// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// All imports must be in all FFI patch files to not depend on the order
// the patches are applied.
import "dart:_internal" show patch;
import 'dart:typed_data' show TypedData;

@patch
int sizeOf<T extends NativeType>() native "Ffi_sizeOf";

Pointer<T> _allocate<T extends NativeType>(int count) native "Ffi_allocate";

Pointer<T> _fromAddress<T extends NativeType>(int ptr) native "Ffi_fromAddress";

// The real implementation of this function (for interface calls) lives in
// BuildFfiAsFunctionCall in the Kernel frontend. No calls can actually reach
// this function.
DS _asFunctionInternal<DS extends Function, NS extends Function>(
    Pointer<NativeFunction<NS>> ptr) native "Ffi_asFunctionInternal";

dynamic _asExternalTypedData(Pointer ptr, int count)
    native "Ffi_asExternalTypedData";

// Returns a Function object for a native callback.
//
// Calls to [Pointer.fromFunction] are re-written by the FE into calls to this
// method + _pointerFromFunction. All three arguments must be constants.
//
// In AOT we evaluate calls to this function during precompilation and replace
// them with Constant instruction referencing the callback trampoline, to ensure
// that it will be precompiled.
//
// In all JIT modes we call a native runtime entry. We *cannot* use the IL
// implementation, since that would pull the callback trampoline into JIT
// snapshots. The callback trampolines can only be serialized into AOT snapshots
// because they embed the addresses of runtime routines in JIT mode.
Object _nativeCallbackFunction<NS extends Function>(Function target,
    Object exceptionalReturn) native "Ffi_nativeCallbackFunction";

Pointer<NS> _pointerFromFunction<NS extends NativeFunction>(Object function)
    native "Ffi_pointerFromFunction";

@patch
@pragma("vm:entry-point")
class Pointer<T extends NativeType> {
  @patch
  factory Pointer.allocate({int count: 1}) => _allocate<T>(count);

  @patch
  factory Pointer.fromAddress(int ptr) => _fromAddress(ptr);

  // All static calls to this method are replaced by the FE into
  // _nativeCallbackFunction + _pointerFromFunction.
  //
  // We still need to throw an error on a dynamic invocations, invocations
  // through tearoffs or reflective calls.
  @patch
  static Pointer<NativeFunction<T>> fromFunction<T extends Function>(
      @DartRepresentationOf("T") Function f,
      [Object exceptionalReturn]) {
    throw UnsupportedError(
        "Pointer.fromFunction cannot be called dynamically.");
  }

  // TODO(sjindel): When NNBD is available, we should change `value` to be
  // non-null.
  @patch
  void store(Object value) native "Ffi_store";

  @patch
  R load<R>() native "Ffi_load";

  @patch
  int get address native "Ffi_address";

  // Note this could also be implmented without an extra native as offsetBy
  // (elementSize()*index). This would be 2 native calls rather than one. What
  // would be better?
  @patch
  Pointer<T> elementAt(int index) native "Ffi_elementAt";

  // Note this could also be implmented without an extra  native as
  // fromAddress(address). This would be 2 native calls rather than one.
  // What would be better?
  @patch
  Pointer<T> offsetBy(int offsetInBytes) native "Ffi_offsetBy";

  // Note this could also be implemented without an extra native as
  // fromAddress(address). This would be 2 native calls rather than one.
  // What would be better?
  @patch
  Pointer<U> cast<U extends NativeType>() native "Ffi_cast";

  @patch
  R asFunction<R extends Function>() {
    throw UnsupportedError("Pointer.asFunction cannot be called dynamically.");
  }

  @patch
  void free() native "Ffi_free";

  @patch
  TypedData asExternalTypedData({int count: 1}) =>
      _asExternalTypedData(this, count);
}

// Returns the ABI used for size and alignment calculations.
// See pkg/vm/lib/transformations/ffi.dart.
@pragma('vm:prefer-inline')
int _abi()
    native "Recognized method: method is directly interpreted by the bytecode interpreter or IR graph is built in the flow graph builder.";