Commit ae3b867b authored by Rémi Denis-Courmont's avatar Rémi Denis-Courmont

libvlc: simplify and clean up external logging API (fixes #8129)

 - Scope the callback to its instance.
 - Avoid leaking the layout of an internal data structure.
 - Future-proof passing of extra informations through an opaque pointer.
parent dde93dd5
......@@ -336,79 +336,56 @@ enum libvlc_log_level
LIBVLC_ERROR=4 /**< Error message */
};
typedef struct vlc_log_t libvlc_log_t;
/**
* Callback prototype for LibVLC log message handler.
* \param data data pointer as given to libvlc_log_subscribe()
* \param data data pointer as given to libvlc_log_set()
* \param level message level (@ref enum libvlc_log_level)
* \param ctx message context (meta-informations about the message)
* \param fmt printf() format string (as defined by ISO C11)
* \param args variable argument list for the format
* \note Log message handlers <b>must</b> be thread-safe.
*/
typedef void (*libvlc_log_cb)(void *data, int level, const char *fmt,
va_list args);
typedef void (*libvlc_log_cb)(void *data, int level, const libvlc_log_t *ctx,
const char *fmt, va_list args);
/**
* Data structure for a LibVLC logging callbacks.
* \note This structure contains exactly 4 pointers and will never change.
* Nevertheless, it should not be accessed directly outside of LibVLC.
* (In fact, doing so would fail the thread memory model.)
* Unsets the logging callback for a LibVLC instance. This is rarely needed:
* the callback is implicitly unset when the instance is destroyed.
* This function will wait for any pending callbacks invocation to complete
* (causing a deadlock if called from within the callback).
*
* \version LibVLC 2.1.0 or later
*/
typedef struct libvlc_log_subscriber
{
struct libvlc_log_subscriber *prev, *next;
libvlc_log_cb func;
void *opaque;
} libvlc_log_subscriber_t;
LIBVLC_API void libvlc_log_unset( libvlc_instance_t * );
/**
* Registers a logging callback to LibVLC.
* This function is thread-safe.
* Sets the logging callback for a LibVLC instance.
* This function is thread-safe: it will wait for any pending callbacks
* invocation to complete.
*
* \param sub uninitialized subscriber structure
* \param cb callback function pointer
* \param data opaque data pointer for the callback function
*
* \note Some log messages (especially debug) are emitted by LibVLC while
* initializing, before any LibVLC instance even exists.
* Thus this function does not require a LibVLC instance parameter.
* is being initialized. These messages cannot be captured with this interface.
*
* \warning As a consequence of not depending on a LibVLC instance,
* all logging callbacks are shared by all LibVLC instances within the
* process / address space. This also enables log messages to be emitted
* by LibVLC components that are not specific to any given LibVLC instance.
* \warning A deadlock may occur if this function is called from the callback.
*
* \warning Do not call this function from within a logging callback.
* It would trigger a dead lock.
* \version LibVLC 2.1.0 or later
*/
LIBVLC_API void libvlc_log_subscribe( libvlc_log_subscriber_t *sub,
libvlc_log_cb cb, void *data );
LIBVLC_API void libvlc_log_set( libvlc_instance_t *,
libvlc_log_cb cb, void *data );
/**
* Registers a logging callback to a file.
* Sets up logging to a file.
* \param stream FILE pointer opened for writing
* (the FILE pointer must remain valid until libvlc_log_unsubscribe())
* \version LibVLC 2.1.0 or later
*/
LIBVLC_API void libvlc_log_subscribe_file( libvlc_log_subscriber_t *sub,
FILE *stream );
/**
* Deregisters a logging callback from LibVLC.
* This function is thread-safe.
*
* \note After (and only after) libvlc_log_unsubscribe() has returned,
* LibVLC warrants that there are no more pending calls of the subscription
* callback function.
*
* \warning Do not call this function from within a logging callback.
* It would trigger a dead lock.
*
* \param sub initialized subscriber structure
* (the FILE pointer must remain valid until libvlc_log_unset())
* \version LibVLC 2.1.0 or later
*/
LIBVLC_API void libvlc_log_unsubscribe( libvlc_log_subscriber_t *sub );
LIBVLC_API void libvlc_log_set_file( libvlc_instance_t *, FILE *stream );
/**
* Always returns minus one.
......
......@@ -52,9 +52,6 @@ typedef int64_t libvlc_time_t;
* @{
*/
/** This structure is opaque. It represents a libvlc log instance */
typedef struct libvlc_log_t libvlc_log_t;
/** This structure is opaque. It represents a libvlc log iterator */
typedef struct libvlc_log_iterator_t libvlc_log_iterator_t;
......
......@@ -37,10 +37,7 @@ void libvlc_threads_init (void)
{
vlc_mutex_lock (&lock);
if (refs++ == 0)
{
vlc_threadvar_create (&context, free);
libvlc_log_init ();
}
vlc_mutex_unlock (&lock);
}
......@@ -49,10 +46,7 @@ void libvlc_threads_deinit (void)
vlc_mutex_lock (&lock);
assert (refs > 0);
if (--refs == 0)
{
libvlc_log_deinit ();
vlc_threadvar_delete (&context);
}
vlc_mutex_unlock (&lock);
}
......
......@@ -45,8 +45,9 @@ libvlc_get_fullscreen
libvlc_get_input_thread
libvlc_get_log_verbosity
libvlc_get_version
libvlc_log_subscribe
libvlc_log_unsubscribe
libvlc_log_set
libvlc_log_set_file
libvlc_log_unset
libvlc_log_clear
libvlc_log_close
libvlc_log_count
......
......@@ -72,6 +72,11 @@ struct libvlc_instance_t
unsigned ref_count;
vlc_mutex_t instance_lock;
struct libvlc_callback_entry_list_t *p_callback_list;
struct
{
void (*cb) (void *, int, const libvlc_log_t *, const char *, va_list);
void *data;
} log;
};
......
......@@ -34,88 +34,60 @@
/*** Logging core dispatcher ***/
static vlc_rwlock_t log_lock = VLC_STATIC_RWLOCK;
static libvlc_log_subscriber_t *log_first = NULL;
static msg_subscription_t sub;
VLC_FORMAT(2,3)
static void libvlc_log (int level, const char *fmt, ...)
VLC_FORMAT(4,5)
static void libvlc_log (libvlc_instance_t *inst, int level,
const libvlc_log_t *ctx, const char *fmt, ...)
{
libvlc_log_subscriber_t *sub;
va_list ap;
switch (level)
{
case VLC_MSG_INFO: level = LIBVLC_NOTICE; break;
case VLC_MSG_ERR: level = LIBVLC_ERROR; break;
case VLC_MSG_WARN: level = LIBVLC_WARNING; break;
case VLC_MSG_DBG: level = LIBVLC_DEBUG; break;
}
va_start (ap, fmt);
vlc_rwlock_rdlock (&log_lock);
for (sub = log_first; sub != NULL; sub = sub->next)
sub->func (sub->opaque, level, fmt, ap);
vlc_rwlock_unlock (&log_lock);
inst->log.cb (inst->log.data, level, ctx, fmt, ap);
va_end (ap);
}
static void libvlc_logf (void *dummy, int level, const vlc_log_t *item,
static void libvlc_logf (void *data, int level, const vlc_log_t *item,
const char *fmt, va_list ap)
{
char *msg;
if (unlikely(vasprintf (&msg, fmt, ap) == -1))
msg = NULL;
return;
switch (level)
{
case VLC_MSG_INFO: level = LIBVLC_NOTICE; break;
case VLC_MSG_ERR: level = LIBVLC_ERROR; break;
case VLC_MSG_WARN: level = LIBVLC_WARNING; break;
case VLC_MSG_DBG: level = LIBVLC_DEBUG; break;
}
if (item->psz_header != NULL)
libvlc_log (level, "[%p] [%s]: %s %s %s", (void *)item->i_object_id,
item->psz_header, item->psz_module, item->psz_object_type,
msg ? msg : "Not enough memory");
libvlc_log (data, level, item, "[%p] [%s]: %s %s %s",
(void *)item->i_object_id, item->psz_header,
item->psz_module, item->psz_object_type, msg);
else
libvlc_log (level, "[%p]: %s %s %s", (void *)item->i_object_id,
item->psz_module, item->psz_object_type,
msg ? msg : "Not enough memory");
libvlc_log (data, level, item, "[%p]: %s %s %s",
(void *)item->i_object_id, item->psz_module,
item->psz_object_type, msg);
free (msg);
(void) dummy;
}
void libvlc_log_init (void)
void libvlc_log_unset (libvlc_instance_t *inst)
{
vlc_Subscribe (&sub, libvlc_logf, NULL);
vlc_LogSet (inst->p_libvlc_int, NULL, NULL);
}
void libvlc_log_deinit (void)
void libvlc_log_set (libvlc_instance_t *inst, libvlc_log_cb cb, void *data)
{
vlc_Unsubscribe (&sub);
}
void libvlc_log_subscribe (libvlc_log_subscriber_t *sub,
libvlc_log_cb cb, void *data)
{
sub->prev = NULL;
sub->func = cb;
sub->opaque = data;
vlc_rwlock_wrlock (&log_lock);
sub->next = log_first;
log_first = sub;
vlc_rwlock_unlock (&log_lock);
}
void libvlc_log_unsubscribe( libvlc_log_subscriber_t *sub )
{
vlc_rwlock_wrlock (&log_lock);
if (sub->next != NULL)
sub->next->prev = sub->prev;
if (sub->prev != NULL)
sub->prev->next = sub->next;
else
log_first = sub->next;
vlc_rwlock_unlock (&log_lock);
libvlc_log_unset (inst); /* <- Barrier before modifying the callback */
inst->log.cb = cb;
inst->log.data = data;
vlc_LogSet (inst->p_libvlc_int, libvlc_logf, inst);
}
/*** Helpers for logging to files ***/
static void libvlc_log_file (void *data, int level, const char *fmt,
va_list ap)
static void libvlc_log_file (void *data, int level, const libvlc_log_t *log,
const char *fmt, va_list ap)
{
FILE *stream = data;
......@@ -123,12 +95,12 @@ static void libvlc_log_file (void *data, int level, const char *fmt,
vfprintf (stream, fmt, ap);
fputc ('\n', stream);
funlockfile (stream);
(void) level;
(void) level; (void) log;
}
void libvlc_log_subscribe_file (libvlc_log_subscriber_t *sub, FILE *stream)
void libvlc_log_set_file (libvlc_instance_t *inst, FILE *stream)
{
libvlc_log_subscribe (sub, libvlc_log_file, stream);
libvlc_log_set (inst, libvlc_log_file, stream);
}
/*** Stubs for the old interface ***/
......
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