let scout = ImageScout()

    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)")
        }
    }

This is especially problematic in Debug mode, where no tail recursion exists! I found this when some JPEGs crashed my App. This could also easily be used as an attack vector with specially crafted data.

My Solution for parsing JPEGs is to translate the parse function into a looped version:

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)
        }
    }
}

👋

I finished the upgrade to Swift 3 with minor code changes. I let XCode change a few things regarding new compiler warnings and removing code signing for frameworks, but can undo that if it's a problem.

Hi, i use IOS 9.3 and the log not print anithing

let scout = ImageScout()

scout.scoutImageWithURI("http://.../image-scout-logo.png") { error, size, type in if let unwrappedError = error { println(unwrappedError.code) } else { println("Size: (size)") println("Type: (type.rawValue)") } }

with error code: The following build commands failed: CompileSwift normal arm64 /Users/BourneWang/Desktop/ImageScout-master/Demo/Carthage/Checkouts/ImageScout/Source/ImageScout.swift CompileSwiftSources normal arm64 com.apple.xcode.tools.swift.compiler (2 failures)

with error: dyld: Library not loaded: @rpath/ImageScout.framework/ImageScout Referenced from: /private/var/mobile/Containers/Bundle/Application/F9A9E333-019B-46B8-8DA9-CA5B4437D2C3/Demo.app/Demo Reason: image not found

Separate out the source of the ImageScout library from the tests and example code. This way someone could still copy the source code into their own project if they wanted, but now it can also support Carthage and Cocoapods.