Bytes.swift

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import Foundation

public typealias GUID = String

/**
 * Utilities for futzing with bytes and such.
 */
open class Bytes {
    open class func generateRandomBytes(_ len: UInt) -> Data {
        let len = Int(len)
        var data = Data(count: len)
        data.withUnsafeMutableBytes { (p: UnsafeMutablePointer<UInt8>) in
            if (SecRandomCopyBytes(kSecRandomDefault, len, p) != errSecSuccess) {
                fatalError("Random byte generation failed.")
            }
        }
        return data
    }
    
    open class func generateGUID() -> GUID {
        // Turns the standard NSData encoding into the URL-safe variant that Sync expects.
        return generateRandomBytes(9)
            .base64EncodedString(options: NSData.Base64EncodingOptions())
            .replacingOccurrences(of: "/", with: "_", options: NSString.CompareOptions(), range: nil)
            .replacingOccurrences(of: "+", with: "-", options: NSString.CompareOptions(), range: nil)
    }
    
    open class func decodeBase64(_ b64: String) -> Data? {
        return Data(base64Encoded: b64,
                    options: NSData.Base64DecodingOptions())
    }
    
    /**
     * Turn a string of base64 characters into an NSData *without decoding*.
     * This is to allow HMAC to be computed of the raw base64 string.
     */
    open class func dataFromBase64(_ b64: String) -> Data? {
        return b64.data(using: String.Encoding.ascii, allowLossyConversion: false)
    }
    
    func fromHex(_ str: String) -> Data {
        // TODO
        return Data()
    }
}