C++: Wrap resource access API

Introduce a ResourceReader delegate class with virtual methods
corresponding to the C callback functions.

bindings/cxx/classes.cpp

@@ -72,6 +72,50 @@ Error::~Error() throw()
 {
 }
 
+ResourceReader::~ResourceReader()
+{
+}
+
+SR_PRIV int ResourceReader::open_callback(struct sr_resource *res,
+		const char *name, void *cb_data)
+{
+	try {
+		auto *const reader = static_cast<ResourceReader*>(cb_data);
+		reader->open(res, name);
+	} catch (const Error &err) {
+		return err.result;
+	} catch (...) {
+		return SR_ERR;
+	}
+	return SR_OK;
+}
+
+SR_PRIV int ResourceReader::close_callback(struct sr_resource *res, void *cb_data)
+{
+	try {
+		auto *const reader = static_cast<ResourceReader*>(cb_data);
+		reader->close(res);
+	} catch (const Error &err) {
+		return err.result;
+	} catch (...) {
+		return SR_ERR;
+	}
+	return SR_OK;
+}
+
+SR_PRIV ssize_t ResourceReader::read_callback(const struct sr_resource *res,
+		void *buf, size_t count, void *cb_data)
+{
+	try {
+		auto *const reader = static_cast<ResourceReader*>(cb_data);
+		return reader->read(res, buf, count);
+	} catch (const Error &err) {
+		return err.result;
+	} catch (...) {
+		return SR_ERR;
+	}
+}
+
 shared_ptr<Context> Context::create()
 {
 	return shared_ptr<Context>(new Context(), Context::Deleter());
@@ -196,13 +240,26 @@ void Context::set_log_callback(LogCallbackFunction callback)
 {
 	_log_callback = callback;
 	check(sr_log_callback_set(call_log_callback, &_log_callback));
-} 
+}
 
 void Context::set_log_callback_default()
 {
 	check(sr_log_callback_set_default());
 	_log_callback = nullptr;
-} 
+}
+
+void Context::set_resource_reader(ResourceReader *reader)
+{
+	if (reader) {
+		check(sr_resource_set_hooks(_structure,
+				&ResourceReader::open_callback,
+				&ResourceReader::close_callback,
+				&ResourceReader::read_callback, reader));
+	} else {
+		check(sr_resource_set_hooks(_structure,
+				nullptr, nullptr, nullptr, nullptr));
+	}
+}
 
 shared_ptr<Session> Context::create_session()
 {

bindings/cxx/include/libsigrokcxx/libsigrokcxx.hpp

@@ -232,6 +232,29 @@ protected:
 /** Type of log callback */
 typedef function<void(const LogLevel *, string message)> LogCallbackFunction;
 
+/** Resource reader delegate. */
+class SR_API ResourceReader
+{
+public:
+	ResourceReader() {}
+	virtual ~ResourceReader();
+private:
+	/** Resource open hook. */
+	virtual void open(struct sr_resource *res, string name) = 0;
+	/** Resource close hook. */
+	virtual void close(struct sr_resource *res) = 0;
+	/** Resource read hook. */
+	virtual size_t read(const struct sr_resource *res, void *buf, size_t count) = 0;
+
+	static SR_PRIV int open_callback(struct sr_resource *res,
+			const char *name, void *cb_data);
+	static SR_PRIV int close_callback(struct sr_resource *res,
+			void *cb_data);
+	static SR_PRIV ssize_t read_callback(const struct sr_resource *res,
+			void *buf, size_t count, void *cb_data);
+	friend class Context;
+};
+
 /** The global libsigrok context */
 class SR_API Context : public UserOwned<Context, struct sr_context>
 {
@@ -258,6 +281,9 @@ public:
 	void set_log_callback(LogCallbackFunction callback);
 	/** Set the log callback to the default handler. */
 	void set_log_callback_default();
+	/** Install a delegate for reading resource files.
+	 * @param reader The resource reader delegate, or nullptr to unset. */
+	void set_resource_reader(ResourceReader *reader);
 	/** Create a new session. */
 	shared_ptr<Session> create_session();
 	/** Create a new user device. */