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More efficient encoding of floats and doubles without an exponent #1320

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Feb 17, 2025
Merged

More efficient encoding of floats and doubles without an exponent #1320

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54 changes: 36 additions & 18 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 @@ -190,14 +190,19 @@ object SafeNumbers {
}) out.write('0')
writeMantissa(stripTrailingZeros(dv), out)
} else {
exp += 1
if (exp < len) {
val w = writes.get
writeMantissa(stripTrailingZeros(dv), w)
val cs = w.getChars
out.write(cs, 0, exp)
var pow10i = len - exp - 1
if (pow10i > 0) {
val pow10 = pow10longs(pow10i)
val q = dv / pow10
val r = dv - q * pow10
writeMantissa(q, out)
out.write('.')
out.write(cs, exp, w.length)
pow10i -= digitCount(r)
while (pow10i > 0) {
out.write('0')
pow10i -= 1
}
writeMantissa(stripTrailingZeros(r), out)
} else {
writeMantissa(dv.toInt, out)
out.write('.', '0')
Expand Down Expand Up @@ -286,14 +291,19 @@ object SafeNumbers {
}) out.write('0')
writeMantissa(stripTrailingZeros(dv), out)
} else {
exp += 1
if (exp < len) {
val w = writes.get
writeMantissa(stripTrailingZeros(dv), w)
val cs = w.getChars
out.write(cs, 0, exp)
var pow10i = len - exp - 1
if (pow10i > 0) {
val pow10 = pow10ints(pow10i)
val q = dv / pow10
val r = dv - q * pow10
writeMantissa(q, out)
out.write('.')
out.write(cs, exp, w.length)
pow10i -= digitCount(r)
while (pow10i > 0) {
out.write('0')
pow10i -= 1
}
writeMantissa(stripTrailingZeros(r), out)
} else {
writeMantissa(dv, out)
out.write('.', '0')
Expand Down Expand Up @@ -394,7 +404,7 @@ object SafeNumbers {
q0
}

@inline private[this] def stripTrailingZeros(x: Int): Int = {
private[this] def stripTrailingZeros(x: Int): Int = {
var q0, q1 = x
while ({
q0 = q1
Expand All @@ -415,7 +425,7 @@ object SafeNumbers {
}
}
var q = q0.toInt
if (q0 == q) write(q, out)
if (q0 == q) writeMantissa(q, out)
else {
var last: Char = 0
if (q0 >= 1000000000000000000L) {
Expand All @@ -436,10 +446,10 @@ object SafeNumbers {
}
val q1 = ((q0 >>> 8) * 2.56e-6).toLong // divide a medium positive long by 100000000
q = q1.toInt
if (q1 == q) write(q, out)
if (q1 == q) writeMantissa(q, out)
else {
q = ((q1 >>> 8) * 1441151881L >>> 49).toInt // divide a small positive long by 100000000
write(q, out)
writeMantissa(q, out)
write8Digits((q1 - q * 100000000L).toInt, out)
}
write8Digits((q0 - q1 * 100000000L).toInt, out)
Expand Down Expand Up @@ -593,6 +603,14 @@ object SafeNumbers {
@inline private[json] def write2Digits(x: Int, out: Write): Unit =
out.write(digits(x))

private[this] final val pow10ints: Array[Int] =
Array(1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000)

private[this] final val pow10longs: Array[Long] =
Array(1L, 10L, 100L, 1000L, 10000L, 100000L, 1000000L, 10000000L, 100000000L, 1000000000L, 10000000000L,
100000000000L, 1000000000000L, 10000000000000L, 100000000000000L, 1000000000000000L, 10000000000000000L,
100000000000000000L)

private[this] final val digits: Array[Short] = Array(
12336, 12592, 12848, 13104, 13360, 13616, 13872, 14128, 14384, 14640, 12337, 12593, 12849, 13105, 13361, 13617,
13873, 14129, 14385, 14641, 12338, 12594, 12850, 13106, 13362, 13618, 13874, 14130, 14386, 14642, 12339, 12595,
Expand Down
52 changes: 35 additions & 17 deletions zio-json/jvm-native/src/main/scala/zio/json/internal/SafeNumbers.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -181,14 +181,19 @@ object SafeNumbers {
}) out.write('0')
writeMantissa(stripTrailingZeros(dv), out)
} else {
exp += 1
if (exp < len) {
val w = writes.get
writeMantissa(stripTrailingZeros(dv), w)
val cs = w.getChars
out.write(cs, 0, exp)
var pow10i = len - exp - 1
if (pow10i > 0) {
val pow10 = pow10longs(pow10i)
val q = dv / pow10
val r = dv - q * pow10
writeMantissa(q, out)
out.write('.')
out.write(cs, exp, w.length)
pow10i -= digitCount(r)
while (pow10i > 0) {
out.write('0')
pow10i -= 1
}
writeMantissa(stripTrailingZeros(r), out)
} else {
writeMantissa(dv.toInt, out)
out.write('.', '0')
Expand Down Expand Up @@ -277,14 +282,19 @@ object SafeNumbers {
}) out.write('0')
writeMantissa(stripTrailingZeros(dv), out)
} else {
exp += 1
if (exp < len) {
val w = writes.get
writeMantissa(stripTrailingZeros(dv), w)
val cs = w.getChars
out.write(cs, 0, exp)
var pow10i = len - exp - 1
if (pow10i > 0) {
val pow10 = pow10ints(pow10i)
val q = dv / pow10
val r = dv - q * pow10
writeMantissa(q, out)
out.write('.')
out.write(cs, exp, w.length)
pow10i -= digitCount(r.toLong)
while (pow10i > 0) {
out.write('0')
pow10i -= 1
}
writeMantissa(stripTrailingZeros(r), out)
} else {
writeMantissa(dv, out)
out.write('.', '0')
Expand Down Expand Up @@ -382,14 +392,14 @@ object SafeNumbers {
}
}
val m1 = 100000000L
if (q0 < m1) write(q0.toInt, out)
if (q0 < m1) writeMantissa(q0.toInt, out)
else {
val m2 = 6189700196426901375L
val q1 = Math.multiplyHigh(q0, m2) >>> 25 // divide a positive long by 100000000
if (q1 < m1) write(q1.toInt, out)
if (q1 < m1) writeMantissa(q1.toInt, out)
else {
val q2 = Math.multiplyHigh(q1, m2) >>> 25 // divide a small positive long by 100000000
write(q2.toInt, out)
writeMantissa(q2.toInt, out)
write8Digits((q1 - q2 * m1).toInt, out)
}
write8Digits((q0 - q1 * m1).toInt, out)
Expand Down Expand Up @@ -542,6 +552,14 @@ object SafeNumbers {
@inline private[json] def write2Digits(x: Int, out: Write): Unit =
out.write(digits(x))

private[this] final val pow10ints: Array[Int] =
Array(1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000)

private[this] final val pow10longs: Array[Long] =
Array(1L, 10L, 100L, 1000L, 10000L, 100000L, 1000000L, 10000000L, 100000000L, 1000000000L, 10000000000L,
100000000000L, 1000000000000L, 10000000000000L, 100000000000000L, 1000000000000000L, 10000000000000000L,
100000000000000000L)

private[this] final val digits: Array[Short] = Array(
12336, 12592, 12848, 13104, 13360, 13616, 13872, 14128, 14384, 14640, 12337, 12593, 12849, 13105, 13361, 13617,
13873, 14129, 14385, 14641, 12338, 12594, 12850, 13106, 13362, 13618, 13874, 14130, 14386, 14642, 12339, 12595,
Expand Down
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