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+/* Pausing execution of the current thread.
+ Copyright (C) 2009-2017 Free Software Foundation, Inc.
+ Written by Eric Blake <ebb9@byu.net>, 2009.
+
+ This program 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.
+
+ This program 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 <https://www.gnu.org/licenses/>. */
+
+/* This file is _intentionally_ light-weight. Rather than using
+ select or nanosleep, both of which drag in external libraries on
+ some platforms, this merely rounds up to the nearest second if
+ usleep() does not exist. If sub-second resolution is important,
+ then use a more powerful interface to begin with. */
+
+#include <config.h>
+
+/* Specification. */
+#include <unistd.h>
+
+#include <errno.h>
+
+#ifndef HAVE_USLEEP
+# define HAVE_USLEEP 0
+#endif
+
+/* Sleep for MICRO microseconds, which can be greater than 1 second.
+ Return -1 and set errno to EINVAL on range error (about 4295
+ seconds), or 0 on success. Interaction with SIGALARM is
+ unspecified. */
+
+int
+usleep (useconds_t micro)
+{
+ unsigned int seconds = micro / 1000000;
+ if (sizeof seconds < sizeof micro && micro / 1000000 != seconds)
+ {
+ errno = EINVAL;
+ return -1;
+ }
+ if (!HAVE_USLEEP && micro % 1000000)
+ seconds++;
+ while ((seconds = sleep (seconds)) != 0);
+
+#undef usleep
+#if !HAVE_USLEEP
+# define usleep(x) 0
+#endif
+ return usleep (micro % 1000000);
+}