openmsx::DivModBySame Class Reference

Helper class to divide multiple times by the same number. More...

#include <DivModBySame.hh>

Public Member Functions
void	setDivisor (uint32_t divisor)
uint32_t	getDivisor () const
uint32_t	div (uint64_t dividend) const
uint32_t	divInC (uint64_t dividend) const
std::pair< uint32_t, uint32_t >	divMod (uint64_t dividend) const
uint32_t	mod (uint64_t dividend) const

Detailed Description

Helper class to divide multiple times by the same number.

Binary division can be performed by:

• multiplication by a magic number
• followed by an addition of a magic number
• followed by a right shift over some magic number of bits These magic constants only depend on the divisor, but they are quite expensive to calculate. However if you know you will divide many times by the same number this algorithm does make sense and can result in a big speedup, especially on CPUs which lack a hardware division instruction (like ARM).

If the divisor is a compile-time constant, it's even faster to use the DivModByConst utility class.

Definition at line 25 of file DivModBySame.hh.

Member Function Documentation

div()

uint32_t openmsx::DivModBySame::div ( uint64_t  dividend ) const

inline

Definition at line 31 of file DivModBySame.hh.

References divInC(), and t.

Referenced by divMod(), openmsx::DynamicClock::getTicksTill(), openmsx::DynamicClock::getTicksTill(), and openmsx::DynamicClock::getTicksTillUp().

divInC()

uint32_t openmsx::DivModBySame::divInC ( uint64_t  dividend ) const

inline

Definition at line 41 of file DivModBySame.hh.

Referenced by div().

divMod()

std::pair< uint32_t, uint32_t > openmsx::DivModBySame::divMod ( uint64_t  dividend ) const

inline

Definition at line 61 of file DivModBySame.hh.

References div().

Referenced by openmsx::DynamicClock::getTicksTillAsIntFloat(), and mod().

getDivisor()

uint32_t openmsx::DivModBySame::getDivisor ( ) const

inline

Definition at line 29 of file DivModBySame.hh.

mod()

uint32_t openmsx::DivModBySame::mod ( uint64_t  dividend ) const

inline

Definition at line 71 of file DivModBySame.hh.

References divMod().

Referenced by openmsx::DynamicClock::advance().

setDivisor()

void openmsx::DivModBySame::setDivisor

(

uint32_t

divisor

)

Definition at line 7 of file DivModBySame.cc.

References t.

Referenced by openmsx::DynamicClock::setPeriod().

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The documentation for this class was generated from the following files:

• DivModBySame.hh
• DivModBySame.cc