mraleph

Dart VM FFI Vision

Background

The aim of Dart FFI project (tracked as Issue #34452) is to provide a low boilerplate, low ceremony & low overhead way of interoperating with native C/C++ code.

The motivation behind this project is twofold:

mraleph

There are two types (actually more, but for the problem at hand only these two are important):

• flat strings are immutable arrays of characters

• cons strings are pairs of strings, result of concatenation.

If you concat a and b you get a cons-string (a, b) that represents result of concatenation. If you later concat d to that you get another cons-string ((a, b), d).

Indexing into such a "tree-like" string is not O(1) so to make it faster V8 flattens the string when you index: copies all characters into a flat string.

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new Fn(...) vs Object.create(P)

Basics of object layout in V8

Each JavaScript object in V8 looks like this

+-------+
|  map  | -> pointer to the hidden class
+-------+

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Making iteration faster in Array built-ins.

Lets imagine we have forEach method. The core loop of this method in V8 is implemented in JavaScript and looks like this:

for (var i = 0; i < length; i++) {
  if (i in array) {
    var element = array[i];
    %_CallFunction(receiver, element, i, array, f);
 }

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// Based on Martin Kustermann's version and adding support for 
// finalization of memory mapped views.
 
import 'dart:ffi';
import 'dart:io';
import 'dart:typed_data';
import 'dart:math' as math;
 
import 'package:ffi/ffi.dart';
 

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library mirrors.src.decode;

import 'dart:mirrors' as mirrors;
import 'dart:convert';

/// Create an object of the given type [t] from the given JSON string.
decode(String json, Type t) {
  // Get deserialization descriptor for the given type.
  // This descriptor describes how to handle the type and all its fields.
  final TypeDesc desc = getDesc(t);

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void main() {
  final count = 1000000;
  final names = ['good', 'bad', 'whatever'];
  final tests = [_test1, _test2, _test3];
  final sw = Stopwatch();
  var repeat = 10;
  sw.start();
  while (repeat-- > 0) {
    for (var i = 0; i < tests.length; i++) {
      final name = names[i];

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library writer;

import 'dart:typed_data';

/// Writer wraps a fixed size Uint8List and writes values into it using
/// big-endian byte order.
class Writer {
  /// Output buffer.
  final Uint8List out;

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$ cat test.js
function foo () { while (true) { } }
function bar () { return foo(); }
bar();
$ node test.js &
$ gdb attach $(pidof node)
0x00000bf778c63d5f in ?? ()
(gdb) b v8::internal::Runtime_StackGuard
Breakpoint 1 at 0x84a1f0
(gdb) print 'v8::V8::TerminateExecution'(0)

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| Library                                                                                  | Method                                                                                                                                                 | Diff (Bytes) |
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