From f02b1e033a0f1a0049148b5e4e6e4d4125d57311 Mon Sep 17 00:00:00 2001
From: Justin Mazzocchi <2831158+jzzocc@users.noreply.github.com>
Date: Tue, 8 Sep 2020 02:07:15 -0700
Subject: [PATCH] Bloom filter data property and initialization

---
 .../Sources/CodableBloomFilter/BitArray.swift |  6 ++++--
 .../CodableBloomFilter/BloomFilter.swift      | 21 ++++++++++++++-----
 .../CodableBloomFilterTests.swift             | 18 ++++++++++++++++
 3 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/CodableBloomFilter/Sources/CodableBloomFilter/BitArray.swift b/CodableBloomFilter/Sources/CodableBloomFilter/BitArray.swift
index 1c1cdf9..f0cc651 100644
--- a/CodableBloomFilter/Sources/CodableBloomFilter/BitArray.swift
+++ b/CodableBloomFilter/Sources/CodableBloomFilter/BitArray.swift
@@ -7,14 +7,16 @@ import Foundation
 struct BitArray {
     private var bytes: [UInt8]
 
-    init(byteCount: Int) {
-        bytes = [UInt8](repeating: 0, count: byteCount)
+    init(data: Data) {
+        bytes = Array(data)
     }
 }
 
 extension BitArray {
     var bitCount: Int { bytes.count * Self.bitsInByte }
 
+    var data: Data { Data(bytes) }
+
     subscript(index: Int) -> Bool {
         get {
             let (byteIndex, bitIndex) = Self.byteAndBitIndices(index: index)
diff --git a/CodableBloomFilter/Sources/CodableBloomFilter/BloomFilter.swift b/CodableBloomFilter/Sources/CodableBloomFilter/BloomFilter.swift
index 3b1d3b7..1497c4d 100644
--- a/CodableBloomFilter/Sources/CodableBloomFilter/BloomFilter.swift
+++ b/CodableBloomFilter/Sources/CodableBloomFilter/BloomFilter.swift
@@ -11,32 +11,43 @@ enum BloomFilterError: Error {
 }
 
 public struct BloomFilter<T: DeterministicallyHashable>: Codable {
+    enum CodingKeys: String, CodingKey {
+        case hashes
+        case bits = "data"
+    }
+
     public let hashes: [Hash]
 
-    private var data: BitArray
+    private var bits: BitArray
 
     public init(hashes: Set<Hash>, byteCount: Int) throws {
+        try self.init(hashes: hashes, data: Data(repeating: 0, count: byteCount))
+    }
+
+    public init(hashes: Set<Hash>, data: Data) throws {
         guard !hashes.isEmpty else { throw BloomFilterError.noHashesProvided }
         // Sort the hashes for consistent decoding output
         self.hashes = Array(hashes.sorted { $0.rawValue < $1.rawValue })
-        data = BitArray(byteCount: byteCount)
+        bits = BitArray(data: data)
     }
 }
 
 public extension BloomFilter {
+    var data: Data { bits.data }
+
     mutating func insert(_ newMember: T) {
         for index in indices(newMember) {
-            data[index] = true
+            bits[index] = true
         }
     }
 
     func contains(_ member: T) -> Bool {
-        indices(member).allSatisfy { data[$0] }
+        indices(member).allSatisfy { bits[$0] }
     }
 }
 
 private extension BloomFilter {
     func indices(_ member: T) -> [Int] {
-        hashes.map { abs($0.apply(member)) % data.bitCount }
+        hashes.map { abs($0.apply(member)) % bits.bitCount }
     }
 }
diff --git a/CodableBloomFilter/Tests/CodableBloomFilterTests/CodableBloomFilterTests.swift b/CodableBloomFilter/Tests/CodableBloomFilterTests/CodableBloomFilterTests.swift
index 5e68479..e7af542 100644
--- a/CodableBloomFilter/Tests/CodableBloomFilterTests/CodableBloomFilterTests.swift
+++ b/CodableBloomFilter/Tests/CodableBloomFilterTests/CodableBloomFilterTests.swift
@@ -34,6 +34,24 @@ final class CodableBloomFilterTests: XCTestCase {
         XCTAssertFalse(sut.contains("no"))
     }
 
+    func testData() throws {
+        var sut = try BloomFilter<String>(hashes: [.sdbm32, .djb232], byteCount: 8)
+
+        sut.insert("lol")
+        sut.insert("ok")
+
+        XCTAssertEqual(sut.data, Data([0, 16, 0, 0, 0, 2, 0, 144]))
+    }
+
+    func testFromData() throws {
+        let sut = try BloomFilter<String>(hashes: [.sdbm32, .djb232], data: Data([0, 16, 0, 0, 0, 2, 0, 144]))
+
+        XCTAssert(sut.contains("lol"))
+        XCTAssert(sut.contains("ok"))
+        XCTAssertFalse(sut.contains("wtf"))
+        XCTAssertFalse(sut.contains("no"))
+    }
+
     func testCoding() throws {
         var sut = try BloomFilter<String>(hashes: [.sdbm32, .djb232], byteCount: 8)
         let expectedData = Data(#"{"data":"ABAAAAACAJA=","hashes":["djb232","sdbm32"]}"#.utf8)