Add clone to reader

onevcat · Mar 8, 2022 · 4ff0656 · 4ff0656
1 parent c64347a
commit 4ff0656
Show file tree

Hide file tree

Showing 3 changed files with 64 additions and 2 deletions.
diff --git a/Source/APNGKit/Reader.swift b/Source/APNGKit/Reader.swift
@@ -24,10 +24,13 @@ protocol Reader {
 
     // Returns the current pointer offset for later use.
     func offset() throws -> UInt64
+
+    // Returns a clone of current reader.
+    func clone() throws -> Self
 }
 
 // Read data from a loaded data object.
-class DataReader: Reader {
+final class DataReader: Reader {
 
     private var cursor: Int = 0
     private let data: Data
@@ -64,14 +67,22 @@ class DataReader: Reader {
     func offset() throws -> UInt64 {
         UInt64(cursor)
     }
+
+    func clone() throws -> DataReader {
+        let reader = DataReader(data: data)
+        try reader.seek(toOffset: offset())
+        return reader
+    }
 }
 
 // Read data from a file with `FileHandle`.
-class FileReader: Reader {
+final class FileReader: Reader {
     private let handle: FileHandle
+    private let url: URL
 
     init(url: URL) throws {
         do {
+            self.url = url
             self.handle = try FileHandle(forReadingFrom: url)
         } catch {
             throw APNGKitError.decoderError(.fileHandleCreatingFailed(url, error))
@@ -140,6 +151,12 @@ class FileReader: Reader {
             return false
         }
     }
+
+    func clone() throws -> FileReader {
+        let reader = try FileReader(url: url)
+        try reader.seek(toOffset: offset())
+        return reader
+    }
 }
 
 extension Reader {

diff --git a/Tests/APNGKitTests/DataReaderTests.swift b/Tests/APNGKitTests/DataReaderTests.swift
@@ -125,4 +125,26 @@ class DataReaderTests: XCTestCase {
         _ = try normalReader.read(upToCount: 4)
         XCTAssertEqual(5, try normalReader.offset())
     }
+
+    func testDataReaderClone() throws {
+        let reader1 = DataReader(bytes: [1,2,3,4,5])
+        let data1 = try reader1.read(upToCount: 1)
+        XCTAssertEqual([1], data1?.bytes)
+
+        let reader2 = try reader1.clone()
+        let data2_1 = try reader1.read(upToCount: 2)
+        let data2_2 = try reader2.read(upToCount: 2)
+        XCTAssertEqual([2,3], data2_1?.bytes)
+        XCTAssertEqual([2,3], data2_2?.bytes)
+
+        let data3_1 = try reader1.read(upToCount: 2)
+        XCTAssertEqual([4,5], data3_1?.bytes)
+
+        try reader1.seek(toOffset: 0)
+        let data1_1 = try reader1.read(upToCount: 2)
+        XCTAssertEqual([1, 2], data1_1?.bytes)
+
+        let data3_2 = try reader2.read(upToCount: 2)
+        XCTAssertEqual([4,5], data3_2?.bytes)
+    }
 }
diff --git a/Tests/APNGKitTests/FileReaderTests.swift b/Tests/APNGKitTests/FileReaderTests.swift
@@ -159,4 +159,27 @@ class FileReaderTests: XCTestCase {
         _ = try normalReader.read(upToCount: 4)
         XCTAssertEqual(5, try normalReader.offset())
     }
+
+    func testFileReaderClone() throws {
+        let reader1 = try FileReader(url: Self.tmpFileURL)
+        let data1 = try reader1.read(upToCount: 1)
+        XCTAssertEqual([1], data1?.bytes)
+
+        let reader2 = try reader1.clone()
+
+        let data2_1 = try reader1.read(upToCount: 2)
+        let data2_2 = try reader2.read(upToCount: 2)
+        XCTAssertEqual([2,3], data2_1?.bytes)
+        XCTAssertEqual([2,3], data2_2?.bytes)
+
+        let data3_1 = try reader1.read(upToCount: 2)
+        XCTAssertEqual([4,5], data3_1?.bytes)
+
+        try reader1.seek(toOffset: 0)
+        let data1_1 = try reader1.read(upToCount: 2)
+        XCTAssertEqual([1, 2], data1_1?.bytes)
+
+        let data3_2 = try reader2.read(upToCount: 2)
+        XCTAssertEqual([4,5], data3_2?.bytes)
+    }
 }