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#region Copyright notice and license
// Copyright 2018 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.
#endregion
using System;
using System.Linq;
using Grpc.Core.Utils;
namespace Grpc.Core.Interceptors
{
/// <summary>
/// Extends the CallInvoker class to provide the interceptor facility on the client side.
/// This is an EXPERIMENTAL API.
/// </summary>
public static class CallInvokerExtensions
{
/// <summary>
/// Returns a <see cref="Grpc.Core.CallInvoker" /> instance that intercepts
/// the invoker with the given interceptor.
/// </summary>
/// <param name="invoker">The underlying invoker to intercept.</param>
/// <param name="interceptor">The interceptor to intercept calls to the invoker with.</param>
/// <remarks>
/// Multiple interceptors can be added on top of each other by calling
/// "invoker.Intercept(a, b, c)". The order of invocation will be "a", "b", and then "c".
/// Interceptors can be later added to an existing intercepted CallInvoker, effectively
/// building a chain like "invoker.Intercept(c).Intercept(b).Intercept(a)". Note that
/// in this case, the last interceptor added will be the first to take control.
/// </remarks>
public static CallInvoker Intercept(this CallInvoker invoker, Interceptor interceptor)
{
return new InterceptingCallInvoker(invoker, interceptor);
}
/// <summary>
/// Returns a <see cref="Grpc.Core.CallInvoker" /> instance that intercepts
/// the invoker with the given interceptors.
/// </summary>
/// <param name="invoker">The channel to intercept.</param>
/// <param name="interceptors">
/// An array of interceptors to intercept the calls to the invoker with.
/// Control is passed to the interceptors in the order specified.
/// </param>
/// <remarks>
/// Multiple interceptors can be added on top of each other by calling
/// "invoker.Intercept(a, b, c)". The order of invocation will be "a", "b", and then "c".
/// Interceptors can be later added to an existing intercepted CallInvoker, effectively
/// building a chain like "invoker.Intercept(c).Intercept(b).Intercept(a)". Note that
/// in this case, the last interceptor added will be the first to take control.
/// </remarks>
public static CallInvoker Intercept(this CallInvoker invoker, params Interceptor[] interceptors)
{
GrpcPreconditions.CheckNotNull(invoker, "invoker");
GrpcPreconditions.CheckNotNull(interceptors, "interceptors");
foreach (var interceptor in interceptors.Reverse())
{
invoker = Intercept(invoker, interceptor);
}
return invoker;
}
/// <summary>
/// Returns a <see cref="Grpc.Core.CallInvoker" /> instance that intercepts
/// the invoker with the given interceptor.
/// </summary>
/// <param name="invoker">The underlying invoker to intercept.</param>
/// <param name="interceptor">
/// An interceptor delegate that takes the request metadata to be sent with an outgoing call
/// and returns a <see cref="Grpc.Core.Metadata" /> instance that will replace the existing
/// invocation metadata.
/// </param>
/// <remarks>
/// Multiple interceptors can be added on top of each other by
/// building a chain like "invoker.Intercept(c).Intercept(b).Intercept(a)". Note that
/// in this case, the last interceptor added will be the first to take control.
/// </remarks>
public static CallInvoker Intercept(this CallInvoker invoker, Func<Metadata, Metadata> interceptor)
{
return new InterceptingCallInvoker(invoker, new MetadataInterceptor(interceptor));
}
private class MetadataInterceptor : GenericInterceptor
{
readonly Func<Metadata, Metadata> interceptor;
/// <summary>
/// Creates a new instance of MetadataInterceptor given the specified interceptor function.
/// </summary>
public MetadataInterceptor(Func<Metadata, Metadata> interceptor)
{
this.interceptor = GrpcPreconditions.CheckNotNull(interceptor, "interceptor");
}
protected override ClientCallHooks<TRequest, TResponse> InterceptCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, bool clientStreaming, bool serverStreaming, TRequest request)
{
var metadata = context.Options.Headers ?? new Metadata();
return new ClientCallHooks<TRequest, TResponse>
{
ContextOverride = new ClientInterceptorContext<TRequest, TResponse>(context.Method, context.Host, context.Options.WithHeaders(interceptor(metadata))),
};
}
}
}
}
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