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Bloom filter data property and initialization
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parent
6e0dcd6398
commit
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3 changed files with 38 additions and 7 deletions
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@ -7,14 +7,16 @@ import Foundation
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struct BitArray {
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struct BitArray {
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private var bytes: [UInt8]
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private var bytes: [UInt8]
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init(byteCount: Int) {
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init(data: Data) {
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bytes = [UInt8](repeating: 0, count: byteCount)
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bytes = Array(data)
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}
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}
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}
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}
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extension BitArray {
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extension BitArray {
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var bitCount: Int { bytes.count * Self.bitsInByte }
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var bitCount: Int { bytes.count * Self.bitsInByte }
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var data: Data { Data(bytes) }
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subscript(index: Int) -> Bool {
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subscript(index: Int) -> Bool {
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get {
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get {
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let (byteIndex, bitIndex) = Self.byteAndBitIndices(index: index)
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let (byteIndex, bitIndex) = Self.byteAndBitIndices(index: index)
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@ -11,32 +11,43 @@ enum BloomFilterError: Error {
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}
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}
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public struct BloomFilter<T: DeterministicallyHashable>: Codable {
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public struct BloomFilter<T: DeterministicallyHashable>: Codable {
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enum CodingKeys: String, CodingKey {
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case hashes
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case bits = "data"
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}
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public let hashes: [Hash]
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public let hashes: [Hash]
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private var data: BitArray
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private var bits: BitArray
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public init(hashes: Set<Hash>, byteCount: Int) throws {
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public init(hashes: Set<Hash>, byteCount: Int) throws {
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try self.init(hashes: hashes, data: Data(repeating: 0, count: byteCount))
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}
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public init(hashes: Set<Hash>, data: Data) throws {
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guard !hashes.isEmpty else { throw BloomFilterError.noHashesProvided }
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guard !hashes.isEmpty else { throw BloomFilterError.noHashesProvided }
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// Sort the hashes for consistent decoding output
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// Sort the hashes for consistent decoding output
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self.hashes = Array(hashes.sorted { $0.rawValue < $1.rawValue })
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self.hashes = Array(hashes.sorted { $0.rawValue < $1.rawValue })
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data = BitArray(byteCount: byteCount)
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bits = BitArray(data: data)
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}
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}
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}
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}
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public extension BloomFilter {
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public extension BloomFilter {
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var data: Data { bits.data }
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mutating func insert(_ newMember: T) {
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mutating func insert(_ newMember: T) {
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for index in indices(newMember) {
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for index in indices(newMember) {
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data[index] = true
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bits[index] = true
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}
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}
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}
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}
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func contains(_ member: T) -> Bool {
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func contains(_ member: T) -> Bool {
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indices(member).allSatisfy { data[$0] }
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indices(member).allSatisfy { bits[$0] }
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}
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}
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}
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}
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private extension BloomFilter {
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private extension BloomFilter {
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func indices(_ member: T) -> [Int] {
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func indices(_ member: T) -> [Int] {
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hashes.map { abs($0.apply(member)) % data.bitCount }
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hashes.map { abs($0.apply(member)) % bits.bitCount }
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}
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}
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}
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}
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@ -34,6 +34,24 @@ final class CodableBloomFilterTests: XCTestCase {
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XCTAssertFalse(sut.contains("no"))
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XCTAssertFalse(sut.contains("no"))
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}
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}
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func testData() throws {
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var sut = try BloomFilter<String>(hashes: [.sdbm32, .djb232], byteCount: 8)
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sut.insert("lol")
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sut.insert("ok")
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XCTAssertEqual(sut.data, Data([0, 16, 0, 0, 0, 2, 0, 144]))
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}
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func testFromData() throws {
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let sut = try BloomFilter<String>(hashes: [.sdbm32, .djb232], data: Data([0, 16, 0, 0, 0, 2, 0, 144]))
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XCTAssert(sut.contains("lol"))
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XCTAssert(sut.contains("ok"))
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XCTAssertFalse(sut.contains("wtf"))
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XCTAssertFalse(sut.contains("no"))
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}
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func testCoding() throws {
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func testCoding() throws {
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var sut = try BloomFilter<String>(hashes: [.sdbm32, .djb232], byteCount: 8)
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var sut = try BloomFilter<String>(hashes: [.sdbm32, .djb232], byteCount: 8)
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let expectedData = Data(#"{"data":"ABAAAAACAJA=","hashes":["djb232","sdbm32"]}"#.utf8)
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let expectedData = Data(#"{"data":"ABAAAAACAJA=","hashes":["djb232","sdbm32"]}"#.utf8)
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