Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

can change max precision #5

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

can change max precision #5

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
63 changes: 39 additions & 24 deletions decimal.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,15 +13,17 @@ import (
// currently support 12 precision, this is tunnable,
// more precision => smaller maxInt
// less precision => bigger maxInt
const precision = 12
const scale = 1e12
const maxInt int64 = int64(math.MaxInt64) / scale
const minInt int64 = int64(math.MinInt64) / scale
const maxIntInFixed int64 = maxInt * scale
const minIntInFixed int64 = minInt * scale
const a1000InFixed int64 = 1000 * scale
const aNeg1000InFixed int64 = -1000 * scale
const aCentInFixed int64 = scale / 100
var (
precision int32 = 12
scale int64 = 1e12
maxInt int64 = int64(math.MaxInt64) / scale
minInt int64 = int64(math.MinInt64) / scale
maxIntInFixed int64 = maxInt * scale
minIntInFixed int64 = minInt * scale
a1000InFixed int64 = 1000 * scale
aNeg1000InFixed int64 = -1000 * scale
aCentInFixed int64 = scale / 100
)

var pow10Table []int64 = []int64{
1e0, 1e1, 1e2, 1e3, 1e4,
Expand Down Expand Up @@ -54,6 +56,18 @@ func init() {
}
}

func ChangeMaxPrecision(newPrecision int) {
precision = int32(newPrecision)
scale = int64(math.Pow10(newPrecision))
maxInt = int64(math.MaxInt64) / scale
minInt = int64(math.MinInt64) / scale
maxIntInFixed = maxInt * scale
minIntInFixed = minInt * scale
a1000InFixed = 1000 * scale
aNeg1000InFixed = -1000 * scale
aCentInFixed = scale / 100
}

// API

// APIs are marked as either "optimized" or "fallbacked"
Expand Down Expand Up @@ -118,7 +132,7 @@ func Min(first Decimal, rest ...Decimal) Decimal {
// optimized:
// New returns a new fixed-point decimal, value * 10 ^ exp.
func New(value int64, exp int32) Decimal {
if exp >= -12 {
if exp >= -precision {
if exp <= 0 {
s := pow10Table[-exp]
if value >= minInt*s && value <= maxInt*s {
Expand Down Expand Up @@ -838,8 +852,9 @@ func (d Decimal) String() string {

// "-9223372.000000000000" => max length = 21 bytes
var s [21]byte
start := 7
end := 8
dotStart := int(int32(20) - precision)
start := dotStart - 1
end := dotStart

var ufixed uint64
if d.fixed >= 0 {
Expand All @@ -848,8 +863,8 @@ func (d Decimal) String() string {
ufixed = uint64(d.fixed * -1)
}

integerPart := ufixed / scale
fractionalPart := ufixed % scale
integerPart := ufixed / uint64(scale)
fractionalPart := ufixed % uint64(scale)

// integer part
if integerPart == 0 {
Expand All @@ -865,14 +880,14 @@ func (d Decimal) String() string {

// fractional part
if fractionalPart > 0 {
s[8] = '.'
for i := 20; i > 8; i-- {
s[dotStart] = '.'
for i := 20; i > dotStart; i-- {
is := fractionalPart % 10
fractionalPart /= 10
if is != 0 {
s[i] = byte(is + '0')
end = i + 1
for j := i - 1; j > 8; j-- {
for j := i - 1; j > dotStart; j-- {
s[j] = byte(fractionalPart%10 + '0')
fractionalPart /= 10
}
Expand Down Expand Up @@ -934,12 +949,12 @@ func (d Decimal) Tan() Decimal {

// optimized:
// Truncate truncates off digits from the number, without rounding.
func (d Decimal) Truncate(precision int32) Decimal {
func (d Decimal) Truncate(wantPrecision int32) Decimal {
if d.fallback == nil {
s := pow10Table[12-precision]
s := pow10Table[precision-wantPrecision]
return Decimal{fixed: d.fixed / s * s}
}
return newFromDecimal(d.asFallback().Truncate(precision))
return newFromDecimal(d.asFallback().Truncate(wantPrecision))
}

// fallback:
Expand Down Expand Up @@ -1155,7 +1170,7 @@ func parseFixed[T string | []byte](v T) (int64, bool) {
} else if c == '.' {
// handle fractional part
s := v[i+1:]
if len(s) > 12 {
if int32(len(s)) > precision {
// out of range
return 0, false
}
Expand All @@ -1168,7 +1183,7 @@ func parseFixed[T string | []byte](v T) (int64, bool) {
return 0, false
}
}
fixed *= pow10Table[12-len(s)]
fixed *= pow10Table[precision-int32(len(s))]
if negative {
return -fixed, true
} else {
Expand All @@ -1190,7 +1205,7 @@ func parseFixed[T string | []byte](v T) (int64, bool) {
func (d Decimal) asFallback() decimal.Decimal {
if d.fallback == nil {
x := big.NewInt(d.fixed)
return decimal.NewFromBigInt(x, -12)
return decimal.NewFromBigInt(x, -precision)
}
return *d.fallback
}
Expand Down Expand Up @@ -1298,7 +1313,7 @@ func div(x, y int64) (int64, bool) {
}

fz := float64(x) / float64(y)
z := int64(fz * scale)
z := int64(fz * float64(scale))

// this `mul` check is to ensure we do not
// lose precision from previous float64 operations.
Expand Down
Loading