reactos/sdk/lib/crt/math/arm/__rt_div.c

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/*
* COPYRIGHT: BSD - See COPYING.ARM in the top level directory
* PROJECT: ReactOS CRT library
* FILE: lib/sdk/crt/math/arm/__rt_div.c
* PURPOSE: Implementation of __rt_udiv
* PROGRAMMER: Timo Kreuzer
* REFERENCE: http://research.microsoft.com/en-us/um/redmond/projects/invisible/src/crt/md/arm/_div10.s.htm
* http://research.microsoft.com/en-us/um/redmond/projects/invisible/src/crt/md/arm/_udiv.c.htm
*/
typedef struct _ARM_UDIVRESULT
{
unsigned int quotient; /* to be returned in R0 */
unsigned int modulus; /* to be returned in R1 */
} ARM_UDIVRESULT;
__forceinline
void
__brkdiv0(void)
{
__emit(0xDEF9);
}
__forceinline
void
__rt_udiv_internal(
ARM_UDIVRESULT *result,
unsigned int divisor,
unsigned int dividend)
{
unsigned int shift;
unsigned int mask;
unsigned int quotient;
if (divisor == 0)
{
/* Raise divide by zero error */
__brkdiv0();
}
if (divisor > dividend)
{
result->quotient = 0;
result->modulus = divisor;
return;
}
/* Get the difference in count of leading zeros between dividend and divisor */
shift = _CountLeadingZeros(divisor);
shift -= _CountLeadingZeros(dividend);
/* Shift the divisor to the left, so that it's highest bit is the same
as the highest bit of the dividend */
divisor <<= shift;
mask = 1 << shift;
quotient = 0;
do
{
if (dividend >= divisor)
{
quotient |= mask;
dividend -= divisor;
}
divisor >>= 1;
mask >>= 1;
}
while (mask);
result->quotient = quotient;
result->modulus = dividend;
return;
}
ARM_UDIVRESULT
__rt_udiv(
unsigned int divisor,
unsigned int dividend)
{
ARM_UDIVRESULT result;
__rt_udiv_internal(&result, divisor, dividend);
return result;
}
typedef struct _ARM_SDIVRESULT
{
int quotient; /* to be returned in R0 */
int modulus; /* to be returned in R1 */
} ARM_SDIVRESULT;
ARM_SDIVRESULT
__rt_sdiv(
int divisor,
int dividend)
{
ARM_SDIVRESULT result;
int divisor_sign, dividend_sign;
dividend_sign = divisor & 0x80000000;
if (dividend_sign)
{
dividend = -dividend;
}
divisor_sign = divisor & 0x80000000;
if (divisor_sign)
{
divisor = -divisor;
}
__rt_udiv_internal((ARM_UDIVRESULT*)&result, divisor, dividend);
if (dividend_sign ^ divisor_sign)
{
result.quotient = -result.quotient;
}
if (dividend_sign)
{
result.modulus = -result.modulus;
}
return result;
}