LibVLC: per-thread error message API

include/vlc/libvlc.h

@@ -58,6 +58,7 @@
 extern "C" {
 # endif
 
+#include <stdarg.h>
 #include <vlc/libvlc_structures.h>
 
 /*****************************************************************************
@@ -117,6 +118,49 @@ libvlc_exception_get_message( const libvlc_exception_t *p_exception );
 
 /**@} */
 
+/*****************************************************************************
+ * Error handling
+ *****************************************************************************/
+/** \defgroup libvlc_error libvlc_error
+ * \ingroup libvlc_core
+ * LibVLC error handling
+ * @{
+ */
+
+/**
+ * A human-readable error message for the last LibVLC error in the calling
+ * thread. The resulting string is valid until another error occurs (at least
+ * until the next LibVLC call).
+ *
+ * @warning
+ * This will be NULL if there was no error.
+ */
+const char *libvlc_errmsg (void);
+
+/**
+ * Clears the LibVLC error status for the current thread. This is optional.
+ * By default, the error status is automatically overriden when a new error
+ * occurs, and destroyed when the thread exits.
+ */
+void libvlc_clearerr (void);
+
+/**
+ * Sets the LibVLC error status and message for the current thread.
+ * Any previous error is overriden.
+ * @return a nul terminated string in any case
+ */
+const char *libvlc_vprinterr (const char *fmt, va_list ap);
+
+/**
+ * Sets the LibVLC error status and message for the current thread.
+ * Any previous error is overriden.
+ * @return a nul terminated string in any case
+ */
+const char *libvlc_printerr (const char *fmt, ...);
+
+/**@} */
+
+
 /*****************************************************************************
  * Core handling
  *****************************************************************************/

src/Makefile.am

@@ -460,6 +460,7 @@ SOURCES_libvlc_control = \
 	control/media_list_view_internal.h \
 	control/media_player_internal.h \
 	control/core.c \
+	control/error.c \
 	control/log.c \
 	control/playlist.c \
 	control/vlm.c \

src/control/core.c

@@ -111,11 +111,22 @@ libvlc_instance_t * libvlc_new( int argc, const char *const *argv,
 {
     libvlc_instance_t *p_new;
     int i_ret;
+
+    libvlc_init_threads ();
+
     libvlc_int_t *p_libvlc_int = libvlc_InternalCreate();
-    if( !p_libvlc_int ) RAISENULL( "VLC initialization failed" );
+    if( !p_libvlc_int )
+    {
+        libvlc_deinit_threads ();
+        RAISENULL( "VLC initialization failed" );
+    }
 
     p_new = malloc( sizeof( libvlc_instance_t ) );
-    if( !p_new ) RAISENULL( "Out of memory" );
+    if( !p_new )
+    {
+        libvlc_deinit_threads ();
+        RAISENULL( "Out of memory" );
+    }
 
     const char *my_argv[argc + 2];
 
@@ -132,6 +143,8 @@ libvlc_instance_t * libvlc_new( int argc, const char *const *argv,
     {
         libvlc_InternalDestroy( p_libvlc_int );
         free( p_new );
+        libvlc_deinit_threads ();
+
         if( i_ret == VLC_EEXITSUCCESS )
             return NULL;
         else
@@ -181,6 +194,7 @@ void libvlc_release( libvlc_instance_t *p_instance )
         libvlc_InternalCleanup( p_instance->p_libvlc_int );
         libvlc_InternalDestroy( p_instance->p_libvlc_int );
         free( p_instance );
+        libvlc_deinit_threads ();
     }
 }
 

src/control/error.c

@@ -0,0 +1,131 @@
+/*****************************************************************************
+ * error.c: Error handling for libvlc
+ *****************************************************************************
+ * Copyright (C) 2009 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#include "libvlc_internal.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <assert.h>
+#include <vlc/libvlc.h>
+
+
+static const char oom[] = "Out of memory";
+/* TODO: use only one thread-specific key for whole libvlc */
+static vlc_threadvar_t context;
+
+static void libvlc_setup_threads (bool init)
+{
+    static vlc_mutex_t lock = VLC_STATIC_MUTEX;
+    static uintptr_t refs = 0;
+
+    vlc_mutex_lock (&lock);
+    if (init)
+    {
+        if (refs++ == 0)
+            vlc_threadvar_create (&context, free);
+    }
+    else
+    {
+        assert (refs > 0);
+        if (--refs == 0)
+            vlc_threadvar_delete (&context);
+    }
+    vlc_mutex_unlock (&lock);
+}
+
+void libvlc_init_threads (void)
+{
+    libvlc_setup_threads (true);
+}
+
+void libvlc_deinit_threads (void)
+{
+    libvlc_setup_threads (false);
+}
+
+static char *get_error (void)
+{
+    return vlc_threadvar_get (context);
+}
+
+static void free_error (void)
+{
+    char *msg = get_error ();
+    if (msg != oom)
+        free (msg);
+}
+
+/**
+ * Gets a human-readable error message for the last LibVLC error in the calling
+ * thread. The resulting string is valid until another error occurs (at least
+ * until the next LibVLC call).
+ *
+ * @return NULL if there was no error, a nul-terminated string otherwise.
+ */
+const char *libvlc_errmsg (void)
+{
+    return get_error ();
+}
+
+/**
+ * Clears the LibVLC error status for the current thread. This is optional.
+ * By default, the error status is automatically overriden when a new error
+ * occurs, and destroyed when the thread exits.
+ */
+void libvlc_clearerr (void)
+{
+    free_error ();
+    vlc_threadvar_set (context, NULL);
+}
+
+/**
+ * Sets the LibVLC error status and message for the current thread.
+ * Any previous error is overriden.
+ * @return a nul terminated string (always)
+ */
+const char *libvlc_vprinterr (const char *fmt, va_list ap)
+{
+    char *msg;
+
+    assert (fmt != NULL);
+    if (vasprintf (&msg, fmt, ap) == -1)
+        msg = (char *)oom;
+
+    free_error ();
+    vlc_threadvar_set (context, msg);
+    return msg;
+}
+
+/**
+ * Sets the LibVLC error status and message for the current thread.
+ * Any previous error is overriden.
+ * @return a nul terminated string (always)
+ */
+const char *libvlc_printerr (const char *fmt, ...)
+{
+    va_list ap;
+    const char *msg;
+
+    va_start (ap, fmt);
+    msg = libvlc_vprinterr (fmt, ap);
+    va_end (ap);
+    return msg;
+}
+

src/control/libvlc_internal.h

@@ -83,6 +83,10 @@ struct libvlc_instance_t
  * Other internal functions
  ***************************************************************************/
 
+/* Thread context */
+void libvlc_init_threads (void);
+void libvlc_deinit_threads (void);
+
 /* Events */
 libvlc_event_manager_t * libvlc_event_manager_new(
         void * p_obj, libvlc_instance_t * p_libvlc_inst,

src/libvlc.sym

@@ -1,3 +1,7 @@
+libvlc_errmsg
+libvlc_clearerr
+libvlc_printerr
+libvlc_vprinterr
 libvlc_add_intf
 libvlc_audio_output_device_count
 libvlc_audio_output_device_id