add swiftUI code

2025-01-22 14:09:10 +08:00
parent 68e7b7347c
commit 8a99853829
2531 changed files with 486215 additions and 0 deletions
@@ -0,0 +1,51 @@
+import Dispatch
+
+/// A ReadWriteBox grants multiple readers and single-writer guarantees on a
+/// value. It is backed by a concurrent DispatchQueue.
+@propertyWrapper
+final class ReadWriteBox<T> {
+    private var _wrappedValue: T
+    private var queue: DispatchQueue
+    
+    var wrappedValue: T {
+        get { read { $0 } }
+        set { update { $0 = newValue } }
+    }
+    
+    var projectedValue: ReadWriteBox<T> { self }
+    
+    init(wrappedValue: T) {
+        _wrappedValue = wrappedValue
+        queue = DispatchQueue(label: "GRDB.ReadWriteBox", attributes: [.concurrent])
+    }
+    
+    func read<U>(_ block: (T) throws -> U) rethrows -> U {
+        try queue.sync {
+            try block(_wrappedValue)
+        }
+    }
+    
+    func update<U>(_ block: (inout T) throws -> U) rethrows -> U {
+        try queue.sync(flags: [.barrier]) {
+            try block(&_wrappedValue)
+        }
+    }
+}
+
+extension ReadWriteBox where T: Numeric {
+    @discardableResult
+    func increment() -> T {
+        update { n in
+            n += 1
+            return n
+        }
+    }
+    
+    @discardableResult
+    func decrement() -> T {
+        update { n in
+            n -= 1
+            return n
+        }
+    }
+}