Implement NetworkManager

For now there are two methods:

- `NETWORK:IsUrlAllowed()`: Check whether access to a certain URL is allowed.
- `NETWORK:HttpRequest()`: Perform an HTTP request.

By default access to the network is disabled for all target hosts. It
can be enabled by setting `HttpEnable=1` in the preferences. Individual
hosts have to be added to `HttpAllowHosts` as a comma separated list to
allow access.

See included docs for more details on usage.

extern/IXWebSocket-11.3.2/ixwebsocket/IXHttp.cpp

@@ -0,0 +1,213 @@
+/*
+ *  IXHttp.cpp
+ *  Author: Benjamin Sergeant
+ *  Copyright (c) 2019 Machine Zone, Inc. All rights reserved.
+ */
+
+#include "IXHttp.h"
+
+#include "IXCancellationRequest.h"
+#include "IXGzipCodec.h"
+#include "IXSocket.h"
+#include <sstream>
+#include <vector>
+
+namespace ix
+{
+    std::string Http::trim(const std::string& str)
+    {
+        std::string out;
+        for (auto c : str)
+        {
+            if (c != ' ' && c != '\n' && c != '\r')
+            {
+                out += c;
+            }
+        }
+
+        return out;
+    }
+
+    std::pair<std::string, int> Http::parseStatusLine(const std::string& line)
+    {
+        // Request-Line   = Method SP Request-URI SP HTTP-Version CRLF
+        std::string token;
+        std::stringstream tokenStream(line);
+        std::vector<std::string> tokens;
+
+        // Split by ' '
+        while (std::getline(tokenStream, token, ' '))
+        {
+            tokens.push_back(token);
+        }
+
+        std::string httpVersion;
+        if (tokens.size() >= 1)
+        {
+            httpVersion = trim(tokens[0]);
+        }
+
+        int statusCode = -1;
+        if (tokens.size() >= 2)
+        {
+            std::stringstream ss;
+            ss << trim(tokens[1]);
+            ss >> statusCode;
+        }
+
+        return std::make_pair(httpVersion, statusCode);
+    }
+
+    std::tuple<std::string, std::string, std::string> Http::parseRequestLine(
+        const std::string& line)
+    {
+        // Request-Line   = Method SP Request-URI SP HTTP-Version CRLF
+        std::string token;
+        std::stringstream tokenStream(line);
+        std::vector<std::string> tokens;
+
+        // Split by ' '
+        while (std::getline(tokenStream, token, ' '))
+        {
+            tokens.push_back(token);
+        }
+
+        std::string method;
+        if (tokens.size() >= 1)
+        {
+            method = trim(tokens[0]);
+        }
+
+        std::string requestUri;
+        if (tokens.size() >= 2)
+        {
+            requestUri = trim(tokens[1]);
+        }
+
+        std::string httpVersion;
+        if (tokens.size() >= 3)
+        {
+            httpVersion = trim(tokens[2]);
+        }
+
+        return std::make_tuple(method, requestUri, httpVersion);
+    }
+
+    std::tuple<bool, std::string, HttpRequestPtr> Http::parseRequest(
+        std::unique_ptr<Socket>& socket, int timeoutSecs)
+    {
+        HttpRequestPtr httpRequest;
+
+        std::atomic<bool> requestInitCancellation(false);
+
+        auto isCancellationRequested =
+            makeCancellationRequestWithTimeout(timeoutSecs, requestInitCancellation);
+
+        // Read first line
+        auto lineResult = socket->readLine(isCancellationRequested);
+        auto lineValid = lineResult.first;
+        auto line = lineResult.second;
+
+        if (!lineValid)
+        {
+            return std::make_tuple(false, "Error reading HTTP request line", httpRequest);
+        }
+
+        // Parse request line (GET /foo HTTP/1.1\r\n)
+        auto requestLine = Http::parseRequestLine(line);
+        auto method = std::get<0>(requestLine);
+        auto uri = std::get<1>(requestLine);
+        auto httpVersion = std::get<2>(requestLine);
+
+        // Retrieve and validate HTTP headers
+        auto result = parseHttpHeaders(socket, isCancellationRequested);
+        auto headersValid = result.first;
+        auto headers = result.second;
+
+        if (!headersValid)
+        {
+            return std::make_tuple(false, "Error parsing HTTP headers", httpRequest);
+        }
+
+        std::string body;
+        if (headers.find("Content-Length") != headers.end())
+        {
+            int contentLength = 0;
+            try
+            {
+                contentLength = std::stoi(headers["Content-Length"]);
+            }
+            catch (const std::exception&)
+            {
+                return std::make_tuple(
+                    false, "Error parsing HTTP Header 'Content-Length'", httpRequest);
+            }
+
+            if (contentLength < 0)
+            {
+                return std::make_tuple(
+                    false, "Error: 'Content-Length' should be a positive integer", httpRequest);
+            }
+
+            auto res = socket->readBytes(contentLength, nullptr, isCancellationRequested);
+            if (!res.first)
+            {
+                return std::make_tuple(
+                    false, std::string("Error reading request: ") + res.second, httpRequest);
+            }
+            body = res.second;
+        }
+
+        // If the content was compressed with gzip, decode it
+        if (headers["Content-Encoding"] == "gzip")
+        {
+#ifdef IXWEBSOCKET_USE_ZLIB
+            std::string decompressedPayload;
+            if (!gzipDecompress(body, decompressedPayload))
+            {
+                return std::make_tuple(
+                    false, std::string("Error during gzip decompression of the body"), httpRequest);
+            }
+            body = decompressedPayload;
+#else
+            std::string errorMsg("ixwebsocket was not compiled with gzip support on");
+            return std::make_tuple(false, errorMsg, httpRequest);
+#endif
+        }
+
+        httpRequest = std::make_shared<HttpRequest>(uri, method, httpVersion, body, headers);
+        return std::make_tuple(true, "", httpRequest);
+    }
+
+    bool Http::sendResponse(HttpResponsePtr response, std::unique_ptr<Socket>& socket)
+    {
+        // Write the response to the socket
+        std::stringstream ss;
+        ss << "HTTP/1.1 ";
+        ss << response->statusCode;
+        ss << " ";
+        ss << response->description;
+        ss << "\r\n";
+
+        if (!socket->writeBytes(ss.str(), nullptr))
+        {
+            return false;
+        }
+
+        // Write headers
+        ss.str("");
+        ss << "Content-Length: " << response->body.size() << "\r\n";
+        for (auto&& it : response->headers)
+        {
+            ss << it.first << ": " << it.second << "\r\n";
+        }
+        ss << "\r\n";
+
+        if (!socket->writeBytes(ss.str(), nullptr))
+        {
+            return false;
+        }
+
+        return response->body.empty() ? true : socket->writeBytes(response->body, nullptr);
+    }
+} // namespace ix