Create ThreadSafeCache, which FaviconDownloader uses.

Frameworks/RSCore/RSCore.xcodeproj/project.pbxproj

@@ -86,6 +86,8 @@
 		8461387F1DB3F5BE00048B83 /* RSToolbarItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8461387E1DB3F5BE00048B83 /* RSToolbarItem.swift */; };
 		8479213C1FBA426B004AD08C /* WebViewWindow.xib in Resources */ = {isa = PBXBuildFile; fileRef = 8479213B1FBA426B004AD08C /* WebViewWindow.xib */; };
 		8479213E1FBA4285004AD08C /* WebViewWindowController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8479213D1FBA4285004AD08C /* WebViewWindowController.swift */; };
+		848F6AE91FC2BC50002D422E /* ThreadSafeCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = 848F6AE81FC2BC50002D422E /* ThreadSafeCache.swift */; };
+		848F6AEA1FC2BC50002D422E /* ThreadSafeCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = 848F6AE81FC2BC50002D422E /* ThreadSafeCache.swift */; };
 		849A339D1AC90A0A0015BA09 /* NSTableView+RSCore.h in Headers */ = {isa = PBXBuildFile; fileRef = 849A339B1AC90A0A0015BA09 /* NSTableView+RSCore.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		849A339E1AC90A0A0015BA09 /* NSTableView+RSCore.m in Sources */ = {isa = PBXBuildFile; fileRef = 849A339C1AC90A0A0015BA09 /* NSTableView+RSCore.m */; };
 		849B08971BF7BCE30090CEE4 /* NSPasteboard+RSCore.h in Headers */ = {isa = PBXBuildFile; fileRef = 849B08951BF7BCE30090CEE4 /* NSPasteboard+RSCore.h */; settings = {ATTRIBUTES = (Public, ); }; };
@@ -202,6 +204,7 @@
 		8461387E1DB3F5BE00048B83 /* RSToolbarItem.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RSToolbarItem.swift; sourceTree = "<group>"; };
 		8479213B1FBA426B004AD08C /* WebViewWindow.xib */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = WebViewWindow.xib; path = AppKit/WebViewWindow.xib; sourceTree = "<group>"; };
 		8479213D1FBA4285004AD08C /* WebViewWindowController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = WebViewWindowController.swift; path = AppKit/WebViewWindowController.swift; sourceTree = "<group>"; };
+		848F6AE81FC2BC50002D422E /* ThreadSafeCache.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = ThreadSafeCache.swift; path = RSCore/ThreadSafeCache.swift; sourceTree = "<group>"; };
 		849A339B1AC90A0A0015BA09 /* NSTableView+RSCore.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSTableView+RSCore.h"; sourceTree = "<group>"; };
 		849A339C1AC90A0A0015BA09 /* NSTableView+RSCore.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSTableView+RSCore.m"; sourceTree = "<group>"; };
 		849B08951BF7BCE30090CEE4 /* NSPasteboard+RSCore.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSPasteboard+RSCore.h"; sourceTree = "<group>"; };
@@ -346,6 +349,7 @@
 				842E45CB1ED623C7000A8B52 /* UniqueIdentifier.swift */,
 				84E34DA51F9FA1070077082F /* UndoableCommand.swift */,
 				8402047D1FBCE77900D94C1A /* BatchUpdate.swift */,
+				848F6AE81FC2BC50002D422E /* ThreadSafeCache.swift */,
 				84CFF5241AC3C8A200CEA6C8 /* Foundation */,
 				84CFF5551AC3CF4A00CEA6C8 /* AppKit */,
 				84E72E0F1FBD647500B873C1 /* Inspector */,
@@ -718,6 +722,7 @@
 				842DD7DB1E14996300E061EB /* NSData+RSCore.m in Sources */,
 				842DD7D51E14995C00E061EB /* PlistProviderProtocol.swift in Sources */,
 				842DD7CE1E14995C00E061EB /* RSPlist.m in Sources */,
+				848F6AEA1FC2BC50002D422E /* ThreadSafeCache.swift in Sources */,
 				842DD7EF1E14996300E061EB /* NSString+RSCore.m in Sources */,
 				842DD7F21E14996B00E061EB /* Date+Extensions.swift in Sources */,
 				842DD7ED1E14996300E061EB /* NSSet+RSCore.m in Sources */,
@@ -790,6 +795,7 @@
 				849A339E1AC90A0A0015BA09 /* NSTableView+RSCore.m in Sources */,
 				84CFF51B1AC3C77500CEA6C8 /* RSPlatform.m in Sources */,
 				84CFF52C1AC3CA9700CEA6C8 /* NSData+RSCore.m in Sources */,
+				848F6AE91FC2BC50002D422E /* ThreadSafeCache.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Frameworks/RSCore/RSCore/ThreadSafeCache.swift

@@ -0,0 +1,48 @@
+//
+//  ThreadSafeCache.swift
+//  RSCore
+//
+//  Created by Brent Simmons on 11/19/17.
+//  Copyright © 2017 Ranchero Software, LLC. All rights reserved.
+//
+
+import Foundation
+
+public final class ThreadSafeCache<T> {
+
+	private var cache = [String: T]()
+	private let lock = NSLock()
+
+	public init() {}
+	
+	public subscript(_ key: String) -> T? {
+		get {
+			return cachedObject(key)
+		}
+		set {
+			if let newValue = newValue {
+				cacheObject(key, newValue)
+			}
+		}
+	}
+
+	private func cachedObject(_ key: String) -> T? {
+
+		lock.lock()
+		defer {
+			lock.unlock()
+		}
+
+		return cache[key]
+	}
+
+	private func cacheObject(_ key: String, _ value: T) {
+
+		lock.lock()
+		defer {
+			lock.unlock()
+		}
+
+		cache[key] = value
+	}
+}