1/*
2 *
3 * Copyright 2018 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19#ifndef GRPCPP_IMPL_CODEGEN_CALLBACK_COMMON_H
20#define GRPCPP_IMPL_CODEGEN_CALLBACK_COMMON_H
21
22#include <functional>
23
24#include <grpc/impl/codegen/grpc_types.h>
25#include <grpcpp/impl/codegen/call.h>
26#include <grpcpp/impl/codegen/channel_interface.h>
27#include <grpcpp/impl/codegen/config.h>
28#include <grpcpp/impl/codegen/core_codegen_interface.h>
29#include <grpcpp/impl/codegen/status.h>
30
31namespace grpc {
32namespace internal {
33
34/// An exception-safe way of invoking a user-specified callback function
35// TODO(vjpai): decide whether it is better for this to take a const lvalue
36// parameter or an rvalue parameter, or if it even matters
37template <class Func, class... Args>
38void CatchingCallback(Func&& func, Args&&... args) {
39#if GRPC_ALLOW_EXCEPTIONS
40 try {
41 func(std::forward<Args>(args)...);
42 } catch (...) {
43 // nothing to return or change here, just don't crash the library
44 }
45#else // GRPC_ALLOW_EXCEPTIONS
46 func(std::forward<Args>(args)...);
47#endif // GRPC_ALLOW_EXCEPTIONS
48}
49
50template <class Reactor, class Func, class... Args>
51Reactor* CatchingReactorGetter(Func&& func, Args&&... args) {
52#if GRPC_ALLOW_EXCEPTIONS
53 try {
54 return func(std::forward<Args>(args)...);
55 } catch (...) {
56 // fail the RPC, don't crash the library
57 return nullptr;
58 }
59#else // GRPC_ALLOW_EXCEPTIONS
60 return func(std::forward<Args>(args)...);
61#endif // GRPC_ALLOW_EXCEPTIONS
62}
63
64// The contract on these tags is that they are single-shot. They must be
65// constructed and then fired at exactly one point. There is no expectation
66// that they can be reused without reconstruction.
67
68class CallbackWithStatusTag
69 : public grpc_experimental_completion_queue_functor {
70 public:
71 // always allocated against a call arena, no memory free required
72 static void operator delete(void* /*ptr*/, std::size_t size) {
73 GPR_CODEGEN_ASSERT(size == sizeof(CallbackWithStatusTag));
74 }
75
76 // This operator should never be called as the memory should be freed as part
77 // of the arena destruction. It only exists to provide a matching operator
78 // delete to the operator new so that some compilers will not complain (see
79 // https://github.com/grpc/grpc/issues/11301) Note at the time of adding this
80 // there are no tests catching the compiler warning.
81 static void operator delete(void*, void*) { GPR_CODEGEN_ASSERT(false); }
82
83 CallbackWithStatusTag(grpc_call* call, std::function<void(Status)> f,
84 CompletionQueueTag* ops)
85 : call_(call), func_(std::move(f)), ops_(ops) {
86 g_core_codegen_interface->grpc_call_ref(call);
87 functor_run = &CallbackWithStatusTag::StaticRun;
88 // A client-side callback should never be run inline since they will always
89 // have work to do from the user application. So, set the parent's
90 // inlineable field to false
91 inlineable = false;
92 }
93 ~CallbackWithStatusTag() {}
94 Status* status_ptr() { return &status_; }
95
96 // force_run can not be performed on a tag if operations using this tag
97 // have been sent to PerformOpsOnCall. It is intended for error conditions
98 // that are detected before the operations are internally processed.
99 void force_run(Status s) {
100 status_ = std::move(s);
101 Run(ok: true);
102 }
103
104 private:
105 grpc_call* call_;
106 std::function<void(Status)> func_;
107 CompletionQueueTag* ops_;
108 Status status_;
109
110 static void StaticRun(grpc_experimental_completion_queue_functor* cb,
111 int ok) {
112 static_cast<CallbackWithStatusTag*>(cb)->Run(ok: static_cast<bool>(ok));
113 }
114 void Run(bool ok) {
115 void* ignored = ops_;
116
117 if (!ops_->FinalizeResult(tag: &ignored, status: &ok)) {
118 // The tag was swallowed
119 return;
120 }
121 GPR_CODEGEN_ASSERT(ignored == ops_);
122
123 // Last use of func_ or status_, so ok to move them out
124 auto func = std::move(func_);
125 auto status = std::move(status_);
126 func_ = nullptr; // reset to clear this out for sure
127 status_ = Status(); // reset to clear this out for sure
128 CatchingCallback(func: std::move(func), args: std::move(status));
129 g_core_codegen_interface->grpc_call_unref(call: call_);
130 }
131};
132
133/// CallbackWithSuccessTag can be reused multiple times, and will be used in
134/// this fashion for streaming operations. As a result, it shouldn't clear
135/// anything up until its destructor
136class CallbackWithSuccessTag
137 : public grpc_experimental_completion_queue_functor {
138 public:
139 // always allocated against a call arena, no memory free required
140 static void operator delete(void* /*ptr*/, std::size_t size) {
141 GPR_CODEGEN_ASSERT(size == sizeof(CallbackWithSuccessTag));
142 }
143
144 // This operator should never be called as the memory should be freed as part
145 // of the arena destruction. It only exists to provide a matching operator
146 // delete to the operator new so that some compilers will not complain (see
147 // https://github.com/grpc/grpc/issues/11301) Note at the time of adding this
148 // there are no tests catching the compiler warning.
149 static void operator delete(void*, void*) { GPR_CODEGEN_ASSERT(false); }
150
151 CallbackWithSuccessTag() : call_(nullptr) {}
152
153 CallbackWithSuccessTag(const CallbackWithSuccessTag&) = delete;
154 CallbackWithSuccessTag& operator=(const CallbackWithSuccessTag&) = delete;
155
156 ~CallbackWithSuccessTag() { Clear(); }
157
158 // Set can only be called on a default-constructed or Clear'ed tag.
159 // It should never be called on a tag that was constructed with arguments
160 // or on a tag that has been Set before unless the tag has been cleared.
161 // can_inline indicates that this particular callback can be executed inline
162 // (without needing a thread hop) and is only used for library-provided server
163 // callbacks.
164 void Set(grpc_call* call, std::function<void(bool)> f,
165 CompletionQueueTag* ops, bool can_inline) {
166 GPR_CODEGEN_ASSERT(call_ == nullptr);
167 g_core_codegen_interface->grpc_call_ref(call);
168 call_ = call;
169 func_ = std::move(f);
170 ops_ = ops;
171 functor_run = &CallbackWithSuccessTag::StaticRun;
172 inlineable = can_inline;
173 }
174
175 void Clear() {
176 if (call_ != nullptr) {
177 grpc_call* call = call_;
178 call_ = nullptr;
179 func_ = nullptr;
180 g_core_codegen_interface->grpc_call_unref(call);
181 }
182 }
183
184 CompletionQueueTag* ops() { return ops_; }
185
186 // force_run can not be performed on a tag if operations using this tag
187 // have been sent to PerformOpsOnCall. It is intended for error conditions
188 // that are detected before the operations are internally processed.
189 void force_run(bool ok) { Run(ok); }
190
191 /// check if this tag is currently set
192 operator bool() const { return call_ != nullptr; }
193
194 private:
195 grpc_call* call_;
196 std::function<void(bool)> func_;
197 CompletionQueueTag* ops_;
198
199 static void StaticRun(grpc_experimental_completion_queue_functor* cb,
200 int ok) {
201 static_cast<CallbackWithSuccessTag*>(cb)->Run(ok: static_cast<bool>(ok));
202 }
203 void Run(bool ok) {
204 void* ignored = ops_;
205 // Allow a "false" return value from FinalizeResult to silence the
206 // callback, just as it silences a CQ tag in the async cases
207#ifndef NDEBUG
208 auto* ops = ops_;
209#endif
210 bool do_callback = ops_->FinalizeResult(tag: &ignored, status: &ok);
211 GPR_CODEGEN_DEBUG_ASSERT(ignored == ops);
212
213 if (do_callback) {
214 CatchingCallback(func&: func_, args&: ok);
215 }
216 }
217};
218
219} // namespace internal
220} // namespace grpc
221
222#endif // GRPCPP_IMPL_CODEGEN_CALLBACK_COMMON_H
223

source code of include/grpcpp/impl/codegen/callback_common.h