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Parser optimization

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This commit is contained in:
zhelenskiy 2021-05-12 02:01:49 +03:00
parent 74d14970b9
commit 9184bd55de
1 changed files with 55 additions and 35 deletions
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90
kmath-core/src/commonMain/kotlin/space/kscience/kmath/operations/BigInt.kt
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@ -441,11 +441,11 @@ public fun UIntArray.toBigInt(sign: Byte): BigInt {
return BigInt(sign, copyOf())
}
private val hexChToInt: MutableMap<Char, Int> = hashMapOf(
'0' to 0, '1' to 1, '2' to 2, '3' to 3,
'4' to 4, '5' to 5, '6' to 6, '7' to 7,
'8' to 8, '9' to 9, 'A' to 10, 'B' to 11,
'C' to 12, 'D' to 13, 'E' to 14, 'F' to 15
private val hexChToInt: MutableMap<Char, UInt> = hashMapOf(
'0' to 0U, '1' to 1U, '2' to 2U, '3' to 3U,
'4' to 4U, '5' to 5U, '6' to 6U, '7' to 7U,
'8' to 8U, '9' to 9U, 'A' to 10U, 'B' to 11U,
'C' to 12U, 'D' to 13U, 'E' to 14U, 'F' to 15U
)
/**
@ -454,52 +454,72 @@ private val hexChToInt: MutableMap<Char, Int> = hashMapOf(
public fun String.parseBigInteger(): BigInt? {
if (this.isEmpty()) return null
val sign: Int
val sPositive: String
//TODO substring = O(n). Can be replaced by some drop that is O(1)
when {
this[0] == '+' -> {
val positivePartIndex = when (this[0]) {
'+' -> {
sign = +1
sPositive = this.substring(1)
1
}
this[0] == '-' -> {
'-' -> {
sign = -1
sPositive = this.substring(1)
1
}
else -> {
sPositive = this
sign = +1
0
}
}
var res = BigInt.ZERO
var digitValue = BigInt.ONE
val sPositiveUpper = sPositive.uppercase()
var isEmpty = true
if (sPositiveUpper.startsWith("0X")) {
return if (this.startsWith("0X", startIndex = positivePartIndex, ignoreCase = true)) {
// hex representation
val sHex = sPositiveUpper.substring(2)
if (this.isEmpty()) return null
// TODO optimize O(n2) -> O(n)
for (ch in sHex.reversed()) {
if (ch == '_') continue
res += digitValue * (hexChToInt[ch] ?: return null)
val uInts = mutableListOf(0U)
var offset = 0
fun addDigit(value: UInt) {
uInts[uInts.lastIndex] += value shl offset
offset += 4
if (offset == 32) {
uInts.add(0U)
offset = 0
}
}
for (index in lastIndex downTo positivePartIndex + 2) {
when (val ch = this[index]) {
'_' -> continue
in '0'..'9' -> addDigit((ch - '0').toUInt())
in 'A'..'F' -> addDigit((ch - 'A').toUInt() + 10U)
in 'a'..'f' -> addDigit((ch - 'a').toUInt() + 10U)
else -> return null
}
isEmpty = false
digitValue *= 16.toBigInt()
}
} else for (ch in sPositiveUpper.reversed()) {
// decimal representation
if (ch == '_') continue
if (ch !in '0'..'9') {
return null
}
res += digitValue * (ch.code - '0'.code)
isEmpty = false
digitValue *= 10.toBigInt()
}
return if (isEmpty) null else res * sign
while (uInts.isNotEmpty() && uInts.last() == 0U)
uInts.removeLast()
if (isEmpty) null else BigInt(sign.toByte(), uInts.toUIntArray())
} else {
// hex representation
var res = BigInt.ZERO
var digitValue = BigInt.ONE
for (index in lastIndex downTo positivePartIndex) {
val ch = this[index]
// decimal representation
if (ch == '_') continue
if (ch !in '0'..'9') {
return null
}
res += digitValue * (ch.code - '0'.code)
isEmpty = false
digitValue *= 10.toBigInt()
}
if (isEmpty) null else res * sign
}
}
public inline fun Buffer.Companion.bigInt(size: Int, initializer: (Int) -> BigInt): Buffer<BigInt> =