Celestia

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// tzutil.cpp
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//
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// Copyright (C) 2001, Chris Laurel <claurel@shatters.net>
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//
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// Miscellaneous useful functions.
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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#ifdef _WIN32
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#include <windows.h>
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#include "winutil.h"
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#include "gettext.h"
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#include "logger.h"
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namespace util = celestia::util;
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#else
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// we need the C version of this header to get the POSIX function localtime_r
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#include <time.h>
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#endif
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#include "tzutil.h"
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bool GetTZInfo(std::string& tzName, int& dstBias)
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{
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#ifdef _WIN32
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    using celestia::util::GetLogger;
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    TIME_ZONE_INFORMATION tzi;
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    DWORD dst = GetTimeZoneInformation(&tzi);
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    if (dst == TIME_ZONE_ID_INVALID)
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        return false;
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    LONG bias = 0;
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    WCHAR* name = nullptr;
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    switch (dst)
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    {
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    case TIME_ZONE_ID_STANDARD:
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        bias = tzi.StandardBias;
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        name = tzi.StandardName;
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        break;
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    case TIME_ZONE_ID_DAYLIGHT:
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        bias = tzi.DaylightBias;
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        name = tzi.DaylightName;
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        break;
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    default:
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        GetLogger()->warn(_("Unknown value returned by GetTimeZoneInformation()\n"));
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        return false;
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    }
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    tzName = name == nullptr ? "   " : util::WideToUTF8(name);
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    dstBias = (tzi.Bias + bias) * -60;
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    return true;
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#else
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    tm result;
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    time_t curtime = time(nullptr); // required only to get TZ info
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    if (!localtime_r(&curtime, &result))
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        return false;
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    dstBias = result.tm_gmtoff;
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    tzName = result.tm_zone;
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    return true;
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#endif
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}
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