//! Utility functions for masking data frame payload data
use rand;
use std::mem;

/// Masks data to send to a server
pub fn mask_data(key: [u8; 4], buf: &[u8]) -> Vec<u8> {
	let mut out = Vec::with_capacity(buf.len());
	let zip_iter = buf.iter().zip(key.iter().cycle());
	for (&buf_item, &key_item) in zip_iter {
		out.push(buf_item ^ key_item);
	}
	out
}

/// Generates a random masking key
pub fn gen_mask() -> [u8; 4] {
	// Faster than just calling random() many times

	unsafe { mem::transmute(rand::random::<u32>()) }
}

#[cfg(all(feature = "nightly", test))]
mod tests {
	use super::*;
	use test;
	#[test]
	fn test_mask_data() {
		let key = [1u8, 2u8, 3u8, 4u8];
		let original = vec![10u8, 11u8, 12u8, 13u8, 14u8, 15u8, 16u8, 17u8];
		let expected = vec![11u8, 9u8, 15u8, 9u8, 15u8, 13u8, 19u8, 21u8];
		let obtained = mask_data(key, &original[..]);
		let reversed = mask_data(key, &obtained[..]);
		
		assert_eq!(original, reversed);
		assert_eq!(obtained, expected);
	}
	
	#[bench]
	fn bench_mask_data(b: &mut test::Bencher) {
		let buffer = b"The quick brown fox jumps over the lazy dog";
		let key = gen_mask();
		b.iter(|| {
			let mut output = mask_data(key, buffer);
			test::black_box(&mut output);
		});
	}

	#[bench]
	fn bench_gen_mask(b: &mut test::Bencher) {
		b.iter(|| {
			let mut key = gen_mask();
			test::black_box(&mut key);
		});
	}
}