Check SQLCipher database integrity on key()

Fixes stephencelis#144.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Author: stephencelis

Source/Cipher/Cipher.swift

@@ -26,6 +26,10 @@ extension Connection {
 
     public func key(key: String) throws {
         try check(sqlite3_key(handle, key, Int32(key.utf8.count)))
+        try execute(
+            "CREATE TABLE \"__SQLCipher.swift__\" (\"cipher key check\");\n" +
+            "DROP TABLE \"__SQLCipher.swift__\";"
+        )
     }
 
     public func rekey(key: String) throws {

Tests/CipherTests.swift

@@ -15,12 +15,34 @@ class CipherTests: XCTestCase {
     }
 
     func test_key() {
-        XCTAssertEqual(1, try! db.scalar("SELECT count(*) FROM foo") as! Int64)
+        XCTAssertEqual(1, db.scalar("SELECT count(*) FROM foo") as? Int64)
     }
 
     func test_rekey() {
         try! db.rekey("goodbye")
-        XCTAssertEqual(1, try! db.scalar("SELECT count(*) FROM foo") as! Int64)
+        XCTAssertEqual(1, db.scalar("SELECT count(*) FROM foo") as? Int64)
+    }
+
+    func test_keyFailure() {
+        let path = "\(NSTemporaryDirectory())/db.sqlite3"
+        _ = try? NSFileManager.defaultManager().removeItemAtPath(path)
+
+        let connA = try! Connection(path)
+        defer { try! NSFileManager.defaultManager().removeItemAtPath(path) }
+
+        try! connA.key("hello")
+
+        let connB = try! Connection(path)
+
+        var rc: Int32?
+        do {
+            try connB.key("world")
+        } catch Result.Error(_, let code, _) {
+            rc = code
+        } catch {
+            XCTFail()
+        }
+        XCTAssertEqual(SQLITE_NOTADB, rc)
     }
 
 }