cefpython/src/include/base/cef_bind_helpers.h at cefpython58 · netdebug/cefpython

Repository navigation

History

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

// * Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

// * Neither the name of Google Inc. nor the name Chromium Embedded

// Framework nor the names of its contributors may be used to endorse

// or promote products derived from this software without specific prior

// written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// This defines a set of argument wrappers and related factory methods that

// can be used specify the refcounting and reference semantics of arguments

// that are bound by the Bind() function in base/bind.h.

// It also defines a set of simple functions and utilities that people want

// when using Callback<> and Bind().

// ARGUMENT BINDING WRAPPERS

// The wrapper functions are base::Unretained(), base::Owned(), base::Passed(),

// base::ConstRef(), and base::IgnoreResult().

// Unretained() allows Bind() to bind a non-refcounted class, and to disable

// refcounting on arguments that are refcounted objects.

// Owned() transfers ownership of an object to the Callback resulting from

// bind; the object will be deleted when the Callback is deleted.

// Passed() is for transferring movable-but-not-copyable types (eg. scoped_ptr)

// through a Callback. Logically, this signifies a destructive transfer of

// the state of the argument into the target function. Invoking

// Callback::Run() twice on a Callback that was created with a Passed()

// argument will CHECK() because the first invocation would have already

// transferred ownership to the target function.

// ConstRef() allows binding a constant reference to an argument rather

// than a copy.

// IgnoreResult() is used to adapt a function or Callback with a return type to

// one with a void return. This is most useful if you have a function with,

// say, a pesky ignorable bool return that you want to use with PostTask or

// something else that expect a Callback with a void return.

// EXAMPLE OF Unretained():

// class Foo {

// public:

// void func() { cout << "Foo:f" << endl; }

// };

// // In some function somewhere.

// Foo foo;

// Closure foo_callback =

// Bind(&Foo::func, Unretained(&foo));

// foo_callback.Run(); // Prints "Foo:f".

// Without the Unretained() wrapper on |&foo|, the above call would fail

// to compile because Foo does not support the AddRef() and Release() methods.

// EXAMPLE OF Owned():

// void foo(int* arg) { cout << *arg << endl }

// int* pn = new int(1);

// Closure foo_callback = Bind(&foo, Owned(pn));

// foo_callback.Run(); // Prints "1"

// *n = 2;

// foo_callback.Run(); // Prints "2"

// foo_callback.Reset(); // |pn| is deleted. Also will happen when

// // |foo_callback| goes out of scope.

// Without Owned(), someone would have to know to delete |pn| when the last

// reference to the Callback is deleted.

// EXAMPLE OF ConstRef():

// void foo(int arg) { cout << arg << endl }

// int n = 1;

// Closure no_ref = Bind(&foo, n);

// Closure has_ref = Bind(&foo, ConstRef(n));

// no_ref.Run(); // Prints "1"

// has_ref.Run(); // Prints "1"

// n = 2;

// no_ref.Run(); // Prints "1"

// has_ref.Run(); // Prints "2"

// Note that because ConstRef() takes a reference on |n|, |n| must outlive all

// its bound callbacks.

// EXAMPLE OF IgnoreResult():

// int DoSomething(int arg) { cout << arg << endl; }

// // Assign to a Callback with a void return type.

// Callback<void(int)> cb = Bind(IgnoreResult(&DoSomething));

// cb->Run(1); // Prints "1".

// // Prints "1" on |ml|.

// ml->PostTask(FROM_HERE, Bind(IgnoreResult(&DoSomething), 1);

// EXAMPLE OF Passed():

// void TakesOwnership(scoped_ptr<Foo> arg) { }

// scoped_ptr<Foo> CreateFoo() { return scoped_ptr<Foo>(new Foo()); }

// scoped_ptr<Foo> f(new Foo());

// // |cb| is given ownership of Foo(). |f| is now NULL.

// // You can use f.Pass() in place of &f, but it's more verbose.

// Closure cb = Bind(&TakesOwnership, Passed(&f));

// // Run was never called so |cb| still owns Foo() and deletes

// // it on Reset().

// cb.Reset();

// // |cb| is given a new Foo created by CreateFoo().

// cb = Bind(&TakesOwnership, Passed(CreateFoo()));

// // |arg| in TakesOwnership() is given ownership of Foo(). |cb|

// // no longer owns Foo() and, if reset, would not delete Foo().

// cb.Run(); // Foo() is now transferred to |arg| and deleted.

// cb.Run(); // This CHECK()s since Foo() already been used once.

// Passed() is particularly useful with PostTask() when you are transferring

// ownership of an argument into a task, but don't necessarily know if the

// task will always be executed. This can happen if the task is cancellable

// or if it is posted to a MessageLoopProxy.

// SIMPLE FUNCTIONS AND UTILITIES.

// DoNothing() - Useful for creating a Closure that does nothing when called.

// DeletePointer<T>() - Useful for creating a Closure that will delete a

// pointer when invoked. Only use this when necessary.

// In most cases MessageLoop::DeleteSoon() is a better

// fit.

#ifndef CEF_INCLUDE_BASE_CEF_BIND_HELPERS_H_

#define CEF_INCLUDE_BASE_CEF_BIND_HELPERS_H_

#pragma once

#if defined(BASE_BIND_HELPERS_H_)

// Do nothing if the Chromium header has already been included.

// This can happen in cases where Chromium code is used directly by the

// client application. When using Chromium code directly always include

// the Chromium header first to avoid type conflicts.

#elif defined(USING_CHROMIUM_INCLUDES)

// When building CEF include the Chromium header directly.

#include "base/bind_helpers.h"

#else // !USING_CHROMIUM_INCLUDES

// The following is substantially similar to the Chromium implementation.

// If the Chromium implementation diverges the below implementation should be

// updated to match.

#include "include/base/cef_basictypes.h"

#include "include/base/cef_callback.h"

#include "include/base/cef_template_util.h"

#include "include/base/cef_weak_ptr.h"

namespace base {

namespace cef_internal {

// Use the Substitution Failure Is Not An Error (SFINAE) trick to inspect T

// for the existence of AddRef() and Release() functions of the correct

// signature.

// http://en.wikipedia.org/wiki/Substitution_failure_is_not_an_error

// http://stackoverflow.com/questions/257288/is-it-possible-to-write-a-c-template-to-check-for-a-functions-existence

// http://stackoverflow.com/questions/4358584/sfinae-approach-comparison

// http://stackoverflow.com/questions/1966362/sfinae-to-check-for-inherited-member-functions

// The last link in particular show the method used below.

// For SFINAE to work with inherited methods, we need to pull some extra tricks

// with multiple inheritance. In the more standard formulation, the overloads

// of Check would be:

// template <typename C>

// Yes NotTheCheckWeWant(Helper<&C::TargetFunc>*);

// template <typename C>

// No NotTheCheckWeWant(...);

// static const bool value = sizeof(NotTheCheckWeWant<T>(0)) == sizeof(Yes);

// The problem here is that template resolution will not match

// C::TargetFunc if TargetFunc does not exist directly in C. That is, if

// TargetFunc in inherited from an ancestor, &C::TargetFunc will not match,

// |value| will be false. This formulation only checks for whether or

// not TargetFunc exist directly in the class being introspected.

// To get around this, we play a dirty trick with multiple inheritance.

// First, We create a class BaseMixin that declares each function that we

// want to probe for. Then we create a class Base that inherits from both T

// (the class we wish to probe) and BaseMixin. Note that the function

// signature in BaseMixin does not need to match the signature of the function

// we are probing for; thus it's easiest to just use void(void).

// Now, if TargetFunc exists somewhere in T, then &Base::TargetFunc has an

// ambiguous resolution between BaseMixin and T. This lets us write the

// following:

// template <typename C>

// No GoodCheck(Helper<&C::TargetFunc>*);

// template <typename C>

// Yes GoodCheck(...);

// static const bool value = sizeof(GoodCheck<Base>(0)) == sizeof(Yes);

// Notice here that the variadic version of GoodCheck() returns Yes here

// instead of No like the previous one. Also notice that we calculate |value|

// by specializing GoodCheck() on Base instead of T.

// We've reversed the roles of the variadic, and Helper overloads.

// GoodCheck(Helper<&C::TargetFunc>*), when C = Base, fails to be a valid

// substitution if T::TargetFunc exists. Thus GoodCheck<Base>(0) will resolve

// to the variadic version if T has TargetFunc. If T::TargetFunc does not

// exist, then &C::TargetFunc is not ambiguous, and the overload resolution

// will prefer GoodCheck(Helper<&C::TargetFunc>*).

// This method of SFINAE will correctly probe for inherited names, but it cannot

// typecheck those names. It's still a good enough sanity check though.

// Works on gcc-4.2, gcc-4.4, and Visual Studio 2008.

// TODO(ajwong): Move to ref_counted.h or template_util.h when we've vetted

// this works well.

// TODO(ajwong): Make this check for Release() as well.

// See http://crbug.com/82038.

template <typename T>

class SupportsAddRefAndRelease {

typedef char Yes[1];

typedef char No[2];

struct BaseMixin {

void AddRef();

};

// MSVC warns when you try to use Base if T has a private destructor, the

// common pattern for refcounted types. It does this even though no attempt to

// instantiate Base is made. We disable the warning for this definition.

#if defined(OS_WIN)

#pragma warning(push)

#pragma warning(disable:4624)

#endif

struct Base : public T, public BaseMixin {

};

#if defined(OS_WIN)

#pragma warning(pop)

#endif

template <void(BaseMixin::*)(void)> struct Helper {};

template <typename C>

static No& Check(Helper<&C::AddRef>*);

template <typename >

static Yes& Check(...);

public:

static const bool value = sizeof(Check<Base>(0)) == sizeof(Yes);

};

// Helpers to assert that arguments of a recounted type are bound with a

// scoped_refptr.

template <bool IsClasstype, typename T>

struct UnsafeBindtoRefCountedArgHelper : false_type {

};

template <typename T>

struct UnsafeBindtoRefCountedArgHelper<true, T>

: integral_constant<bool, SupportsAddRefAndRelease<T>::value> {

};

template <typename T>

struct UnsafeBindtoRefCountedArg : false_type {

};

template <typename T>

struct UnsafeBindtoRefCountedArg<T*>

: UnsafeBindtoRefCountedArgHelper<is_class<T>::value, T> {

};

template <typename T>

class HasIsMethodTag {

typedef char Yes[1];

typedef char No[2];

template <typename U>

static Yes& Check(typename U::IsMethod*);

template <typename U>

static No& Check(...);

public:

static const bool value = sizeof(Check<T>(0)) == sizeof(Yes);

};

template <typename T>

class UnretainedWrapper {

public:

explicit UnretainedWrapper(T* o) : ptr_(o) {}

T* get() const { return ptr_; }

private:

T* ptr_;

};

template <typename T>

class ConstRefWrapper {

public:

explicit ConstRefWrapper(const T& o) : ptr_(&o) {}

const T& get() const { return *ptr_; }

private:

const T* ptr_;

};

template <typename T>

struct IgnoreResultHelper {

explicit IgnoreResultHelper(T functor) : functor_(functor) {}

T functor_;

};

template <typename T>

struct IgnoreResultHelper<Callback<T> > {

explicit IgnoreResultHelper(const Callback<T>& functor) : functor_(functor) {}

const Callback<T>& functor_;

};

// An alternate implementation is to avoid the destructive copy, and instead

// specialize ParamTraits<> for OwnedWrapper<> to change the StorageType to

// a class that is essentially a scoped_ptr<>.

// The current implementation has the benefit though of leaving ParamTraits<>

// fully in callback_internal.h as well as avoiding type conversions during

// storage.

template <typename T>

class OwnedWrapper {

public:

explicit OwnedWrapper(T* o) : ptr_(o) {}

~OwnedWrapper() { delete ptr_; }

T* get() const { return ptr_; }

OwnedWrapper(const OwnedWrapper& other) {

ptr_ = other.ptr_;

other.ptr_ = NULL;

}

private:

mutable T* ptr_;

};

// PassedWrapper is a copyable adapter for a scoper that ignores const.

// It is needed to get around the fact that Bind() takes a const reference to

// all its arguments. Because Bind() takes a const reference to avoid

// unnecessary copies, it is incompatible with movable-but-not-copyable

// types; doing a destructive "move" of the type into Bind() would violate

// the const correctness.

// This conundrum cannot be solved without either C++11 rvalue references or

// a O(2^n) blowup of Bind() templates to handle each combination of regular

// types and movable-but-not-copyable types. Thus we introduce a wrapper type

// that is copyable to transmit the correct type information down into

// BindState<>. Ignoring const in this type makes sense because it is only

// created when we are explicitly trying to do a destructive move.

// Two notes:

// 1) PassedWrapper supports any type that has a "Pass()" function.

// This is intentional. The whitelisting of which specific types we

// support is maintained by CallbackParamTraits<>.

// 2) is_valid_ is distinct from NULL because it is valid to bind a "NULL"

// scoper to a Callback and allow the Callback to execute once.

template <typename T>

class PassedWrapper {

public:

explicit PassedWrapper(T scoper) : is_valid_(true), scoper_(scoper.Pass()) {}

PassedWrapper(const PassedWrapper& other)

: is_valid_(other.is_valid_), scoper_(other.scoper_.Pass()) {

}

T Pass() const {

CHECK(is_valid_);

is_valid_ = false;

return scoper_.Pass();

}

private:

mutable bool is_valid_;

mutable T scoper_;

};

// Unwrap the stored parameters for the wrappers above.

template <typename T>

struct UnwrapTraits {

typedef const T& ForwardType;

static ForwardType Unwrap(const T& o) { return o; }

};

template <typename T>

struct UnwrapTraits<UnretainedWrapper<T> > {

typedef T* ForwardType;

static ForwardType Unwrap(UnretainedWrapper<T> unretained) {

return unretained.get();

}

};

template <typename T>

struct UnwrapTraits<ConstRefWrapper<T> > {

typedef const T& ForwardType;

static ForwardType Unwrap(ConstRefWrapper<T> const_ref) {

return const_ref.get();

}

};

template <typename T>

struct UnwrapTraits<scoped_refptr<T> > {

typedef T* ForwardType;

static ForwardType Unwrap(const scoped_refptr<T>& o) { return o.get(); }

};

template <typename T>

struct UnwrapTraits<WeakPtr<T> > {

typedef const WeakPtr<T>& ForwardType;

static ForwardType Unwrap(const WeakPtr<T>& o) { return o; }

};

template <typename T>

struct UnwrapTraits<OwnedWrapper<T> > {

typedef T* ForwardType;

static ForwardType Unwrap(const OwnedWrapper<T>& o) {

return o.get();

}

};

template <typename T>

struct UnwrapTraits<PassedWrapper<T> > {

typedef T ForwardType;

static T Unwrap(PassedWrapper<T>& o) {

return o.Pass();

}

};

// Utility for handling different refcounting semantics in the Bind()

// function.

template <bool is_method, typename T>

struct MaybeRefcount;

template <typename T>

struct MaybeRefcount<false, T> {

static void AddRef(const T&) {}

static void Release(const T&) {}

};

template <typename T, size_t n>

struct MaybeRefcount<false, T[n]> {

static void AddRef(const T*) {}

static void Release(const T*) {}

};

template <typename T>

struct MaybeRefcount<true, T> {

static void AddRef(const T&) {}

static void Release(const T&) {}

};

template <typename T>

struct MaybeRefcount<true, T*> {

static void AddRef(T* o) { o->AddRef(); }

static void Release(T* o) { o->Release(); }

};

// No need to additionally AddRef() and Release() since we are storing a

// scoped_refptr<> inside the storage object already.

template <typename T>

struct MaybeRefcount<true, scoped_refptr<T> > {

static void AddRef(const scoped_refptr<T>& o) {}

static void Release(const scoped_refptr<T>& o) {}

};

template <typename T>

struct MaybeRefcount<true, const T*> {

static void AddRef(const T* o) { o->AddRef(); }

static void Release(const T* o) { o->Release(); }

};

// IsWeakMethod is a helper that determine if we are binding a WeakPtr<> to a

// method. It is used internally by Bind() to select the correct

// InvokeHelper that will no-op itself in the event the WeakPtr<> for

// the target object is invalidated.

// P1 should be the type of the object that will be received of the method.

template <bool IsMethod, typename P1>

struct IsWeakMethod : public false_type {};

template <typename T>

struct IsWeakMethod<true, WeakPtr<T> > : public true_type {};

template <typename T>

struct IsWeakMethod<true, ConstRefWrapper<WeakPtr<T> > > : public true_type {};

} // namespace cef_internal

template <typename T>

static inline cef_internal::UnretainedWrapper<T> Unretained(T* o) {

return cef_internal::UnretainedWrapper<T>(o);

}

template <typename T>

static inline cef_internal::ConstRefWrapper<T> ConstRef(const T& o) {

return cef_internal::ConstRefWrapper<T>(o);

}

template <typename T>

static inline cef_internal::OwnedWrapper<T> Owned(T* o) {

return cef_internal::OwnedWrapper<T>(o);

}

// We offer 2 syntaxes for calling Passed(). The first takes a temporary and

// is best suited for use with the return value of a function. The second

// takes a pointer to the scoper and is just syntactic sugar to avoid having

// to write Passed(scoper.Pass()).

template <typename T>

static inline cef_internal::PassedWrapper<T> Passed(T scoper) {

return cef_internal::PassedWrapper<T>(scoper.Pass());

}

template <typename T>

static inline cef_internal::PassedWrapper<T> Passed(T* scoper) {

return cef_internal::PassedWrapper<T>(scoper->Pass());

}

template <typename T>

static inline cef_internal::IgnoreResultHelper<T> IgnoreResult(T data) {

return cef_internal::IgnoreResultHelper<T>(data);

}

template <typename T>

static inline cef_internal::IgnoreResultHelper<Callback<T> >

IgnoreResult(const Callback<T>& data) {

return cef_internal::IgnoreResultHelper<Callback<T> >(data);

}

void DoNothing();

template<typename T>

void DeletePointer(T* obj) {

delete obj;

}

} // namespace base

#endif // !USING_CHROMIUM_INCLUDES

#endif // CEF_INCLUDE_BASE_CEF_BIND_HELPERS_H_

FilesExpand file tree

cef_bind_helpers.h

Latest commit

History

cef_bind_helpers.h

File metadata and controls