Add NK_login_enum to the C API

As with the C++ API, identifying the model by the first character of a
string is not intuitive.  This patch adds the NK_login_enum function to
the C API that accepts an enum value instead of a string.  It also adds
a new enum NK_device_model as device::DeviceModel is an enum class and
therefore cannot be used in C.

2 files changed, 38 insertions, 0 deletions

diff --git a/NK_C_API.cc b/NK_C_API.cc
index 64355f5..b245940 100644
--- a/NK_C_API.cc
+++ b/NK_C_API.cc
@@ -161,6 +161,22 @@ extern "C" {
 		return 0;
 	}
 
+        NK_C_API int NK_login_enum(NK_device_model device_model) {
+                const char *model_string;
+                switch (device_model) {
+                    case NK_PRO:
+                        model_string = "P";
+                        break;
+                    case NK_STORAGE:
+                        model_string = "S";
+                        break;
+                    default:
+                        /* no such enum value -- return error code */
+                        return 0;
+                }
+                return NK_login(model_string);
+        }
+
 	NK_C_API int NK_logout() {
 		auto m = NitrokeyManager::instance();
 		return get_without_result([&]() {
diff --git a/NK_C_API.h b/NK_C_API.h
index 27730c9..b78bde5 100644
--- a/NK_C_API.h
+++ b/NK_C_API.h
@@ -34,6 +34,21 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+
+        /**
+         * The Nitrokey device models supported by the API.
+         */
+        enum NK_device_model {
+            /**
+             * Nitrokey Pro.
+             */
+            NK_PRO,
+            /**
+             * Nitrokey Storage.
+             */
+            NK_STORAGE
+        };
+
 	/**
 	 * Set debug level of messages written on stderr
 	 * @param state state=True - most messages, state=False - only errors level
@@ -54,6 +69,13 @@ extern "C" {
 	NK_C_API int NK_login(const char *device_model);
 
 	/**
+	 * Connect to device of given model. Currently library can be connected only to one device at once.
+	 * @param device_model NK_device_model: NK_PRO: Nitrokey Pro, NK_STORAGE: Nitrokey Storage
+	 * @return 1 if connected, 0 if wrong model or cannot connect
+	 */
+        NK_C_API int NK_login_enum(NK_device_model device_model);
+
+	/**
 	 * Connect to first available device, starting checking from Pro 1st to Storage 2nd.
 	 * @return 1 if connected, 0 if wrong model or cannot connect
 	 */