stat: support high resolution time stamps.

* configure (have_sys_stat): New variable. Set to y when our
test detects <sys/stat.h>. New test added for the presence of
high resolution time stamps in struct stat. If we have these,
we #define HAVE_STAT_NSEC 1 in config.h.

* share/txr/stdlib/path-test.tl (path-newer): Compare
nanosecond parts of the modification time if the seconds are
equal, improving the resolution of the test.

* sysif.c (atime_nsec_s, mtime_nsec_s, ctime_nsec_s): New
symbol variables.
(stat_to_struct): If nanosecond resolution is available, set
the new nanosecond slots from the three tv_nsec fields in
struct stat. Otherwise, set the new slots to zero.
(sysif_init): Initialize the new symbol variables. Add the
three new slots to the stat struct.

* sysif.c (atime_nsec_s, mtime_nsec_s, ctime_nsec_s):
Declared.

* txr.1: Documented new atime-nsec, mtime-nsec and ctime-nsec
slots of stat structure. Added note to path-newer mentioning
high resolution support.

1 files changed, 7 insertions, 1 deletions

diff --git a/share/txr/stdlib/path-test.tl b/share/txr/stdlib/path-test.tl
index 59b24b13..4e26f1f8 100644
--- a/share/txr/stdlib/path-test.tl
+++ b/share/txr/stdlib/path-test.tl
@@ -153,7 +153,13 @@
 (defun path-newer (path-0 path-1)
   (sys:path-examine (s0 stat path-0)
     (sys:path-examine (s1 stat path-1)
-      (and s0 (or (not s1) (> s0.mtime s1.mtime))))))
+      (if s0
+        (or (null s1)
+            (let ((mt0 s0.mtime)
+                  (mt1 s1.mtime))
+              (or (> mt0 mt1)
+                  (and (= mt0 mt1)
+                       (> s0.mtime-nsec s1.mtime-nsec)))))))))
 
 (defun path-older (path-0 path-1)
   (path-newer path-1 path-0))