Add Data extension tests. Fix bug around reading last byte in data range

Author: kylehickinson

FastImage.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		27B63D652249AB5A004BCC5B /* DataTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 27B63D642249AB5A004BCC5B /* DataTests.swift */; };
 		27CF9392223352940093543E /* FastImage.h in Headers */ = {isa = PBXBuildFile; fileRef = 27CF9390223352940093543E /* FastImage.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		27CF9397223352C20093543E /* FastImage.swift in Sources */ = {isa = PBXBuildFile; fileRef = 27CF9396223352C20093543E /* FastImage.swift */; };
 		27CF939922335E490093543E /* FastImageTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 27CF939822335E490093543E /* FastImageTests.swift */; };
@@ -25,6 +26,7 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
+		27B63D642249AB5A004BCC5B /* DataTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DataTests.swift; sourceTree = "<group>"; };
 		27CF938E223352940093543E /* FastImage.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = FastImage.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		27CF9390223352940093543E /* FastImage.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = FastImage.h; sourceTree = "<group>"; };
 		27CF9391223352940093543E /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
@@ -123,6 +125,7 @@
 			isa = PBXGroup;
 			children = (
 				27CF939822335E490093543E /* FastImageTests.swift */,
+				27B63D642249AB5A004BCC5B /* DataTests.swift */,
 				A1B48FDA1A0DD89F001BB364 /* Supporting Files */,
 			);
 			path = FastImageTests;
@@ -265,6 +268,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				27CF939922335E490093543E /* FastImageTests.swift in Sources */,
+				27B63D652249AB5A004BCC5B /* DataTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

FastImage/DataExtensions.swift

@@ -9,7 +9,7 @@
 import Foundation
 
 extension Data {
-  struct DataAccessError: Error {
+  struct AccessError: Error {
     let range: Range<Data.Index>
     let data: Data
   }
@@ -20,18 +20,18 @@ extension Data {
     return try read(index..<index+1) as UInt8
   }
   func read<ResultType>(_ range: Range<Data.Index>) throws -> ResultType {
-    if range.upperBound < count {
+    if range.upperBound <= count {
       return subdata(in: range).withUnsafeBytes({ $0.pointee })
     }
-    throw DataAccessError(range: range, data: self)
+    throw AccessError(range: range, data: self)
   }
   func readBytes(_ range: Range<Data.Index>) throws -> [UInt8] {
-    if range.upperBound < count {
+    if range.upperBound <= count {
       return subdata(in: range).withUnsafeBytes { bytes in
         Array(UnsafeBufferPointer(start: bytes, count: range.count / MemoryLayout<UInt8>.stride))
       }
     }
-    throw DataAccessError(range: range, data: self)
+    throw AccessError(range: range, data: self)
   }
 }
 

FastImage/Size Decoders/ImageSizeDecoder.swift

@@ -20,10 +20,10 @@ protocol ImageSizeDecoder {
   ///
   /// For example, a GIF size decoder will check the first 3 bytes to see if they match "GIF"
   ///
-  /// - throws: DataAccessError
+  /// - throws: Data.AccessError
   static func isDecoder(for data: Data) throws -> Bool
   /// Get the size of the image given the data available
   ///
-  /// - throws: SizeNotFoundError, DataAccessError
+  /// - throws: SizeNotFoundError, Data.AccessError
   static func size(for data: Data) throws -> CGSize
 }

FastImageTests/DataTests.swift

@@ -0,0 +1,59 @@
+//
+//  DataTests.swift
+//  FastImageTests
+//
+//  Created by Kyle Hickinson on 2019-03-25.
+//  Copyright © 2019 Kyle Hickinson. All rights reserved.
+//
+
+import XCTest
+@testable import FastImage
+
+class DataTests: XCTestCase {
+  
+  func testSingleByteRead() {
+    let data = Data([0x01, 0x02])
+    do {
+      XCTAssertEqual(try data.read(0), 0x01)
+      XCTAssertEqual(try data.read(1), 0x02)
+    }
+  }
+  
+  func testDataAccessError() {
+    let data = Data([0x01, 0x02])
+    do {
+      _ = try data.read(3)
+      XCTFail("Should have failed to read from 3")
+    } catch {
+      XCTAssertTrue(error is Data.AccessError)
+    }
+  }
+  
+  func testReadBytes() {
+    let bytes: [UInt8] = [0xdd, 0xee, 0xff]
+    let data = Data(bytes)
+    XCTAssertEqual(try data.readBytes(0..<3), bytes)
+  }
+  
+  func testReadToType() {
+    let value: UInt16 = 4096
+    let data = Data(withUnsafeBytes(of: value, { Array($0) }))
+    XCTAssertEqual(data.count, 2)
+    XCTAssertEqual(try data.read(0..<2) as UInt16, value)
+  }
+  
+  func testReadToStruct() {
+    struct TestType: Equatable {
+      let a: UInt16
+      let b: UInt16
+      let c: UInt32
+    }
+    let value = TestType(a: 0x800, b: 0x1000, c: 0x10000)
+    let data = Data(withUnsafeBytes(of: value, { Array($0) }))
+    let structSize = MemoryLayout<TestType>.size
+    XCTAssertEqual(data.count, structSize)
+    XCTAssertEqual(try data.read(0..<structSize) as TestType, value)
+    XCTAssertEqual(try data.read(2..<4) as UInt16, value.b)
+    XCTAssertEqual(try data.read(4..<8) as UInt32, value.c)
+  }
+}