Resource Encoder

A script to encode project resources as byte arrays. Swift only, but feel free to add your own languages.

Why?

When developing mobile apps, there are many cases where you shouldn't have certain strings as literals in your binary (or, even worse, have them in resource files). For example, an API key stored as a string in your code could easily be retrieved by hackers and used to your detriment.

How?

Encoding strings as byte-arrays makes identifying them in your binary much more difficult. This script takes an input file and generates a class that will give you easy access and secure access to the content of the file at runtime. There are two ways you can use this.

Single file

Given the file APIKey.txt that contains the string Abcd123, run:

$ resource-encoder.sh APIKey.txt APIKey.swift

This generates APIKey.swift containing the following:

import Foundation

struct APIKey {

    static func string() -> String {
        return String(data: data(), encoding: .ascii)!
    }

    static func data() -> Data {
        var bytes = self.bytes()
        bytes.removeLast()
        return Data(bytes: bytes, count: bytes.count)
    }

    // Contains an extra 0x0 at the end to prevent reading of the array running into random memory
    private static func bytes() -> [UInt8] {
        return [0x41, 0x62, 0x63, 0x64, 0x31, 0x32, 0x33, 0x0a, 0x0]
    }
}

Multiple files

In an Xcode Runscript Build Phase, run bash /path/to/resource-encoder.sh. The script will use the input and output files for generation. For example, in a command-line app I am building, I want to bundle some resources for use at runtime. This isn't possible by default, so resource-encoder.sh helps me:

Ensure that input files are NOT in your target's membership - that would defeat the purpose of this entirely!

What's next?

If you want to support Android, feel free to make a PR. I'd suggest something like using a flag like --kotlin to identify the output language.