Throw error

CHANGELOG.md

@@ -8,6 +8,7 @@ Change Log
 ### Changes
 
 - Migrate code to Swift 2.0
+- Change to throw error instead returning `nil`.
 
 
 

Project/Tests/NSData_GZIPTests.swift

@@ -39,9 +39,9 @@ class NSData_GZIPTests: XCTestCase
         let encoding = NSUTF8StringEncoding
 
         let data = testSentence.dataUsingEncoding(encoding, allowLossyConversion: true)!
-        let gzipped = data.gzippedData()
-        let uncompressed = gzipped?.gunzippedData()
-        let uncompressedSentence = NSString(data: uncompressed!, encoding: encoding)! as String
+        let gzipped = try! data.gzippedData()
+        let uncompressed = try! gzipped.gunzippedData()
+        let uncompressedSentence = NSString(data: uncompressed, encoding: encoding) as! String
 
         XCTAssertEqual(uncompressedSentence, testSentence)
     }
@@ -51,15 +51,23 @@ class NSData_GZIPTests: XCTestCase
     {
         let zeroLengthData = NSData()
 
-        XCTAssertEqual(zeroLengthData.gzippedData()!, zeroLengthData)
-        XCTAssertEqual(zeroLengthData.gunzippedData()!, zeroLengthData)
+        XCTAssertEqual(try! zeroLengthData.gzippedData(), zeroLengthData)
+        XCTAssertEqual(try! zeroLengthData.gunzippedData(), zeroLengthData)
     }
 
+
     func testWrongUngzip()
     {
         // data not compressed
         let data = ("testString" as NSString).dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!
 
-        XCTAssertNil(data.gunzippedData())
+        var uncompressed: NSData?
+        do {
+            uncompressed = try data.gunzippedData()
+        } catch GzipError.Data(let message){
+            XCTAssertEqual(message, "incorrect header check")
+        } catch _ {
+        }
+        XCTAssertNil(uncompressed)
     }
 }

README.md

@@ -13,20 +13,10 @@ __NSData+GZIP.swift__ is an extension of NSData written in Swift 2.0. It enables
 
 ```swift
 // gzip
-let compressedData : NSData = data.gzippedData()
+let compressedData : NSData = try! data.gzippedData()
 
 // gunzip
-let decompressedData : NSData = compressedData.gunzippedData()
-```
-
-```objc
-#import "ProjectName-Swift.h"
-
-// gzip
-NSData *compressedData = [data gzippedData];
-
-// gunzip
-NSData *decompressedData = [compressedData gunzippedData];
+let decompressedData : NSData = try! compressedData.gunzippedData()
 ```
 
 

Sources/NSData+GZIP.swift

@@ -33,15 +33,98 @@ private let CHUNK_SIZE: Int = 2 ^ 14
 private let STREAM_SIZE: Int32 = Int32(sizeof(z_stream))
 
 
+/**
+Errors on gzipping/gunzipping based on the zlib error codes.
+*/
+public enum GzipError: ErrorType {
+    // cf. http://www.zlib.net/manual.html
+
+    /**
+    The stream structure was inconsistent.
+
+    - underlying zlib error: `Z_STREAM_ERROR` (-2)
+    - parameter message: returned message by zlib
+    */
+    case Stream(message: String)
+
+    /**
+    The input data was corrupted (input stream not conforming to the zlib format or incorrect check value).
+
+    - underlying zlib error: `Z_DATA_ERROR` (-3)
+    - parameter message: returned message by zlib
+    */
+    case Data(message: String)
+
+    /**
+    There was not enough memory.
+
+    - underlying zlib error: `Z_MEM_ERROR` (-4)
+    - parameter message: returned message by zlib
+    */
+    case Memory(message: String)
+
+    /**
+    No progress is possible or there was not enough room in the output buffer.
+
+    - underlying zlib error: `Z_BUF_ERROR` (-5)
+    - parameter message: returned message by zlib
+    */
+    case Buffer(message: String)
+
+    /**
+    The zlib library version is incompatible with the version assumed by the caller.
+
+    - underlying zlib error: `Z_VERSION_ERROR` (-6)
+    - parameter message: returned message by zlib
+    */
+    case Version(message: String)
+
+    /**
+    An unknown error occurred.
+
+    - parameter message: returned message by zlib
+    - parameter code: return error by zlib
+    */
+    case Unknown(message: String, code: Int)
+
+
+    private init(code: Int32, msg: UnsafePointer<CChar>)
+    {
+        let message =  String.fromCString(msg) ?? "Unknown error"
+
+        switch code {
+        case Z_STREAM_ERROR:
+            self = .Stream(message: message)
+
+        case Z_DATA_ERROR:
+            self = .Data(message: message)
+
+        case Z_MEM_ERROR:
+            self = .Memory(message: message)
+
+        case Z_BUF_ERROR:
+            self = .Buffer(message: message)
+
+        case Z_VERSION_ERROR:
+            self = .Version(message: message)
+
+        default:
+            self = .Unknown(message: message, code: Int(code))
+        }
+    }
+}
+
+
 public extension NSData
 {
     /**
     Create a new `NSData` object by compressing the reciver using zlib.
-    Returns `nil` if decompression failed.
+    Throws an error if compression failed.
 
-    - returns: Gzip-compressed `NSData` object or `nil`.
+    - throws: `GzipError`
+    - returns: Gzip-compressed `NSData` object.
     */
-    public func gzippedData() -> NSData?
+    public func gzippedData() throws -> NSData
     {
         guard self.length > 0 else {
             return NSData()
@@ -53,10 +136,12 @@ public extension NSData
         status = deflateInit2_(&stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, MAX_WBITS + 16, MAX_MEM_LEVEL, Z_DEFAULT_STRATEGY, ZLIB_VERSION, STREAM_SIZE)
 
         guard status == Z_OK else {
-            let errorMessage =  String.fromCString(stream.msg) ?? "Unknown error"
-            print("Compression failed: " + errorMessage)
+            // deflateInit2 returns:
+            // Z_VERSION_ERROR  The zlib library version is incompatible with the version assumed by the caller.
+            // Z_MEM_ERROR      There was not enough memory.
+            // Z_STREAM_ERROR   A parameter is invalid.
 
-            return nil
+            throw GzipError(code: status, msg: stream.msg)
         }
 
         let data = NSMutableData(length: CHUNK_SIZE)!
@@ -80,11 +165,12 @@ public extension NSData
 
     /**
     Create a new `NSData` object by decompressing the reciver using zlib.
-    Returns `nil` if decompression failed.
+    Throws an error if decompression failed.
 
-    - returns: Gzip-decompressed `NSData` object or `nil`.
+    - throws: `GzipError`
+    - returns: Gzip-decompressed `NSData` object.
     */
-    public func gunzippedData() -> NSData?
+    public func gunzippedData() throws -> NSData
     {
         guard self.length > 0 else {
             return NSData()
@@ -96,10 +182,12 @@ public extension NSData
         status = inflateInit2_(&stream, MAX_WBITS + 32, ZLIB_VERSION, STREAM_SIZE)
 
         guard status == Z_OK else {
-            let errorMessage =  String.fromCString(stream.msg) ?? "Unknown error"
-            print("Decompression failed: " + errorMessage)
+            // inflateInit2 returns:
+            // Z_VERSION_ERROR   The zlib library version is incompatible with the version assumed by the caller.
+            // Z_MEM_ERROR       There was not enough memory.
+            // Z_STREAM_ERROR    A parameters are invalid.
 
-            return nil
+            throw GzipError(code: status, msg: stream.msg)
         }
 
         let data = NSMutableData(length: self.length * 2)!
@@ -116,10 +204,13 @@ public extension NSData
         } while status == Z_OK
 
         guard inflateEnd(&stream) == Z_OK && status == Z_STREAM_END else {
-            let errorMessage =  String.fromCString(stream.msg) ?? "Unknown error"
-            print("Decompression failed: " + errorMessage)
+            // inflate returns:
+            // Z_DATA_ERROR   The input data was corrupted (input stream not conforming to the zlib format or incorrect check value).
+            // Z_STREAM_ERROR The stream structure was inconsistent (for example if next_in or next_out was NULL).
+            // Z_MEM_ERROR    There was not enough memory.
+            // Z_BUF_ERROR    No progress is possible or there was not enough room in the output buffer when Z_FINISH is used.
 
-            return nil
+            throw GzipError(code: status, msg: stream.msg)
         }
 
         data.length = Int(stream.total_out)