changes complete. Tests not yet

Author: Sergey Kanzhelev

Microsoft.AspNet.TelemetryCorrelation.sln

@@ -7,12 +7,13 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{CE6B50B2-34A
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "test", "test", "{258D5057-81B9-40EC-A872-D21E27452749}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.AspNet.TelemetryCorrelation", "src\Microsoft.AspNet.TelemetryCorrelation\Microsoft.AspNet.TelemetryCorrelation.csproj", "{4C8E592C-C532-4CF2-80EF-3BDD0D788D12}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.AspNet.TelemetryCorrelation", "src\Microsoft.AspNet.TelemetryCorrelation\Microsoft.AspNet.TelemetryCorrelation.csproj", "{4C8E592C-C532-4CF2-80EF-3BDD0D788D12}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.AspNet.TelemetryCorrelation.Tests", "test\Microsoft.AspNet.TelemetryCorrelation.Tests\Microsoft.AspNet.TelemetryCorrelation.Tests.csproj", "{9FAE5C43-F56C-4D87-A23C-6D2D57B4ABED}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.AspNet.TelemetryCorrelation.Tests", "test\Microsoft.AspNet.TelemetryCorrelation.Tests\Microsoft.AspNet.TelemetryCorrelation.Tests.csproj", "{9FAE5C43-F56C-4D87-A23C-6D2D57B4ABED}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{504D7010-38CC-4B07-BC57-D7030209D631}"
 	ProjectSection(SolutionItems) = preProject
+		tools\Common.props = tools\Common.props
 		README.md = README.md
 	EndProjectSection
 EndProject

src/Microsoft.AspNet.TelemetryCorrelation/ActivityExtensions.cs

@@ -5,7 +5,6 @@
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Diagnostics;
-using System.Net.Http.Headers;
 
 namespace Microsoft.AspNet.TelemetryCorrelation
 {

src/Microsoft.AspNet.TelemetryCorrelation/Internal/BaseHeaderParser.cs

@@ -0,0 +1,69 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNet.TelemetryCorrelation
+{
+    internal abstract class BaseHeaderParser<T> : HttpHeaderParser<T>
+    {
+        protected BaseHeaderParser(bool supportsMultipleValues)
+            : base(supportsMultipleValues)
+        {
+        }
+
+        public sealed override bool TryParseValue(string value, ref int index, out T parsedValue)
+        {
+            parsedValue = default(T);
+
+            // If multiple values are supported (i.e. list of values), then accept an empty string: The header may
+            // be added multiple times to the request/response message. E.g.
+            //  Accept: text/xml; q=1
+            //  Accept:
+            //  Accept: text/plain; q=0.2
+            if (string.IsNullOrEmpty(value) || (index == value.Length))
+            {
+                return SupportsMultipleValues;
+            }
+
+            var separatorFound = false;
+            var current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(value, index, SupportsMultipleValues, out separatorFound);
+
+            if (separatorFound && !SupportsMultipleValues)
+            {
+                return false; // leading separators not allowed if we don't support multiple values.
+            }
+
+            if (current == value.Length)
+            {
+                if (SupportsMultipleValues)
+                {
+                    index = current;
+                }
+
+                return SupportsMultipleValues;
+            }
+
+            T result;
+            var length = GetParsedValueLength(value, current, out result);
+
+            if (length == 0)
+            {
+                return false;
+            }
+
+            current = current + length;
+            current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(value, current, SupportsMultipleValues, out separatorFound);
+
+            // If we support multiple values and we've not reached the end of the string, then we must have a separator.
+            if ((separatorFound && !SupportsMultipleValues) || (!separatorFound && (current < value.Length)))
+            {
+                return false;
+            }
+
+            index = current;
+            parsedValue = result;
+            return true;
+        }
+
+        protected abstract int GetParsedValueLength(string value, int startIndex, out T parsedValue);
+    }
+}

src/Microsoft.AspNet.TelemetryCorrelation/Internal/GenericHeaderParser.cs

@@ -0,0 +1,30 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNet.TelemetryCorrelation
+{
+    internal sealed class GenericHeaderParser<T> : BaseHeaderParser<T>
+    {
+        private GetParsedValueLengthDelegate getParsedValueLength;
+
+        internal GenericHeaderParser(bool supportsMultipleValues, GetParsedValueLengthDelegate getParsedValueLength)
+            : base(supportsMultipleValues)
+        {
+            if (getParsedValueLength == null)
+            {
+                throw new ArgumentNullException(nameof(getParsedValueLength));
+            }
+
+            this.getParsedValueLength = getParsedValueLength;
+        }
+
+        internal delegate int GetParsedValueLengthDelegate(string value, int startIndex, out T parsedValue);
+
+        protected override int GetParsedValueLength(string value, int startIndex, out T parsedValue)
+        {
+            return getParsedValueLength(value, startIndex, out parsedValue);
+        }
+    }
+}

src/Microsoft.AspNet.TelemetryCorrelation/Internal/HeaderUtilities.cs

@@ -0,0 +1,45 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Diagnostics.Contracts;
+
+namespace Microsoft.AspNet.TelemetryCorrelation
+{
+    internal static class HeaderUtilities
+    {
+        internal static int GetNextNonEmptyOrWhitespaceIndex(
+            string input,
+            int startIndex,
+            bool skipEmptyValues,
+            out bool separatorFound)
+        {
+            Contract.Requires(input != null);
+            Contract.Requires(startIndex <= input.Length); // it's OK if index == value.Length.
+
+            separatorFound = false;
+            var current = startIndex + HttpRuleParser.GetWhitespaceLength(input, startIndex);
+
+            if ((current == input.Length) || (input[current] != ','))
+            {
+                return current;
+            }
+
+            // If we have a separator, skip the separator and all following whitespaces. If we support
+            // empty values, continue until the current character is neither a separator nor a whitespace.
+            separatorFound = true;
+            current++; // skip delimiter.
+            current = current + HttpRuleParser.GetWhitespaceLength(input, current);
+
+            if (skipEmptyValues)
+            {
+                while ((current < input.Length) && (input[current] == ','))
+                {
+                    current++; // skip delimiter.
+                    current = current + HttpRuleParser.GetWhitespaceLength(input, current);
+                }
+            }
+
+            return current;
+        }
+    }
+}

src/Microsoft.AspNet.TelemetryCorrelation/Internal/HttpHeaderParser.cs

@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNet.TelemetryCorrelation
+{
+    internal abstract class HttpHeaderParser<T>
+    {
+        private bool supportsMultipleValues;
+
+        protected HttpHeaderParser(bool supportsMultipleValues)
+        {
+            this.supportsMultipleValues = supportsMultipleValues;
+        }
+
+        public bool SupportsMultipleValues
+        {
+            get { return supportsMultipleValues; }
+        }
+
+        // If a parser supports multiple values, a call to ParseValue/TryParseValue should return a value for 'index'
+        // pointing to the next non-whitespace character after a delimiter. E.g. if called with a start index of 0
+        // for string "value , second_value", then after the call completes, 'index' must point to 's', i.e. the first
+        // non-whitespace after the separator ','.
+        public abstract bool TryParseValue(string value, ref int index, out T parsedValue);
+    }
+}

src/Microsoft.AspNet.TelemetryCorrelation/Internal/HttpParseResult.cs

@@ -0,0 +1,23 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNet.TelemetryCorrelation
+{
+    internal enum HttpParseResult
+    {
+        /// <summary>
+        /// Parsed succesfully.
+        /// </summary>
+        Parsed,
+
+        /// <summary>
+        /// Was not parsed.
+        /// </summary>
+        NotParsed,
+
+        /// <summary>
+        /// Invalid format.
+        /// </summary>
+        InvalidFormat,
+    }
+}