new file mode 100644
--- /dev/null
+++ b/src/core/ngx_log.h
@@ -0,0 +1,118 @@
+#ifndef _NGX_LOG_H_INCLUDED_
+#define _NGX_LOG_H_INCLUDED_
+
+
+#include <ngx_errno.h>
+
+typedef enum {
+    NGX_LOG_EMERG = 0,
+    NGX_LOG_ALERT,
+    NGX_LOG_CRIT,
+    NGX_LOG_ERR,
+    NGX_LOG_WARN,
+    NGX_LOG_NOTICE,
+    NGX_LOG_INFO,
+    NGX_LOG_DEBUG
+} ngx_log_e;
+
+/*
+    "... while ", action = "reading client request headers"
+    "... while reading client request headers"
+    "... while ", action = "reading client request headers"
+                  context: pop3 user account
+    "... while reading client command for 'john_doe'"
+*/
+
+typedef struct {
+    int    log_level;
+    char  *action;
+    char  *context;
+/*  char  *func(ngx_log_t *log); */
+} ngx_log_t;
+
+#define MAX_ERROR_STR	2048
+
+#define _               ,
+
+
+#if (HAVE_GCC_VARIADIC_MACROS)
+
+#define HAVE_VARIADIC_MACROS  1
+
+#define ngx_log_error(level, log, args...) \
+        if (log->log_level >= level) ngx_log_error_core(level, log, args)
+
+#ifdef NGX_DEBUG
+#define ngx_log_debug(log, args...) \
+    if (log->log_level == NGX_LOG_DEBUG) \
+        ngx_log_error_core(NGX_LOG_DEBUG, log, 0, args)
+#else
+#define ngx_log_debug(log, args...)
+#endif
+
+#define ngx_assert(assert, fallback, log, args...) \
+        if (!(assert)) { \
+            if (log->log_level >= NGX_LOG_ALERT) \
+                ngx_log_error_core(NGX_LOG_ALERT, log, 0, args); \
+            fallback; \
+        }
+
+void ngx_log_error_core(int level, ngx_log_t *log, ngx_err_t err,
+                        const char *fmt, ...);
+
+#elif (HAVE_C99_VARIADIC_MACROS)
+
+#define HAVE_VARIADIC_MACROS  1
+
+#define ngx_log_error(level, log, ...) \
+        if (log->log_level >= level) ngx_log_error_core(level, log, __VA_ARGS__)
+
+#ifdef NGX_DEBUG
+#define ngx_log_debug(log, ...) \
+    if (log->log_level == NGX_LOG_DEBUG) \
+        ngx_log_error_core(NGX_LOG_DEBUG, log, 0, __VA_ARGS__)
+#else
+#define ngx_log_debug(log, ...)
+#endif
+
+#define ngx_assert(assert, fallback, log, ...) \
+        if (!(assert)) { \
+            if (log->log_level >= NGX_LOG_ALERT) \
+                ngx_log_error_core(NGX_LOG_ALERT, log, 0, __VA_ARGS__); \
+            fallback; \
+        }
+
+void ngx_log_error_core(int level, ngx_log_t *log, ngx_err_t err,
+                        const char *fmt, ...);
+
+#else /* NO VARIADIC MACROS */
+
+#include <stdarg.h>
+
+#ifdef NGX_DEBUG
+#define ngx_log_debug(log, text) \
+    if (log->log_level == NGX_LOG_DEBUG) \
+        ngx_log_debug_core(log, text)
+#else
+#define ngx_log_debug(log, text)
+#endif
+
+#define ngx_assert(assert, fallback, log, text) \
+        if (!(assert)) { \
+            if (log->log_level >= NGX_LOG_ALERT) \
+                ngx_assert_core(log, text); \
+            fallback; \
+        }
+
+void ngx_log_error(int level, ngx_log_t *log, ngx_err_t err,
+                   const char *fmt, ...);
+void ngx_log_error_core(int level, ngx_log_t *log, ngx_err_t err,
+                        const char *fmt, va_list args);
+void ngx_log_debug_core(ngx_log_t *log, const char *fmt, ...);
+void ngx_assert_core(ngx_log_t *log, const char *fmt, ...);
+
+
+#endif /* VARIADIC MACROS */
+
+
+#endif /* _NGX_LOG_H_INCLUDED_ */