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223 lines
7.1 KiB
C
223 lines
7.1 KiB
C
/*
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* COPYRIGHT: See COPYING in the top level directory
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* PROJECT: ReactOS system libraries
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* FILE: lib/msvcrt/time/time.c
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* PURPOSE: Get system time
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* PROGRAMER: Ariadne
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* UPDATE HISTORY:
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* 28/12/98: Created
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*/
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/*
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* DOS file system functions
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*
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* Copyright 1993 Erik Bos
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* Copyright 1996 Alexandre Julliard
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*/
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#include <precomp.h>
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VOID STDCALL GetSystemTimeAsFileTime(LPFILETIME lpSystemTimeAsFileTime);
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/*
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* @implemented
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*/
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time_t time(time_t* t)
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{
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FILETIME SystemTime;
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DWORD Remainder;
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time_t tt;
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GetSystemTimeAsFileTime(&SystemTime);
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tt = FileTimeToUnixTime(&SystemTime,&Remainder);
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if (t)
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*t = tt;
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return tt;
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}
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/***********************************************************************
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* DOSFS_UnixTimeToFileTime
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*
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* Convert a Unix time to FILETIME format.
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* The FILETIME structure is a 64-bit value representing the number of
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* 100-nanosecond intervals since January 1, 1601, 0:00.
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* 'remainder' is the nonnegative number of 100-ns intervals
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* corresponding to the time fraction smaller than 1 second that
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* couldn't be stored in the time_t value.
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*/
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void UnixTimeToFileTime( time_t unix_time, FILETIME *filetime,
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DWORD remainder )
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{
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/* NOTES:
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CONSTANTS:
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The time difference between 1 January 1601, 00:00:00 and
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1 January 1970, 00:00:00 is 369 years, plus the leap years
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from 1604 to 1968, excluding 1700, 1800, 1900.
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This makes (1968 - 1600) / 4 - 3 = 89 leap days, and a total
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of 134774 days.
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Any day in that period had 24 * 60 * 60 = 86400 seconds.
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The time difference is 134774 * 86400 * 10000000, which can be written
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116444736000000000
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27111902 * 2^32 + 3577643008
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413 * 2^48 + 45534 * 2^32 + 54590 * 2^16 + 32768
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If you find that these constants are buggy, please change them in all
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instances in both conversion functions.
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VERSIONS:
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There are two versions, one of them uses long long variables and
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is presumably faster but not ISO C. The other one uses standard C
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data types and operations but relies on the assumption that negative
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numbers are stored as 2's complement (-1 is 0xffff....). If this
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assumption is violated, dates before 1970 will not convert correctly.
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This should however work on any reasonable architecture where WINE
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will run.
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DETAILS:
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Take care not to remove the casts. I have tested these functions
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(in both versions) for a lot of numbers. I would be interested in
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results on other compilers than GCC.
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The operations have been designed to account for the possibility
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of 64-bit time_t in future UNICES. Even the versions without
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internal long long numbers will work if time_t only is 64 bit.
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A 32-bit shift, which was necessary for that operation, turned out
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not to work correctly in GCC, besides giving the warning. So I
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used a double 16-bit shift instead. Numbers are in the ISO version
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represented by three limbs, the most significant with 32 bit, the
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other two with 16 bit each.
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As the modulo-operator % is not well-defined for negative numbers,
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negative divisors have been avoided in DOSFS_FileTimeToUnixTime.
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There might be quicker ways to do this in C. Certainly so in
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assembler.
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Claus Fischer, fischer@iue.tuwien.ac.at
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*/
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unsigned long a0; /* 16 bit, low bits */
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unsigned long a1; /* 16 bit, medium bits */
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unsigned long a2; /* 32 bit, high bits */
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/* Copy the unix time to a2/a1/a0 */
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a0 = unix_time & 0xffff;
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a1 = (unix_time >> 16) & 0xffff;
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/* This is obsolete if unix_time is only 32 bits, but it does not hurt.
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Do not replace this by >> 32, it gives a compiler warning and it does
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not work. */
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a2 = (unix_time >= 0 ? (unix_time >> 16) >> 16 :
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~((~unix_time >> 16) >> 16));
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/* Multiply a by 10000000 (a = a2/a1/a0)
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Split the factor into 10000 * 1000 which are both less than 0xffff. */
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a0 *= 10000;
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a1 = a1 * 10000 + (a0 >> 16);
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a2 = a2 * 10000 + (a1 >> 16);
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a0 &= 0xffff;
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a1 &= 0xffff;
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a0 *= 1000;
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a1 = a1 * 1000 + (a0 >> 16);
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a2 = a2 * 1000 + (a1 >> 16);
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a0 &= 0xffff;
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a1 &= 0xffff;
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/* Add the time difference and the remainder */
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a0 += 32768 + (remainder & 0xffff);
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a1 += 54590 + (remainder >> 16 ) + (a0 >> 16);
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a2 += 27111902 + (a1 >> 16);
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a0 &= 0xffff;
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a1 &= 0xffff;
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/* Set filetime */
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filetime->dwLowDateTime = (a1 << 16) + a0;
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filetime->dwHighDateTime = a2;
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}
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/***********************************************************************
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* DOSFS_FileTimeToUnixTime
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*
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* Convert a FILETIME format to Unix time.
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* If not NULL, 'remainder' contains the fractional part of the filetime,
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* in the range of [0..9999999] (even if time_t is negative).
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*/
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time_t FileTimeToUnixTime( const FILETIME *filetime, DWORD *remainder )
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{
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/* Read the comment in the function DOSFS_UnixTimeToFileTime. */
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unsigned long a0; /* 16 bit, low bits */
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unsigned long a1; /* 16 bit, medium bits */
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unsigned long a2; /* 32 bit, high bits */
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unsigned long r; /* remainder of division */
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unsigned int carry; /* carry bit for subtraction */
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int negative; /* whether a represents a negative value */
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/* Copy the time values to a2/a1/a0 */
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a2 = (unsigned long)filetime->dwHighDateTime;
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a1 = ((unsigned long)filetime->dwLowDateTime ) >> 16;
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a0 = ((unsigned long)filetime->dwLowDateTime ) & 0xffff;
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/* Subtract the time difference */
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if (a0 >= 32768 ) a0 -= 32768 , carry = 0;
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else a0 += (1 << 16) - 32768 , carry = 1;
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if (a1 >= 54590 + carry) a1 -= 54590 + carry, carry = 0;
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else a1 += (1 << 16) - 54590 - carry, carry = 1;
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a2 -= 27111902 + carry;
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/* If a is negative, replace a by (-1-a) */
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negative = (a2 >= ((unsigned long)1) << 31);
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if (negative)
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{
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/* Set a to -a - 1 (a is a2/a1/a0) */
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a0 = 0xffff - a0;
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a1 = 0xffff - a1;
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a2 = ~a2;
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}
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/* Divide a by 10000000 (a = a2/a1/a0), put the rest into r.
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Split the divisor into 10000 * 1000 which are both less than 0xffff. */
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a1 += (a2 % 10000) << 16;
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a2 /= 10000;
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a0 += (a1 % 10000) << 16;
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a1 /= 10000;
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r = a0 % 10000;
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a0 /= 10000;
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a1 += (a2 % 1000) << 16;
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a2 /= 1000;
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a0 += (a1 % 1000) << 16;
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a1 /= 1000;
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r += (a0 % 1000) * 10000;
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a0 /= 1000;
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/* If a was negative, replace a by (-1-a) and r by (9999999 - r) */
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if (negative)
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{
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/* Set a to -a - 1 (a is a2/a1/a0) */
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a0 = 0xffff - a0;
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a1 = 0xffff - a1;
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a2 = ~a2;
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r = 9999999 - r;
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}
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if (remainder) *remainder = r;
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/* Do not replace this by << 32, it gives a compiler warning and it does
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not work. */
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return ((((time_t)a2) << 16) << 16) + (a1 << 16) + a0;
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}
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