X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=daemon.c;h=dd5420a6eab92de518e3af60ea49d094ae5db6bb;hb=2bad70d84e763b4d866d7b97dbc1cdc8e030bd45;hp=ddfe680cebc63dc1c7af89fde333c665873765eb;hpb=2031b9cab9304b02c0372f73eef54d9501277031;p=paraslash.git

diff --git a/daemon.c b/daemon.c
index ddfe680c..dd5420a6 100644
--- a/daemon.c
+++ b/daemon.c
@@ -31,6 +31,12 @@ struct daemon {
 	/** Used for colored log messages. */
 	char log_colors[NUM_LOGLEVELS][COLOR_MAXLEN];
 	char *old_cwd;
+	/*
+	 * If these pointers are non-NULL, the functions are called from
+	 * daemon_log() before and after writing each log message.
+	 */
+	void (*pre_log_hook)(void);
+	void (*post_log_hook)(void);
 };
 
 static struct daemon the_daemon, *me = &the_daemon;
@@ -52,9 +58,9 @@ static void daemon_set_default_log_colors(void)
 }
 
 /**
- * Set the color for one loglevel.
+ * Set the color for log messages of the given severity level.
  *
- * \param arg Must be of the form "ll:[fg [bg]] [attr]".
+ * \param arg Must be of the form "severity:[fg [bg]] [attr]".
  */
 void daemon_set_log_color_or_die(const char *arg)
 {
@@ -140,6 +146,28 @@ void daemon_set_loglevel(const char *loglevel)
 	me->loglevel = ret;
 }
 
+/**
+ * Register functions to be called before and after a message is logged.
+ *
+ * \param pre_log_hook Called before the message is logged.
+ * \param post_log_hook Called after the message is logged.
+ *
+ * The purpose of this function is to provide a primitive for multi-threaded
+ * applications to serialize the access to the log facility, preventing
+ * interleaving log messages. This can be achieved by having the pre-log hook
+ * acquire a lock which blocks the other threads on the attempt to log a
+ * message at the same time.  The post-log hook is responsible for releasing
+ * the lock.
+ *
+ * If these hooks are unnecessary, for example because the application is
+ * single-threaded, this function does not need to be called.
+ */
+void daemon_set_hooks(void (*pre_log_hook)(void), void (*post_log_hook)(void))
+{
+	me->pre_log_hook = pre_log_hook;
+	me->post_log_hook = post_log_hook;
+}
+
 /**
  * Set one of the daemon config flags.
  *
@@ -409,6 +437,8 @@ __printf_2_3 void daemon_log(int ll, const char* fmt,...)
 		return;
 
 	fp = me->logfile? me->logfile : stderr;
+	if (me->pre_log_hook)
+		me->pre_log_hook();
 	color = daemon_test_flag(DF_COLOR_LOG)? me->log_colors[ll] : NULL;
 	if (color)
 		fprintf(fp, "%s", color);
@@ -441,4 +471,6 @@ __printf_2_3 void daemon_log(int ll, const char* fmt,...)
 	va_end(argp);
 	if (color)
 		fprintf(fp, "%s", COLOR_RESET);
+	if (me->post_log_hook)
+		me->post_log_hook();
 }