Ticket #2136: implement user-friendly interruption of long-time operations.

Initial step: created a simple timer.

Unlike GTimer, mc timer doesn't use a lot of multiplications and
divisions to convert seconds to nanoseconds and back. mc timer use only
multiplications to convert seconds to microseconds.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

lib/Makefile.am

@@ -40,7 +40,8 @@ libmc_la_SOURCES = \
 	keybind.c keybind.h \
 	lock.c lock.h \
 	serialize.c serialize.h \
-	timefmt.c timefmt.h
+	timefmt.c timefmt.h \
+	timer.c timer.h
 
 if USE_MAINTAINER_MODE
 libmc_la_SOURCES += logging.c logging.h

lib/timer.c

@@ -0,0 +1,114 @@
+/*
+   Simple timer for the Midnight Commander.
+
+   Copyright (C) 2013-2014
+   Free Software Foundation, Inc.
+
+   Written by:
+   Andrew Borodin 2013
+
+   This file is part of the Midnight Commander.
+
+   The Midnight Commander 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 3 of the License,
+   or (at your option) any later version.
+
+   The Midnight Commander 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, see <http://www.gnu.org/licenses/>.
+ */
+
+/** \file
+ *  \brief Source: simple timer
+ */
+
+#include <config.h>
+
+#include <sys/time.h>
+
+#include "lib/global.h"
+#include "lib/timer.h"
+
+/*** global variables ****************************************************************************/
+
+/**
+ * mc_timer_t:
+ *
+ * Opaque datatype that records a start time.
+ * #mc_timer_t records a start time, and counts microseconds elapsed since
+ * that time.
+ **/
+struct mc_timer_t
+{
+    guint64 start;
+};
+
+/*** file scope macro definitions ****************************************************************/
+
+/*** file scope type declarations ****************************************************************/
+
+/*** file scope variables ************************************************************************/
+
+/*** file scope functions ************************************************************************/
+
+/* --------------------------------------------------------------------------------------------- */
+/*** public functions ****************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+/**
+ * Creates a new timer, and starts timing.
+ *
+ * @return: a new #mc_timer_t.
+ **/
+mc_timer_t *
+mc_timer_new (void)
+{
+    mc_timer_t *timer;
+    struct timeval tv;
+
+    timer = g_new (mc_timer_t, 1);
+    gettimeofday (&tv, NULL);
+    timer->start = (guint64) tv.tv_sec * G_USEC_PER_SEC + (guint64) tv.tv_usec;
+
+    return timer;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/**
+ * Destroys a timer, freeing associated resources.
+ *
+ * @timer: an #mc_timer_t to destroy.
+ **/
+void
+mc_timer_destroy (mc_timer_t * timer)
+{
+    g_free (timer);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/**
+ * Obtains the time since the timer was started.
+ *
+ * @timer: an #mc_timer_t.
+ *
+ * @return: microseconds elapsed, the time since the timer was started
+ *
+ **/
+guint64
+mc_timer_elapsed (const mc_timer_t * timer)
+{
+    struct timeval tv;
+
+    gettimeofday (&tv, NULL);
+
+    return ((guint64) tv.tv_sec * G_USEC_PER_SEC + (guint64) tv.tv_usec - timer->start);
+}
+
+/* --------------------------------------------------------------------------------------------- */

lib/timer.h

@@ -0,0 +1,27 @@
+/** \file timer.h
+ *  \brief Header: simple timer
+ */
+
+#ifndef MC_TIMER_H
+#define MC_TIMER_H
+
+/*** typedefs(not structures) and defined constants **********************************************/
+
+/*** enums ***************************************************************************************/
+
+/*** structures declarations (and typedefs of structures)*****************************************/
+
+struct mc_timer_t;
+typedef struct mc_timer_t mc_timer_t;
+
+/*** global variables defined in .c file *********************************************************/
+
+/*** declarations of public functions ************************************************************/
+
+mc_timer_t *mc_timer_new (void);
+void mc_timer_destroy (mc_timer_t * timer);
+guint64 mc_timer_elapsed (const mc_timer_t * timer);
+
+/*** inline functions **************************************************/
+
+#endif /* MC_TIMER_H */