update: library management code

Signed-off-by: Lorenzo Fontana <lo@linux.com>

userspace/libhawk/exception.h

@@ -34,4 +34,11 @@ class hawk_library_load_exception : public hawk_library_exception
 		hawk_library_load_exception(const std::string&library_name, const std::string&message):
 			hawk_library_exception("library loading error, library: " + library_name + " error: " + message) {}
 };
+
+class hawk_library_unload_exception : public hawk_library_exception
+{
+	public:
+		hawk_library_unload_exception(const std::string&library_name, const std::string&message):
+			hawk_library_exception("library unloading error, library: " + library_name + " error: " + message) {}
+};
 } // namespace libhawk

userspace/libhawk/library.cpp

@@ -19,16 +19,41 @@ limitations under the License.
 
 #include <dlfcn.h>
 
-libhawk::library::library(const std::string &filename) : m_library_filename(filename) {};
+libhawk::library::library(const std::string &filename):
+	m_library_filename(filename){};
 
 bool libhawk::library::load()
 {
-	void *handler = nullptr;
+	library_handle handler = nullptr;
 	handler = dlopen(m_library_filename.c_str(), RTLD_NOW);
-	if (!handler) {
+	if(!handler)
+	{
 		std::string errmsg(dlerror());
 		throw hawk_library_load_exception(m_library_filename, errmsg);
 	}
-	//todo(fntlnz): need to store the handler or anything to use the library?
+	m_library_handle.store(handler);
 	return (handler != nullptr);
 }
+
+bool libhawk::library::unload()
+{
+	if(!m_library_handle.load())
+	{
+		return false;
+	}
+
+	library_handle handler = m_library_handle.load();
+	if(!dlclose(handler))
+	{
+		std::string errmsg(dlerror());
+		throw hawk_library_unload_exception(m_library_filename, errmsg);
+		return false;
+	}
+	m_library_handle.store(nullptr);
+	return true;
+}
+
+bool libhawk::library::is_loaded() const
+{
+	return m_library_handle && m_library_handle.load();
+}

userspace/libhawk/library.h

@@ -17,15 +17,22 @@ limitations under the License.
 #pragma once
 
 #include <string>
+#include <atomic>
+
 namespace libhawk
 {
 class library
 {
 public:
+	using library_handle = void *;
 	library(const std::string &filename);
 	bool load();
+	bool unload();
+	bool is_loaded() const;
 	~library();
+
 private:
 	std::string m_library_filename;
+	std::atomic<library_handle> m_library_handle;
 };
 }; // namespace libhawk