A Swift enum that recognizes basic mimetypes in a NSData

DocumentType.swift

//  Inspired by: http://stackoverflow.com/questions/4147311/finding-image-type-from-nsdata-or-uiimage/5042365#5042365

import Foundation

enum DocumentType: String {
    
    case jpeg = "image/jpeg"
    case png = "image/png"
    case gif = "image/gif"
    case tiff = "image/tiff"
    case pdf = "application/pdf"
    case vnd = "application/vnd"
    case plainText = "text/plain"
    case anyBinary = "application/octet-stream"
    
    func mimeType(data: NSData) -> DocumentType {
        var firstByte: __uint8_t = 0x00
        data.getBytes(&firstByte, length: 1)
        
        switch firstByte {
        case 0xFF:
            return .jpeg
        case 0x89:
            return .png
        case 0x47:
            return .gif
        case 0x49, 0x4D:
            return .tiff
        case 0x25:
            return .pdf
        case 0xD0:
            return .vnd
        case 0x46:
            return .plainText
        default:
            return .anyBinary
        }
    }
}