add new header implementation for game<->launcher communication

include/Utils.h

@@ -13,9 +13,22 @@
 #include <openssl/err.h>
 #include <openssl/evp.h>
 #include <regex>
+#include <cstdint>
+#include <cstring>
 #include <string>
 #include <variant>
 #include <vector>
+#include <array>
+#include <cerrno>
+#include <cstring>
+#include <stdexcept>
+#if defined(__linux__)
+#include <sys/socket.h>
+#include "linuxfixes.h"
+#else
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#endif
 
 #ifdef _WIN32
 #define beammp_fs_string std::wstring
@@ -286,4 +299,40 @@ namespace Utils {
             return "";
         }
     }
-};
+};
+
+    template<typename T>
+    inline std::vector<char> PrependHeader(const T& data) {
+        std::vector<char> size_buffer(4);
+        uint32_t len = data.size();
+        std::memcpy(size_buffer.data(), &len, 4);
+        std::vector<char> buffer;
+        buffer.reserve(size_buffer.size() + data.size());
+        buffer.insert(buffer.begin(), size_buffer.begin(), size_buffer.end());
+        buffer.insert(buffer.end(), data.begin(), data.end());
+        return buffer;
+    }
+
+    inline uint32_t RecvHeader(SOCKET socket) {
+        std::array<uint8_t, sizeof(uint32_t)> header_buffer {};
+        auto n = recv(socket, reinterpret_cast<char*>(header_buffer.data()), header_buffer.size(), MSG_WAITALL);
+        if (n < 0) {
+            throw std::runtime_error(std::string("recv() of header failed: ") + std::strerror(errno));
+        } else if (n == 0) {
+            throw std::runtime_error("Game disconnected");
+        }
+        return *reinterpret_cast<uint32_t*>(header_buffer.data());
+    }
+
+    /// Throws!!!
+    inline void ReceiveFromGame(SOCKET socket, std::vector<char>& out_data) {
+        auto header = RecvHeader(socket);
+        out_data.resize(header);
+        auto n = recv(socket, reinterpret_cast<char*>(out_data.data()), out_data.size(), MSG_WAITALL);
+        if (n < 0) {
+            throw std::runtime_error(std::string("recv() of data failed: ") + std::strerror(errno));
+        } else if (n == 0) {
+            throw std::runtime_error("Game disconnected");
+        }
+    }
+};