Fixed a bug that caused a crash when decompressing gzip data caused by an Swift 5.7 internal spec change.

Author: mw99

DataCompression.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "DataCompression"
-  s.version      = "3.6.0"
+  s.version      = "3.7.0"
   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"

Package.swift

@@ -4,7 +4,7 @@ import PackageDescription
 
 let package = Package(
     name: "DataCompression",
-    platforms: [.macOS(.v10_11), .iOS(.v9), .tvOS(.v9), .watchOS(.v2)], 
+    platforms: [.macOS(.v10_11), .iOS(.v9), .tvOS(.v9), .watchOS(.v2)],
     products: [
         .library(
             name: "DataCompression",

README.md

@@ -21,6 +21,7 @@
 #### Swift version support
 | Library Version | Swift Version |
 |-----------------|---------------|
+| 3.7.0           | 5.7 (Xcode 14)|
 | 3.6.0           | 5.1 (Xcode 11)|
 | 3.5.0           | 5.0           |
 | 3.1.0           | 4.2           |
@@ -190,6 +191,8 @@ You only need one file located at `Sources/DataCompression.swift`. Drag and drop
 
 ## Change log / Upgrading guide
 
+##### Version `3.6.0` to `3.7.0`
+- Support for Xcode 14 with Swift 5.7
 
 ##### Version `3.5.0` to `3.6.0`
 - Target platforms finally added to the SPM Package file

Sources/DataCompression/DataCompression.swift

@@ -183,7 +183,7 @@ public extension Data
     /// - returns: uncompressed data
     func gunzip() -> Data?
     {
-        // 10 byte header + data +  8 byte footer. See https://tools.ietf.org/html/rfc1952#section-2
+        // 10 byte header + data + 8 byte footer. See https://tools.ietf.org/html/rfc1952#section-2
         let overhead = 10 + 8
         guard count >= overhead else { return nil }
 
@@ -195,17 +195,15 @@ public extension Data
             // +---+---+---+---+---+---+---+---+---+---+
             return (id1: ptr[0], id2: ptr[1], cm: ptr[2], flg: ptr[3], xfl: ptr[8], os: ptr[9])
         }
-        
+
         typealias GZipFooter = (crc32: UInt32, isize: UInt32)
-        let ftr: GZipFooter = withUnsafeBytes { (bptr: UnsafePointer<UInt8>) -> GZipFooter in
+        let ftr: GZipFooter = advanced(by: count - 8).withUnsafeBytes { (ptr: UnsafePointer<UInt32>) -> GZipFooter in
             // +---+---+---+---+---+---+---+---+
             // |     CRC32     |     ISIZE     |
             // +---+---+---+---+---+---+---+---+
-            return bptr.advanced(by: count - 8).withMemoryRebound(to: UInt32.self, capacity: 2) { ptr in
-                return (ptr[0].littleEndian, ptr[1].littleEndian)
-            }
+            return (ptr[0].littleEndian, ptr[1].littleEndian)
         }
-        
+
         // Wrong gzip magic or unsupported compression method
         guard hdr.id1 == 0x1f && hdr.id2 == 0x8b && hdr.cm == 0x08 else { return nil }
 

Tests/DataCompressionTests/CompressionTest.swift

@@ -283,5 +283,31 @@ class CompressionTest: XCTestCase
     {
         XCTAssertEqual(CompressionTest.blob16mb, CompressionTest.blob16mb.lzfse_delzfse())
     }
+
+    func testGzipCrcFail()
+    {
+        let b = 1024 * 16
+        let ints = [UInt32](repeating: 0xcafeabee, count: b / 4)
+        var zipped_blob = Data(bytes: ints, count: b).gzip()!
+
+        let wrong_crc = Data(bytes: [0xcafeabee], count: 1)
+        let range = (zipped_blob.count - 8)..<(zipped_blob.count - 4)
+        zipped_blob.replaceSubrange(range, with: wrong_crc)
+
+        XCTAssertNil(zipped_blob.gunzip())
+    }
+
+    func testGzipISizeFail()
+    {
+        let b = 1024 * 16
+        let ints = [UInt32](repeating: 0xcafeabee, count: b / 4)
+        var zipped_blob = Data(bytes: ints, count: b).gzip()!
+
+        let wrong_isize = Data(bytes: [0xcafeabee], count: 1)
+        let range = (zipped_blob.count - 4)..<(zipped_blob.count)
+        zipped_blob.replaceSubrange(range, with: wrong_isize)
+
+        XCTAssertNil(zipped_blob.gunzip())
+    }
 }
 

Tests/DataCompressionTests/XCTestManifests.swift

@@ -30,5 +30,7 @@ extension CompressionTest
         ("testRandomDataBlob_16MB_lz4_delz4", testRandomDataBlob_16MB_lz4_delz4),
         ("testRandomDataBlob_16MB_lzma_delzma", testRandomDataBlob_16MB_lzma_delzma),
         ("testRandomDataBlob_16MB_lzfse_delzfse", testRandomDataBlob_16MB_lzfse_delzfse),
+        ("testGzipCrcFail", testGzipCrcFail),
+        ("testGzipISizeFail", testGzipISizeFail),
     ]
 }