Feature/mbedtls (#84)

* try to import mbedtls and build it

* add stubs socket class

* some boilterplate, read and write function implemented

* more boilterplate / current error in handshake because no CA cert is setup

* add something so skip ca verification, can ws curl https://google.com !

* cleanup / close implemented

* tweak CMakefiles

* typo in include

* update readme

* disable unittests

ixwebsocket/IXSocketMbedTLS.h

@@ -0,0 +1,47 @@
+/*
+ *  IXSocketMbedTLS.h
+ *  Author: Benjamin Sergeant
+ *  Copyright (c) 2017-2018 Machine Zone, Inc. All rights reserved.
+ */
+
+#pragma once
+
+#include "IXSocket.h"
+#include <mbedtls/ctr_drbg.h>
+#include <mbedtls/debug.h>
+#include <mbedtls/entropy.h>
+#include <mbedtls/error.h>
+#include <mbedtls/net.h>
+#include <mbedtls/platform.h>
+#include <mutex>
+
+namespace ix
+{
+    class SocketMbedTLS final : public Socket
+    {
+    public:
+        SocketMbedTLS() = default;
+        ~SocketMbedTLS();
+
+        virtual bool connect(const std::string& host,
+                             int port,
+                             std::string& errMsg,
+                             const CancellationRequest& isCancellationRequested) final;
+        virtual void close() final;
+
+        virtual ssize_t send(char* buffer, size_t length) final;
+        virtual ssize_t send(const std::string& buffer) final;
+        virtual ssize_t recv(void* buffer, size_t length) final;
+
+    private:
+        mbedtls_ssl_context _ssl;
+        mbedtls_ssl_config _conf;
+        mbedtls_entropy_context _entropy;
+        mbedtls_ctr_drbg_context _ctr_drbg;
+
+        std::mutex _mutex;
+
+        bool init(const std::string& host, std::string& errMsg);
+    };
+
+} // namespace ix