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decimal: Remove unnecessary allocation in bankers round chop (#2030) 

This is done by making the function mutative. A non-mutative variant
is created for functions that depend on it being non-mutative.
This commit is contained in:
Dev Ojha 2018-08-14 18:49:40 -07:00 committed by Rigel
parent 4b13529f2d
commit d37de06762
1 changed files with 10 additions and 7 deletions
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17
types/decimal.go
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@ -249,7 +249,7 @@ func (d Dec) ToLeftPaddedWithDecimals(totalDigits int8) string {
// TODO panic if negative or if totalDigits < len(initStr)???
// evaluate as an integer and return left padded string
func (d Dec) ToLeftPadded(totalDigits int8) string {
chopped := chopPrecisionAndRound(d.Int)
chopped := chopPrecisionAndRoundNonMutative(d.Int)
intStr := chopped.String()
fcode := `%0` + strconv.Itoa(int(totalDigits)) + `s`
return fmt.Sprintf(fcode, intStr)
@ -268,9 +268,7 @@ func (d Dec) ToLeftPadded(totalDigits int8) string {
// Remove a Precision amount of rightmost digits and perform bankers rounding
// on the remainder (gaussian rounding) on the digits which have been removed.
//
// TODO We should make this function mutate the input. The functions here
// don't need to allocate different memory for chopped after computing the
// result
// Mutates the input. Use the non-mutative version if that is undesired
func chopPrecisionAndRound(d *big.Int) *big.Int {
// remove the negative and add it back when returning
@ -283,7 +281,7 @@ func chopPrecisionAndRound(d *big.Int) *big.Int {
}
// get the trucated quotient and remainder
quo, rem := big.NewInt(0), big.NewInt(0)
quo, rem := d, big.NewInt(0)
quo, rem = quo.QuoRem(d, precisionReuse, rem)
if rem.Sign() == 0 { // remainder is zero
@ -304,9 +302,14 @@ func chopPrecisionAndRound(d *big.Int) *big.Int {
}
}
func chopPrecisionAndRoundNonMutative(d *big.Int) *big.Int {
tmp := new(big.Int).Set(d)
return chopPrecisionAndRound(tmp)
}
// RoundInt64 rounds the decimal using bankers rounding
func (d Dec) RoundInt64() int64 {
chopped := chopPrecisionAndRound(d.Int)
chopped := chopPrecisionAndRoundNonMutative(d.Int)
if !chopped.IsInt64() {
panic("Int64() out of bound")
}
@ -315,7 +318,7 @@ func (d Dec) RoundInt64() int64 {
// RoundInt round the decimal using bankers rounding
func (d Dec) RoundInt() Int {
return NewIntFromBigInt(chopPrecisionAndRound(d.Int))
return NewIntFromBigInt(chopPrecisionAndRoundNonMutative(d.Int))
}
//___________________________________________________________________________________