This function simply calls usleep() if this is available.  On
Windows, the Sleep() function can be used as a fallback.  The
conditional #includes in time.c are simplified by including
unistd.h and windows.h whenever these are available rather than
having these lines triggered by specific functions.

Signed-off-by: Mans Rullgard <[email protected]>
---
Changed in v2:
- mention possibility of limited precision system timer
- use nanosleep if available
---
 configure        |    7 +++++++
 libavutil/time.c |   24 +++++++++++++++++++++++-
 libavutil/time.h |   10 ++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index fe036c4..bba30ed 100755
--- a/configure
+++ b/configure
@@ -1121,6 +1121,7 @@ HAVE_LIST="
     memalign
     mkstemp
     mmap
+    nanosleep
     netinet_sctp_h
     poll_h
     posix_memalign
@@ -1131,6 +1132,7 @@ HAVE_LIST="
     sdl_video_size
     setmode
     setrlimit
+    Sleep
     sndio_h
     socklen_t
     soundcard_h
@@ -1159,8 +1161,10 @@ HAVE_LIST="
     trunc
     truncf
     unistd_h
+    usleep
     vfp_args
     VirtualAlloc
+    windows_h
     winsock2_h
     WSAPoll
     xform_asm
@@ -2891,12 +2895,14 @@ check_func  strtok_r
 check_func  sched_getaffinity
 check_func  sysconf
 check_func  sysctl
+check_func  usleep
 check_func_headers io.h setmode
 check_lib2 "windows.h psapi.h" GetProcessMemoryInfo -lpsapi
 check_func_headers windows.h GetProcessAffinityMask
 check_func_headers windows.h GetProcessTimes
 check_func_headers windows.h GetSystemTimeAsFileTime
 check_func_headers windows.h MapViewOfFile
+check_func_headers windows.h Sleep
 check_func_headers windows.h VirtualAlloc
 
 check_header dlfcn.h
@@ -2910,6 +2916,7 @@ check_header sys/select.h
 check_header unistd.h
 check_header vdpau/vdpau.h
 check_header vdpau/vdpau_x11.h
+check_header windows.h
 check_header X11/extensions/XvMClib.h
 
 disabled  zlib || check_lib   zlib.h      zlibVersion -lz   || disable  zlib
diff --git a/libavutil/time.c b/libavutil/time.c
index 80c4029..51779c5 100644
--- a/libavutil/time.c
+++ b/libavutil/time.c
@@ -20,13 +20,19 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <time.h>
 #if HAVE_GETTIMEOFDAY
 #include <sys/time.h>
-#elif HAVE_GETSYSTEMTIMEASFILETIME
+#endif
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#if HAVE_WINDOWS_H
 #include <windows.h>
 #endif
 
 #include "libavutil/time.h"
+#include "error.h"
 
 int64_t av_gettime(void)
 {
@@ -44,3 +50,19 @@ int64_t av_gettime(void)
     return -1;
 #endif
 }
+
+int av_usleep(unsigned usec)
+{
+#if HAVE_NANOSLEEP
+    struct timespec ts = { usec / 1000000, usec % 1000000 * 1000 };
+    while (nanosleep(&ts, &ts) < 0 && errno == EINTR);
+    return 0;
+#elif HAVE_USLEEP
+    return usleep(usec);
+#elif HAVE_SLEEP
+    Sleep(usec / 1000);
+    return 0;
+#else
+    return AVERROR(ENOSYS);
+#endif
+}
diff --git a/libavutil/time.h b/libavutil/time.h
index 2ee7e08..b01a97d 100644
--- a/libavutil/time.h
+++ b/libavutil/time.h
@@ -26,4 +26,14 @@
  */
 int64_t av_gettime(void);
 
+/**
+ * Sleep for a period of time.  Although the duration is expressed in
+ * microseconds, the actual delay may be rounded to the precision of the
+ * system timer.
+ *
+ * @param  usec Number of microseconds to sleep.
+ * @return zero on success or (negative) error code.
+ */
+int av_usleep(unsigned usec);
+
 #endif /* AVUTIL_TIME_H */
-- 
1.7.10.2

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