1 files changed, 106 insertions, 0 deletions
diff --git a/tz/asctime.c b/tz/asctime.c
new file mode 100644
index 0000000..f0159f8
--- /dev/null
+++ b/tz/asctime.c
@@ -0,0 +1,106 @@
+/* asctime and asctime_r a la POSIX and ISO C, except pad years before 1000.  */
+
+/*
+** This file is in the public domain, so clarified as of
+** 1996-06-05 by Arthur David Olson.
+*/
+
+/*
+** Avoid the temptation to punt entirely to strftime;
+** the output of strftime is supposed to be locale specific
+** whereas the output of asctime is supposed to be constant.
+*/
+
+/*LINTLIBRARY*/
+
+#include "private.h"
+#include <stdio.h>
+
+/*
+** All years associated with 32-bit time_t values are exactly four digits long;
+** some years associated with 64-bit time_t values are not.
+** Vintage programs are coded for years that are always four digits long
+** and may assume that the newline always lands in the same place.
+** For years that are less than four digits, we pad the output with
+** leading zeroes to get the newline in the traditional place.
+** The -4 ensures that we get four characters of output even if
+** we call a strftime variant that produces fewer characters for some years.
+** The ISO C and POSIX standards prohibit padding the year,
+** but many implementations pad anyway; most likely the standards are buggy.
+*/
+static char const ASCTIME_FMT[] = "%s %s%3d %.2d:%.2d:%.2d %-4s\n";
+/*
+** For years that are more than four digits we put extra spaces before the year
+** so that code trying to overwrite the newline won't end up overwriting
+** a digit within a year and truncating the year (operating on the assumption
+** that no output is better than wrong output).
+*/
+static char const ASCTIME_FMT_B[] = "%s %s%3d %.2d:%.2d:%.2d     %s\n";
+
+enum { STD_ASCTIME_BUF_SIZE = 26 };
+/*
+** Big enough for something such as
+** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
+** (two three-character abbreviations, five strings denoting integers,
+** seven explicit spaces, two explicit colons, a newline,
+** and a trailing NUL byte).
+** The values above are for systems where an int is 32 bits and are provided
+** as an example; the size expression below is a bound for the system at
+** hand.
+*/
+static char buf_asctime[2*3 + 5*INT_STRLEN_MAXIMUM(int) + 7 + 2 + 1 + 1];
+
+char *
+asctime_r(register const struct tm *timeptr, char *buf)
+{
+	static const char	wday_name[][4] = {
+		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
+	};
+	static const char	mon_name[][4] = {
+		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
+		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
+	};
+	register const char *	wn;
+	register const char *	mn;
+	char			year[INT_STRLEN_MAXIMUM(int) + 2];
+	char result[sizeof buf_asctime];
+
+	if (timeptr == NULL) {
+		errno = EINVAL;
+		return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
+	}
+	if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
+		wn = "???";
+	else	wn = wday_name[timeptr->tm_wday];
+	if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
+		mn = "???";
+	else	mn = mon_name[timeptr->tm_mon];
+	/*
+	** Use strftime's %Y to generate the year, to avoid overflow problems
+	** when computing timeptr->tm_year + TM_YEAR_BASE.
+	** Assume that strftime is unaffected by other out-of-range members
+	** (e.g., timeptr->tm_mday) when processing "%Y".
+	*/
+	strftime(year, sizeof year, "%Y", timeptr);
+	/*
+	** We avoid using snprintf since it's not available on all systems.
+	*/
+	sprintf(result,
+		((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
+		wn, mn,
+		timeptr->tm_mday, timeptr->tm_hour,
+		timeptr->tm_min, timeptr->tm_sec,
+		year);
+	if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
+		return strcpy(buf, result);
+	else {
+		errno = EOVERFLOW;
+		return NULL;
+	}
+}
+
+char *
+asctime(register const struct tm *timeptr)
+{
+	return asctime_r(timeptr, buf_asctime);
+}