Teach date @unixtime[.fraction], switch -s to be -D (matching busybox and

not stomping on gnu's "an extra argument tells it to set the time so let's
add -s to do the same thing" extension).

Nanoseconds aren't uniformly supported by these apis, so had to stick it in
GLOBALS() and pull it out later. Awkward, open to suggestions for a better way.
(Also, the setting API is microseconds, not nanoseconds. Collect nano, convert
to micro so we can switch APIs later without changing date's external UI again.)

Oh, and shrink really_long_name_mktime() with a for() loop (and rename it)
although I may go back and redo that for portability to hypothetical libraries
if I can convert this mess to struct timespec with proper nanoseconds support.
But that needs an extended strptime() which needs an extended struct tm,
and between us and that is convincing posix computers got fast enough to
care about fractions of a second.

(Yes, I'm aware gnu added %N to date without adding it to strptime, implying
they reimplemented strptime longhand inside date. I'm not doing that.)

1 files changed, 70 insertions, 45 deletions

diff --git a/toys/posix/date.c b/toys/posix/date.c
index 84e04fc..5719fd2 100644
--- a/toys/posix/date.c
+++ b/toys/posix/date.c
@@ -7,22 +7,23 @@
  * Note: setting a 2 year date is 50 years back/forward from today,
  * not posix's hardwired magic dates.
 
-USE_DATE(NEWTOY(date, "d:s:r:u[!dr]", TOYFLAG_BIN))
+USE_DATE(NEWTOY(date, "d:D:r:u[!dr]", TOYFLAG_BIN))
 
 config DATE
   bool "date"
   default y
   help
-    usage: date [-u] [-r FILE] [-d DATE] [+DISPLAY_FORMAT] [-s SET_FORMAT] [SET]
+    usage: date [-u] [-r FILE] [-d DATE] [+DISPLAY_FORMAT] [-D SET_FORMAT] [SET]
 
     Set/get the current date/time. With no SET shows the current date.
 
     Default SET format is "MMDDhhmm[[CC]YY][.ss]", that's (2 digits each)
     month, day, hour (0-23), and minute. Optionally century, year, and second.
+    Also accepts "@UNIXTIME[.FRACTION]" as seconds since midnight Jan 1 1970.
 
     -d	Show DATE instead of current time (convert date format)
+    -D	+FORMAT for SET or -d (instead of MMDDhhmm[[CC]YY][.ss])
     -r	Use modification time of FILE instead of current date
-    -s	+FORMAT for SET or -d (instead of MMDDhhmm[[CC]YY][.ss])
     -u	Use UTC instead of current timezone
 
     +FORMAT specifies display format string using these escapes:
@@ -49,33 +50,73 @@ GLOBALS(
   char *file;
   char *setfmt;
   char *showdate;
+
+  char *tz;
+  unsigned nano;
 )
 
 // mktime(3) normalizes the struct tm fields, but date(1) shouldn't.
-// If we round trip via localtime_r(3) and get back where we started,
-// we know 'tm' is already in normal form.
-static time_t non_normalizing_mktime(struct tm *tm)
+static time_t chkmktime(struct tm *tm)
 {
-  struct tm tm0 = *tm;
+  struct tm tm2;
   time_t t = mktime(tm);
-  struct tm tm1;
+  int *tt1 = (void *)tm, *tt2=(void *)&tm2, i;
+
+  if (t != -1 && localtime_r(&t, &tm2)) {
+    for (i=0; i<6; i++) if (tt1[i] != tt2[i]) break;
+    if (i == 5) return t;
+  }
 
-  if (t == -1 || !localtime_r(&t, &tm1) ||
-      tm0.tm_sec != tm1.tm_sec || tm0.tm_min != tm1.tm_min ||
-      tm0.tm_hour != tm1.tm_hour || tm0.tm_mday != tm1.tm_mday ||
-      tm0.tm_mon != tm1.tm_mon)
-    return -1;
+  return -1;
+}
 
-  return t;
+static void utzset(void)
+{
+  if (!(TT.tz = getenv("TZ"))) TT.tz = (char *)1;
+  setenv("TZ", "UTC", 1);
+  tzset();
+}
+
+static void utzreset(void)
+{
+  if (TT.tz) {
+    if (TT.tz != (char *)1) setenv("TZ", TT.tz, 1);
+    else unsetenv("TZ");
+    tzset();
+  }
 }
 
-// Handle default posix date format: mmddhhmm[[cc]yy]
+// Handle default posix date format (mmddhhmm[[cc]yy]) or @UNIX[.FRAC]
 // returns 0 success, nonzero for error
-static int parse_posixdate(char *str, struct tm *tm)
+static int parse_default(char *str, struct tm *tm)
 {
-  int len;
+  int len = 0;
+
+  // Parse @UNIXTIME[.FRACTION]
+  if (*str == '@') {
+    long long ll;
+    time_t tt;
+
+    // Collect seconds and nanoseconds
+    // Note: struct tm hasn't got a fractional seconds field, thus strptime()
+    // doesn't support it, so store nanoseconds out of band (in globals).
+    // tt and ll are separate because we can't guarantee time_t is 64 bit (yet).
+    sscanf(str, "@%lld%n", &ll, &len);
+    if (str[len]=='.') {
+      str += len+1;
+      for (len = 0; len<9; len++) {
+        TT.nano *= 10;
+        if (isdigit(str[len])) TT.nano += str[len]-'0';
+      }
+    }
+    if (str[len]) return 1;
+    tt = ll;
+    gmtime_r(&tt, tm);
+
+    return 0;
+  }
 
-  len = 0;
+  // Posix format
   sscanf(str, "%2u%2u%2u%2u%n", &tm->tm_mon, &tm->tm_mday, &tm->tm_hour,
     &tm->tm_min, &len);
   if (len != 8) return 1;
@@ -112,16 +153,11 @@ static int parse_posixdate(char *str, struct tm *tm)
 
 void date_main(void)
 {
-  char *setdate = *toys.optargs, *format_string = "%a %b %e %H:%M:%S %Z %Y",
-       *tz = 0;
+  char *setdate = *toys.optargs, *format_string = "%a %b %e %H:%M:%S %Z %Y";
   struct tm tm;
 
   // We can't just pass a timezone to mktime because posix.
-  if (toys.optflags & FLAG_u) {
-    if (CFG_TOYBOX_FREE) tz = getenv("TZ");
-    setenv("TZ", "UTC", 1);
-    tzset();
-  }
+  if (toys.optflags & FLAG_u) utzset();
 
   if (TT.showdate) {
     setdate = TT.showdate;
@@ -129,7 +165,7 @@ void date_main(void)
       char *s = strptime(TT.showdate, TT.setfmt+(*TT.setfmt=='+'), &tm);
 
       if (!s || *s) goto bad_date;
-    } else if (parse_posixdate(TT.showdate, &tm)) goto bad_date;
+    } else if (parse_default(TT.showdate, &tm)) goto bad_date;
   } else {
     time_t now;
 
@@ -155,33 +191,22 @@ void date_main(void)
   } else if (setdate) {
     struct timeval tv;
 
-    if (parse_posixdate(setdate, &tm)) goto bad_date;
+    if (parse_default(setdate, &tm)) goto bad_date;
 
     if (toys.optflags & FLAG_u) {
-      char *tz = CFG_TOYBOX_FREE ? getenv("TZ") : 0;
-
       // We can't just pass a timezone to mktime because posix.
-      setenv("TZ", "UTC", 1);
-      tzset();
-      tv.tv_sec = non_normalizing_mktime(&tm);
-      if (CFG_TOYBOX_FREE) {
-        if (tz) setenv("TZ", tz, 1);
-        else unsetenv("TZ");
-        tzset();
-      }
-    } else tv.tv_sec = non_normalizing_mktime(&tm);
+      utzset();
+      tv.tv_sec = chkmktime(&tm);
+      utzreset();
+    } else tv.tv_sec = chkmktime(&tm);
     if (tv.tv_sec == (time_t)-1) goto bad_date;
 
-    tv.tv_usec = 0;
+    tv.tv_usec = TT.nano/1000;
+exit(1);
     if (settimeofday(&tv, NULL) < 0) perror_msg("cannot set date");
   }
 
-  if (toys.optflags & FLAG_u) {
-    if (tz) setenv("TZ", tz, 1);
-    else unsetenv("TZ");
-    tzset();
-  }
-
+  utzreset();
   if (!strftime(toybuf, sizeof(toybuf), format_string, &tm))
     perror_exit("bad format '%s'", format_string);
   puts(toybuf);