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More efficient encoding of floats and doubles #1319

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Feb 17, 2025
Merged

More efficient encoding of floats and doubles #1319

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139 changes: 99 additions & 40 deletions zio-json/js/src/main/scala/zio/json/internal/SafeNumbers.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -178,34 +178,28 @@ object SafeNumbers {
exp += len - 1
if (exp < -3 || exp >= 7) {
val sdv = stripTrailingZeros(dv)
if (sdv < 10) out.write((sdv.toInt | '0').toChar, '.', '0', 'E')
else {
val w = writes.get
write(sdv, w)
val cs = w.getChars
out.write(cs(0), '.')
out.write(cs, 1, w.length)
out.write('E')
}
writeMantissaWithDot(sdv, out)
if (sdv >= 10) out.write('E')
else out.write('0', 'E')
write(exp, out)
} else if (exp < 0) {
out.write('0', '.')
while ({
exp += 1
exp != 0
}) out.write('0')
write(stripTrailingZeros(dv), out)
writeMantissa(stripTrailingZeros(dv), out)
} else {
exp += 1
if (exp < len) {
val w = writes.get
write(stripTrailingZeros(dv), w)
writeMantissa(stripTrailingZeros(dv), w)
val cs = w.getChars
out.write(cs, 0, exp)
out.write('.')
out.write(cs, exp, w.length)
} else {
write(dv.toInt, out)
writeMantissa(dv.toInt, out)
out.write('.', '0')
}
}
Expand Down Expand Up @@ -280,34 +274,28 @@ object SafeNumbers {
exp += len - 1
if (exp < -3 || exp >= 7) {
val sdv = stripTrailingZeros(dv)
if (sdv < 10) out.write((sdv | '0').toChar, '.', '0', 'E')
else {
val w = writes.get
write(sdv, w)
val cs = w.getChars
out.write(cs(0), '.')
out.write(cs, 1, w.length)
out.write('E')
}
writeMantissaWithDot(sdv, out)
if (sdv >= 10) out.write('E')
else out.write('0', 'E')
write(exp, out)
} else if (exp < 0) {
out.write('0', '.')
while ({
exp += 1
exp != 0
}) out.write('0')
write(stripTrailingZeros(dv), out)
writeMantissa(stripTrailingZeros(dv), out)
} else {
exp += 1
if (exp < len) {
val w = writes.get
write(stripTrailingZeros(dv), w)
writeMantissa(stripTrailingZeros(dv), w)
val cs = w.getChars
out.write(cs, 0, exp)
out.write('.')
out.write(cs, exp, w.length)
} else {
write(dv, out)
writeMantissa(dv, out)
out.write('.', '0')
}
}
Expand Down Expand Up @@ -379,42 +367,40 @@ object SafeNumbers {
}

@inline private[this] def stripTrailingZeros(x: Long): Long = {
var q0 = x.toInt
var q0, q1 = x
if (
q0 == x || {
q0 = ((x >>> 8) * 2.56e-6).toInt // divide a medium positive long by 100000000
(q1 << 56 == 0L) && {
q0 = ((q1 >>> 8) * 2.56e-6).toLong // divide a medium positive long by 100000000
q0 * 100000000L == x
}
) return stripTrailingZeros(q0).toLong
var q1, y, z = x
var r1 = 0
) return stripTrailingZeros(q0.toInt).toLong
while ({
q0 = q1
var z = q1
q1 = (q1 >>> 1) + (q1 >>> 2) // Based upon the divu10() code from Hacker's Delight 2nd Edition by Henry Warren
q1 += q1 >>> 4
q1 += q1 >>> 8
q1 += q1 >>> 16
q1 += q1 >>> 32
z -= q1 & 0xfffffffffffffff8L
q1 >>>= 3
r1 = (z - (q1 << 1)).toInt
var r1 = (z - (q1 << 1)).toInt
if (r1 >= 10) {
q1 += 1L
r1 -= 10
}
r1 == 0
}) {
y = q1
z = q1
}
y
}) ()
q0
}

@inline private[this] def stripTrailingZeros(x: Int): Int = {
var q0, q1 = x
while ({
q0 = q1
q1 /= 10
q1 * 10 == q0 // check if q is divisible by 100
}) q0 = q1
}) ()
q0
}

Expand Down Expand Up @@ -461,8 +447,23 @@ object SafeNumbers {
}
}

@inline def write(a: Int, out: Write): Unit = {
val ds = digits
@inline private[this] def writeMantissa(q0: Long, out: Write): Unit =
if (q0.toInt == q0) writeMantissa(q0.toInt, out)
else {
val q1 = ((q0 >>> 8) * 2.56e-6).toLong // divide a medium positive long by 100000000
writeMantissa(q1.toInt, out)
write8Digits((q0 - q1 * 100000000L).toInt, out)
}

@inline private[this] def writeMantissaWithDot(q0: Long, out: Write): Unit =
if (q0.toInt == q0) writeMantissaWithDot(q0.toInt, out)
else {
val q1 = ((q0 >>> 8) * 2.56e-6).toLong // divide a medium positive long by 100000000
writeMantissaWithDot(q1.toInt, out)
write8Digits((q0 - q1 * 100000000L).toInt, out)
}

def write(a: Int, out: Write): Unit = {
var q0 = a
if (q0 < 0) {
q0 = -q0
Expand All @@ -472,6 +473,11 @@ object SafeNumbers {
q0 = 147483648
}
}
writeMantissa(q0, out)
}

private[this] def writeMantissa(q0: Int, out: Write): Unit = {
val ds = digits
if (q0 < 100) {
if (q0 < 10) out.write((q0 | '0').toChar)
else out.write(ds(q0))
Expand Down Expand Up @@ -509,7 +515,60 @@ object SafeNumbers {
}
}

@inline private[this] def write8Digits(x: Int, out: Write): Unit = {
private[this] def writeMantissaWithDot(q0: Int, out: Write): Unit = {
val ds = digits
if (q0 < 100) {
if (q0 < 10) out.write((q0 | '0').toChar, '.')
else {
val d1 = ds(q0)
out.write((d1 & 0xff).toChar, '.', (d1 >> 8).toChar)
}
} else if (q0 < 10000) {
val q1 = q0 * 5243 >> 19 // divide a small positive int by 100
val d2 = ds(q0 - q1 * 100)
if (q0 < 1000) out.write((q1 | '0').toChar, '.')
else {
val d1 = ds(q1)
out.write((d1 & 0xff).toChar, '.', (d1 >> 8).toChar)
}
out.write(d2)
} else if (q0 < 1000000) {
val q1 = q0 / 100
val r1 = q0 - q1 * 100
val q2 = q1 * 5243 >> 19 // divide a small positive int by 100
val r2 = q1 - q2 * 100
if (q0 < 100000) out.write((q2 | '0').toChar, '.')
else {
val d1 = ds(q2)
out.write((d1 & 0xff).toChar, '.', (d1 >> 8).toChar)
}
out.write(ds(r2), ds(r1))
} else if (q0 < 100000000) {
val q1 = q0 / 100
val r1 = q0 - q1 * 100
val q2 = q1 / 100
val r2 = q1 - q2 * 100
val q3 = q2 * 5243 >> 19 // divide a small positive int by 100
val r3 = q2 - q3 * 100
if (q0 < 10000000) out.write((q3 | '0').toChar, '.')
else {
val d1 = ds(q3)
out.write((d1 & 0xff).toChar, '.', (d1 >> 8).toChar)
}
out.write(ds(r3), ds(r2), ds(r1))
} else {
val q1 = q0 / 100000000
val r1 = q0 - q1 * 100000000
if (q0 < 1000000000) out.write((q1 | '0').toChar, '.')
else {
val d1 = ds(q1)
out.write((d1 & 0xff).toChar, '.', (d1 >> 8).toChar)
}
write8Digits(r1, out)
}
}

private[this] def write8Digits(x: Int, out: Write): Unit = {
val ds = digits
val q1 = x / 10000
val q2 = q1 * 5243 >> 19 // divide a small positive int by 100
Expand Down
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