Fix blob equality

Sources/SQLite/Core/Blob.swift

@@ -36,6 +36,10 @@ public final class Blob {
     }
 
     public convenience init(bytes: [UInt8]) {
+        guard bytes.count > 0 else {
+            self.init(data: NSData())
+            return
+        }
         let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bytes.count)
         for idx in 0..<bytes.count {
             buffer.advanced(by: idx).pointee = bytes[idx]
@@ -54,10 +58,12 @@ public final class Blob {
     }
 
     public init(data: NSData) {
+        precondition(!(data is NSMutableData), "Blob cannot be initialized with mutable data")
         self.data = data
     }
 
     public func toHex() -> String {
+        guard length > 0 else { return "" }
         let bytes = bytes.assumingMemoryBound(to: UInt8.self)
 
         var hex = ""
@@ -85,5 +91,5 @@ extension Blob: Equatable {
 }
 
 public func ==(lhs: Blob, rhs: Blob) -> Bool {
-    lhs.bytes == rhs.bytes
+    lhs.data == rhs.data
 }

Tests/SQLiteTests/Core/BlobTests.swift

@@ -5,10 +5,14 @@ class BlobTests: XCTestCase {
 
     func test_toHex() {
         let blob = Blob(bytes: [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 250, 255])
-
         XCTAssertEqual(blob.toHex(), "000a141e28323c46505a6496faff")
     }
 
+    func test_toHex_empty() {
+        let blob = Blob(bytes: [])
+        XCTAssertEqual(blob.toHex(), "")
+    }
+
     func test_init_array() {
         let blob = Blob(bytes: [42, 42, 42])
         XCTAssertEqual(blob.byteArray, [42, 42, 42])
@@ -20,6 +24,16 @@ class BlobTests: XCTestCase {
         let blob = Blob(bytes: pointer, length: 3)
         XCTAssertEqual(blob.byteArray, [42, 42, 42])
     }
+
+    func test_equality() {
+        let blob1 = Blob(bytes: [42, 42, 42])
+        let blob2 = Blob(bytes: [42, 42, 42])
+        let blob3 = Blob(bytes: [42, 42, 43])
+
+        XCTAssertEqual(Blob(bytes: []), Blob(bytes: []))
+        XCTAssertEqual(blob1, blob2)
+        XCTAssertNotEqual(blob1, blob3)
+    }
 }
 
 extension Blob {