easy integration with remote images

[S1D1T1]

I've used PNG on local mac files. usually they arrive via drag/drop & I call PNG with the file path.
Users may also drag in a link or remote image, and my app receives a URL. the swift Data object easily represents remote data - it basically does a curl. Using PNG's stream api & a little glue, my app now treats remote links the same as local files. worked on the first try.
very clean.

/// glue for URL Data to PNG stream
public  struct URLDataSource : PNG.BytestreamSource{
     let data: Data
     var position: Int = 0

    public init(data: Data) {
        self.data = data
    }
    public mutating func read(count capacity: Int) -> [UInt8]? {
        guard position + capacity <= data.count else {
            return nil
        }
        let range = position..<(position + capacity)
        position += capacity
        return Array(data[range])
    }

    public var count: Int? {
        return data.count
    }
}


// remote data extraction

static func extractMetadata(from url:URL) -> MetadataSource? {
  // this basically does a curl
  if let data = try Data(contentsOf: url) {
    var source = URLDataSource(data: data)

    guard let image = try? PNG.Image.decompress(stream: &source) else {
      return MetadataSource(metadata: [:], sourceLocation: .unknown)
    }
    return processImage(image)
  }
  return nil
}