Add cancel operation feature

Author: jwelton

Zip/Zip.swift

@@ -17,13 +17,16 @@ public enum ZipError: Error {
     case unzipFail
     /// Zip fail
     case zipFail
-    
+    /// Operation Cancelled
+    case operationCancelled
+
     /// User readable description
     public var description: String {
         switch self {
         case .fileNotFound: return NSLocalizedString("File not found.", comment: "")
         case .unzipFail: return NSLocalizedString("Failed to unzip file.", comment: "")
         case .zipFail: return NSLocalizedString("Failed to zip file.", comment: "")
+        case .operationCancelled: return NSLocalizedString("Operation cancelled", comment: "")
         }
     }
 }
@@ -50,12 +53,16 @@ public enum ZipCompression: Int {
 
 /// Zip class
 public class Zip {
-    
     /**
      Set of vaild file extensions
      */
     internal static var customFileExtensions: Set<String> = []
 
+    /**
+     Cancellation block. This is set once the progress tracker is has been created
+    */
+    public static var cancelCurrentOperation: (()->Void) = { }
+    
     // MARK: Lifecycle
 
     /**
@@ -113,6 +120,8 @@ public class Zip {
         progressTracker.isPausable = false
         progressTracker.kind = ProgressKind.file
 
+        cancelCurrentOperation = { progressTracker.cancel() }
+        
         // Begin unzipping
         let zip = unzOpen64(path)
         defer {
@@ -234,16 +243,19 @@ public class Zip {
             }
 
             progressTracker.completedUnitCount = Int64(currentPosition)
-            
-        } while (ret == UNZ_OK && ret != UNZ_END_OF_LIST_OF_FILE)
+                        
+        } while (ret == UNZ_OK && ret != UNZ_END_OF_LIST_OF_FILE) && !progressTracker.isCancelled
+        
+        guard !progressTracker.isCancelled else {
+            throw ZipError.operationCancelled
+        }
 
         // Completed. Update progress handler.
         if let progressHandler = progress{
             progressHandler(1.0)
         }
 
         progressTracker.completedUnitCount = Int64(totalSize)
-        
     }
 
     // MARK: Zip
@@ -297,6 +309,8 @@ public class Zip {
         progressTracker.isPausable = false
         progressTracker.kind = ProgressKind.file
 
+        cancelCurrentOperation = { progressTracker.cancel() }
+        
         // Begin Zipping
         let zip = zipOpen(destinationPath, APPEND_STATUS_CREATE)
         for path in processedPaths {
@@ -338,6 +352,10 @@ public class Zip {
                 }
                 var length: Int = 0
                 while (feof(input) == 0) {
+                    guard !progressTracker.isCancelled else {
+                        throw ZipError.operationCancelled
+                    }
+                    
                     length = fread(buffer, 1, chunkSize, input)
                     zipWriteInFileInZip(zip, buffer, UInt32(length))
                 }

ZipTests/ZipTests.swift

@@ -315,4 +315,69 @@ class ZipTests: XCTestCase {
         XCTAssertTrue(Zip.isValidFileExtension("cbz"))
     }
 
+    func testCancelDuringZipCancels() {
+        var currentProgress: Double = 0
+        
+        let expect = expectation(description: "Zip operation should throw .OperationCancelled")
+        
+        do {
+            let progress = Progress()
+            progress.totalUnitCount = 1
+            
+            let imageURL1 = Bundle(for: ZipTests.self).url(forResource: "3crBXeO", withExtension: "gif")!
+            let imageURL2 = Bundle(for: ZipTests.self).url(forResource: "kYkLkPf", withExtension: "gif")!
+            let documentsFolder = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0] as NSURL
+            let zipFilePath = documentsFolder.appendingPathComponent("archive.zip")!
+            
+            try Zip.zipFiles(paths: [imageURL1, imageURL2], zipFilePath: zipFilePath, password: nil) { progress in
+                currentProgress = progress
+                
+                if progress > 0 {
+                    Zip.cancelCurrentOperation()
+                }
+            }
+            
+        }
+        catch {
+            XCTAssertEqual(error as? ZipError, .operationCancelled)
+            XCTAssertLessThan(currentProgress, 1, "Progress should be less than 1 when cancelling the current operation")
+            expect.fulfill()
+        }
+        
+        waitForExpectations(timeout: 5) { error in
+            XCTAssertNil(error)
+        }
+    }
+    
+    func testCancelDuringUnzipCancels() {
+        var currentProgress: Double = 0
+        let expect = expectation(description: "Unzip operation should throw .OperationCancelled")
+        
+        do {
+            let progress = Progress()
+            progress.totalUnitCount = 1
+            
+            let bookURL = Bundle(for: ZipTests.self).url(forResource: "bb8", withExtension: "zip")!
+            let documentsFolder = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0] as NSURL
+            let zipFilePath = documentsFolder.appendingPathComponent("contents")!
+            
+            try Zip.unzipFile(bookURL, destination: zipFilePath, overwrite: true, password: nil, progress: { progress in
+                currentProgress = progress
+                
+                if progress > 0 {
+                    Zip.cancelCurrentOperation()
+                }
+            }) { _ in }
+        }
+        catch {
+            XCTAssertEqual(error as? ZipError, .operationCancelled)
+            XCTAssertLessThan(currentProgress, 1, "Progress should be less than 1 when cancelling the current operation")
+            expect.fulfill()
+        }
+        
+        waitForExpectations(timeout: 5) { error in
+            XCTAssertNil(error)
+        }
+    }
+    
 }