reactos/lib/rtl/largeint.c

/* COPYRIGHT:       See COPYING in the top level directory
 * PROJECT:         ReactOS system libraries
 * FILE:            lib/rtl/largeint.c
 * PURPOSE:         Large integer operations
 * PROGRAMMERS:
 */

/* INCLUDES *****************************************************************/

#include <rtl.h>

#define NDEBUG
#include <debug.h>

/* FUNCTIONS *****************************************************************/

/* HACK: ld is too stupid to understand that we need the functions
   when we export them, so we force it to be linked this way. */
#ifdef __GNUC__
#undef RtlUshortByteSwap
USHORT FASTCALL RtlUshortByteSwap(USHORT Source);
PVOID Dummy = RtlUshortByteSwap;
#endif

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlConvertLongToLargeInteger (
   LONG SignedInteger
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = SignedInteger;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlConvertUlongToLargeInteger (
   ULONG UnsignedInteger
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = UnsignedInteger;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlEnlargedIntegerMultiply (
   LONG Multiplicand,
   LONG Multiplier
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = (LONGLONG) Multiplicand * Multiplier;

   return RC;
}

/*
 * @implemented
 */
ULONG
NTAPI
RtlEnlargedUnsignedDivide (
   ULARGE_INTEGER Dividend,
   ULONG  Divisor,
   PULONG  Remainder
)
{
   if (Remainder)
      *Remainder = (ULONG)(Dividend.QuadPart % Divisor);

   return (ULONG)(Dividend.QuadPart / Divisor);
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlEnlargedUnsignedMultiply (
   ULONG Multiplicand,
   ULONG Multiplier
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = (ULONGLONG) Multiplicand * Multiplier;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlExtendedIntegerMultiply (
   LARGE_INTEGER Multiplicand,
   LONG  Multiplier
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = Multiplicand.QuadPart * Multiplier;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlExtendedLargeIntegerDivide (
   LARGE_INTEGER Dividend,
   ULONG  Divisor,
   PULONG  Remainder
)
{
   LARGE_INTEGER RC;

   if (Remainder)
      *Remainder = (ULONG)(Dividend.QuadPart % Divisor);

   RC.QuadPart = Dividend.QuadPart / Divisor;

   return RC;
}


/******************************************************************************
 * RtlExtendedMagicDivide
 *
 * Allows replacing a division by a longlong constant with a multiplication by
 * the inverse constant.
 *
 * RETURNS
 *  (Dividend * MagicDivisor) >> (64 + ShiftCount)
 *
 * NOTES
 *  If the divisor of a division is constant, the constants MagicDivisor and
 *  shift must be chosen such that
 *  MagicDivisor = 2^(64 + ShiftCount) / Divisor.
 *
 *  Then we have RtlExtendedMagicDivide(Dividend,MagicDivisor,ShiftCount) ==
 *  Dividend * MagicDivisor / 2^(64 + ShiftCount) == Dividend / Divisor.
 *
 *  The Parameter MagicDivisor although defined as LONGLONG is used as
 *  ULONGLONG.
 */

#define LOWER_32(A) ((A) & 0xffffffff)
#define UPPER_32(A) ((A) >> 32)

/*
 * @implemented
 */
LARGE_INTEGER NTAPI
RtlExtendedMagicDivide (LARGE_INTEGER Dividend,
                        LARGE_INTEGER MagicDivisor,
                        CCHAR ShiftCount)
{
   ULONGLONG dividend_high;
   ULONGLONG dividend_low;
   ULONGLONG inverse_divisor_high;
   ULONGLONG inverse_divisor_low;
   ULONGLONG ah_bl;
   ULONGLONG al_bh;
   LARGE_INTEGER result;
   BOOLEAN positive;

   if (Dividend.QuadPart < 0)
   {
      dividend_high = UPPER_32((ULONGLONG) -Dividend.QuadPart);
      dividend_low =  LOWER_32((ULONGLONG) -Dividend.QuadPart);
      positive = FALSE;
   }
   else
   {
      dividend_high = UPPER_32((ULONGLONG) Dividend.QuadPart);
      dividend_low =  LOWER_32((ULONGLONG) Dividend.QuadPart);
      positive = TRUE;
   }
   inverse_divisor_high = UPPER_32((ULONGLONG) MagicDivisor.QuadPart);
   inverse_divisor_low =  LOWER_32((ULONGLONG) MagicDivisor.QuadPart);

   ah_bl = dividend_high * inverse_divisor_low;
   al_bh = dividend_low * inverse_divisor_high;

   result.QuadPart =
      (LONGLONG) ((dividend_high * inverse_divisor_high +
                   UPPER_32(ah_bl) +
                   UPPER_32(al_bh) +
                   UPPER_32(LOWER_32(ah_bl) + LOWER_32(al_bh) +
                            UPPER_32(dividend_low * inverse_divisor_low))) >> ShiftCount);
   if (!positive)
   {
      result.QuadPart = -result.QuadPart;
   }

   return result;
}


/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlLargeIntegerAdd (
   LARGE_INTEGER Addend1,
   LARGE_INTEGER Addend2
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = Addend1.QuadPart + Addend2.QuadPart;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlLargeIntegerArithmeticShift (
   LARGE_INTEGER LargeInteger,
   CCHAR  ShiftCount
)
{
   LARGE_INTEGER RC;
   CHAR Shift;

   Shift = ShiftCount % 64;

   if (Shift < 32)
   {
      RC.QuadPart = LargeInteger.QuadPart >> Shift;
   }
   else
   {
      /* copy the sign bit */
      RC.u.HighPart = (LargeInteger.u.HighPart & 0x80000000);
      RC.u.LowPart = LargeInteger.u.HighPart >> Shift;
   }

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlLargeIntegerDivide (
   LARGE_INTEGER Dividend,
   LARGE_INTEGER Divisor,
   PLARGE_INTEGER Remainder
)
{
   LARGE_INTEGER RC;

   if (Remainder)
      Remainder->QuadPart = Dividend.QuadPart % Divisor.QuadPart;

   RC.QuadPart = Dividend.QuadPart / Divisor.QuadPart;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlLargeIntegerNegate (
   LARGE_INTEGER Subtrahend
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = - Subtrahend.QuadPart;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlLargeIntegerShiftLeft (
   LARGE_INTEGER LargeInteger,
   CCHAR  ShiftCount
)
{
   LARGE_INTEGER RC;
   CCHAR Shift;

   Shift = ShiftCount % 64;
   RC.QuadPart = LargeInteger.QuadPart << Shift;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlLargeIntegerShiftRight (
   LARGE_INTEGER LargeInteger,
   CCHAR  ShiftCount
)
{
   LARGE_INTEGER RC;
   CCHAR Shift;

   Shift = ShiftCount % 64;
   RC.QuadPart = LargeInteger.QuadPart >> Shift;

   return RC;
}

/*
 * @implemented
 */
LARGE_INTEGER
NTAPI
RtlLargeIntegerSubtract (
   LARGE_INTEGER Minuend,
   LARGE_INTEGER Subtrahend
)
{
   LARGE_INTEGER RC;

   RC.QuadPart = Minuend.QuadPart - Subtrahend.QuadPart;

   return RC;
}

/* EOF */