6 +11,8 @@ import 'dart:ffi';
 import "package:expect/expect.dart";
 import "package:ffi/ffi.dart";
 
+import 'ffi_test_helpers.dart';
+
 void main() {
   testPointerBasic();
   testPointerFromPointer();
@@ -114,7 +116,7 @@ void testPointerAllocateZero() {
 
 void testPointerCast() {
   Pointer<Int64> p = allocate();
-  Pointer<Int32> p2 = p.cast(); // gets the correct type args back
+  p.cast<Int32>(); // gets the correct type args back
   free(p);
 }
 

tests/ffi/ffi_test_helpers.dart

@@ -4,21 +4,25 @@
 //
 // Helpers for tests which trigger GC in delicate places.
 
-import 'dart:ffi' as ffi;
+import 'dart:ffi';
 
 import 'dylib_utils.dart';
 
-typedef NativeNullaryOp = ffi.Void Function();
+typedef NativeNullaryOp = Void Function();
 typedef NullaryOpVoid = void Function();
 
-typedef NativeUnaryOp = ffi.Void Function(ffi.IntPtr);
+typedef NativeUnaryOp = Void Function(IntPtr);
 typedef UnaryOpVoid = void Function(int);
 
-final ffi.DynamicLibrary ffiTestFunctions =
+final DynamicLibrary ffiTestFunctions =
     dlopenPlatformSpecific("ffi_test_functions");
 
 final triggerGc = ffiTestFunctions
     .lookupFunction<NativeNullaryOp, NullaryOpVoid>("TriggerGC");
 
 final collectOnNthAllocation = ffiTestFunctions
     .lookupFunction<NativeUnaryOp, UnaryOpVoid>("CollectOnNthAllocation");
+
+extension PointerOffsetBy<T extends NativeType> on Pointer<T> {
+  Pointer<T> offsetBy(int bytes) => Pointer.fromAddress(address + bytes);
+}

tests/ffi/function_callbacks_test.dart

@@ -251,6 +251,8 @@ double testExceptionalReturn() {
   Pointer.fromFunction<Double Function()>(testExceptionalReturn, "abc");  //# 61: compile-time error
   Pointer.fromFunction<Double Function()>(testExceptionalReturn, 0);  //# 62: compile-time error
   Pointer.fromFunction<Double Function()>(testExceptionalReturn);  //# 63: compile-time error
+
+  return 0.0;  // not used
 }
 
 void main() async {

tests/ffi/function_gc_test.dart

@@ -18,7 +18,6 @@
 // SharedObjects=ffi_test_functions
 
 import 'dart:ffi' as ffi;
-import 'dylib_utils.dart';
 import "package:expect/expect.dart";
 import 'ffi_test_helpers.dart';
 

tests/ffi/highmem_32bit_test.dart

@@ -8,6 +8,8 @@ import 'dart:typed_data';
 
 import 'package:expect/expect.dart';
 
+import 'ffi_test_helpers.dart';
+
 // void* mmap(void* addr, size_t length,
 //            int prot, int flags,
 //            int fd, off_t offset)

tests/ffi/snapshot_test.dart

@@ -5,9 +5,7 @@
 // Checks that the VM throws an appropriate exception when FFI objects are
 // passed between isolates.
 
-import 'dart:async';
 import 'dart:ffi';
-import 'dart:io';
 import 'dart:isolate';
 
 import 'package:expect/expect.dart';

tests/ffi/structs_test.dart

@@ -13,6 +13,7 @@ import 'dart:ffi';
 import "package:expect/expect.dart";
 import "package:ffi/ffi.dart";
 
+import 'ffi_test_helpers.dart';
 import 'coordinate_bare.dart' as bare;
 import 'coordinate.dart';