Time.cpp

/**
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0.
 */
/*
  This is free and unencumbered software released into the public domain.

  Anyone is free to copy, modify, publish, use, compile, sell, or
  distribute this software, either in source code form or as a compiled
  binary, for any purpose, commercial or non-commercial, and by any
  means.

  In jurisdictions that recognize copyright laws, the author or authors
  of this software dedicate any and all copyright interest in the
  software to the public domain. We make this dedication for the benefit
  of the public at large and to the detriment of our heirs and
  successors. We intend this dedication to be an overt act of
  relinquishment in perpetuity of all present and future rights to this
  software under copyright law.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  OTHER DEALINGS IN THE SOFTWARE.

  For more information, please refer to <https://unlicense.org>
  <https://github.com/lzsiga/timegm/blob/main/aix-timegm.c>

  Modified the above code to align with C++ constructs.
*/

#include <aws/core/platform/Time.h>

#include <time.h>

namespace Aws
{
namespace Time
{
namespace
{
    const Aws::Array<Aws::Array<int, 12>, 2> msum{{
        {{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334}},       /* normal years */
        {{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335}}        /* leap years */
    }};
    const Aws::Array<Aws::Array<int, 12>, 2> msummlen{{
        {{ 31, 28, 31, 30,  31,  30,  31,  31,  30,  31,  30, 31}},
        {{ 31, 29, 31, 30,  31,  30,  31,  31,  30,  31,  30, 31}}
    }};

    const int tmstr_year = 1900;   /* base of 'tm_year' in 'struct tm' */
    const int epoch_year = 1970;   /* unix timestamp epoch */
    const int base_year = -9999;   /* start of a 400-year period: used to be 1601,
                                      but this allows larger range (in 64 bit)
                                      mind you, this is proleptic Gregorian */
}

time_t TimeGM(struct tm* const t)
{
    int year, ytmp, dtmp, ytmpe, dtmpe;
    int isleapyear;
    long long ret_val;

    if (!t){
        errno = EINVAL;
        return (time_t)-1;
    }

    year = t->tm_year + tmstr_year;
    isleapyear= (year%4==0) - (year%100==0) + (year%400==0);

    if (year<-9999    || year>9999  ||
        t->tm_mon<0  || t->tm_mon>11 ||
        t->tm_mday<1 || t->tm_mday>msummlen[isleapyear][t->tm_mon] ||
        t->tm_hour<0 || t->tm_hour>23 ||
        t->tm_min<0  || t->tm_min>59 ||
        t->tm_sec<0  || t->tm_sec>59) {

        errno = EINVAL;
        return (time_t)-1;
    }
/* days between 'current year' and 'epoch_year' has to be calculated
   in three steps: */

/* 1. days between current year and 'base_year' */
    ytmp = year - base_year;
    dtmp = ytmp*365 + ytmp/4 - ytmp/100 + ytmp/400;

/* 2. days between 'epoch year' and 'base_year' */
    ytmpe = epoch_year - base_year;
    dtmpe = ytmpe*365 + ytmpe/4 - ytmpe/100 + ytmpe/400;

/* 3. days between 'current year' and 'epoch_year' */
    ret_val  = dtmp - dtmpe;

    ret_val += msum[isleapyear][t->tm_mon];
    ret_val += t->tm_mday-1;

    t->tm_wday = (ret_val+4)%7;/* 0..6=Sun..Sat; adding 4 to adjust 1970.01.01.=Thursday; */
    if (t->tm_wday<0) t->tm_wday += 7;
    t->tm_yday = msum[isleapyear][t->tm_mon] + t->tm_mday-1;
    t->tm_isdst= 0;

    ret_val  = ret_val*24 + t->tm_hour;
    ret_val  = ret_val*60 + t->tm_min;
    ret_val  = ret_val*60 + t->tm_sec;

#if LONG_MAX == 2147483647L
    if (ret_val<LONG_MIN || ret_val>LONG_MAX) {
        errno = EOVERFLOW;
        return (time_t)-1;
    }
#endif

    return (time_t)ret_val;
}

void LocalTime(tm* t, std::time_t time)
{
    localtime_r(&time, t);
}

void GMTime(tm* t, std::time_t time)
{
    gmtime_r(&time, t);
}

} // namespace Time
} // namespace Aws