create interface for write data api, implement in CRT

src/aws-cpp-sdk-core/include/aws/core/client/CoreErrors.h

@@ -47,6 +47,7 @@ namespace Aws
             REQUEST_TIMEOUT = 24,
             NOT_INITIALIZED = 25,
             MEMORY_ALLOCATION = 26,
+            NOT_IMPLEMENTED = 27,
 
             NETWORK_CONNECTION = 99, // General failure to send message to service
 

src/aws-cpp-sdk-core/include/aws/core/http/HttpClient.h

@@ -6,11 +6,14 @@
 #pragma once
 
 #include <aws/core/Core_EXPORTS.h>
+#include <aws/core/http/HttpConnection.h>
+#include <aws/core/utils/Outcome.h>
+#include <aws/core/client/AWSError.h>
 
-#include <memory>
 #include <atomic>
-#include <mutex>
 #include <condition_variable>
+#include <memory>
+#include <mutex>
 
 namespace Aws
 {
@@ -77,6 +80,16 @@ namespace Aws
                return !m_bad;
             }
 
+            using AcquireConnectionOutcome = Aws::Utils::Outcome<std::shared_ptr<Aws::Http::Connection>,
+              Aws::Client::AWSError<Aws::Client::CoreErrors>>;
+            virtual AcquireConnectionOutcome AcquireConnection(const std::shared_ptr<HttpRequest>& request) {
+              AWS_UNREFERENCED_PARAM(request);
+              return Aws::Client::AWSError<Aws::Client::CoreErrors>{Aws::Client::CoreErrors::NOT_IMPLEMENTED,
+                "NotImplemented",
+                "creating a connection is not supported on this http client",
+                false};
+            }
+
         protected:
             bool m_bad;
 

src/aws-cpp-sdk-core/include/aws/core/http/HttpClientStream.h

@@ -0,0 +1,25 @@
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+#pragma once
+#include <aws/core/utils/memory/stl/AWSStreamFwd.h>
+
+#include <functional>
+#include <memory>
+
+namespace Aws {
+namespace Http {
+class HttpResponse;
+class AWS_CORE_API ClientStream {
+ public:
+  virtual ~ClientStream() = default;
+  virtual bool Activate() = 0;
+  virtual int WriteData(std::shared_ptr<Aws::IOStream> stream,
+    const std::function<void(int errorCode)>& onComplete,
+    bool endStream = false) = 0;
+  virtual std::shared_ptr<Aws::Http::HttpResponse> GetResponse() const = 0;
+};
+}  // namespace Http
+}  // namespace Aws

src/aws-cpp-sdk-core/include/aws/core/http/HttpConnection.h

@@ -0,0 +1,23 @@
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+#pragma once
+#include <aws/core/http/HttpClientStream.h>
+
+#include <functional>
+#include <memory>
+
+namespace Aws {
+namespace Http {
+class HttpRequest;
+class AWS_CORE_API Connection {
+ public:
+  virtual ~Connection() = default;
+  virtual std::shared_ptr<Aws::Http::ClientStream> NewClientStream(
+    const std::shared_ptr<HttpRequest>& request,
+    std::function<void(int errorCode)> onStreamComplete) = 0;
+};
+}  // namespace Http
+}  // namespace Aws

src/aws-cpp-sdk-core/include/aws/core/http/crt/CRTHttpClient.h

@@ -54,6 +54,8 @@ namespace Aws
 
             bool IsDefaultAwsHttpClient() const override { return true; }
 
+            AcquireConnectionOutcome AcquireConnection(const std::shared_ptr<HttpRequest>& request) override;
+
         private:
             // Yeah, I know, but someone made MakeRequest() const and didn't think about the fact that
             // making an HTTP request most certainly mutates state. It was me. I'm the person that did that, and