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Code Issues Releases Wiki Activity

Simplify bit array

This commit is contained in:
Justin Mazzocchi 2020-09-13 02:06:52 -07:00
parent 1b49ec2515
commit 59b5f64720
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GPG Key ID: E223E6937AAFB01C
1 changed files with 3 additions and 20 deletions
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23
CodableBloomFilter/Sources/CodableBloomFilter/BitArray.swift
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@ -1,7 +1,5 @@
// Copyright © 2020 Metabolist. All rights reserved. // Copyright © 2020 Metabolist. All rights reserved.
// Adapted from https://github.com/dduan/BitArray
import Foundation import Foundation
struct BitArray { struct BitArray {
@ -19,13 +17,13 @@ extension BitArray {
subscript(index: Int) -> Bool { subscript(index: Int) -> Bool {
get { get {
let (byteIndex, bitIndex) = Self.byteAndBitIndices(index: index) let (byteIndex, bitIndex) = index.quotientAndRemainder(dividingBy: Self.bitsInByte)
return bytes[byteIndex] & Self.mask(bitIndex: bitIndex) > 0 return bytes[byteIndex] & Self.mask(bitIndex: bitIndex) > 0
} }
set { set {
let (byteIndex, bitIndex) = Self.byteAndBitIndices(index: index) let (byteIndex, bitIndex) = index.quotientAndRemainder(dividingBy: Self.bitsInByte)
if newValue { if newValue {
bytes[byteIndex] |= Self.mask(bitIndex: bitIndex) bytes[byteIndex] |= Self.mask(bitIndex: bitIndex)
@ -51,22 +49,7 @@ extension BitArray: Codable {
private extension BitArray { private extension BitArray {
static let bitsInByte = 8 static let bitsInByte = 8
static func byteAndBitIndices(index: Int) -> (Int, Int) {
index.quotientAndRemainder(dividingBy: bitsInByte)
}
static func mask(bitIndex: Int) -> UInt8 { static func mask(bitIndex: Int) -> UInt8 {
switch bitIndex { UInt8(2 << (bitIndex - 1))
case 0: return 0b00000001
case 1: return 0b00000010
case 2: return 0b00000100
case 3: return 0b00001000
case 4: return 0b00010000
case 5: return 0b00100000
case 6: return 0b01000000
case 7: return 0b10000000
default:
fatalError("Invalid bit index: \(bitIndex)")
}
} }
} }