LabsSearch CharacterEncoder

A set of tools in Swift to find the character encoding of a webpage and, later, format URLs in that encoding so that site's server will understand.

Project background

This class is broken out of LabsSearch (an early attempt at coding, so the code here, too, is messy) and can theoretically be used in other projects. It overcomes the headaches involved mainly with creating URLs that use GET on sites that do not use UTF-8 encoding.

Usage

Get webpage encoding

var characterEncoder: CharacterEncoder?
var encoding: String.Encoding? {
    characterEncoder?.encoding.value
}
let url = URL(string: "https://www.example.com/")!

let task = URLSession.shared.dataTask(with: url) { _, response, _ in
    let encodingName = response?.textEncodingName ?? "nil"
    self.characterEncoder = CharacterEncoder(encoding: encodingName)
}
task.resume()

Covert string to percent-encoded URL

let urlString = url.absoluteString
var encodedUrl: URL? = urlString.encodedUrl(characterEncoder: characterEncoder)

Change encoding of percent-encoded URL

let newEncoder = CharacterEncoder(encoding: "euc-kr")
CharacterEncoder.updateCharacterEncoding(newEncoder: newEncoder,
                                         oldEncoder: characterEncoder,
                                         url: encodedUrl!) { encoder, url in
    self.characterEncoder = encoder
    self.encodedUrl = url
}

Get query items

let components = URLComponents(url: encodedUrl!, resolvingAgainstBaseURL: true)
let encodedQueryItems = components?.queryItems(encoder: characterEncoder, keepPercentEncoding: true)

Files

Swift file	Description
CharacterEncoder	Takes an encoding name and URL and returns the properly formatted URL
CharacterEncoder+updateEncoding	Extension for safely re-encoding an already encoded URL with a different encoding
CharacterSet+union	Convenience functions for mixing and matching CharacterSets
CharacterSet+urlAllowedSets	Various URL-safe CharacterSets
String+encodedUrl	String extension to convert URL as String into encoded URL
String.Encoding+alias	Converts human-readable encoding names to Swift equivalents
URLComponents+URLEncodedQueryItem	Convenience functions to handle encoded query items regardless of iOS version or nil values

To do

Currently only the encoding as set in the response header is retrieved. XMLParser could be used to check meta tags as well.

Attributions

The encoding list is adapted from WHATWG.

The code itself is based on code which manually mapped each ASCII character and outputted a string for use with Korean encoding. I found the same code posted in multiple places without any attribution, so I admit I'm unsure who wrote the original. If you know, please speak up!