Refactor timestamp handling

Handle all date/time stamps uniformly, taking in account the host
endianness. Respect the local time zone and the '-Z' option for
all ipmitool commands. Unify the date and time formatting.
Add correct handling of IPMI timestamps 'since system startup'
and for 'unspecified' timestamps.

Partially resolves ipmitool/ipmitool#23

Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>

lib/ipmi_time.c

@@ -0,0 +1,217 @@
+/*
+ * Copyright (c) 2018 Alexander Amelkin.  All Rights Reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 
+ * Redistribution of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 
+ * Redistribution in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 
+ * Neither the name of the copyright holder, nor the names of
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * 
+ * This software is provided "AS IS," without a warranty of any kind.
+ * ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
+ * INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
+ * PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED.
+ * THE COPYRIGHT HOLDER AND ITS LICENSORS SHALL NOT BE LIABLE
+ * FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
+ * OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.  IN NO EVENT WILL
+ * THE COPYRIGHT HOLDER OR ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE,
+ * PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
+ * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE
+ * THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS
+ * SOFTWARE, EVEN IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGES.
+ */
+
+#include <time.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h> /* snprintf */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <ipmitool/ipmi_time.h>
+
+bool time_in_utc; /* Set by '-Z' command line option */
+
+time_t
+ipmi_localtime2utc(time_t local)
+{
+	struct tm tm;
+	gmtime_r(&local, &tm);
+	tm.tm_isdst = (-1);
+	return mktime(&tm);
+}
+
+/**
+ * @brief Convert a timestamp to a formatted string,
+ *        considering the '-Z' option. Acts as if tzset() was called.
+ *
+ * @param[out] s          The output string buffer
+ * @param[in]  max        The size of the output string buffer including the
+ *                        terminating null byte
+ * @param[in]  format     The format string, as in strftime(), ignored for
+ *                        special timestamp values as per section 37.1 of
+ *                        IPMI v2.0 specification rev 1.1.
+ * @param[in]  stamp      The time stamp to convert
+ *
+ * @returns the number of bytes written to s or 0, see strftime()
+ */
+size_t
+ipmi_strftime(char *s, int max, const char *format, time_t stamp)
+{
+	struct tm tm;
+
+	if (IPMI_TIME_UNSPECIFIED == stamp) {
+		return snprintf(s, max, "Unknown");
+	}
+	else if (stamp <= IPMI_TIME_INIT_DONE) {
+		/* Timestamp is relative to BMC start, no GMT offset */
+		gmtime_r(&stamp, &tm);
+
+		return strftime(s, max, format, &tm);
+	}
+
+	if (time_in_utc || ipmi_timestamp_is_special(stamp)) {
+		/*
+		 * The user wants the time reported in UTC or the stamp represents the
+		 * number of seconds since system power on. In any case, don't apply
+		 * the timezone offset.
+		 */
+		gmtime_r(&stamp, &tm);
+		daylight = -1;
+	} else {
+		/*
+		 * The user wants the time reported in local time zone.
+		 */
+		localtime_r(&stamp, &tm);
+	}
+	return strftime(s, max, format, &tm);
+}
+
+/**
+ * @brief Convert a timestamp to string, considering the '-Z' option.
+ *        Similar to asctime_r(), but takes time_t instead of struct tm,
+ *        and the string is in form "Wed Jun 30 21:49:08 1993 TZD" without
+ *        the new line at the end.
+ *
+ * @param[in]  stamp      The timestamp to convert
+ * @param[out] outbuf     The buffer to write the string to.
+ * @param[in]  len        The maximum length of the output buffer.
+ *                        Recommended size is IPMI_ASCTIME_SZ.
+ *
+ * @returns outbuf
+ */
+char *
+ipmi_asctime_r(const time_t stamp, ipmi_datebuf_t outbuf)
+{
+	const char *format = "%c %Z";
+	if (ipmi_timestamp_is_special(stamp)) {
+		if (stamp < SECONDS_A_DAY) {
+			format = "S+%H:%M:%S";
+		}
+		/*
+		 * IPMI_TIME_INIT_DONE is over 17 years. This should never
+		 * happen normally, but we'll support this anyway.
+		 */
+		else {
+			format = "S+%yy %jd %H:%M:%S";
+		}
+	}
+
+	ipmi_strftime(outbuf, IPMI_ASCTIME_SZ, format, stamp);
+	return outbuf;
+}
+
+char *
+ipmi_timestamp_fmt(uint32_t stamp, const char *fmt)
+{
+	/*
+	 * It's assumed that supplied 'fmt' is never longer
+	 * than IPMI_ASCTIME_SZ
+	 */
+	static ipmi_datebuf_t datebuf;
+	ipmi_strftime(datebuf, sizeof(datebuf), fmt, stamp);
+	return datebuf;
+}
+
+char *
+ipmi_timestamp_string(uint32_t stamp)
+{
+	const char *format = "%c %Z";
+	if (!ipmi_timestamp_is_valid(stamp)) {
+		return "Unspecified";
+	}
+
+	if (ipmi_timestamp_is_special(stamp)) {
+		if (stamp < SECONDS_A_DAY) {
+			format = "S+ %H:%M:%S";
+		}
+		/*
+		 * IPMI_TIME_INIT_DONE is over 17 years. This should never
+		 * happen normally, but we'll support this anyway.
+		 */
+		else {
+			format = "S+ %y years %j days %H:%M:%S";
+		}
+	}
+	return ipmi_timestamp_fmt(stamp, format);
+}
+
+char *
+ipmi_timestamp_numeric(uint32_t stamp)
+{
+	const char *format = "%x %X %Z";
+	if (!ipmi_timestamp_is_valid(stamp)) {
+		return "Unspecified";
+	}
+
+	if (ipmi_timestamp_is_special(stamp)) {
+		if (stamp < SECONDS_A_DAY) {
+			format = "S+ %H:%M:%S";
+		}
+		/*
+		 * IPMI_TIME_INIT_DONE is over 17 years. This should never
+		 * happen normally, but we'll support this anyway.
+		 */
+		else {
+			format = "S+ %y/%j %H:%M:%S";
+		}
+	}
+	return ipmi_timestamp_fmt(stamp, format);
+}
+
+char *
+ipmi_timestamp_date(uint32_t stamp)
+{
+	const char *format = "%x";
+	if (!ipmi_timestamp_is_valid(stamp)) {
+		return "Unspecified";
+	}
+
+	if (ipmi_timestamp_is_special(stamp)) {
+		format = "S+ %y/%j";
+	}
+	return ipmi_timestamp_fmt(stamp, format);
+}
+
+char *
+ipmi_timestamp_time(uint32_t stamp)
+{
+	if (!ipmi_timestamp_is_valid(stamp)) {
+		return "Unspecified";
+	}
+
+	/* Format is the same for both normal and special timestamps */
+	return ipmi_timestamp_fmt(stamp, "%X %Z");
+}