帮Windows Mobile实现gmtime，localtime，mktime和strftime

帮Windows Mobile实现gmtime，localtime，mktime和strftime

偶尔发现Windows Mobile连一些标准的C语言库函数都没有实现，而这些函数的在头文件中的声明却是有的，实在有些不方便，上网一搜索，才知道原来Windows CE也没实现，而Windows Mobile这方面照搬了Windows CE的，如果真要用这些函数，只能自己来写了，我写了这几个：gmtime，localtime，mktime，strftime，其中用到了Variant Time这个类型，它实质上是个浮点数，浮点数就意味着有时候不太精确，我实践下来确实发觉有时候会有1秒钟的偏差，在计算time_t的时候，不过暂时懒得去管它了。使用方法很简单，把代码复制一份，保存到一个叫“TimeFunctions.cpp”的文件中去，然后在你的project中添加这个文件即可。

#include  < time.h >
#include  < windows.h >

static  BOOL IsLeapYear(WORD nYear)
{
     return   ! (nYear  %   4 )  &&  (nYear  %   100 )  ||   ! (nYear  %   400 );
}

static   int  DaysFromJan1st(WORD wYear, WORD wMonth)
{
     static  WORD monthday[]  =  { 0 ,  31 ,  59 ,  90 ,  120 ,  151 ,  181 ,  212 ,  243 ,  273 ,  304 ,  334 };
     return  monthday[wMonth  -   1 ]  +  (IsLeapYear(wYear)  &&  wMonth  >   2   ?   1  :  0 );
}

static  tm *  GetTmByVariant(DOUBLE dTime)
{
    SYSTEMTIME stResult;
    VariantTimeToSystemTime(dTime,  & stResult);
     static  tm s_tm;
    s_tm.tm_sec  =  stResult.wSecond;
    s_tm.tm_min  =  stResult.wMinute;
    s_tm.tm_hour  =  stResult.wHour;
    s_tm.tm_mday  =  stResult.wDay;
    s_tm.tm_mon  =  stResult.wMonth - 1 ;
    s_tm.tm_year  =  stResult.wYear - 1900 ;
    s_tm.tm_wday  =  stResult.wDayOfWeek;
    s_tm.tm_yday  =  DaysFromJan1st(stResult.wYear, stResult.wMonth);
    s_tm.tm_isdst  =   0 ;
     return   & s_tm;
}

const  DOUBLE VT_SECOND_1970  =   2209161600.0 ;
const  DOUBLE SECONDS_IN_ONE_DAY  =   86400 ;

tm *  __cdecl gmtime( const  time_t *  pTT)
{
     return  GetTmByVariant((VT_SECOND_1970  +  ( * pTT)) / SECONDS_IN_ONE_DAY);
}

tm *  __cdecl localtime( const  time_t *  pTT)
{
    TIME_ZONE_INFORMATION tz;
    GetTimeZoneInformation( & tz);
     return  GetTmByVariant((VT_SECOND_1970  +  ( * pTT)  -  tz.Bias * 60 ) / SECONDS_IN_ONE_DAY);
}

time_t __cdecl mktime(tm *  pTM)
{
    SYSTEMTIME stToConvert  =  {
        pTM -> tm_year + 1900 ,
        pTM -> tm_mon + 1 ,
        pTM -> tm_wday,
        pTM -> tm_mday,
        pTM -> tm_hour,
        pTM -> tm_min,
        pTM -> tm_sec,
         0 };
    DOUBLE dToCal;
    SystemTimeToVariantTime( & stToConvert,  & dToCal);
     return  (time_t)(dToCal * SECONDS_IN_ONE_DAY  -  VT_SECOND_1970);
}

static   void  strfmt( char   * str,  const   char   * fmt, )
{
     int  ival, ilen;
     char   * sval;
     static   int  pow[ 5 ]  =  {  1 ,  10 ,  100 ,  1000 ,  10000  };
    va_list vp;

    va_start(vp, fmt);
     while  ( * fmt)
    {
         if  ( * fmt ++   ==   ' % ' )
        {
            ilen  =   * fmt ++   -   ' 0 ' ;
             if  (ilen  ==   0 )                 //  zero means string arg
            {
                sval  =  va_arg(vp,  char * );
                 while  ( * sval)
                     * str ++   =   * sval ++ ;
            }
             else                            //  always leading zeros
            {
                ival  =  va_arg(vp,  int );
                 while  (ilen)
                {
                    ival  %=  pow[ilen -- ];
                     * str ++   =  ( char )( ' 0 '   +  ival  /  pow[ilen]);
                }
            }
        }
         else    * str ++   =  fmt[ - 1 ];
    }
     * str  =   ' \0 ' ;
    va_end(vp);
}

#define  DAYSPERWEEK 7

size_t __cdecl strftime( char *  pTimeStr, size_t stStrLen,  const   char *  pFmt,  const  tm *  pTM)
{
     static   char   * aday[]  =  { " Sun " ,  " Mon " ,  " Tue " ,  " Wed " ,  " Thu " ,  " Fri " ,  " Sat " };
     static   char   * day[]  =  { " Sunday " ,  " Monday " ,  " Tuesday " ,  " Wednesday " ,  " Thursday " ,  " Friday " ,  " Saturday " };
     static   char   * amonth[]  =  { " Jan " ,  " Feb " ,  " Mar " ,  " Apr " ,  " May " ,  " Jun " ,  " Jul " ,  " Aug " ,  " Sep " ,  " Oct " ,  " Nov " ,  " Dec " };
     static   char   * month[]  =  { " January " ,  " February " ,  " March " ,  " April " ,  " May " ,  " June " ,  " July " ,  " August " ,  " September " ,  " October " ,  " November " ,  " December " };

     int             w;
     char          * p,  * q,  * r;
     static   char     buf[ 26 ];

    p  =  pTimeStr;
    q  =  pTimeStr  +  stStrLen  -   1 ;
     while  (( * pFmt  !=   ' \0 ' ))
    {
         if  ( * pFmt ++   ==   ' % ' )
        {
            r  =  buf;
             switch  ( * pFmt ++ )
            {
             case   ' % '  :
                r  =   " % " ;
                 break ;

             case   ' a '  :
                r  =  aday[pTM -> tm_wday];
                 break ;

             case   ' A '  :
                r  =  day[pTM -> tm_wday];
                 break ;

             case   ' b '  :
                r  =  amonth[pTM -> tm_mon];
                 break ;

             case   ' B '  :
                r  =  month[pTM -> tm_mon];
                 break ;

             case   ' c '  :
                strfmt(r,  " %0 %0 %2 %2:%2:%2 %4 " ,
                    aday[pTM -> tm_wday], amonth[pTM -> tm_mon],
                    pTM -> tm_mday,pTM -> tm_hour, pTM -> tm_min,
                    pTM -> tm_sec, pTM -> tm_year + 1900 );
                 break ;

             case   ' d '  :
                strfmt(r, " %2 " ,pTM -> tm_mday);
                 break ;

             case   ' H '  :
                strfmt(r, " %2 " ,pTM -> tm_hour);
                 break ;

             case   ' I '  :
                strfmt(r, " %2 " ,(pTM -> tm_hour % 12 ) ? pTM -> tm_hour % 12 : 12 );
                 break ;

             case   ' j '  :
                strfmt(r, " %3 " ,pTM -> tm_yday + 1 );
                 break ;

             case   ' m '  :
                strfmt(r, " %2 " ,pTM -> tm_mon + 1 );
                 break ;

             case   ' M '  :
                strfmt(r, " %2 " ,pTM -> tm_min);
                 break ;

             case   ' p '  :
                r  =  (pTM -> tm_hour > 11 ) ? " PM " : " AM " ;
                 break ;

             case   ' S '  :
                strfmt(r, " %2 " ,pTM -> tm_sec);
                 break ;

             case   ' U '  :
                w  =  pTM -> tm_yday / 7 ;
                 if  (pTM -> tm_yday % 7   >  pTM -> tm_wday)
                    w ++ ;
                strfmt(r,  " %2 " , w);
                 break ;

             case   ' W '  :
                w  =  (pTM -> tm_yday  +  DAYSPERWEEK  -
                    (pTM -> tm_wday  ?
                    (pTM -> tm_wday  -   1 ) :
                (DAYSPERWEEK  -   1 )))  /  DAYSPERWEEK;
                strfmt(r,  " %2 " , w);
                 break ;

             case   ' w '  :
                strfmt(r, " %1 " ,pTM -> tm_wday);
                 break ;

             case   ' x '  :
                strfmt(r,  " %2/%2/%2 " , pTM -> tm_mon  +   1 ,
                    pTM -> tm_mday, pTM -> tm_year + 1900 );
                 break ;

             case   ' X '  :
                strfmt(r,  " %2:%2:%2 " , pTM -> tm_hour,
                    pTM -> tm_min, pTM -> tm_sec);
                 break ;

             case   ' y '  :
                strfmt(r, " %2 " ,pTM -> tm_year % 100 );
                 break ;

             case   ' Y '  :
                strfmt(r, " %4 " ,pTM -> tm_year + 1900 );
                 break ;

             case   ' Z '  :
//                 r = (pTM->tm_isdst && tz_name[1][0])?tz_name[1]:tz_name[0];
                 break ;

             default :
                buf[ 0 ]  =   ' % ' ;         //  reconstruct the format
                buf[ 1 ]  =  pFmt[ - 1 ];
                buf[ 2 ]  =   ' \0 ' ;
                 if  (buf[ 1 ]  ==   0 )
                    pFmt -- ;             //  back up if at end of string
            }
             while  ( * r)
            {
                 if  (p  ==  q)
                {
                     * q  =   ' \0 ' ;
                     return   0 ;
                }
                 * p ++   =   * r ++ ;
            }
        }
         else
        {
             if  (p  ==  q)
            {
                 * q  =   ' \0 ' ;
                 return   0 ;
            }
             * p ++   =  pFmt[ - 1 ];
        }
    }
     * p  =   ' \0 ' ;
     return  p  -  pTimeStr;
}