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decimal64decParts.go
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/
decimal64decParts.go
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package decimal
// decParts stores the constituting decParts of a decimal64.
type decParts struct {
fl flavor
sign int
exp int
significand uint128T
original Decimal64
}
func unpack(d Decimal64) decParts {
var dp decParts
dp.unpack(d)
return dp
}
func (dp *decParts) decimal64() Decimal64 {
return newFromParts(dp.sign, dp.exp, dp.significand.lo)
}
// add128 adds two decParts with full precision in 128 bits of significand
func (dp *decParts) add128(ep *decParts) decParts {
dp.matchScales128(ep)
var ans decParts
ans.exp = dp.exp
if dp.sign == ep.sign {
ans.sign = dp.sign
ans.significand = dp.significand.add(ep.significand)
} else {
if dp.significand.lt(ep.significand) {
ans.sign = ep.sign
ans.significand = ep.significand.sub(dp.significand)
} else if ep.significand.lt(dp.significand) {
ans.sign = dp.sign
ans.significand = dp.significand.sub(ep.significand)
} else {
ans.significand = uint128T{0, 0}
}
}
return ans
}
func (dp *decParts) matchScales128(ep *decParts) {
expDiff := ep.exp - dp.exp
if (ep.significand != uint128T{0, 0}) {
if expDiff < 0 {
dp.significand = dp.significand.mul(tenToThe128[-expDiff])
dp.exp += expDiff
} else if expDiff > 0 {
ep.significand = ep.significand.mul(tenToThe128[expDiff])
ep.exp -= expDiff
}
}
}
func (dp *decParts) roundToLo() discardedDigit {
var rndStatus discardedDigit
if dsig := dp.significand; dsig.hi > 0 || dsig.lo >= 10*decimal64Base {
var remainder uint64
expDiff := dsig.numDecimalDigits() - 16
dp.exp += expDiff
dp.significand, remainder = dsig.divrem64(tenToThe[expDiff])
rndStatus = roundStatus(remainder, 0, expDiff)
}
return rndStatus
}
func (dp *decParts) isZero() bool {
return (dp.significand == uint128T{}) && dp.significand.hi == 0 && dp.fl == flNormal
}
func (dp *decParts) isInf() bool {
return dp.fl == flInf
}
func (dp *decParts) isNaN() bool {
return dp.fl&(flQNaN|flSNaN) != 0
}
func (dp *decParts) isSNaN() bool {
return dp.fl == flSNaN
}
func (dp *decParts) isSubnormal() bool {
return (dp.significand != uint128T{}) && dp.significand.lo < decimal64Base && dp.fl == flNormal
}
// separation gets the separation in decimal places of the MSD's of two decimal 64s
func (dp *decParts) separation(ep *decParts) int {
return dp.significand.numDecimalDigits() + dp.exp - ep.significand.numDecimalDigits() - ep.exp
}
// removeZeros removes zeros and increments the exponent to match.
func (dp *decParts) removeZeros() {
zeros := countTrailingZeros(dp.significand.lo)
dp.significand.lo /= tenToThe[zeros]
dp.exp += zeros
}
// isinf returns true if the decimal is an infinty
func (dp *decParts) isinf() bool {
return dp.fl == flInf
}
func (dp *decParts) rescale(targetExp int) (rndStatus discardedDigit) {
expDiff := targetExp - dp.exp
mag := dp.significand.numDecimalDigits()
rndStatus = roundStatus(dp.significand.lo, dp.exp, targetExp)
if expDiff > mag {
dp.significand.lo, dp.exp = 0, targetExp
return
}
divisor := tenToThe[expDiff]
dp.significand.lo = dp.significand.lo / divisor
dp.exp = targetExp
return
}
func (dp *decParts) unpack(d Decimal64) {
dp.original = d
dp.sign = int(d.bits >> 63)
switch (d.bits >> (63 - 4)) & 0xf {
case 15:
switch (d.bits >> (63 - 6)) & 3 {
case 0, 1:
dp.fl = flInf
case 2:
dp.fl = flQNaN
dp.significand.lo = d.bits & (1<<51 - 1) // Payload
return
case 3:
dp.fl = flSNaN
dp.significand.lo = d.bits & (1<<51 - 1) // Payload
return
}
case 12, 13, 14:
// s 11EEeeeeeeee (100)t tttttttttt tttttttttt tttttttttt tttttttttt tttttttttt
// EE ∈ {00, 01, 10}
dp.fl = flNormal
dp.exp = int((d.bits>>(63-12))&(1<<10-1)) - expOffset
dp.significand.lo = d.bits&(1<<51-1) | (1 << 53)
default:
// s EEeeeeeeee (0)ttt tttttttttt tttttttttt tttttttttt tttttttttt tttttttttt
// EE ∈ {00, 01, 10}
dp.fl = flNormal
dp.exp = int((d.bits>>(63-10))&(1<<10-1)) - expOffset
dp.significand.lo = d.bits & (1<<53 - 1)
if dp.significand.lo == 0 {
dp.exp = 0
}
}
}