45 lines
1.1 KiB
Scala
45 lines
1.1 KiB
Scala
package com.htmlism
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import scala.annotation.tailrec
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/**
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* Given an `Int`, destructure it into smaller `Int`s that use less bits
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*/
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trait BitExtractor[A]:
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self =>
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def length: Int
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def unapply(n: Int): Option[A]
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/**
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* A combinator for appending one extractor to another
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*/
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def >>[B](that: BitExtractor[B]): BitExtractor[(A, B)] =
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new BitExtractor[(A, B)]:
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def length: Int = self.length + that.length
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def unapply(n: Int): Option[(A, B)] =
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for {
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b <- that.unapply(n)
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shifted = n >> that.length
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a <- self.unapply(shifted)
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} yield (a, b)
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object AtomExtractor:
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@tailrec
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def pow(ex: Int, acc: Int = 1): Int =
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if ex == 0 then acc
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else pow(ex - 1, acc * 2)
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abstract class PrimitiveBitExtractor(val length: Int) extends BitExtractor[Int]:
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private lazy val mask =
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AtomExtractor.pow(length) - 1
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def unapply(n: Int): Option[Int] =
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Some(n & mask)
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object OneBit extends PrimitiveBitExtractor(1)
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object TwoBits extends PrimitiveBitExtractor(2)
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object ThreeBits extends PrimitiveBitExtractor(3)
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