From 1cddaea7aeca441b733c31990a3f139dd2d346f6 Mon Sep 17 00:00:00 2001 From: Laine Stump Date: Sat, 24 May 2014 08:21:26 -0600 Subject: [PATCH] util: new function virTimeLocalOffsetFromUTC Since there isn't a single libc API to get this value, this patch supplies one which gets the value by grabbing current time, then converting that into a struct tm with gmtime_r(), then back to a time_t using mktime. The returned value is the difference between UTC and localtime in seconds. If localtime is ahead of UTC (east) the offset will be a positive number, and if localtime is behind UTC (west) the offset will be negative. This function should be POSIX-compliant, and is threadsafe, but not async signal safe. If it was ever necessary to know this value in a child process, we could cache it with a one-time init function when libvirtd starts, then just supply the cached value, but that complexity isn't needed for current usage; that would also have the problem that it might not be accurate after a local daylight savings boundary. (If it weren't for DST, we could simply replace this entire function with "-timezone"; timezone contains the offset of the current timezone (negated from what we want) but doesn't account for DST. And in spite of being guaranteed by POSIX, it isn't available on older versions of mingw.) Signed-off-by: Eric Blake --- src/libvirt_private.syms | 1 + src/util/virtime.c | 45 ++++++++++++++++++++++++++++++- src/util/virtime.h | 5 ++-- tests/virtimetest.c | 58 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 106 insertions(+), 3 deletions(-) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index c3332c9b2c..cb635cd5e0 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -1984,6 +1984,7 @@ virTimeFieldsNow; virTimeFieldsNowRaw; virTimeFieldsThen; virTimeFieldsThenRaw; +virTimeLocalOffsetFromUTC; virTimeMillisNow; virTimeMillisNowRaw; virTimeStringNow; diff --git a/src/util/virtime.c b/src/util/virtime.c index caa4e241f6..3a56400fe2 100644 --- a/src/util/virtime.c +++ b/src/util/virtime.c @@ -1,7 +1,7 @@ /* * virtime.c: Time handling functions * - * Copyright (C) 2006-2012 Red Hat, Inc. + * Copyright (C) 2006-2014 Red Hat, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -344,3 +344,46 @@ char *virTimeStringThen(unsigned long long when) return ret; } + +/** + * virTimeLocalOffsetFromUTC: + * + * This function is threadsafe, but is *not* async signal safe (due to + * localtime_r()). + * + * @offset: pointer to time_t that will be set to the difference + * between localtime and UTC in seconds (east of UTC is a + * positive number, and west of UTC is a negative number. + * + * Returns 0 on success, -1 on error with error reported + */ +int +virTimeLocalOffsetFromUTC(long *offset) +{ + struct tm gmtimeinfo; + time_t current, utc; + + /* time() gives seconds since Epoch in current timezone */ + if ((current = time(NULL)) == (time_t)-1) { + virReportSystemError(errno, "%s", + _("failed to get current system time")); + return -1; + } + + /* treat current as if it were in UTC */ + if (!gmtime_r(¤t, &gmtimeinfo)) { + virReportSystemError(errno, "%s", + _("gmtime_r failed")); + return -1; + } + + /* mktime() also obeys current timezone rules */ + if ((utc = mktime(&gmtimeinfo)) == (time_t)-1) { + virReportSystemError(errno, "%s", + _("mktime failed")); + return -1; + } + + *offset = current - utc; + return 0; +} diff --git a/src/util/virtime.h b/src/util/virtime.h index a5bd652602..25332dba93 100644 --- a/src/util/virtime.h +++ b/src/util/virtime.h @@ -1,7 +1,7 @@ /* * virtime.h: Time handling functions * - * Copyright (C) 2006-2011 Red Hat, Inc. + * Copyright (C) 2006-2011, 2014 Red Hat, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -50,7 +50,6 @@ int virTimeStringNowRaw(char *buf) int virTimeStringThenRaw(unsigned long long when, char *buf) ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK; - /* These APIs are *not* async signal safe and return -1, * raising a libvirt error on failure */ @@ -63,5 +62,7 @@ int virTimeFieldsThen(unsigned long long when, struct tm *fields) char *virTimeStringNow(void); char *virTimeStringThen(unsigned long long when); +int virTimeLocalOffsetFromUTC(long *offset) + ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK; #endif diff --git a/tests/virtimetest.c b/tests/virtimetest.c index 73a3c3ed5c..bf27682533 100644 --- a/tests/virtimetest.c +++ b/tests/virtimetest.c @@ -72,6 +72,35 @@ static int testTimeFields(const void *args) } +typedef struct { + const char *zone; + long offset; +} testTimeLocalOffsetData; + +static int +testTimeLocalOffset(const void *args) +{ + const testTimeLocalOffsetData *data = args; + long actual; + + if (setenv("TZ", data->zone, 1) < 0) { + perror("setenv"); + return -1; + } + tzset(); + + if (virTimeLocalOffsetFromUTC(&actual) < 0) { + return -1; + } + + if (data->offset != actual) { + VIR_DEBUG("Expect Offset %ld got %ld\n", + data->offset, actual); + return -1; + } + return 0; +} + static int mymain(void) { @@ -119,6 +148,35 @@ mymain(void) TEST_FIELDS(2147483648000ull, 2038, 1, 19, 3, 14, 8); +#define TEST_LOCALOFFSET(tz, off) \ + do { \ + testTimeLocalOffsetData data = { \ + .zone = tz, \ + .offset = off, \ + }; \ + if (virtTestRun("Test localtime offset for " #tz, \ + testTimeLocalOffset, &data) < 0) \ + ret = -1; \ + } while (0) + + TEST_LOCALOFFSET("VIR00:30", -30 * 60); + TEST_LOCALOFFSET("VIR01:30", -90 * 60); + TEST_LOCALOFFSET("UTC", 0); + TEST_LOCALOFFSET("VIR-00:30", 30 * 60); + TEST_LOCALOFFSET("VIR-01:30", 90 * 60); +#if __TEST_DST + /* test DST processing with timezones that always + * have DST in effect; what's more, cover a zone with + * with an unusual DST different than a usual one hour + */ + /* NB: These tests fail at certain times of the day, so + * must be disabled until we figure out why + */ + TEST_LOCALOFFSET("VIR-00:30VID,0,365", 90 * 60); + TEST_LOCALOFFSET("VIR-02:30VID,0,365", 210 * 60); + TEST_LOCALOFFSET("VIR-02:30VID-04:30,0,365", 270 * 60); +#endif + return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE; }