Add System.Formats.Sse

src/libraries/System.Formats.Sse/System.Formats.Sse.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
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+MinimumVisualStudioVersion = 10.0.40219.1
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+EndProject
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+EndProject
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+		{ACB7E0BF-015F-43DC-A2F5-85506173B223}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{ACB7E0BF-015F-43DC-A2F5-85506173B223}.Release|Any CPU.Build.0 = Release|Any CPU
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+		{804B5D44-05A3-491E-A6AB-35C592E6703E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
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+	EndGlobalSection
+EndGlobal

src/libraries/System.Formats.Sse/ref/System.Formats.Sse.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// ------------------------------------------------------------------------------
+// Changes to this file must follow the https://aka.ms/api-review process.
+// ------------------------------------------------------------------------------
+
+namespace System.Formats.Sse
+{
+    public sealed partial class SseEnumerable<T> : System.Collections.Generic.IAsyncEnumerable<System.Formats.Sse.SseItem<T>>, System.Collections.Generic.IEnumerable<System.Formats.Sse.SseItem<T>>, System.Collections.IEnumerable
+    {
+        internal SseEnumerable() { }
+        public string LastEventId { get { throw null; } }
+        public System.TimeSpan ReconnectionInterval { get { throw null; } }
+        public System.Collections.Generic.IAsyncEnumerator<System.Formats.Sse.SseItem<T>> GetAsyncEnumerator(System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public System.Collections.Generic.IEnumerator<System.Formats.Sse.SseItem<T>> GetEnumerator() { throw null; }
+        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw null; }
+    }
+    public delegate T SseItemParser<out T>(string eventType, System.ReadOnlySpan<byte> data);
+    public readonly partial struct SseItem<T>
+    {
+        private readonly T _Data_k__BackingField;
+        private readonly object _dummy;
+        private readonly int _dummyPrimitive;
+        public SseItem(T data, string eventType) { throw null; }
+        public T Data { get { throw null; } }
+        public string EventType { get { throw null; } }
+    }
+    public static partial class SseParser
+    {
+        public static System.Formats.Sse.SseEnumerable<string> Parse(System.IO.Stream sseStream) { throw null; }
+        public static System.Formats.Sse.SseEnumerable<T> Parse<T>(System.IO.Stream sseStream, System.Formats.Sse.SseItemParser<T> itemParser) { throw null; }
+    }
+}

src/libraries/System.Formats.Sse/ref/System.Formats.Sse.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppPrevious);$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="System.Formats.Sse.cs" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">
+    <PackageReference Include="System.Memory" Version="$(SystemMemoryVersion)" />
+    <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Bcl.AsyncInterfaces\ref\Microsoft.Bcl.AsyncInterfaces.csproj" />
+  </ItemGroup>
+
+</Project>

src/libraries/System.Formats.Sse/src/PACKAGE.md

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+## About
+
+<!-- A description of the package and where one can find more documentation -->
+
+System.Formats.Sse introduces the `SseParser` type, which provides factory methods for creating enumerables of the events in a stream of server-sent events (SSE).
+
+## Key Features
+
+<!-- The key features of this package -->
+
+* Parser for server-sent events (SSE)
+
+## How to Use
+
+<!-- A compelling example on how to use this package with code, as well as any specific guidelines for when to use the package -->
+
+Asynchronously parsing event contents as strings
+
+```csharp
+using HttpClient client = new();
+using Stream response = await client.GetStreamAsync("https://localhost:12345/sse");
+await foreach (SseItem<string> item in SseParser.Parse(response))
+{
+    Console.WriteLine(item.Data);
+}
+```
+
+Synchronously parsing event contents as JSON
+
+```csharp
+MemoryStream stream = new MemoryStream(data);
+foreach (SseItem<Book> item in SseParser.Parse(response, (eventType, bytes) => JsonSerializer.Deserialize<Book>(bytes)))
+{
+    Console.WriteLine(item.Author);
+}
+```
+
+## Main Types
+
+<!-- The main types provided in this library -->
+
+The main types provided by this library are:
+
+* `System.Formats.Sse.SseParser`
+
+## Feedback & Contributing
+
+<!-- How to provide feedback on this package and contribute to it -->
+
+System.Formats.Sse is released as open source under the [MIT license](https://licenses.nuget.org/MIT). Bug reports and contributions are welcome at [the GitHub repository](https://github.com/dotnet/runtime).

src/libraries/System.Formats.Sse/src/Resources/Strings.resx

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+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!-- 
+    Microsoft ResX Schema 
+    
+    Version 2.0
+    
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
+    associated with the data types.
+    
+    Example:
+    
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+                
+    There are any number of "resheader" rows that contain simple 
+    name/value pairs.
+    
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
+    mimetype set.
+    
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
+    extensible. For a given mimetype the value must be set accordingly:
+    
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
+    read any of the formats listed below.
+    
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+    
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array 
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <data name="InvalidOperation_EnumerateOnlyOnce" xml:space="preserve">
+    <value>The enumerable may be enumerated only once.</value>
+  </data>
+  <data name="InvalidOperation_InvalidStreamNegativeBytes" xml:space="preserve">
+    <value>The Stream implementation is invalid, returning a negative number from a read operation.</value>
+  </data>
+</root>

src/libraries/System.Formats.Sse/src/System.Formats.Sse.csproj

@@ -0,0 +1,32 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppPrevious);$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <UseCompilerGeneratedDocXmlFile>true</UseCompilerGeneratedDocXmlFile>
+    <IsPackable>true</IsPackable>
+    <PackageDescription>Provides a simple parser for server-sent events (SSE).
+
+Commonly Used Types:
+System.Formats.Sse.SseParser</PackageDescription>
+
+    <!-- Disabling baseline validation since this is a brand new package.
+         Once this package has shipped a stable version, the following line
+         should be removed in order to re-enable validation. -->
+    <DisablePackageBaselineValidation>true</DisablePackageBaselineValidation>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="System\Formats\Sse\SseEnumerable.cs" />
+    <Compile Include="System\Formats\Sse\SseItem.cs" />
+    <Compile Include="System\Formats\Sse\SseItemParser.cs" />
+    <Compile Include="System\Formats\Sse\SseParser.cs" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">
+    <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Bcl.AsyncInterfaces\src\Microsoft.Bcl.AsyncInterfaces.csproj" />
+    <PackageReference Include="System.Memory" Version="$(SystemMemoryVersion)" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="$(SystemThreadingTasksExtensionsVersion)" />
+  </ItemGroup>
+
+</Project>