COVIDSafe code from version 2.0 (#37)

CovidSafe/Herald/Sensor/BLE/BLEUtilities.swift

@@ -0,0 +1,195 @@
+//
+//  BLEUtilities.swift
+//
+//  Copyright 2020 VMware, Inc.
+//  SPDX-License-Identifier: MIT
+//
+
+import Foundation
+import CoreBluetooth
+
+/**
+ Extension to make the state human readable in logs.
+ */
+@available(iOS 10.0, *)
+extension CBManagerState: CustomStringConvertible {
+    /**
+     Get plain text description of state.
+     */
+    public var description: String {
+        switch self {
+        case .poweredOff: return ".poweredOff"
+        case .poweredOn: return ".poweredOn"
+        case .resetting: return ".resetting"
+        case .unauthorized: return ".unauthorized"
+        case .unknown: return ".unknown"
+        case .unsupported: return ".unsupported"
+        @unknown default: return "undefined"
+        }
+    }
+}
+
+extension CBPeripheralManagerState : CustomStringConvertible {
+    /**
+     Get plain text description of state.
+     */
+    public var description: String {
+        switch self {
+        case .poweredOff: return ".poweredOff"
+        case .poweredOn: return ".poweredOn"
+        case .resetting: return ".resetting"
+        case .unauthorized: return ".unauthorized"
+        case .unknown: return ".unknown"
+        case .unsupported: return ".unsupported"
+        @unknown default: return "undefined"
+        }
+    }
+}
+
+extension CBCentralManagerState : CustomStringConvertible {
+    /**
+     Get plain text description of state.
+     */
+    public var description: String {
+        switch self {
+        case .poweredOff: return ".poweredOff"
+        case .poweredOn: return ".poweredOn"
+        case .resetting: return ".resetting"
+        case .unauthorized: return ".unauthorized"
+        case .unknown: return ".unknown"
+        case .unsupported: return ".unsupported"
+        @unknown default: return "undefined"
+        }
+    }
+}
+
+
+/**
+ Extension to make the state human readable in logs.
+ */
+extension CBPeripheralState: CustomStringConvertible {
+    /**
+     Get plain text description fo state.
+     */
+    public var description: String {
+        switch self {
+        case .connected: return ".connected"
+        case .connecting: return ".connecting"
+        case .disconnected: return ".disconnected"
+        case .disconnecting: return ".disconnecting"
+        @unknown default: return "undefined"
+        }
+    }
+}
+
+/**
+ Extension to make the time intervals more human readable in code.
+ */
+extension TimeInterval {
+    static var day: TimeInterval { get { TimeInterval(86400) } }
+    static var hour: TimeInterval { get { TimeInterval(3600) } }
+    static var minute: TimeInterval { get { TimeInterval(60) } }
+    static var never: TimeInterval { get { TimeInterval(Int.max) } }
+}
+
+/**
+ Sample statistics.
+ */
+class Sample {
+    private var n:Int64 = 0
+    private var m1:Double = 0.0
+    private var m2:Double = 0.0
+    private var m3:Double = 0.0
+    private var m4:Double = 0.0
+    
+    /**
+     Minimum sample value.
+     */
+    var min:Double? = nil
+    /**
+     Maximum sample value.
+     */
+    var max:Double? = nil
+    /**
+     Sample size.
+     */
+    var count:Int64 { get { n } }
+    /**
+     Mean sample value.
+     */
+    var mean:Double? { get { n > 0 ? m1 : nil } }
+    /**
+     Sample variance.
+     */
+    var variance:Double? { get { n > 1 ? m2 / Double(n - 1) : nil } }
+    /**
+     Sample standard deviation.
+     */
+    var standardDeviation:Double? { get { n > 1 ? sqrt(m2 / Double(n - 1)) : nil } }
+    /**
+     String representation of mean, standard deviation, min and max
+     */
+    var description: String { get {
+        let sCount = n.description
+        let sMean = (mean == nil ? "-" : mean!.description)
+        let sStandardDeviation = (standardDeviation == nil ? "-" : standardDeviation!.description)
+        let sMin = (min == nil ? "-" : min!.description)
+        let sMax = (max == nil ? "-" : max!.description)
+        return "count=" + sCount + ",mean=" + sMean + ",sd=" + sStandardDeviation + ",min=" + sMin + ",max=" + sMax
+        } }
+    
+    /**
+     Add sample value.
+     */
+    func add(_ x:Double) {
+        // Sample value accumulation algorithm avoids reiterating sample to compute variance.
+        let n1 = n
+        n += 1
+        let d = x - m1
+        let d_n = d / Double(n)
+        let d_n2 = d_n * d_n;
+        let t = d * d_n * Double(n1);
+        m1 += d_n;
+        m4 += t * d_n2 * Double(n * n - 3 * n + 3) + 6 * d_n2 * m2 - 4 * d_n * m3;
+        m3 += t * d_n * Double(n - 2) - 3 * d_n * m2;
+        m2 += t;
+        if min == nil || x < min! {
+            min = x;
+        }
+        if max == nil || x > max! {
+            max = x;
+        }
+    }
+}
+
+/**
+ Time interval samples for collecting elapsed time statistics.
+ */
+class TimeIntervalSample : Sample {
+    private var startTime: Date?
+    private var timestamp: Date?
+    var period: TimeInterval? { get {
+        (startTime == nil ? nil : timestamp?.timeIntervalSince(startTime!))
+        }}
+    
+    override var description: String { get {
+        let sPeriod = (period == nil ? "-" : period!.description)
+        return super.description + ",period=" + sPeriod
+        }}
+    
+    /**
+     Add elapsed time since last call to add() as sample.
+     */
+    func add() {
+        guard timestamp != nil else {
+            timestamp = Date()
+            startTime = timestamp
+            return
+        }
+        let now = Date()
+        if let timestamp = timestamp {
+            add(now.timeIntervalSince(timestamp))
+        }
+        timestamp = now
+    }
+}