esp_modem: Move common C definitions in to separate header

Separate header for C API created.
It can be used by C DTE extensions.

components/esp_modem/include/esp_private/c_api_wrapper.hpp

@@ -0,0 +1,45 @@
+// Copyright 2022 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include "cxx_include/esp_modem_dce_factory.hpp"
+#include "esp_modem_c_api_types.h"
+
+using namespace esp_modem;
+
+struct esp_modem_dce_wrap { // need to mimic the polymorphic dispatch as CPP uses templated dispatch
+    enum class modem_wrap_dte_type { UART, VFS, USB } dte_type;
+    dce_factory::ModemType modem_type;
+    DCE *dce;
+};
+
+inline dce_factory::ModemType convert_modem_enum(esp_modem_dce_device_t module)
+{
+    switch (module) {
+    case ESP_MODEM_DCE_SIM7600:
+        return esp_modem::dce_factory::ModemType::SIM7600;
+    case ESP_MODEM_DCE_SIM7070:
+        return esp_modem::dce_factory::ModemType::SIM7070;
+    case ESP_MODEM_DCE_SIM7000:
+        return esp_modem::dce_factory::ModemType::SIM7000;
+    case ESP_MODEM_DCE_BG96:
+        return esp_modem::dce_factory::ModemType::BG96;
+    case ESP_MODEM_DCE_SIM800:
+        return esp_modem::dce_factory::ModemType::SIM800;
+    default:
+    case ESP_MODEM_DCE_GENETIC:
+        return esp_modem::dce_factory::ModemType::GenericModule;
+    }
+}