optimized decoding

mobile/ios/Runner/Images/RemoteImagesImpl.swift

@@ -0,0 +1,181 @@
+import Accelerate
+import Flutter
+import MobileCoreServices
+import Photos
+
+class RemoteImageRequest {
+  weak var task: URLSessionDataTask?
+  var isCancelled = false
+  let imageSource: CGImageSource
+  var data: CFMutableData?
+  let completion: (Result<[String: Int64], any Error>) -> Void
+  
+  init(task: URLSessionDataTask, imageSource: CGImageSource, completion: @escaping (Result<[String: Int64], any Error>) -> Void) {
+    self.task = task
+    self.imageSource = imageSource
+    self.data = nil
+    self.completion = completion
+  }
+}
+
+class RemoteImageApiImpl: NSObject, RemoteImageApi {
+  private static let delegate = RemoteImageApiDelegate()
+  static let session = {
+    let config = URLSessionConfiguration.default
+    let thumbnailPath = FileManager.default.temporaryDirectory.appendingPathComponent("thumbnails", isDirectory: true)
+    try! FileManager.default.createDirectory(at: thumbnailPath, withIntermediateDirectories: true)
+    config.urlCache = URLCache(
+      memoryCapacity: 0,
+      diskCapacity: 10 << 20,
+      directory: thumbnailPath
+    )
+    config.httpMaximumConnectionsPerHost = 16
+    return URLSession(configuration: config, delegate: delegate, delegateQueue: nil)
+  }()
+  
+  func requestImage(url: String, headers: [String : String], requestId: Int64, completion: @escaping (Result<[String : Int64], any Error>) -> Void) {
+    print("Got image request \(requestId) for \(url)")
+    var urlRequest = URLRequest(url: URL(string: url)!)
+    for (key, value) in headers {
+      urlRequest.setValue(value, forHTTPHeaderField: key)
+    }
+    let task = Self.session.dataTask(with: urlRequest)
+    task.taskDescription = String(requestId)
+    
+    let imageRequest = RemoteImageRequest(
+      task: task,
+      imageSource: CGImageSourceCreateIncremental(
+        [kCGImageSourceShouldCache: false] as CFDictionary),
+      completion: completion
+    )
+    Self.delegate.add(requestId: requestId, request: imageRequest)
+    
+    task.resume()
+    print("Started task for \(requestId)")
+  }
+  
+  func cancelRequest(requestId: Int64) {
+    print("Cancelling task for \(requestId)")
+    Self.delegate.cancel(requestId: requestId)
+  }
+}
+
+class RemoteImageApiDelegate: NSObject, URLSessionDataDelegate {
+  private static let requestQueue = DispatchQueue(label: "thumbnail.requests", qos: .userInitiated)
+  private static var rgbaFormat = vImage_CGImageFormat(
+    bitsPerComponent: 8,
+    bitsPerPixel: 32,
+    colorSpace: CGColorSpaceCreateDeviceRGB(),
+    bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue),
+    renderingIntent: .perceptual
+  )!
+  private static var requests = [Int64: RemoteImageRequest]()
+  private static let cancelledResult = Result<[String: Int64], any Error>.success([:])
+  
+  func urlSession(
+    _ session: URLSession, dataTask: URLSessionDataTask,
+    didReceive response: URLResponse,
+    completionHandler: @escaping (URLSession.ResponseDisposition) -> Void
+  ) {
+    guard let taskDescription = dataTask.taskDescription,
+          let requestId = Int64(taskDescription),
+          let request = (Self.requestQueue.sync { Self.requests[requestId] })
+    else {
+      return completionHandler(.cancel)
+    }
+    
+    let capacity = max(Int(response.expectedContentLength), 0)
+    request.data = CFDataCreateMutable(nil, capacity)
+    
+    completionHandler(.allow)
+  }
+  
+  func urlSession(_ session: URLSession, dataTask: URLSessionDataTask,
+                  didReceive data: Data) {
+    print("Got data")
+    guard let taskDescription = dataTask.taskDescription,
+          let requestId = Int64(taskDescription),
+          let request = get(requestId: requestId),
+          let accumulatedData = request.data
+    else { return }
+    
+    data.withUnsafeBytes { bytes in
+      CFDataAppendBytes(request.data, bytes.bindMemory(to: UInt8.self).baseAddress, data.count)
+    }
+    CGImageSourceUpdateData(request.imageSource, accumulatedData, false)
+  }
+  
+  func urlSession(_ session: URLSession, task: URLSessionTask,
+                  didCompleteWithError error: Error?) {
+    print("Task ended")
+    guard let taskDescription = task.taskDescription,
+          let requestId = Int64(taskDescription),
+          let request = get(requestId: requestId),
+          let accumulatedData = request.data
+    else { return }
+    
+    if let error = error {
+      print("Task failed for \(requestId): \(error)")
+      remove(requestId: requestId)
+      return request.completion(.failure(error))
+    }
+    
+    CGImageSourceUpdateData(request.imageSource, accumulatedData, true)
+    
+    let options = [kCGImageSourceShouldCacheImmediately: true] as CFDictionary
+    guard let cgImage = CGImageSourceCreateImageAtIndex(request.imageSource, 0, nil) else {
+      print("No image for \(requestId)")
+      remove(requestId: requestId)
+      return request.completion(.failure(PigeonError(code: "", message: "Failed to decode image for request \(requestId)", details: nil)))
+    }
+    print("Got image for \(requestId)")
+    
+    if request.isCancelled {
+      remove(requestId: requestId)
+      return request.completion(Self.cancelledResult)
+    }
+    
+    do {
+      let buffer = try vImage_Buffer(cgImage: cgImage, format: Self.rgbaFormat)
+      
+      if request.isCancelled {
+        buffer.free()
+        remove(requestId: requestId)
+        return request.completion(Self.cancelledResult)
+      }
+      
+      request.completion(
+        .success([
+          "pointer": Int64(Int(bitPattern: buffer.data)),
+          "width": Int64(buffer.width),
+          "height": Int64(buffer.height),
+          "rowBytes": Int64(buffer.rowBytes),
+        ]))
+      print("Successful response for \(requestId)")
+      
+      remove(requestId: requestId)
+    } catch {
+      print("vImage conversion failed for \(requestId): \(error)")
+      remove(requestId: requestId)
+      return request.completion(.failure(PigeonError(code: "", message: "Failed to convert image for request \(requestId): \(error)", details: nil)))
+    }
+  }
+  
+  func get(requestId: Int64) -> RemoteImageRequest? {
+    Self.requestQueue.sync { Self.requests[requestId] }
+  }
+  
+  func add(requestId: Int64, request: RemoteImageRequest) -> Void {
+    Self.requestQueue.sync { Self.requests[requestId] = request }
+  }
+  
+  func remove(requestId: Int64) -> Void {
+    Self.requestQueue.sync { Self.requests[requestId] = nil }
+  }
+  
+  func cancel(requestId: Int64) -> Void {
+    guard let request = (Self.requestQueue.sync { Self.requests[requestId] }) else { return }
+    request.isCancelled = true
+    request.task?.cancel()
+  }
+}