I was trying to learn how JNA works, so I decided to use the spotify API (libspotify 0.0.7). I managed to load my dll correctly, but then it looks like my code is not finding any of the method defined in the API.
Here is my code:
My main file:
public class Test{
private static final int SPOTIFY_API_VERSION = 7;
private static final char[] APP_KEY = { /* MY APP KEY HERE */ };
static{
System.loadLibrary("libspotify");
}
public static void main(String[] args){
JLibspotify libs = JLibspotify.INSTANCE;
sp_session mySession = new sp_session();
sp_session_config cfg = new sp_session_config();
cfg.api_version = SPOTIFY_API_VERSION;
cfg.cache_location = "tmp";
cfg.settings_location = "tmp";
cfg.application_key = APP_KEY;
cfg.application_key_size = APP_KEY.length;
cfg.user_agent = "spshell";
cfg.callbacks = null;
libs.sp_session_create(cfg, mySession);
}
}
My Library interface:
public interface JLibspotify extends Library {
JLibspotify INSTANCE = (JLibspotify)Native.loadLibrary("libspotify", JLibspotify.class);
// Methods definitions
sp_error sp_session_create(sp_session_config config, sp_session sess);
}
My sp_session Object (opaque C struct)
public class sp_session extends PointerType{
public sp_session(Pointer address) {
super(address);
}
public sp_session() {
super();
}
}
My sp_session_config object
public class sp_session_config extends Structure{
public int api_version; // The version of the Spotify API your application is compiled with.
public String cache_location;
public String settings_location;
public char[] application_key}; // Your application key.
public int application_key_size; // The size of the application key in bytes
public String user_agent;
public sp_session_callbacks callbacks; // Delivery callbacks for session events. NULL if not interested in any callbacks
public Pointer userdata; // User supplied data for your application
public boolean compress_playlists;
public boolean dont_save_metadata_for_playlists;
public boolean initially_unload_playlists;
}
My sp_error enum
public enum sp_error {
SP_ERROR_OK,
SP_ERROR_BAD_API_VERSION,
SP_ERROR_API_INITIALIZATION_FAILED,
SP_ERROR_TRACK_NOT_PLAYABLE,
SP_ERROR_RESOURCE_NOT_LOADED,
SP_ERROR_BAD_APPLICATION_KEY,
SP_ERROR_BAD_USERNAME_OR_PASSWORD,
SP_ERROR_USER_BANNED,
SP_ERROR_UNABLE_TO_CONTACT_SERVER,
SP_ERROR_CLIENT_TOO_OLD,
SP_ERROR_OTHER_PERMANENT,
SP_ERROR_BAD_USER_AGENT,
SP_ERROR_MISSING_CALLBACK,
SP_ERROR_INVALID_INDATA,
SP_ERROR_INDEX_OUT_OF_RANGE,
SP_ERROR_USER_NEEDS_PREMIUM,
SP_ERROR_OTHER_TRANSIENT,
SP_ERROR_IS_LOADING,
SP_ERROR_NO_STREAM_AVAILABLE,
SP_ERROR_PERMISSION_DENIED,
SP_ERROR_INBOX_IS_FULL,
SP_ERROR_NO_CACHE,
SP_ERROR_NO_SUCH_USER
}
My Exception Stack Trace
Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up function 'sp_session_create': The specified procedure could not be found.
at com.sun.jna.Function.<init>(Function.java:129)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:250)
at com.sun.jna.Library$Handler.invoke(Library.java:191)
at $Proxy0.sp_session_create(Unknown Source)
at com.nbarraille.jspotify.main.Test.main(Test.java:49)
The C++ declaration of the method I'm trying to run
/**
* Initialize a session. The session returned will be initialized, but you will need
* to log in before you can perform any other operation
*
* Here is a snippet from \c spshell.c:
* @dontinclude spshell.c
* @skip config.api_version
* @until }
*
* @param[in] config The configuration to use for the session
* @param[out] sess If successful, a new session - otherwise NULL
*
* @return One of the following errors, from ::sp_error
* SP_ERROR_OK
* SP_ERROR_BAD_API_VERSION
* SP_ERROR_BAD_USER_AGENT
* SP_ERROR_BAD_APPLICATION_KEY
* SP_ERROR_API_INITIALIZATION_FAILED
*/
SP_LIBEXPORT(sp_error) sp_session_create(const sp_session_config *config, sp_session **sess);
I finally found the solution by opening the libspotify.dll with Dependency Walker: The compiler added some extra information to the method name (a underscore prefix and a @4 or @8 suffix).
I had to: