Add UnsafePointer extension (#139)

Author: Kyle-Ye

Sources/OpenSwiftUICore/Util/UnsafePointer+Extension.swift

@@ -0,0 +1,49 @@
+//
+//  UnsafePointer+Extension.swift
+//  OpenSwiftUICore
+//
+//  Audited for RELEASE_2024
+//  Status: Complete
+
+extension UnsafePointer {
+    package subscript() -> Pointee {
+        @_transparent
+        unsafeAddress {
+            self
+        }
+    }
+    
+    @_transparent
+    package static var null: UnsafePointer<Pointee> {
+        UnsafePointer(bitPattern: Int(bitPattern: 0xffff_ffff_ffff_ff00) | (-MemoryLayout<Pointee>.alignment))!
+    }
+}
+
+extension UnsafeMutablePointer {
+    package subscript() -> Pointee {
+        @_transparent
+        unsafeAddress { UnsafePointer(self) }
+        @_transparent
+        nonmutating unsafeMutableAddress { self }
+    }
+    
+    @_transparent
+    package static var null: UnsafeMutablePointer<Pointee> {
+        UnsafeMutablePointer(bitPattern: Int(bitPattern: 0xffff_ffff_ffff_ff00) | (-MemoryLayout<Pointee>.alignment))!
+    }
+}
+
+extension UnsafeBufferPointer {
+    @_transparent
+    package var startAddress: UnsafePointer<Element> {
+        baseAddress ?? .null
+    }
+}
+
+
+extension UnsafeMutableBufferPointer {
+    @_transparent
+    package var startAddress: UnsafeMutablePointer<Element> {
+        baseAddress ?? .null
+    }
+}

Tests/OpenSwiftUICoreTests/Util/UnsafePointer+ExtensionTests.swift

@@ -0,0 +1,17 @@
+//
+//  UnsafePointer+ExtensionTests.swift
+//  OpenSwiftUICoreTests
+
+import Testing
+import OpenSwiftUICore
+
+struct UnsafePointer_ExtensionTests {
+    @Test
+    func nullPointer() {
+        #expect(UnsafePointer<Int64>.null == UnsafePointer(bitPattern: Int(bitPattern: 0xffff_ffff_ffff_fff8)))
+        #expect(UnsafePointer<Int32>.null == UnsafePointer(bitPattern: Int(bitPattern: 0xffff_ffff_ffff_fffc)))
+        #expect(UnsafePointer<Int16>.null == UnsafePointer(bitPattern: Int(bitPattern: 0xffff_ffff_ffff_fffe)))
+        #expect(UnsafePointer<Int8>.null == UnsafePointer(bitPattern: Int(bitPattern: 0xffff_ffff_ffff_ffff)))
+        #expect(UnsafePointer<Bool>.null == UnsafePointer(bitPattern: Int(bitPattern: 0xffff_ffff_ffff_ffff)))
+    }
+}