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.
 */
public class Bytes {
    public class func generateRandomBytes(len: UInt) -> NSData {
        let len = Int(len)
        let data: NSMutableData! = NSMutableData(length: len)
        let bytes = UnsafeMutablePointer<UInt8>(data.mutableBytes)
        let result: Int32 = SecRandomCopyBytes(kSecRandomDefault, len, bytes)

        assert(result == 0, "Random byte generation failed.");
        return data
    }

    public class func generateGUID() -> GUID {
        // Turns the standard NSData encoding into the URL-safe variant that Sync expects.
        return generateRandomBytes(9)
            .base64EncodedStringWithOptions(NSDataBase64EncodingOptions())
            .stringByReplacingOccurrencesOfString("/", withString: "_", options: NSStringCompareOptions(), range: nil)
            .stringByReplacingOccurrencesOfString("+", withString: "-", options: NSStringCompareOptions(), range: nil)
    }

    public class func decodeBase64(b64: String) -> NSData {
        return NSData(base64EncodedString: b64,
                      options: NSDataBase64DecodingOptions())!
    }

    /**
     * Turn a string of base64 characters into an NSData *without decoding*.
     * This is to allow HMAC to be computed of the raw base64 string.
     */
    public class func dataFromBase64(b64: String) -> NSData? {
        return b64.dataUsingEncoding(NSASCIIStringEncoding, allowLossyConversion: false)
    }

    func fromHex(str: String) -> NSData {
       // TODO
        return NSData()
    }
}