Bug fixes for Swift 5.7 (unaligned pointer problem)

Author: mw99

.gitignore

@@ -40,6 +40,7 @@ playground.xcworkspace
 # Packages/
 # Package.pins
 .build/
+.swiftpm/
 
 # CocoaPods
 #

DataCompression.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "DataCompression"
-  s.version      = "3.7.0"
+  s.version      = "3.8.0"
   s.summary      = "Swift libcompression wrapper as an extension for the Data type (GZIP, ZLIB, LZFSE, LZMA, LZ4, deflate, RFC-1950, RFC-1951, RFC-1952)"
   s.authors      = { "Markus Wanke" => "mw99@users.noreply.github.com" }
   s.homepage     = "https://github.com/mw99/DataCompression"

README.md

@@ -21,7 +21,7 @@
 #### Swift version support
 | Library Version | Swift Version |
 |-----------------|---------------|
-| 3.7.0           | 5.7 (Xcode 14)|
+| 3.8.0           | 5.7 (Xcode 14)|
 | 3.6.0           | 5.1 (Xcode 11)|
 | 3.5.0           | 5.0           |
 | 3.1.0           | 4.2           |
@@ -191,6 +191,10 @@ You only need one file located at `Sources/DataCompression.swift`. Drag and drop
 
 ## Change log / Upgrading guide
 
+
+##### Version `3.7.0` to `3.8.0`
+- Solved a bug causing crashes when using `.unzip()`, because of unaligned pointer loading caused by internal changes in Swift 5.7.
+
 ##### Version `3.6.0` to `3.7.0`
 - Support for Xcode 14 with Swift 5.7
 

Sources/DataCompression/DataCompression.swift

@@ -122,7 +122,7 @@ public extension Data
         let header: UInt16 = withUnsafeBytes { (ptr: UnsafePointer<UInt16>) -> UInt16 in
             return ptr.pointee.bigEndian
         }
-        
+
         // check for the deflate stream bit
         guard header >> 8 & 0b1111 == 0b1000 else { return nil }
         // check the header checksum
@@ -137,14 +137,11 @@ public extension Data
         guard let inflated = cresult else { return nil }
 
         if skipCheckSumValidation { return inflated }
-        
-        let cksum: UInt32 = withUnsafeBytes { (bytePtr: UnsafePointer<UInt8>) -> UInt32 in
-            let last = bytePtr.advanced(by: count - 4)
-            return last.withMemoryRebound(to: UInt32.self, capacity: 1) { (intPtr) -> UInt32 in
-                return intPtr.pointee.bigEndian
-            }
+
+        let cksum = Data(self.suffix(from: count - 4)).withUnsafeBytes { rawPtr in
+            return rawPtr.load(as: UInt32.self).bigEndian
         }
-        
+
         return cksum == inflated.adler32().checksum ? inflated : nil
     }
 
@@ -197,7 +194,8 @@ public extension Data
         }
 
         typealias GZipFooter = (crc32: UInt32, isize: UInt32)
-        let ftr: GZipFooter = advanced(by: count - 8).withUnsafeBytes { (ptr: UnsafePointer<UInt32>) -> GZipFooter in
+        let alignedFtr = Data(self.suffix(from: count - 8))
+        let ftr: GZipFooter = alignedFtr.withUnsafeBytes { (ptr: UnsafePointer<UInt32>) -> GZipFooter in
             // +---+---+---+---+---+---+---+---+
             // |     CRC32     |     ISIZE     |
             // +---+---+---+---+---+---+---+---+

Tests/DataCompressionTests/CompressionTest.swift

@@ -18,7 +18,7 @@ extension Data
     func c_inflate()  -> Data? { let res: Data? = self.inflate(); XCTAssertNotNil(res, "\(#function) failed"); return res }
 
     func c_zip()      -> Data? { let res: Data? = self.zip();     XCTAssertNotNil(res, "\(#function) failed"); return res }
-    func c_unzip()    -> Data? { let res: Data? = self.unzip();   XCTAssertNotNil(res, "\(#function) failed"); return res }
+    func c_unzip()    -> Data? { let res: Data? = self.unzip(skipCheckSumValidation: false);   XCTAssertNotNil(res, "\(#function) failed"); return res }
 
     func c_gzip()     -> Data? { let res: Data? = self.gzip();     XCTAssertNotNil(res, "\(#function) failed"); return res }
     func c_gunzip()   -> Data? { let res: Data? = self.gunzip();   XCTAssertNotNil(res, "\(#function) failed"); return res }