libgpsmm: add is_open method

The gpsmm constructor effectively hides the useful status flag returned
by the underlying gps_open call.

It is extremely useful for client code to be able to check that the
gpsmm constructor was successful. To this end, add a gpsmm::is_open method
which simply checks that the gpsmm::to_user member is non-NULL. A NULL
gpsmm::to_user member can only mean that the constructor was not successful.

Signed-off-by: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Eric S. Raymond <esr@thyrsus.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/libgpsmm.h b/libgpsmm.h
index 2b87b898..ab656b66 100644
--- a/libgpsmm.h
+++ b/libgpsmm.h
@@ -45,6 +45,7 @@ class LIBQGPSMMSHARED_EXPORT gpsmm {
 		bool waiting(int);	// blocking check for data waiting
 		void clear_fix(void);
 		void enable_debug(int, FILE*);
+		bool is_open(void);	// check for constructor success
 	private:
 		struct gps_data_t *to_user;	//we return the user a copy of the internal structure. This way she can modify it without
 						//integrity loss for the entire class