Kit: move types from WireGuardKit to WireGuardKitTypes.

This prevents linking against wg-go when 3rd-party application needs to
use the WireGuardKit types from within the main bundle, therefore
prevents wg-go from spinning off Golang threads where not applicable.

Signed-off-by: Andrej Mihajlov <and@mullvad.net>

Sources/WireGuardKitTypes/IPAddressRange.swift

@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: MIT
+// Copyright © 2018-2021 WireGuard LLC. All Rights Reserved.
+
+import Foundation
+import Network
+
+public struct IPAddressRange {
+    public let address: IPAddress
+    public let networkPrefixLength: UInt8
+
+    init(address: IPAddress, networkPrefixLength: UInt8) {
+        self.address = address
+        self.networkPrefixLength = networkPrefixLength
+    }
+}
+
+extension IPAddressRange: Equatable {
+    public static func == (lhs: IPAddressRange, rhs: IPAddressRange) -> Bool {
+        return lhs.address.rawValue == rhs.address.rawValue && lhs.networkPrefixLength == rhs.networkPrefixLength
+    }
+}
+
+extension IPAddressRange: Hashable {
+    public func hash(into hasher: inout Hasher) {
+        hasher.combine(address.rawValue)
+        hasher.combine(networkPrefixLength)
+    }
+}
+
+extension IPAddressRange {
+    public var stringRepresentation: String {
+        return "\(address)/\(networkPrefixLength)"
+    }
+
+    public init?(from string: String) {
+        guard let parsed = IPAddressRange.parseAddressString(string) else { return nil }
+        address = parsed.0
+        networkPrefixLength = parsed.1
+    }
+
+    private static func parseAddressString(_ string: String) -> (IPAddress, UInt8)? {
+        let endOfIPAddress = string.lastIndex(of: "/") ?? string.endIndex
+        let addressString = String(string[string.startIndex ..< endOfIPAddress])
+        let address: IPAddress
+        if let addr = IPv4Address(addressString) {
+            address = addr
+        } else if let addr = IPv6Address(addressString) {
+            address = addr
+        } else {
+            return nil
+        }
+
+        let maxNetworkPrefixLength: UInt8 = address is IPv4Address ? 32 : 128
+        var networkPrefixLength: UInt8
+        if endOfIPAddress < string.endIndex { // "/" was located
+            let indexOfNetworkPrefixLength = string.index(after: endOfIPAddress)
+            guard indexOfNetworkPrefixLength < string.endIndex else { return nil }
+            let networkPrefixLengthSubstring = string[indexOfNetworkPrefixLength ..< string.endIndex]
+            guard let npl = UInt8(networkPrefixLengthSubstring) else { return nil }
+            networkPrefixLength = min(npl, maxNetworkPrefixLength)
+        } else {
+            networkPrefixLength = maxNetworkPrefixLength
+        }
+
+        return (address, networkPrefixLength)
+    }
+
+    public func subnetMask() -> IPAddress {
+        if address is IPv4Address {
+            let mask = networkPrefixLength > 0 ? ~UInt32(0) << (32 - networkPrefixLength) : UInt32(0)
+            let bytes = Data([
+                UInt8(truncatingIfNeeded: mask >> 24),
+                UInt8(truncatingIfNeeded: mask >> 16),
+                UInt8(truncatingIfNeeded: mask >> 8),
+                UInt8(truncatingIfNeeded: mask >> 0)
+            ])
+            return IPv4Address(bytes)!
+        }
+        if address is IPv6Address {
+            var bytes = Data(repeating: 0, count: 16)
+            for i in 0..<Int(networkPrefixLength/8) {
+                bytes[i] = 0xff
+            }
+            let nibble = networkPrefixLength % 32
+            if nibble != 0 {
+                let mask = ~UInt32(0) << (32 - nibble)
+                let i = Int(networkPrefixLength / 32 * 4)
+                bytes[i + 0] = UInt8(truncatingIfNeeded: mask >> 24)
+                bytes[i + 1] = UInt8(truncatingIfNeeded: mask >> 16)
+                bytes[i + 2] = UInt8(truncatingIfNeeded: mask >> 8)
+                bytes[i + 3] = UInt8(truncatingIfNeeded: mask >> 0)
+            }
+            return IPv6Address(bytes)!
+        }
+        fatalError()
+    }
+
+    public func maskedAddress() -> IPAddress {
+        let subnet = subnetMask().rawValue
+        var masked = Data(address.rawValue)
+        if subnet.count != masked.count {
+            fatalError()
+        }
+        for i in 0..<subnet.count {
+            masked[i] &= subnet[i]
+        }
+        if subnet.count == 4 {
+            return IPv4Address(masked)!
+        }
+        if subnet.count == 16 {
+            return IPv6Address(masked)!
+        }
+        fatalError()
+    }
+}