kaishin / imagescout Goto Github PK

    scout.scoutImageWithURI("http://f.hiphotos.baidu.com/zhidao/pic/item/5d6034a85edf8db16efebe470b23dd54574e74c5.jpg") { error, size, type in
        if let unwrappedError = error {
            print(unwrappedError.code)
        } else {
            print("Size: \(size)")
            print("Type: \(type.rawValue)")
        }
    }

private typealias JPEGParseTuple = (data: NSData, offset: Int, segment: JPEGHeaderSegment)

private enum JPEGParseResult {
    case Size(CGSize)
    case Tuple(JPEGParseTuple)
}

private static func parseJPEG(tuple: JPEGParseTuple) -> JPEGParseResult {
    let data = tuple.data
    let offset = tuple.offset
    let segment = tuple.segment

    if segment == .EOISegment
        || (data.length <= offset + 1)
        || (data.length <= offset + 2) && segment == .SkipSegment
        || (data.length <= offset + 7) && segment == .ParseSegment {
            return .Size(CGSizeZero)
    }
    switch segment {
    case .NextSegment:
        let newOffset = offset + 1
        var byte = 0x0; data.getBytes(&byte, range: NSRange(location: newOffset, length: 1))

        if byte == 0xFF {
            return .Tuple(JPEGParseTuple(data, offset: newOffset, segment: .SOFSegment))
        } else {
            return .Tuple(JPEGParseTuple(data, offset: newOffset, segment: .NextSegment))
        }
    case .SOFSegment:
        let newOffset = offset + 1
        var byte = 0x0; data.getBytes(&byte, range: NSRange(location: newOffset, length: 1))

        switch byte {
        case 0xE0...0xEF:
            return .Tuple(JPEGParseTuple(data, offset: newOffset, segment: .SkipSegment))
        case 0xC0...0xC3, 0xC5...0xC7, 0xC9...0xCB, 0xCD...0xCF:
            return .Tuple(JPEGParseTuple(data, offset: newOffset, segment: .ParseSegment))
        case 0xFF:
            return .Tuple(JPEGParseTuple(data, offset: newOffset, segment: .SOFSegment))
        case 0xD9:
            return .Tuple(JPEGParseTuple(data, offset: newOffset, segment: .EOISegment))
        default:
            return .Tuple(JPEGParseTuple(data, offset: newOffset, segment: .SkipSegment))
        }

    case .SkipSegment:
        var length = UInt16(0)
        data.getBytes(&length, range: NSRange(location: offset + 1, length: 2))

        let newOffset = offset + Int(CFSwapInt16(length)) - 1
        return .Tuple(JPEGParseTuple(data, offset: Int(newOffset), segment: .NextSegment))

    case .ParseSegment:
        var size = JPEGSize(); data.getBytes(&size, range: NSRange(location: offset + 4, length: 4))
        return .Size(CGSize(width: Int(CFSwapInt16(size.width)), height: Int(CFSwapInt16(size.height))))
    default:
        return .Size(CGSizeZero)
    }

}

private static func parseJPEGData(data: NSData, offset: Int, segment: JPEGHeaderSegment) -> CGSize {
    var tuple: JPEGParseResult = .Tuple(JPEGParseTuple(data, offset: offset, segment: segment))
    while true {
        switch tuple {
        case .Size(let size):
            return size
        case .Tuple(let newTuple):
            tuple = parseJPEG(newTuple)
        }
    }
}