diff --git a/src/llog.h b/src/llog.h
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--- /dev/null
+++ b/src/llog.h
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+/*
+ * Library Log/Debug Interface
+ * Copyright (c) 2012 David Herrmann <dh.herrmann@googlemail.com>
+ * Dedicated to the Public Domain
+ */
+
+/*
+ * Library Log/Debug Interface
+ * Libraries should always avoid producing side-effects. This includes writing
+ * log-messages of any kind. However, you often don't want to disable debugging
+ * entirely, therefore, the core objects often contain a pointer to a function
+ * which performs logging. If that pointer is NULL (default), logging is
+ * disabled.
+ *
+ * This header should never be installed into the system! This is _no_ public
+ * header. Instead, copy it into your application if you want and use it there.
+ * Your public library API should include something like this:
+ *
+ *   typedef void (*MYPREFIX_log_t) (const char *file,
+ *                                   int line,
+ *                                   const char *func,
+ *                                   const char *subs,
+ *                                   unsigned int sev,
+ *                                   const char *format,
+ *                                   va_list args);
+ *
+ * And then the user can supply such a function when creating a new context
+ * object of your library or simply supply NULL. Internally, you have a field of
+ * type "MYPREFIX_log_t llog" in your main structure. If you pass this to the
+ * convenience helpers like llog_dbg(), llog_warn() etc. it will automatically
+ * use the "llog" field to print the message. If it is NULL, nothing is done.
+ *
+ * The arguments of the log-function are defined as:
+ *   file: Zero terminated string of the file-name where the log-message
+ *         occurred. Can be NULL.
+ *   line: Line number of @file where the message occurred. Set to 0 or smaller
+ *         if not available.
+ *   func: Function name where the log-message occurred. Can be NULL.
+ *   subs: Subsystem where the message occurred (zero terminated). Can be NULL.
+ *   sev: Severity of log-message. An integer between 0 and 7 as defined below.
+ *        These are identical to the linux-kernel severities so there is no need
+ *        to include these in your public API. Every app can define them
+ *        themself, if they need it.
+ *   format: Format string. Must not be NULL.
+ *   args: Argument array
+ */
+
+#ifndef LLOG_H_INCLUDED
+#define LLOG_H_INCLUDED
+
+#include <stdarg.h>
+#include <stdlib.h>
+
+enum llog_severity {
+	LLOG_FATAL = 0,
+	LLOG_ALERT = 1,
+	LLOG_CRITICAL = 2,
+	LLOG_ERROR = 3,
+	LLOG_WARNING = 4,
+	LLOG_NOTICE = 5,
+	LLOG_INFO = 6,
+	LLOG_DEBUG = 7,
+	LLOG_SEV_NUM,
+};
+
+typedef void (*llog_submit_t) (const char *file,
+			       int line,
+			       const char *func,
+			       const char *subs,
+			       unsigned int sev,
+			       const char *format,
+			       va_list args);
+
+static void llog_format(llog_submit_t llog,
+			const char *file,
+			int line,
+			const char *func,
+			const char *subs,
+			unsigned int sev,
+			const char *format,
+			...)
+{
+	va_list list;
+
+	if (llog) {
+		va_start(list, format);
+		llog(file, line, func, subs, sev, format, list);
+		va_end(list);
+	}
+}
+
+#ifndef LLOG_SUBSYSTEM
+static const char *LLOG_SUBSYSTEM __attribute__((__unused__));
+#endif
+
+#define LLOG_DEFAULT __FILE__, __LINE__, __func__, LLOG_SUBSYSTEM
+
+#define llog_printf(obj, sev, format, ...) \
+	llog_format((obj)->llog, LLOG_DEFAULT, (sev), (format), ##__VA_ARGS__)
+
+/*
+ * Helpers
+ * They pick-up all the default values and submit the message to the
+ * llog-subsystem. The llog_debug() function produces zero-code if
+ * LLOG_ENABLE_DEBUG is not defined. Therefore, it can be heavily used for
+ * debugging and will not have any side-effects.
+ */
+
+#ifdef LLOG_ENABLE_DEBUG
+	#define llog_debug(obj, format, ...) \
+		llog_printf((obj), LLOG_DEBUG, (format), ##__VA_ARGS__)
+#else
+	#define llog_debug(obj, format, ...)
+#endif
+
+#define llog_info(obj, format, ...) \
+	llog_printf((obj), LLOG_INFO, (format), ##__VA_ARGS__)
+#define llog_notice(obj, format, ...) \
+	llog_printf((obj), LLOG_NOTICE, (format), ##__VA_ARGS__)
+#define llog_warning(obj, format, ...) \
+	llog_printf((obj), LLOG_WARNING, (format), ##__VA_ARGS__)
+#define llog_error(obj, format, ...) \
+	llog_printf((obj), LLOG_ERROR, (format), ##__VA_ARGS__)
+#define llog_critical(obj, format, ...) \
+	llog_printf((obj), LLOG_CRITICAL, (format), ##__VA_ARGS__)
+#define llog_alert(obj, format, ...) \
+	llog_printf((obj), LLOG_ALERT, (format), ##__VA_ARGS__)
+#define llog_fatal(obj, format, ...) \
+	llog_printf((obj), LLOG_FATAL, (format), ##__VA_ARGS__)
+
+#define llog_dbg llog_debug
+#define llog_warn llog_warning
+#define llog_err llog_error
+#define llog_crit llog_critical
+
+#endif /* LLOG_H_INCLUDED */