text: /*
   *
   * Copyright 2016 gRPC authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   */
  
  package grpc
  
  import (
  	"context"
  )
  
  // UnaryInvoker is called by UnaryClientInterceptor to complete RPCs.
  type UnaryInvoker func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, opts ...CallOption) error
  
  // UnaryClientInterceptor intercepts the execution of a unary RPC on the client. invoker is the handler to complete the RPC
  // and it is the responsibility of the interceptor to call it.
  // This is an EXPERIMENTAL API.
  type UnaryClientInterceptor func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, invoker UnaryInvoker, opts ...CallOption) error
  
  // Streamer is called by StreamClientInterceptor to create a ClientStream.
  type Streamer func(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, opts ...CallOption) (ClientStream, error)
  
  // StreamClientInterceptor intercepts the creation of ClientStream. It may return a custom ClientStream to intercept all I/O
  // operations. streamer is the handler to create a ClientStream and it is the responsibility of the interceptor to call it.
  // This is an EXPERIMENTAL API.
  type StreamClientInterceptor func(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, streamer Streamer, opts ...CallOption) (ClientStream, error)
  
  // UnaryServerInfo consists of various information about a unary RPC on
  // server side. All per-rpc information may be mutated by the interceptor.
  type UnaryServerInfo struct {
  	// Server is the service implementation the user provides. This is read-only.
  	Server interface{}
  	// FullMethod is the full RPC method string, i.e., /package.service/method.
  	FullMethod string
  }
  
  // UnaryHandler defines the handler invoked by UnaryServerInterceptor to complete the normal
  // execution of a unary RPC. If a UnaryHandler returns an error, it should be produced by the
  // status package, or else gRPC will use codes.Unknown as the status code and err.Error() as
  // the status message of the RPC.
  type UnaryHandler func(ctx context.Context, req interface{}) (interface{}, error)
  
  // UnaryServerInterceptor provides a hook to intercept the execution of a unary RPC on the server. info
  // contains all the information of this RPC the interceptor can operate on. And handler is the wrapper
  // of the service method implementation. It is the responsibility of the interceptor to invoke handler
  // to complete the RPC.
  type UnaryServerInterceptor func(ctx context.Context, req interface{}, info *UnaryServerInfo, handler UnaryHandler) (resp interface{}, err error)
  
  // StreamServerInfo consists of various information about a streaming RPC on
  // server side. All per-rpc information may be mutated by the interceptor.
  type StreamServerInfo struct {
  	// FullMethod is the full RPC method string, i.e., /package.service/method.
  	FullMethod string
  	// IsClientStream indicates whether the RPC is a client streaming RPC.
  	IsClientStream bool
  	// IsServerStream indicates whether the RPC is a server streaming RPC.
  	IsServerStream bool
  }
  
  // StreamServerInterceptor provides a hook to intercept the execution of a streaming RPC on the server.
  // info contains all the information of this RPC the interceptor can operate on. And handler is the
  // service method implementation. It is the responsibility of the interceptor to invoke handler to
  // complete the RPC.
  type StreamServerInterceptor func(srv interface{}, ss ServerStream, info *StreamServerInfo, handler StreamHandler) error
  