Unified callback system.

base/bind_unittest.cc

Index: base/bind_unittest.cc
diff --git a/base/bind_unittest.cc b/base/bind_unittest.cc
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+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/bind.h"
+
+#if defined(BASE_CALLBACK_H_)
+// We explicitly do not want to include callback.h so people are not tempted
+// to use bind.h in a headerfile for getting the Callback types.
+#error "base/bind.h should avoid pulling in callback.h by default."
+#endif
+
+#include "base/callback.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using ::testing::Mock;
+using ::testing::Return;
+using ::testing::StrictMock;
+
+namespace base {
+namespace {
+
+class NoRef {
+ public:
+  NoRef() {}
+
+  MOCK_METHOD0(VoidMethod0, void(void));
+  MOCK_CONST_METHOD0(VoidConstMethod0, void(void));
+
+  MOCK_METHOD0(IntMethod0, int(void));
+  MOCK_CONST_METHOD0(IntConstMethod0, int(void));
+
+ private:
+  // Particularly important in this test to ensure no copies are made.
+  DISALLOW_COPY_AND_ASSIGN(NoRef);
+};
+
+class HasRef : public NoRef {
+ public:
+  HasRef() {}
+
+  MOCK_CONST_METHOD0(AddRef, void(void));
+  MOCK_CONST_METHOD0(Release, bool(void));
+
+ private:
+  // Particularly important in this test to ensure no copies are made.
+  DISALLOW_COPY_AND_ASSIGN(HasRef);
+};
+
+static const int kParentValue = 1;
+static const int kChildValue = 2;
+
+class Parent {
+ public:
+  void AddRef(void) const {}
+  void Release(void) const {}
+  virtual void VirtualSet() { value = kParentValue; }
+  void NonVirtualSet() { value = kParentValue; }
+  int value;
+};
+
+class Child : public Parent {
+ public:
+  virtual void VirtualSet() { value = kChildValue; }
+  void NonVirtualSet() { value = kChildValue; }
+};
+
+class NoRefParent {
+ public:
+  virtual void VirtualSet() { value = kParentValue; }
+  void NonVirtualSet() { value = kParentValue; }
+  int value;
+};
+
+class NoRefChild : public NoRefParent {
+  virtual void VirtualSet() { value = kChildValue; }
+  void NonVirtualSet() { value = kChildValue; }
+};
+
+// Used for probing the number of copies that occur if a type must be coerced
+// during argument forwarding in the Run() methods.
+struct DerivedCopyCounter {
+  DerivedCopyCounter(int* copies, int* assigns)
+      : copies_(copies), assigns_(assigns) {
+  }
+  int* copies_;
+  int* assigns_;
+};
+
+// Used for probing the number of copies in an argument.
+class CopyCounter {
+ public:
+  CopyCounter(int* copies, int* assigns)
+      : copies_(copies), assigns_(assigns) {
+  }
+
+  CopyCounter(const CopyCounter& other)
+      : copies_(other.copies_),
+        assigns_(other.assigns_) {
+    (*copies_)++;
+  }
+
+  // Probing for copies from coerscion.
+  CopyCounter(const DerivedCopyCounter& other)
+      : copies_(other.copies_),
+        assigns_(other.assigns_) {
+    (*copies_)++;
+  }
+
+  const CopyCounter& operator=(const CopyCounter& rhs) {
+    copies_ = rhs.copies_;
+    assigns_ = rhs.assigns_;
+
+    if (assigns_) {
+      (*assigns_)++;
+    }
+
+    return *this;
+  }
+
+  int copies() const {
+    return *copies_;
+  }
+
+  int assigns() const {
+    return *assigns_;
+  }
+
+ private:
+  int* copies_;
+  int* assigns_;
+};
+
+// Some test functions that we can Bind to.
+template <typename T>
+T PolymorphicIdentity(T t) {
+  return t;
+}
+
+template <typename T>
+void VoidPolymorphic1(T t) {
+}
+
+int Identity(int n) {
+  return n;
+}
+
+int ArrayGet(const int array[], int n) {
+  return array[n];
+}
+
+int Sum(int a, int b, int c, int d, int e, int f) {
+  return a + b + c + d + e + f;
+}
+
+const char* CStringIdentity(const char* s) {
+  return s;
+}
+
+int GetCopies(const CopyCounter& counter) {
+  return counter.copies();
+}
+
+int UnwrapNoRefParent(NoRefParent p) {
+  return p.value;
+}
+
+int UnwrapNoRefParentPtr(NoRefParent* p) {
+  return p->value;
+}
+
+int UnwrapNoRefParentConstRef(const NoRefParent& p) {
+  return p.value;
+}
+
+// Only useful in no-compile tests.
+int UnwrapNoRefParentRef(Parent& p) {
+  return p.value;
+}
+
+class BindTest : public ::testing::Test {
+ public:
+  BindTest() {
+    const_has_ref_ptr_ = &has_ref_;
+    const_no_ref_ptr_ = &no_ref_;
+    static_func_mock_ptr = &static_func_mock_;
+  }
+
+  virtual ~BindTest() {
+  }
+
+  static void VoidFunc0(void) {
+    static_func_mock_ptr->VoidMethod0();
+  }
+
+  static int IntFunc0(void) { return static_func_mock_ptr->IntMethod0(); }
+
+ protected:
+  StrictMock<NoRef> no_ref_;
+  StrictMock<HasRef> has_ref_;
+  const HasRef* const_has_ref_ptr_;
+  const NoRef* const_no_ref_ptr_;
+  StrictMock<NoRef> static_func_mock_;
+
+  // Used by the static functions to perform expectations.
+  static StrictMock<NoRef>* static_func_mock_ptr;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BindTest);
+};
+
+StrictMock<NoRef>* BindTest::static_func_mock_ptr;
+
+// Ensure we can create unbound callbacks. We need this to be able to store
+// them in class members that can be initialized later.
+TEST_F(BindTest, DefaultConstruction) {
+  Callback<void(void)> c0;
+  Callback<void(int)> c1;
+  Callback<void(int,int)> c2;
+  Callback<void(int,int,int)> c3;
+  Callback<void(int,int,int,int)> c4;
+  Callback<void(int,int,int,int,int)> c5;
+  Callback<void(int,int,int,int,int,int)> c6;
+}
+
+// Sanity check that we can instantiate a callback for each arity.
+TEST_F(BindTest, ArityTest) {
+  Callback<int(void)> c0 = Bind(&Sum, 32, 16, 8, 4, 2, 1);
+  EXPECT_EQ(63, c0.Run());
+
+  Callback<int(int)> c1 = Bind(&Sum, 32, 16, 8, 4, 2);
+  EXPECT_EQ(75, c1.Run(13));
+
+  Callback<int(int,int)> c2 = Bind(&Sum, 32, 16, 8, 4);
+  EXPECT_EQ(85, c2.Run(13, 12));
+
+  Callback<int(int,int,int)> c3 = Bind(&Sum, 32, 16, 8);
+  EXPECT_EQ(92, c3.Run(13, 12, 11));
+
+  Callback<int(int,int,int,int)> c4 = Bind(&Sum, 32, 16);
+  EXPECT_EQ(94, c4.Run(13, 12, 11, 10));
+
+  Callback<int(int,int,int,int,int)> c5 = Bind(&Sum, 32);
+  EXPECT_EQ(87, c5.Run(13, 12, 11, 10, 9));
+
+  Callback<int(int,int,int,int,int,int)> c6 = Bind(&Sum);
+  EXPECT_EQ(69, c6.Run(13, 12, 11, 10, 9, 14));
+}
+
+// Function type support.
+//   - Normal function.
+//   - Method bound to non-const object.
+//   - Const method bound to non-const object.
+//   - Const method bound to const object.
+//   - Derived classes can be used with pointers to non-virtual base functions.
+//   - Derived classes can be used with pointers to virtual base functions (and
+//     preserve virtual dispatch).
+TEST_F(BindTest, FunctionTypeSupport) {
+  EXPECT_CALL(static_func_mock_, VoidMethod0());
+  EXPECT_CALL(has_ref_, AddRef()).Times(3);
+  EXPECT_CALL(has_ref_, Release()).Times(3);
+  EXPECT_CALL(has_ref_, VoidMethod0());
+  EXPECT_CALL(has_ref_, VoidConstMethod0()).Times(2);
+
+  Closure normal_cb = Bind(&VoidFunc0);
+  Closure method_cb = Bind(&HasRef::VoidMethod0, &has_ref_);
+  Closure const_method_nonconst_obj_cb = Bind(&HasRef::VoidConstMethod0,
+                                              &has_ref_);
+  Closure const_method_const_obj_cb = Bind(&HasRef::VoidConstMethod0,
+                                           const_has_ref_ptr_);
+  normal_cb.Run();
+  method_cb.Run();
+  const_method_nonconst_obj_cb.Run();
+  const_method_const_obj_cb.Run();
+
+  Child child;
+  child.value = 0;
+  Closure virtual_set_cb = Bind(&Parent::VirtualSet, &child);
+  virtual_set_cb.Run();
+  EXPECT_EQ(kChildValue, child.value);
+
+  child.value = 0;
+  Closure non_virtual_set_cb = Bind(&Parent::NonVirtualSet, &child);
+  non_virtual_set_cb.Run();
+  EXPECT_EQ(kParentValue, child.value);
+}
+
+// Return value support.
+//   - Function with return value.
+//   - Method with return value.
+//   - Const method with return value.
+TEST_F(BindTest, ReturnValues) {
+  EXPECT_CALL(static_func_mock_, IntMethod0()).WillOnce(Return(1337));
+  EXPECT_CALL(has_ref_, AddRef()).Times(3);
+  EXPECT_CALL(has_ref_, Release()).Times(3);
+  EXPECT_CALL(has_ref_, IntMethod0()).WillOnce(Return(31337));
+  EXPECT_CALL(has_ref_, IntConstMethod0())
+      .WillOnce(Return(41337))
+      .WillOnce(Return(51337));
+
+  Callback<int(void)> normal_cb = Bind(&IntFunc0);
+  Callback<int(void)> method_cb = Bind(&HasRef::IntMethod0, &has_ref_);
+  Callback<int(void)> const_method_nonconst_obj_cb =
+      Bind(&HasRef::IntConstMethod0, &has_ref_);
+  Callback<int(void)> const_method_const_obj_cb =
+      Bind(&HasRef::IntConstMethod0, const_has_ref_ptr_);
+  EXPECT_EQ(1337, normal_cb.Run());
+  EXPECT_EQ(31337, method_cb.Run());
+  EXPECT_EQ(41337, const_method_nonconst_obj_cb.Run());
+  EXPECT_EQ(51337, const_method_const_obj_cb.Run());
+}
+
+// Argument binding tests.
+//   - Argument binding to primitive.
+//   - Argument binding to primitive pointer.
+//   - Argument binding to a literal integer.
+//   - Argument binding to a literal string.
+//   - Argument binding with template function.
+//   - Argument binding to an object.
+//   - Argument gets type converted.
+//   - Pointer argument gets converted.
+//   - Const Reference forces conversion.
+TEST_F(BindTest, ArgumentBinding) {
+  int n = 2;
+
+  Callback<int(void)> bind_primitive_cb = Bind(&Identity, n);
+  EXPECT_EQ(n, bind_primitive_cb.Run());
+
+  Callback<int*(void)> bind_primitive_pointer_cb =
+      Bind(&PolymorphicIdentity<int*>, &n);
+  EXPECT_EQ(&n, bind_primitive_pointer_cb.Run());
+
+  Callback<int(void)> bind_int_literal_cb = Bind(&Identity, 3);
+  EXPECT_EQ(3, bind_int_literal_cb.Run());
+
+  Callback<const char*(void)> bind_string_literal_cb =
+      Bind(&CStringIdentity, "hi");
+  EXPECT_STREQ("hi", bind_string_literal_cb.Run());
+
+  Callback<int(void)> bind_template_function_cb =
+      Bind(&PolymorphicIdentity<int>, 4);
+  EXPECT_EQ(4, bind_template_function_cb.Run());
+
+  NoRefParent p;
+  p.value = 5;
+  Callback<int(void)> bind_object_cb = Bind(&UnwrapNoRefParent, p);
+  EXPECT_EQ(5, bind_object_cb.Run());
+
+  NoRefChild c;
+  c.value = 6;
+  Callback<int(void)> bind_promotes_cb = Bind(&UnwrapNoRefParent, c);
+  EXPECT_EQ(6, bind_promotes_cb.Run());
+
+  c.value = 7;
+  Callback<int(void)> bind_pointer_promotes_cb =
+      Bind(&UnwrapNoRefParentPtr, &c);
+  EXPECT_EQ(7, bind_pointer_promotes_cb.Run());
+
+  c.value = 8;
+  Callback<int(void)> bind_const_reference_promotes_cb =
+      Bind(&UnwrapNoRefParentConstRef, c);
+  EXPECT_EQ(8, bind_const_reference_promotes_cb.Run());
+}
+
+// Functions that take reference parameters.
+//  - Forced reference parameter type still stores a copy.
+//  - Forced const reference parameter type still stores a copy.
+TEST_F(BindTest, ReferenceArgumentBinding) {
+  int n = 1;
+  int& ref_n = n;
+  const int& const_ref_n = n;
+
+  Callback<int(void)> ref_copies_cb = Bind(&Identity, ref_n);
+  EXPECT_EQ(n, ref_copies_cb.Run());
+  n++;
+  EXPECT_EQ(n - 1, ref_copies_cb.Run());
+
+  Callback<int(void)> const_ref_copies_cb = Bind(&Identity, const_ref_n);
+  EXPECT_EQ(n, const_ref_copies_cb.Run());
+  n++;
+  EXPECT_EQ(n - 1, const_ref_copies_cb.Run());
+}
+
+// Check that we can pass in arrays and have them be stored as a pointer.
+//  - Array of values stores a pointer.
+//  - Array of const values stores a pointer.
+TEST_F(BindTest, ArrayArgumentBinding) {
+  int array[4] = {1, 1, 1, 1};
+  const int (*const_array_ptr)[4] = &array;
+
+  Callback<int(void)> array_cb = Bind(&ArrayGet, array, 1);
+  EXPECT_EQ(1, array_cb.Run());
+
+  Callback<int(void)> const_array_cb = Bind(&ArrayGet, *const_array_ptr, 1);
+  EXPECT_EQ(1, const_array_cb.Run());
+
+  array[1] = 3;
+  EXPECT_EQ(3, array_cb.Run());
+  EXPECT_EQ(3, const_array_cb.Run());
+}
+
+// Verify SupportsAddRefAndRelease correctly introspects the class type for
+// AddRef() and Release().
+TEST_F(BindTest, SupportsAddRefAndRelease) {
+  EXPECT_TRUE(internal::SupportsAddRefAndRelease<HasRef>::value);
+  EXPECT_FALSE(internal::SupportsAddRefAndRelease<NoRef>::value);
+
+  // StrictMock<T> is a derived class of T.  So, we use StrictMock<HasRef> and
+  // StrictMock<NoRef> to test that SupportsAddRefAndRelease works over
+  // inheritance.
+  EXPECT_TRUE(internal::SupportsAddRefAndRelease<StrictMock<HasRef> >::value);
+  EXPECT_FALSE(internal::SupportsAddRefAndRelease<StrictMock<NoRef> >::value);
+}
+
+// Unretained() wrapper support.
+//   - Method bound to Unretained() non-object.
+//   - Const method bound to Unretained() non-const object.
+//   - Const method bound to Unretained() const object.
+TEST_F(BindTest, Unretained) {
+  EXPECT_CALL(no_ref_, VoidMethod0());
+  EXPECT_CALL(no_ref_, VoidConstMethod0()).Times(2);
+
+  Callback<void(void)> method_cb =
+      Bind(&NoRef::VoidMethod0, Unretained(&no_ref_));
+  method_cb.Run();
+
+  Callback<void(void)> const_method_cb =
+      Bind(&NoRef::VoidConstMethod0, Unretained(&no_ref_));
+  const_method_cb.Run();
+
+  Callback<void(void)> const_method_const_ptr_cb =
+      Bind(&NoRef::VoidConstMethod0, Unretained(const_no_ref_ptr_));
+  const_method_const_ptr_cb.Run();
+}
+
+// ConstRef() wrapper support.
+//   - Binding w/o ConstRef takes a copy.
+//   - Binding a ConstRef takes a reference.
+//   - Binding ConstRef to a function ConstRef does not copy on invoke.
+TEST_F(BindTest, ConstRef) {
+  int n = 1;
+
+  Callback<int(void)> copy_cb = Bind(&Identity, n);
+  Callback<int(void)> const_ref_cb = Bind(&Identity, ConstRef(n));
+  EXPECT_EQ(n, copy_cb.Run());
+  EXPECT_EQ(n, const_ref_cb.Run());
+  n++;
+  EXPECT_EQ(n - 1, copy_cb.Run());
+  EXPECT_EQ(n, const_ref_cb.Run());
+
+  int copies = 0;
+  int assigns = 0;
+  CopyCounter counter(&copies, &assigns);
+  Callback<int(void)> all_const_ref_cb =
+      Bind(&GetCopies, ConstRef(counter));
+  EXPECT_EQ(0, all_const_ref_cb.Run());
+  EXPECT_EQ(0, copies);
+  EXPECT_EQ(0, assigns);
+}
+
+// Argument Copy-constructor usage for non-reference parameters.
+//   - Bound arguments are only copied once.
+//   - Forwarded arguments are only copied once.
+//   - Forwarded arguments with coerscions are only copied twice (once for the
+//     coerscion, and one for the final dispatch).
+TEST_F(BindTest, ArgumentCopies) {
+  int copies = 0;
+  int assigns = 0;
+
+  CopyCounter counter(&copies, &assigns);
+
+  Callback<void(void)> copy_cb =
+      Bind(&VoidPolymorphic1<CopyCounter>, counter);
+  EXPECT_GE(1, copies);
+  EXPECT_EQ(0, assigns);
+
+  copies = 0;
+  assigns = 0;
+  Callback<void(CopyCounter)> forward_cb =
+      Bind(&VoidPolymorphic1<CopyCounter>);
+  forward_cb.Run(counter);
+  EXPECT_GE(1, copies);
+  EXPECT_EQ(0, assigns);
+
+  copies = 0;
+  assigns = 0;
+  DerivedCopyCounter dervied(&copies, &assigns);
+  Callback<void(CopyCounter)> coerce_cb =
+      Bind(&VoidPolymorphic1<CopyCounter>);
+  coerce_cb.Run(dervied);
+  EXPECT_GE(2, copies);
+  EXPECT_EQ(0, assigns);
+}
+
+// Callback construction and assignment tests.
+//   - Construction from an InvokerStorageHolder should not cause ref/deref.
+//   - Assignment from other callback should only cause one ref
+//
+// TODO(ajwong): Is there actually a way to test this?
+
+// No-compile tests. These should not compile. If they do, we are allowing
+// error-prone, or incorrect behavior in the callback system.  Uncomment the
+// tests to check.
+TEST_F(BindTest, NoCompile) {
+  // - Method bound to const-object.
+  //
+  // Only const methods should be allowed to work with const objects.
+  //
+  // Callback<void(void)> method_to_const_cb =
+  //     Bind(&HasRef::VoidMethod0, const_has_ref_ptr_);
+  // method_to_const_cb.Run();
+
+  // - Method bound to non-refcounted object.
+  // - Const Method bound to non-refcounted object.
+  //
+  // We require refcounts unless you have Unretained().
+  //
+  // Callback<void(void)> no_ref_cb =
+  //     Bind(&NoRef::VoidMethod0, &no_ref_);
+  // no_ref_cb.Run();
+  // Callback<void(void)> no_ref_const_cb =
+  //     Bind(&NoRef::VoidConstMethod0, &no_ref_);
+  // no_ref_const_cb.Run();
+
+  // - Unretained() used with a refcounted object.
+  //
+  // If the object supports refcounts, unretaining it in the callback is a
+  // memory management contract break.
+  // Callback<void(void)> unretained_cb =
+  //     Bind(&HasRef::VoidConstMethod0, Unretained(&has_ref_));
+  // unretained_cb.Run();
+
+  // - Const argument used with non-const pointer parameter of same type.
+  // - Const argument used with non-const pointer parameter of super type.
+  //
+  // This is just a const-correctness check.
+  //
+  // const Parent* const_parent_ptr;
+  // const Child* const_child_ptr;
+  // Callback<Parent*(void)> pointer_same_cb =
+  //     Bind(&PolymorphicIdentity<Parent*>, const_parent_ptr);
+  // pointer_same_cb.Run();
+  // Callback<Parent*(void)> pointer_super_cb =
+  //     Bind(&PolymorphicIdentity<Parent*>, const_child_ptr);
+  // pointer_super_cb.Run();
+
+  // - Construction of Callback<A> from Callback<B> if A is supertype of B.
+  //   Specific example: Callback<void(void)> a; Callback<int(void)> b; a = b;
+  //
+  // While this is technically safe, most people aren't used to it when coding
+  // C++ so if this is happening, it is almost certainly an error.
+  //
+  // Callback<int(void)> cb_a0 = Bind(&Identity, 1);
+  // Callback<void(void)> cb_b0 = cb_a0;
+
+  // - Assignment of Callback<A> from Callback<B> if A is supertype of B.
+  // See explanation above.
+  //
+  // Callback<int(void)> cb_a1 = Bind(&Identity, 1);
+  // Callback<void(void)> cb_b1;
+  // cb_a1 = cb_b1;
+
+  // - Functions with reference parameters, unsupported.
+  //
+  // First, non-const reference parameters are disallowed by the Google
+  // style guide. Seconds, since we are doing argument forwarding it becomes
+  // very tricky to avoid copies, maintain const correctness, and not
+  // accidentally have the function be modifying a temporary, or a copy.
+  //
+  // NoRefParent p;
+  // Callback<int(Parent&)> ref_arg_cb = Bind(&UnwrapNoRefParentRef);
+  // ref_arg_cb.Run(p);
+  // Callback<int(void)> ref_cb = Bind(&UnwrapNoRefParentRef, p);
+  // ref_cb.Run();
+
+  // - A method should not be bindable with an array of objects.
+  //
+  // This is likely not wanted behavior. We specifically check for it though
+  // because it is possible, depending on how you implement prebinding, to
+  // implicitly convert an array type to a pointer type.
+  //
+  // HasRef p[10];
+  // Callback<void(void)> method_bound_to_array_cb =
+  //    Bind(&HasRef::VoidConstMethod0, p);
+  // method_bound_to_array_cb.Run();
+
+  // - Refcounted types should not be bound as a raw pointer.
+  // HasRef for_raw_ptr;
+  // Callback<void(void)> ref_count_as_raw_ptr =
+  //     Bind(&VoidPolymorphic1<HasRef*>, &for_raw_ptr);
+  // ASSERT_EQ(&for_raw_ptr, ref_count_as_raw_ptr.Run());
+
+}
+
+}  // namespace
+}  // namespace base