CapCarrierHeaderCollection.cs

/*
 * Licensed to the SkyAPM under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The SkyAPM licenses this file to You 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.
 *
 */

using System.Collections;
using System.Collections.Generic;
using DotNetCore.CAP.Messages;
using SkyApm.Tracing;

namespace SkyApm.Diagnostics.CAP
{
    public class CapCarrierHeaderCollection : ICarrierHeaderDictionary
    {
        private readonly IDictionary<string,string> _messageHeaders;

        public CapCarrierHeaderCollection(TransportMessage message)
        {
            _messageHeaders = message.Headers;
        }

        public CapCarrierHeaderCollection(Message message)
        {
            _messageHeaders = message.Headers;
        }
        
        public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
        {
            return _messageHeaders.GetEnumerator();
        }

        public void Add(string key, string value)
        {
            // Overwrite rather than Dictionary.Add: a message can already carry an sw8 header when
            // the transport re-publishes it (e.g. CAP's in-memory queue), and Add throws on a
            // duplicate key. Injecting the carrier must be idempotent.
            _messageHeaders[key] = value;
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        public string Get(string key)
        {
            if (_messageHeaders.TryGetValue(key, out var value))
                return value;
            return null;
        }
    }
}