1 /* 2 * 3 * Copyright 2016 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 GRPC_CORE_LIB_SURFACE_CHANNEL_INIT_H 20 #define GRPC_CORE_LIB_SURFACE_CHANNEL_INIT_H 21 22 #include <grpc/support/port_platform.h> 23 24 #include <functional> 25 #include <vector> 26 27 #include "src/core/lib/surface/channel_stack_type.h" 28 29 #define GRPC_CHANNEL_INIT_BUILTIN_PRIORITY 10000 30 31 /// This module provides a way for plugins (and the grpc core library itself) 32 /// to register mutators for channel stacks. 33 /// It also provides a universal entry path to run those mutators to build 34 /// a channel stack for various subsystems. 35 36 typedef struct grpc_channel_stack_builder grpc_channel_stack_builder; 37 38 namespace grpc_core { 39 40 class ChannelInit { 41 public: 42 /// One stage of mutation: call functions against \a builder to influence the 43 /// finally constructed channel stack 44 using Stage = std::function<bool(grpc_channel_stack_builder* builder)>; 45 46 class Builder { 47 public: 48 /// Register one stage of mutators. 49 /// Stages are run in priority order (lowest to highest), and then in 50 /// registration order (in the case of a tie). 51 /// Stages are registered against one of the pre-determined channel stack 52 /// types. 53 /// If the channel stack type is GRPC_CLIENT_SUBCHANNEL, the caller should 54 /// ensure that subchannels with different filter lists will always have 55 /// different channel args. This requires setting a channel arg in case the 56 /// registration function relies on some condition other than channel args 57 /// to decide whether to add a filter or not. 58 void RegisterStage(grpc_channel_stack_type type, int priority, Stage stage); 59 60 /// Finalize registration. No more calls to grpc_channel_init_register_stage 61 /// are allowed. 62 ChannelInit Build(); 63 64 private: 65 struct Slot { SlotSlot66 Slot(Stage stage, int priority) 67 : stage(std::move(stage)), priority(priority) {} 68 Stage stage; 69 int priority; 70 }; 71 std::vector<Slot> slots_[GRPC_NUM_CHANNEL_STACK_TYPES]; 72 }; 73 74 /// Construct a channel stack of some sort: see channel_stack.h for details 75 /// \a type is the type of channel stack to create 76 /// \a builder is the channel stack builder to build into. 77 bool CreateStack(grpc_channel_stack_builder* builder, 78 grpc_channel_stack_type type) const; 79 80 private: 81 std::vector<Stage> slots_[GRPC_NUM_CHANNEL_STACK_TYPES]; 82 }; 83 84 } // namespace grpc_core 85 86 #endif /* GRPC_CORE_LIB_SURFACE_CHANNEL_INIT_H */ 87