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_SUPPORT_CALLBACK_COMMON_H
20#define GRPCPP_SUPPORT_CALLBACK_COMMON_H
21
22#include <functional>
23
24#include <grpc/impl/codegen/grpc_types.h>
25#include <grpcpp/impl/call.h>
26#include <grpcpp/impl/codegen/channel_interface.h>
27#include <grpcpp/impl/codegen/completion_queue_tag.h>
28#include <grpcpp/impl/codegen/core_codegen_interface.h>
29#include <grpcpp/support/config.h>
30#include <grpcpp/support/status.h>
31
32namespace grpc {
33namespace internal {
34
35/// An exception-safe way of invoking a user-specified callback function
36// TODO(vjpai): decide whether it is better for this to take a const lvalue
37// parameter or an rvalue parameter, or if it even matters
38template <class Func, class... Args>
39void CatchingCallback(Func&& func, Args&&... args) {
40#if GRPC_ALLOW_EXCEPTIONS
41 try {
42 func(std::forward<Args>(args)...);
43 } catch (...) {
44 // nothing to return or change here, just don't crash the library
45 }
46#else // GRPC_ALLOW_EXCEPTIONS
47 func(std::forward<Args>(args)...);
48#endif // GRPC_ALLOW_EXCEPTIONS
49}
50
51template <class Reactor, class Func, class... Args>
52Reactor* CatchingReactorGetter(Func&& func, Args&&... args) {
53#if GRPC_ALLOW_EXCEPTIONS
54 try {
55 return func(std::forward<Args>(args)...);
56 } catch (...) {
57 // fail the RPC, don't crash the library
58 return nullptr;
59 }
60#else // GRPC_ALLOW_EXCEPTIONS
61 return func(std::forward<Args>(args)...);
62#endif // GRPC_ALLOW_EXCEPTIONS
63}
64
65// The contract on these tags is that they are single-shot. They must be
66// constructed and then fired at exactly one point. There is no expectation
67// that they can be reused without reconstruction.
68
69class CallbackWithStatusTag : public grpc_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_completion_queue_functor* cb, int ok) {
111 static_cast<CallbackWithStatusTag*>(cb)->Run(ok: static_cast<bool>(ok));
112 }
113 void Run(bool ok) {
114 void* ignored = ops_;
115
116 if (!ops_->FinalizeResult(tag: &ignored, status: &ok)) {
117 // The tag was swallowed
118 return;
119 }
120 GPR_CODEGEN_ASSERT(ignored == ops_);
121
122 // Last use of func_ or status_, so ok to move them out
123 auto func = std::move(func_);
124 auto status = std::move(status_);
125 func_ = nullptr; // reset to clear this out for sure
126 status_ = Status(); // reset to clear this out for sure
127 CatchingCallback(func: std::move(func), args: std::move(status));
128 g_core_codegen_interface->grpc_call_unref(call: call_);
129 }
130};
131
132/// CallbackWithSuccessTag can be reused multiple times, and will be used in
133/// this fashion for streaming operations. As a result, it shouldn't clear
134/// anything up until its destructor
135class CallbackWithSuccessTag : public grpc_completion_queue_functor {
136 public:
137 // always allocated against a call arena, no memory free required
138 static void operator delete(void* /*ptr*/, std::size_t size) {
139 GPR_CODEGEN_ASSERT(size == sizeof(CallbackWithSuccessTag));
140 }
141
142 // This operator should never be called as the memory should be freed as part
143 // of the arena destruction. It only exists to provide a matching operator
144 // delete to the operator new so that some compilers will not complain (see
145 // https://github.com/grpc/grpc/issues/11301) Note at the time of adding this
146 // there are no tests catching the compiler warning.
147 static void operator delete(void*, void*) { GPR_CODEGEN_ASSERT(false); }
148
149 CallbackWithSuccessTag() : call_(nullptr) {}
150
151 CallbackWithSuccessTag(const CallbackWithSuccessTag&) = delete;
152 CallbackWithSuccessTag& operator=(const CallbackWithSuccessTag&) = delete;
153
154 ~CallbackWithSuccessTag() { Clear(); }
155
156 // Set can only be called on a default-constructed or Clear'ed tag.
157 // It should never be called on a tag that was constructed with arguments
158 // or on a tag that has been Set before unless the tag has been cleared.
159 // can_inline indicates that this particular callback can be executed inline
160 // (without needing a thread hop) and is only used for library-provided server
161 // callbacks.
162 void Set(grpc_call* call, std::function<void(bool)> f,
163 CompletionQueueTag* ops, bool can_inline) {
164 GPR_CODEGEN_ASSERT(call_ == nullptr);
165 g_core_codegen_interface->grpc_call_ref(call);
166 call_ = call;
167 func_ = std::move(f);
168 ops_ = ops;
169 functor_run = &CallbackWithSuccessTag::StaticRun;
170 inlineable = can_inline;
171 }
172
173 void Clear() {
174 if (call_ != nullptr) {
175 grpc_call* call = call_;
176 call_ = nullptr;
177 func_ = nullptr;
178 g_core_codegen_interface->grpc_call_unref(call);
179 }
180 }
181
182 CompletionQueueTag* ops() { return ops_; }
183
184 // force_run can not be performed on a tag if operations using this tag
185 // have been sent to PerformOpsOnCall. It is intended for error conditions
186 // that are detected before the operations are internally processed.
187 void force_run(bool ok) { Run(ok); }
188
189 /// check if this tag is currently set
190 /* NOLINTNEXTLINE(google-explicit-constructor) */
191 operator bool() const { return call_ != nullptr; }
192
193 private:
194 grpc_call* call_;
195 std::function<void(bool)> func_;
196 CompletionQueueTag* ops_;
197
198 static void StaticRun(grpc_completion_queue_functor* cb, int ok) {
199 static_cast<CallbackWithSuccessTag*>(cb)->Run(ok: static_cast<bool>(ok));
200 }
201 void Run(bool ok) {
202 void* ignored = ops_;
203 // Allow a "false" return value from FinalizeResult to silence the
204 // callback, just as it silences a CQ tag in the async cases
205#ifndef NDEBUG
206 auto* ops = ops_;
207#endif
208 bool do_callback = ops_->FinalizeResult(tag: &ignored, status: &ok);
209 GPR_CODEGEN_DEBUG_ASSERT(ignored == ops);
210
211 if (do_callback) {
212 CatchingCallback(func&: func_, args&: ok);
213 }
214 }
215};
216
217} // namespace internal
218} // namespace grpc
219
220#endif // GRPCPP_SUPPORT_CALLBACK_COMMON_H
221

source code of include/grpcpp/support/callback_common.h